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Vertosols are widely used for cotton production globally. One main advantage of this soil type is its capacity to improve its structure gradually due to natural processes over time. However, Vertosols are highly susceptible to compaction, especially under wet soil conditions. This study investigated the change in characteristics of Australian Vertosols due to the impact of rainfall, seasonal variability, and John Deere 7760 cotton picker traffic. Soil cores were collected between October 2016 and May 2017. Measurements of soil physical properties (soil water content, dry bulk density, and soil penetration resistance) were carried out in the 0-80 cm depth profile during the study period. Increasing soil water content due to rainfall caused the Vertosol to swell, providing some degree of natural compaction alleviation and decreasing the dry bulk density and soil penetration resistance. Increased temperatures from October 2016 to January 2017 resulted in increased moisture evapotranspiration. This led to shrinkage of the Vertosol and resulted in increased dry bulk density and soil penetration resistance, particularly in the top 0-30 cm of soil. Traffic from the JD7760 cotton picker induced significant compaction throughout the depth profile. These findings have important implications for farmers intending to grow crops in Vertosols and managing the issue of soil compaction. Keywords: compaction, cotton picker, soil density, Vertosols., Introduction Vertosols are a collection of soils dominated by cracking clay soil (black earths and grey and brown clays) with clay texture (Eswaran et al. 1988; McKenzie 1998). Vertosols exist [...]

The effect of different specimen preparation methods (compaction, reconstitution) on the hydromechanical behaviour and microstructure of soil was studied through a series of soil-water retention tests, triaxial tests, and mercury intrusion porosimetry (MIP) tests on an unsaturated clayey silt. Key findings from this experimental study include the following. (i) The air-entry value of the reconstituted specimen is higher than that of the compacted specimen with the same initial void ratio. (ii) The reconstituted specimen exhibits a unimodal pore-size distribution and the compacted specimen exhibits a bimodal pore-size distribution, according to results of the MIP tests. (iii) The soil-water characteristic curves and residual gravimetric water content of compacted and reconstituted specimens are almost the same in the high suction range. (iv) The void ratio of a reconstituted specimen decreases sharply with increasing suction value under an isotropic net stress (such as 20 kPa), while the void ratio of a compacted specimen shows a small change for the same suction change process. (v) Under the same net confining pressure, the shear strength of both compacted and reconstituted specimens increases with the suction increase. The shear strength of the reconstituted specimen is higher than that of the compacted specimen with the same density under the same suction and net confining pressure. Key words: unsaturated soil, reconstituted specimen, compacted specimen, soil-water characteristic curve (SWCC), mercury intrusion porosimetry. Dans le present article, on a etudie les effets de diverses methodes de preparation de specimens (compactagereconstitution) sur le comportement hydromecanique et la microstructure des sols grace une serie d'essais de retention d'eau dans le sol, d'essais triaxiaux et d'essais au porosimetre mercure (PM) realises sur un limon argileux non sature. Les principales observations effectuees grace cette etude experimentale sont notamment les suivantes. (i) La valeur d'entree d'air du specimen reconstitue est superieure celle du specimen compacte, l'indice des vides initial etant le meme pour les deux specimens. (ii) D'apres les resultats obtenus par porosimetrie au mercure, on constate que le specimen reconstitue presente une distribution de taille de pores unimodale et que le specimen compacte presente une distribution de taille de pores bimodale. (iii) Les courbes caracteristiques sol-eau et la teneur en eau residuelle et gravimetrique des echantillons compactes et reconstitues sont presque les memes pour des valeurs de succion elevees et faibles. (iv) L'indice des vides des specimens reconstitues diminue fortement lorsque la valeur de succion augmente dans des conditions de contraintes isotropes nettes (par exemple 20 kPa), alors que l'indice des vides des specimens compactes semble ne varier que legerement en presence d'une variation de succion identique. (v) Pour une meme pression nette de confinement, la resistance au cisaillement des specimens compactes et reconstitues augmente avec la succion. La resistance au cisaillement du specimen reconstitue est plus elevee que celle du specimen compacte, densite, succion et pression de confinement egales. [Traduit par la Redaction] Mots-cles: sol non sature, specimen reconstitue, specimen compacte, courbe caracteristique sol-eau (CCSE), porosimetrie au mercure., Introduction In the past two decades, a great deal of experimental studies have been conducted to investigate the mechanical and hydromechanical behaviour of unsaturated soils. It is noted that existing [...]

In a number of practical cases, a typical one being the investigation of the subsoil properties below roads or foundations, one faces the problem of measuring the elastic properties of a geological layer (here called 'hidden layer') underlying a more compact and rigid surface layer. In such cases, the effectiveness of common surface seismic methods is poor for different reasons, but mostly linked to the reflection--transmission properties of the waves at a stiff-to-soft interface. Borehole methods are more efficient, but expensive and only provide vertical information at certain points. Attempts carried out in the past to characterize the hidden layer properties through surface seismic techniques consisted in placing the seismic source on the surface alongside, but off the stiff artificial layer (road or foundation). An alternative approach is presented based on placing the seismic source just below the stiff artificial layer. In cases where soil improvement--compaction are carried out through injection of expanding resins, then the hidden layer can be easily reached via the injecting tools and in some cases (e.g., urban settings characterized by laterally continuous artificial layers or roads constructed on embankments) this can be the only viable option. The results obtained from this approach using a number of practical cases where roads affected by differential sinking have later been compacted will be presented. The average soil improvement that can be achieved with the specific kind of expanding resin used in this study is then quantified. Key words: surface wave methods, soil improvement, resin injection. Dans un certain nombre de cas pratiques, parmi lesquels figure typiquement l'etude des proprietes du sous-sol des routes ou des fondations, on est confronte au probleme de la mesure des proprietes elastiques d'une couche geologique (nommee ici << couche cachee >>) situee sous une couche de surface plus compacte et plus rigide. Dans de tels cas, l'efficacite des methodes sismiques de surface traditionnelles est limitee pour differentes raisons et principalement liee aux proprietes de reflexion-transmission des ondes a l'interface d'une couche rigide et d'une couche molle. Les methodes consistant a creuser un trou de sonde sont plus efficaces mais plus cheres et ne fournissent que des donnees verticales en quelques points precis. Les tentatives entreprises dans le passe pour caracteriser les proprietes de la couche cachee a l'aide de techniques sismiques de surface consistaient a placer la source sismique sur la surface le long et en retrait de la couche artificielle rigide (route ou fondation). Une autre approche est presentee qui consiste a positionner la source sismique juste en dessous de la couche artificielle rigide. Dans les cas ou des operations d'amelioration-compactage du sol sont realisees par injection de resines expansibles, la couche cachee est facilement accessible fi l'aide d'outils d'injection et, dans certains cas (p. ex. configuration urbaine caracterisee par des couches artificielles continues laterales ou routes construites sur des remblais), il s'agit de la seule solution viable disponible. Les resultats obtenus a partir de cette approche et a l'aide de differents cas pratiques, dans lesquels les routes touchees par un affaissement differentiel ont ete compactees par la suite, seront presentes. L'amelioration globale du sol, amelioration realisee au moyen du type b specifique de resine expansible utilise dans la presente etude sera ensuite mesuree. [Traduit par la Redaction] Mots-cles: methodes des ondes de surface, amelioration du sol, injection de resine., Introduction In practical applications of civil engineering one of the main interests is in measuring the elastic parameters of the subsoil. In this work, the focus of attention is on [...]

In this paper, the volume change behaviour of Maryland clay compacted on the wet side of standard Proctor optimum water content (with lower compaction energy) is studied in reference to the saturated reconstituted state. Oedometer tests over a range of suctions and vertical stresses have been carried out, and the results have shown that the compression index reaches a peak (approximately twice that of the reconstituted material) and then gradually reduces to the reconstituted value as the stress level is increased. The results are analyzed in a framework where the degree of saturation is treated as a state parameter and controls the slope of the unsaturated normal compression line. Tests conducted under constant suction and constant water content have been used to demonstrate the effectiveness of using the degree of saturation as a state variable. Key words: suction, compressibility, partial saturation, degree of saturation. Dans cet article, le comportement associe au changement de volume d'argile du Maryland compactee du cote humide de la teneur en eau a l'optimum du Proctor (avec une energie de compactage plus faible) est etudie en comparaison avec l'etat sature reconstitue. Des essais oedometriques ont ete realises sur une gamme de succions et de contraintes verticales, et les resultats ont demontre que l'indice de compression atteint un maximum (approximativement le double de celui du materiau reconstitue) et ensuite diminue graduellement jusqu'a la valeur reconstituee a mesure que le niveau de contrainte augmente. Les resultats sont analyses dans un cadre ou le degre de saturation est traite comme un parametre d'etat et controle la pente de la ligne de compression normale non saturee. Les essais realises en succion constante et en teneur en eau constante ont ete utilises pour demontrer l'efficacite d'utiliser le degre de saturation en tant que variable d'etat. [Traduit par la Redaction] Mots-cles: succion, compressibilite, saturation partielle, degre de saturation., Introduction Experimental results from tests on unsaturated soils have been found to be difficult to interpret within a consistent framework. This is particularly the case for the volume change behaviour [...]

One of the most distinct characteristics of structured soils is the nonlinearity in the normal compression lines in a plot of specific volume or voids ratio against logarithmic mean or vertical effective stresses, when compared with reconstituted soils. The change in the compressibility (or compression index) with loading is attributed to structure degradation and is expressed as a function of the plastic straining. A direct description of the compression behaviour of structured soil is then established. The validity of this approach is examined via merely incorporating the newly defined normal compression line into the modified Cam-Clay constitutive model. Comparisons against a series of experiments on different types of soils illustrate the feasibility and advantage of the adopted methodology. The dependence of shear strength on the compression behaviour considered initially in critical-state soil mechanics is reemphasized here for structured soils. Analysis also indicates that the stiffness sensitivity coefficient, [S.sub.λ], should be considered together with the traditional strength (or stress) sensitivity coefficient, [S.sub.t] (or [S.sub.σ]), to better characterize the sensitivity of structured soils. Key words: compressibility, structured soil, constitutive relations, plasticity, clays, soft rocks. Une des caracteristiques les plus distinctives des sols structures est la non-linearite dans les lignes de compression normale dans un graphique du volume specifique ou de l'indice des vides versus la contrainte effective verticale ou moyenne logarithmique, lorsque comparee avec des sols reconstitues. La variation de la compressibilite (ou de l'indice de compression) avec les sollicitations est attribuee a la degradation de la structure et est exprimee comme une fonction de la deformation plastique. Une description directe du comportement en compression d'un sol structure est ensuite etablie. La validite de cette approche est evaluee par l'integration des lignes de compression nouvellement definies dans le modele constitutif de Cam-Clay modifie. Des comparaisons entre une serie d'essais sur differents types de sols illustrent la faisabilite et les avantages de la methodologie adoptee. La dependance de la resistance au cisaillement sur le comportement en compression considere initialement en mecanique des sols a l'etat critique est reaffirmee ici pour des sols structures. L'analyse indique aussi que le coefficient de sensibilite a la rigidite, [S.sub.λ], devrait etre considere simultanement avec le coefficient de sensibilite a la resistance (ou contrainte) traditionnel, [S.sub.t] (ou [S.sub.σ]), pour mieux caracteriser la sensibilite des sols structures. [Traduit par la Redaction] Mots-cles: compressibilite, sol structure, relations constitutives, plasticite, argiles, roches molles., Introduction The modified Cam-Clay (MCC) model and critical-state soil mechanics (Roscoe et al. 1958; Roscoe and Burland 1968; Schofield and Wroth 1968) have laid the foundation of modern soil mechanics. [...]

Most levee underseepage and uplift analyses are based on steady-state seepage and can yield conservative results. Although computations are simpler and steady-state seepage parameters are easier to determine and readily available, transient unsaturated seepage analyses are more representative of levee seepage conditions because boundary conditions acting on the levee or floodwall and saturation change with time, which induce pore-water pressure and seepage changes with time in the embankment and foundation strata. In addition, these boundary conditions, e.g., flood surge or storm event, are rapid such that steady-state conditions may not have time to develop in the embankment and some foundation materials. Transient seepage analyses using a floodwall case study indicate that as soil compressibility of the underseepage layer decreases, rapid landside pore-water pressures increase and can approach steady-state values. The transient results also indicate that uplift factors of safety during the flood event are about 22% higher than those at steady state. The effect of soil compressibility can delay or accelerate the onset of uplift water pressure increase from the initial steady-state conditions. Key words: transient seepage analysis, hydraulic conductivity, coefficient of volume compressibility, compressibility, levee, hydraulic gradient, uplift, coefficient of consolidation, slope stability. La plupart des analyses de l'ecoulement et du soulevement des digues sont basees sur l'ecoulement en regime permanent et peuvent donc donner des resultats conservateurs. Malgre que les calculs soient plus simples et que les parametres en regime permanent soient plus faciles a determiner et disponibles, les analyses d'ecoulement en regime transitoire sont plus representatives des conditions d'ecoulement des digues puisque les conditions frontieres qui agissent sur la digue ou sur le mur d'endiguement de meme que la saturation varient avec le temps, ce qui entraine des variations temporelles des pressions interstitielles et de l'ecoulement dans le remblai et dans les couches de fondation. De plus, ces conditions frontieres, par exemple une inondation ou une tempete, sont rapides, donc les conditions du regime permanent peuvent ne pas avoir le temps de se developper dans le remblai et dans certains materiaux de fondation. Des analyses d'ecoulement transitoire faites sur le cas d'un mur d'endiguement indiquent que lorsque la compressibilite du sol de la couche sous l'ecoulement diminue, les pressions interstitielles associees a un glissement de terrain rapide augmentent et peuvent approcher les valeurs en regime permanent. Les resultats transitoires indiquent aussi que les facteurs de securite du soulevement durant l'inondation sont environ 22 % plus eleves qu'en regime permanent. L'effet de la compressibilite du sol peut retarder ou accelerer le declenchement de l'augmentation de la pression d'eau de soulevement a partir des conditions initiales en regime permanent. [Traduit par la Redaction] Mots-cles: analyse d'ecoulement transitoire, conductivite hydraulique, coefficient de compressibilite volumique, compressibilite, digue, gradient hydraulique, soulevement, coefficient de consolidation, stabilite de pente., Introduction Over 100 000 miles of flood protection infrastructure are currently operating in the United States, e.g., along the Mississippi, Sacramento, Trinity, Missouri, and American rivers. The increase in development [...]

Oedometer tests were conducted on dry and saturated kaolinite clay samples to investigate the effects of stress level, stress history, pore fluid type, and drainage path on time-dependent deformation under one-dimensional (1D) constant stress. Different deformation modes involved in the creep compression were identified and quantified: creep deformation of individual particles and creep shear displacement at particle contacts. It was found that the creep compression is a coupled process involving the above creep deformations and induced viscous flow resulting in pore compression. The rate of 1D creep compression is controlled by the drainage path along which the viscous flow occurs. It was also observed that mechanically induced consolidation has an accelerating effect on the creep compression of the test samples existing within the limit time zone. This observation confirms that 1D creep compression is a continuation of 1D consolidation in which the largest existing interaggregate pores collapse under a given effective stress. No creep compression was observed when the test samples were mechanically overconsolidated to a state beyond the limit time zone because the interaggregates were compressed to a stable structure. Reduced creep compression was detected in chemically induced consolidated samples though their states were beyond the limit time line. Key words: creep deformation, viscous behaviour, overconsolidation, chemically induced consolidation. Des essais a l'odometre ont ete realises sur des echantillons d'argile kaolinite secs et satures afin d'etudier les effets du niveau des contraintes, de l'historique des contraintes, du type de fluide interstitiel et du cheminement des contraintes sur la deformation dependante du temps sous une contrainte constante en une dimension (1D). Differents modes de deformation impliques dans la compression en fluage ont ete identifies et quantifies: la deformation en fluage de particules individuelles, et le deplacement en cisaillement en fluage aux points de contact entre les particules. Il a ete demontre que la compression en fluage est un processus couple impliquant les deformations en fluage mentionnees precedemment et l'ecoulement visqueux induit par la compression des pores. Le taux de compression en fluage 1D est controle par le chemin de drainage le long duquel l'ecoulement visqueux se produit. Il a aussi ete observe que la consolidation induite mecaniquement provoque un effet d'acceleration sur la compression en fluage des echantillons a l'interieur d'une periode de temps. Cette observation confirme que la compression en fluage 1D est une continuation de la consolidation 1D durant laquelle les plus grands pores interagreges existants s'effondrent sous une contrainte effective donnee. Aucune compression en fluage n'a ete observee lorsque les echantillons etaient surconsolides mecaniquement a un etat en dehors de la periode de temps limite, puisque les pores interagreges ont ete comprimes jusqu'a l'obtention d'une structure stable. Des compressions en fluage reduites ont ete detectees dans les echantillons consolides chimiquement malgre que leur etat etait au-dela de la ligne de limite de temps. [Traduit par la Redaction] Mots-cles: deformation en fluage, comportement visqueux, surconsolidation, consolidation induite chimiquement., Introduction The time-dependency on the volume change of clay observed in one-dimensional (1D) compression has been an active research area for decades. For practical applications, the volume changes over time [...]

Current guidelines suggest that stabilized rammed earth materials be compacted at their optimum water content to achieve their maximum strength. Although this is true for traditional rammed earth, there is no evidence that this procedure should also be used for cement-stabilized rammed earth. Furthermore, the water content used at compaction is usually difficult to control on a construction site, so that material might be compacted at water contents other than the optimum. In this paper, a novel experimental programme is presented in which the effect of compaction water content on the unconfined compressive strength of crushed limestone stabilized to 5% Portland cement content is investigated for a range of curing periods. Freeze drying of specimens was used to arrest cement hydration to determine the evolution of hydrated cement content. Scanning electron microscope (SEM) analysis was used to identify differences between the final material microstructures. Results are discussed demonstrating the intimate link between the amount of hydrated cement, material microstructure, and compressive strength. Key words: rammed earth, compaction, freeze drying, cement hydration. Les normes actuelles suggerent que les materiaux stabilises avec pise de terre soient compacted a leur teneur en eau optimale afin d'atteindre leur resistance maximale. Malgre que ce soit vrai pour le pise de terre traditionnel, il n'y a pas d'evidence que cette procedure doive aussi etre utilisee pour le pise de terre stabilise avec du ciment. De plus, la teneur en eau utilisee lors du compactage est habituellement difficile a controler sur un site de construction, alors ce materiau peut se retrouver compacte a une teneur en eau autre que l'optimum. Dans cet article, un nouveau programme experimental est presente, dans lequel l'effet de la teneur en eau lors du compactage sur la resistance en compression non confine est etudiee sur du calcaire concasse stabilise avec 5% de ciment Portland, et ce, pour plusieurs temps de cure. Pour arreter l'hydratation du ciment, les echantillons ont ete cryo-desseches afin de determiner revolution du contenu en ciment hydrate. Des analyses au microscope electronique a balayage (MEB) ont ete effectuees pour identifier les differences entre les microstructures des materiaux finaux. Les resultats sont discutes et demontrent le lien intime entre la quantite de ciment hydrate, la microstructure des materiaux et la resistance a la compression. [Traduit par la Redaction] Mots-cles: pise de terre, compactage, cryo-dessiccation, hydratation du ciment., Introduction It is well understood that strength of dry, unstabilized rammed earth (URE) materials is related to the level of suction developed between the soil particles and the material's dry [...]

Backfilling is well known in the mining industry. A basic issue associated with mine backfill design is the determination of the strength of the backfill required to maintain the stability of the backfill body upon removal of a side wall when an adjacent secondary stope is excavated. This task is usually accomplished using a solution proposed by Mitchell et al. in the early 1980s. Recently, this solution has been reviewed and a modified solution has been proposed. These existing solutions, however, were developed for a uniform backfill. In practice, mine stopes are usually divided into primary and secondary stopes. Primary stopes are often backfilled in two stages: a plug pour and a final pour. In many cases, the cement content of the plug pour is higher than that of the final pour. The positive effect of the stronger plug is neglected in both the original and the modified Mitchell et al. solutions. Here, a new analytical solution is developed for estimating the required strength of a laterally exposed backfill by taking the plug into account. The proposed solution reduces to the modified Mitchell et al. solution if the plug pour and final pour have the same cement content. If the plug pour has a cement content higher than that of the final pour, the required backfill strength calculated with the proposed solution is lower than the values estimated with the modified Mitchell et al. solution; the same conclusion can be drawn to the comparison between the proposed solution and the original Mitchell et al. solution when the bond cohesion along the side walls is close to the cohesion of the backfill. Furthermore, the proposed solution indicates that an optimal cohesion ratio between the plug and final pours exists: there is no benefit in using excessively high cement content in the plug pour. It is noted that the proposed solution is valid only for high, narrow backfilled stopes, solutions for low and wide backfilled stopes are under development. Key words: mines, backfill, plug, required strength, analytical solution, Mitchell solution. Le remblayage souterrain est maintenant couramment utilise par l'industrie miniere. Une problematique de base associee a la conception du remblai minier est la determination de la resistance necessaire que le remblai doit atteindre pour maintenir la stabilite de la masse de remblai une fois qu'un mur lateral est retire, par exemple lorsqu'un chantier secondaire adjacent est excave. Cette tache est generalement accomplie a l'aide d'une solution proposee par Mitchell et al. au debut des annees 1980. Recemment, cette solution a ete revue et une solution modifiee a ete proposee. Cependant, ces solutions existantes ont ete developpees pour un remblai uniforme. En pratique, les chantiers miniers sont souvent divises en chantiers primaires et secondaires. Les chantiers primaires sont souvent remblayes en deux etapes, soit la mise en place du bouchon, et le remplissage final. Dans plusieurs cas, la teneur en ciment est plus elevee dans le bouchon que dans le remplissage final. L'effet positif du bouchon plus resistant est neglige dans la solution originale de Mitchell at al. ainsi que dans la solution modifiee. Dans cet article, une nouvelle solution analytique est developpee servant a estimer la resistance requise dans le cas oU un cote de la masse de remblai est expose, tout en considerant l'apport du bouchon. La solution proposee revient a la solution de Mitchell et al. modifiee si le bouchon et le remplissage final contiennent le meme pourcentage de ciment. Si le bouchon contient plus de ciment que le remplissage final, la resistance necessaire calculee avec la solution proposee est inferieure a la valeur estimee par la solution de Mitchell et al. modifiee. La meme conclusion peut etre tiree lors de la comparaison entre la solution proposee et la solution originale de Mitchell et al. dans le cas oU la cohesion le long des murs lateraux est pres de la cohesion du remblai. De plus, la solution proposee indique qu'un ratio de cohesion optimal entre le bouchon et le remplissage final existe; il n'y a donc pas d'avantage a utiliser des quantites excessives de ciment dans le bouchon. Il est note que la solution proposee est valide seulement pour les chantiers remblayes de forme grande et etroite; les solutions pour les chantiers remblayes petits et larges sont en developpement. [Traduit par la Redaction] Mots-cles: mines, remblai minier, bouchon, resistance necessaire, solution analytique, solution de Mitchell., Introduction Backfill composed of tailings or waste rock is commonly used to improve ground stability and to reduce ore dilution (Hassani and Archibald 1998; Li et al. 2003, 2005; Henderson [...]

The fundamental understanding of the behaviour of dry sand as it is being vibrated is necessary to properly address a number of engineering issues, such as the vibrocompaction process. The present paper first summarizes experimental works focusing on the effects of vibrations on the volume change of dry cohesionless soils. Original experiments characterizing the behaviour of dry sand subjected to vertical vibration are then presented. The volume change and the motion pattern displayed by vertically vibrated sand particles are discussed. When cohesionless soil, placed in a cylindrical container, is vertically vibrated under the gravitational field (g), experiments performed on dry Fontainebleau sand allow the distinction between three types of dynamic behaviours depending on the acceleration amplitude (a): the densification behaviour (a/g < 1), the instability surface behaviour (a/g ≅ 1), and the vibrofluid behaviour (a/g > 1). In the densification range, the sand simply settles. When the acceleration amplitude is increased beyond 1g, granular convection is observed and there is an instability in the sand mass leading to the emergence of an inclined free surface. If the acceleration amplitude is further increased, the free surface progressively flattens. There is an impressive dilatation of the whole sample and grain saltation is observed. The sand becomes fully vibrofluidized. The efficiency of the vibrocompaction process is finally discussed especially with regard to these dynamic behaviours. Key words: compaction, dry sand, vibration, vibrocompaction, vibrofluidization. La comprehension fondamentale du comportement d'un sable sec lorsqu'il est soumis a des vibrations est essentielle pour repondre a plusieurs problematiques d'ingenierie, telle que le processus de vibrocompaction. Cet article resume d'abord les travaux experimentaux evaluant les effets des vibrations sur les changements de volume dans les sols secs pulverulents. Les essais originaux, servant a caracteriser le comportement d'un sable sec soumis a des vibrations verticales, sont ensuite presentes. Les variations de volume et les mouvements des particules de sable sont discutes. Lorsqu'un sol pulverulent place dans un recipient cylindrique est vibre verticalement dans le champ gravitationnel (g), les essais realises sur du sable de Fontainebleau sec permettent de distinguer trois types de comportement dynamique, en fonction de l'amplitude de l'acceleration (a): le comportement de densification (a/g < 1), le comportement d'instabilite de surface (a/g ≅ 1), et le comportement vibrofluide (a/g > 1). Dans le domaine de densification, le sable tasse simplement. Lorsque l'amplitude de l'acceleration augmente au-dela de 1g, la convection granulaire est observee et une instabilite dans la masse de sable entraine l'emergence d'une surface libre inclinee. Si l'amplitude de l'acceleration est augmentee davantage, la surface libre s'aplanie progressivement. L'echantillon se dilate de facon impressionnante et la saltation de grains est observee. Le sable devient totalement vibrofluidifie. L'efficacite du processus de vibrocompaction est finalement discutee, en particulier vis-a-vis de ces comportements dynamiques. [Traduit par la Redaction] Mots-cles: compaction, sable sec, vibration, vibrocompaction, vibrofluidification., Introduction The compaction of granular soils by surface vibration was introduced in Germany in the early 1930s. It was then observed that sand could be compacted more efficiently by vibration [...]

Grass is recognized as being beneficial in reducing rainfall infiltration in some kinds of surface cover systems such as landfill cover, because rainwater discharges as surface runoff due to reduced water permeability caused by evapotranspiration-induced soil suction as well as foliage interception. However, the distributions of grass-induced suction in various compacted soils during rainfall are rarely reported. Moreover, it is not straightforward to determine an optimum soil dry density for minimizing rainfall infiltration and at the same time encouraging plant growth. This is because there are conflicting requirements for vegetated cover systems, i.e., compacted soil should not be too dense as to impede root growth, while on the other hand to minimize infiltration. This study thus aims to investigate, quantify, and compare grass-induced suction distributions in silty sand compacted at different densities when subjected to artificial rainfall in the laboratory. A grass species, Cynodon dactylon, which is common in many parts of Asia, was selected for testing. Compacted soil with and without a growing grass patch was tested at three relative compactions (RCs) of 70%, 80%, and 95%, in six test boxes. Test results reveal that at an RC of 95%, suction (40 kPa) retained in vegetated soil after rainfall is 100% higher than that (20 kPa) in bare soil. Among the vegetated soil compacted at the three RCs, suction retained was the highest at an RC of 95% (40 kPa), whereas suction decreased to 0 kPa at an RC of 70% after rainfall. As the average depth of grass roots decreased by 36% due to an increase in RC from 70% to 95%, the depth of influence of suction for vegetated soil at an RC of 95% reduced to less than half of root depth, which was the shallowest among the three compacted soil specimens. Key words: vegetation, suction, Cynodon dactylon, density, rainfall infiltration. L'herbe est reconnue comme etant benefique pour reduire l'infiltration de l'eau de pluie dans le cas de certains types de systeme de recouvrements de surface, comme les couvertures sur les sites d'enfouissement. En effet, l'eau de pluie s'ecoule a la surface en raison de la faible permeabilite a l'eau, qui est causee par la succion du sol induite par l'evapotranspiration et par l'interception de l'eau par les feuillages. Cependant, les distributions de la succion induite par l'herbe dans differents sols compactes durant les precipitations sont rarement rapportees. De plus, il n'est pas evident de determiner une densite seche optimale du sol pour minimiser l'infiltration de l'eau de pluie et en meme temps favoriser la croissance des plantes, puisque les criteres pour les couvertures de vegetation ne sont pas les memes, c'est-a-dire que le sol compacte ne devrait pas etre trop dense pour empecher la croissance des racines mais devrait tout de meme minimiser les infiltrations. Cette etude vise a investiguer, quantifier et comparer les distributions des succions induites par les plantes dans un sable silteux compacte a differentes densites lorsque soumis a des precipitations artificielles en laboratoire. Une espece d'herbe, Cynodon dactylon, qui est commune dans plusieurs parties de l'Asie, a ete selectionnee pour les essais. Le sol compacte avec et sans plante a ete teste a trois niveaux de compaction relative (CR), soit de 70, 80 et 95%, dans six boites d'essais. Les resultats des essais revelent qu'a une CR de 95%, la succion (40 kPa) retenue dans le sol vegete apres la pluie est 100% plus elevee que celle retenue dans le sol nu (20 kPa). Parmi les sols vegetes compactes aux trois CR, la succion retenue etait la plus elevee a une CR de 95% (40 kPa), tandis que la succion etait reduite a 0 kPa a une CR de 70% apres la pluie. La profondeur d'influence de la succion pour un sol vegete ayant une CR de 95% est reduite jusqu'a moins de la moitie de la profondeur des racines, ce qui represente le moins profond des trois echantillons de sol compactes, puisque la profondeur moyenne des racines de l'herbe ont diminue de 36% avec une augmentation de la CR de 70 a 95%. [Traduit par la Redaction] Mots-cles: vegetation, succion, Cynodon dactylon, densite, infiltration de l'eau de pluie., Introduction On most surface cover systems such as landfill covers, vegetation including grass often exists and is considered to be a sustainable and environmentally friendly alternative for minimizing rainfall infiltration, [...]

The 'degree of compactness' is a useful parameter to study soil compaction and represents the current bulk density in relation to the bulk density of the same soil in a reference state. The objectives of this study were to: (i) determine the best compression stress to establish the reference bulk density in the uniaxial compression test using undisturbed samples; (a) quantify the effect of texture on degree of compactness, and (Hi) evaluate the influence of degree of compactness on selected soil physical properties and crop yield. Six soils under no-tillage from southern Brazil were used and the reference bulk density was evaluated on soil samples equilibrated to the matric suction of 33 kPa and subjected to uniaxial compression test. Soil macroporosity, mechanical penetration resistance, root growth, and yield of soybean were also evaluated. For undisturbed soil samples, stresses ≥ 800kPa (particularly the stress of 1600kPa) arc appropriate to determine the reference bulk density. Degree of compactness is independent of clay content and is associated with changes in soil physical properties. A degree of compactness ~100% restricted root growth of soybean, whereas the highest soybean yield was obtained with a DC of 82% for Alfisols and Ultisol, and 85% for Oxisols. Additional keywords: reference bulk density, relative compaction, soil compaction, uniaxial compression., Introduction Soil compaction is defined as the process of decreasing total porosity (especially air-filled porosity), with a consequent increase in bulk density and soil penetration resistance and decrease in water [...]

A newly emerging microbiological soil stabilization method, known as microbially induced calcite precipitation (MICP), has been tested for geotechnical engineering applications. MICP is a promising technique that utilizes the metabolic pathways of bacteria to form calcite precipitation throughout the soil matrix, leading to an increase in soil strength and stiffness. This paper investigates the geotechnical properties of sand bio-cemented under different degrees of saturation. A series of laboratory experiments was conducted, including sieve analysis, permeability, unconfined compressive strength, consolidated undrained triaxial, and durability tests. The results indicate that higher soil strength can be obtained at similar CaC[O.sub.3] content when the treatment is performed under a low degree of saturation. The experimental results are further explained with a mathematical model, which shows that the crystallization efficiency, i.e., actual volume of crystals forming at the contact point where they contribute the most to strength, can be calculated from the degree of saturation and grain size. Fine sand samples exhibited higher cohesion, but lower friction angle than coarse sand samples with similar CaC[O.sub.3] content. The results also confirm the potential of MICP as a viable alternative technique for soil improvement in many geotechnical engineering applications, including liquefiable sand deposits, slope stabilization, and subgrade reinforcement. The freeze-thaw and acid rain resistance of MICP-treated sand has also been tested. Key words: soil stabilization, cementation, microorganisms, calcium carbonate, durability. Une nouvelle methode emergente de stabilisation microbiologique des sols, appelee precipitation de la calcite induite par les microbes (PCIM), est testee pour des applications geotechniques. La PCIM est une technique prometteuse qui utilise les metabolismes des bacteries pour former des precipites de calcite dans la matrice du sol, ce qui entraine une augmentation de la resistance et de la rigidite du sol. Cet article etudie les proprietes geotechniques d'un sable bio-cimente a differents degres de saturation. Une serie d'essais en laboratoire ont ete realises incluant du tamisage, des essais de permeabilite, des essais de resistance en compression non confines, des essais triaxiaux non draines consolides, et des essais de durabilite. Les resultats indiquent qu'une resistance du sol plus elevee peut etre obtenue pour des teneurs en CaC[O.sub.3] similaires lorsque le traitement est effectue a un faible degre de saturation. Les resultats experimentaux sont aussi expliques a l'aide d'un modele mathematique qui montre que l'efficacite de la cristallisation, c'est-a-dire le volume reel de cristaux se formant au point de contact ou ils contribuent le plus au gain de resistance, peut etre calculee a partir du degre de saturation et de la taille des particules. Les echantillons de sable fin demontrent plus de cohesion mais un angle de friction plus faible que les echantillons de sable grossier avec une teneur en CaC[O.sub.3] similaire. Les resultats confirment aussi le potentiel de la PCIM en tant que technique alternative viable pour l'amelioration des sols dans plusieurs applications geotechniques, dont les depots de sables liquefiables, la stabilisation de pentes et le renforcement des fondations. La resistance des sables traites par PCIM aux effets de gel-degel et aux pluies acides a aussi ete testee. [Traduit par la Redaction] Mots-cles: stabilisation des sols, cimentation, microorganismes, carbonate de calcium, durabilite., Introduction Current soil improvement applications include soil replacement, preloading for achieving consolidation, chemical admixture, and grouting stabilization. These techniques are time-consuming, expensive, and in the case of grouting and admixture [...]

The widely used modified Cam clay soil model requires five soil parameters. In simulations of standard triaxial tests these parameters appear in certain combinations. An efficient and practical strategy for deriving these parameters is presented in which visual and numerical optimization techniques are used to estimate the values of these combinations in sequence. Selecting parameters using triaxial tests with stress levels similar to those expected to be important in the ground helps to ensure that the values are appropriate for the application and reduces the extent of the extrapolation required from the region of stress space explored in these tests. Key words: parameter selection, optimization, Cam clay, triaxial test, soil model. Le modele de sol d'argile Cam modifie, qui est couramment utilise, necessite cinq parametres du sol. Lors de simulations d'essais triaxiaux standards, ces parametres apparaissent sous plusieurs combinaisons. Une strategie efficace et pratique pour deriver ces parametres est presentee. Cette strategie utilise des techniques d'optimisation visuelles et numeriques pour estimer les valeurs de ces combinaisons en sequence. La selection des parametres a partir d'essais triaxiaux ayant des niveaux de contraintes similaires aux niveaux importants attendus dans les sols permet de s'assurer que les valeurs sont appropriees pour l'application voulue, et reduit l'ampleur de l'extrapolation requise en-dehors des regions de l'espace des contraintes explore durant les essais. Mots-cles : selection de parametre, optimisation, argile Cam, essai triaxial, modele de sol. [Traduit par la Redaction], Introduction Most soils have a highly nonlinear stress-strain response, which is strongly dependent on recent stress history. To make reliable predictions of field performance, the stress path method (Lambe 1967 [...]

Volumetric behaviour is a fundamental consideration in unsaturated soil constitutive modelling. It is more complex than when the soil is saturated, as unsaturated soils exhibit a range of responses such as swelling and collapse under wetting and shrinkage and cracking during drying. While significant advances have been made, it is still difficult to generally explain all patterns of behaviour. This paper presents a new framework for modelling volumetric response of unsaturated soils with emphasis on compacted soils. The framework uses void ratio (e), moisture ratio ([e.sub.w]), and net stress (p) as the main constitutive variables and suction as a dependent variable. This choice of [e.sub.w] as a main constitutive variable is theoretically sound and is more attractive than the use of suction, which is relatively difficult to measure and displays significant hysteresis during drying and wetting. The framework incorporates the well-known compaction curve making it easily applicable to practical situations. Within the overall e-[e.sub.w]-p space, the operative space is constrained by three main surfaces; namely, loading-wetting state boundary surface, tensile failure surface, and the saturated plane. The conceptual basis for these state surfaces is described and the framework is qualitatively validated against observed behaviour of compacted soils. Key words: unsaturated soils, moisture content, soil compaction, void ratio, constitutive modelling. Le comportement volumetrique est une consideration fondamentale lors de la modelisation constitutive des sols non satures. La complexite est plus grande que lorsque le sol est sature puisque les sols non satures presentent une variete de comportements, comme le gonflement et l'effondrement durant le mouillage, et le retrait et la fissuration lors du sechage. Malgre le fait que plusieurs avancees significatives ont ete realisees, il est encore difficile d'expliquer de facon generale tous les types de comportement. Cet article presente une nouvelle approche pour la modelisation du comportement volumetrique des sols non satures, avec une emphase sur les sols compactes. L'approche utilise l'indice des vides (e), le ratio d'humidite ([e.sub.w]) et la contrainte nette (p) en tant de variables constitutives principales, et la succion en tant que variable dependante. Ce choix de [e.sub.w] comme variable constitutive principale est justifiable de maniere theorique et est plus simple que d'utiliser la succion, puisque la succion est relativement difficile a mesurer et demontre des effets d'hysteresis importants en mouillage et en sechage. Cette approche integre la courbe de compaction bien connue, ce qui la rend applicable aux situations pratiques. A l'interieur de l'espace e-[e.sub.w]-p, l'espace operatoire est contraint par trois surfaces principales: la surface frontiere de l'etat en mouillage-sechage, la surface de rupture en tension, et le plan sature. La base conceptuelle de ces trois surfaces est decrite et l'approche est validee qualitativement a l'aide d'observations du comportement de sols compactes. Mots-cles: sols non satures, teneur en eau, compaction du sol, indice des vides, modelisation constitutive. [Traduit par la Redaction], Introduction A large portion of geotechnical works is associated with unsaturated soil either as compacted fills or natural soil above the water table. In contrast to saturated soils below the [...]

Existing soil nailing design methodologies are essentially based on limit equilibrium principles that together with a lumped factor of safety or a set of partial factors on the material parameters and loads account for uncertainties in design input parameter values. Recent trends in the development of design procedures for earth retaining structures are towards load and resistance factor design (LRFD). In the present study, a methodology for the use of LRFD in the context of soilnail walls is proposed and a procedure to determine reliability-based load and resistance factors is illustrated for important strength limit states with reference to a 10 m high soil-nail wall. The need for separate partial factors for each limit state is highlighted, and the proposed factors are compared with those existing in the literature. Key words: soil-nail walls, limit states, reliability, load and resistance factor design. Les methodes existantes de conception de clous de sol sont basees essentiellement sur les principes de l'equilibre limite qui, combinees avec un facteur de securite regroupe ou un ensemble de facteurs partiels sur les proprietes des materiaux et les charges, tiennent compte des incertitudes dans les valeurs des parametres de conception entres dans le modele. Les tendances recentes dans le developpement de procedures de conception de structures de retention se concentrent sur la conception par facteur de charge et resistance (CFCR). Dans cette etude, une methodologie pour l'utilisation de CFCR dans le contexte des murs de clous de sol est proposee, et une procedure pour determiner les facteurs de charge et de resistance selon la fiabilite est illustree pour des etats limites de resistance importants, en reference a un mur de clous de sol de 10 m de haut. Le besoin d' etablir des facteurs partiels separes pour chaque etat limite est souligne, et les facteurs proposes sont compares a ceux disponibles dans la litterature. Mots-cles : murs de clous de sol, etats limites, fiabilite, conception par facteur de charge et resistance. [Traduit par la Redaction], Introduction Design methodologies for soil nailing are based mainly on the limit state design principle. Soil nailing design codes-recommendations commonly used in European countries, such as Clouterre (1991), Highway Agency [...]

Reducing soil compaction is now an important issue in agriculture due to intensive use of farm machinery in different farm operations. This experiment was designed to study the influence of combinations of external load and soil water on soil compaction. Four soil water levels were combined with four external loads as follows: soil water--air- dry, 50% of field capacity, field capacity, and saturation; external load using different-sized tractors--no load (0 kg), small tractor (2638 kg), medium tractor (3912 kg), and large tractor (6964 kg). Soil bulk density, soil strength, and soil water infiltration rate were measured at 0-100, 100-200, and 200-300 mm soil depths. The 16 treatments were set up in a randomised block design with three replications. Combined increases in soil water and external load increased soil compaction, as indicated by increasing soil bulk density and soil strength and decreasing soil water infiltration rate. There was no significant interaction between soil water and external load for bulk density at all soil depths, but the interaction was significant for soil strength and infiltration rates at all soil depths. The ratio between the weight of the external load and the surface area of contact between the external load and the ground was important in determining the degree of surface soil compaction. Least compaction was produced by the medium tractor because it had the highest tyre/ground surface area contact. In general, the effects of soil water and external load on increasing soil bulk density and soil strength were greater in the topsoil than the subsoil. Additional keywords: external load, soil compaction, soil strength, soil bulk density., Introduction Soil compaction is an important component of land degradation (Batey 2009) and, as such, has become an issue for soil management throughout the world. Soil water content is the [...]

Growth of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seedlings after two growing seasons was reduced by medium and high levels of compaction in loamy sand and silt loam soils that received one of three compaction treatments (low = 0.70 relative bulk density [RBD], medium 0.79-0.82 RBD, and high 0.84 RBD). Survival was reduced on the loamy sand, but not on the silt loam. Soil water content was adjusted with irrigation to levels associated with plant water stress (near wilting point), reduced aeration (near 10% air- filled porosity), and intermediate conditions. Lodgepole pine survival on loamy sand was increased at high water content, but was unaffected by water regime on silt loam. For both soil types, the best lodgepole pine growth was observed for the intermediate watering level. The detrimental effects of compaction were consistent across all water regimes. We also evaluated the response of Douglas-fir [Pseudotsuga menziesii var. glauca (Beissn.) Franco] on silt loam and it was similar to lodgepole pine, except that survival was lower on the compacted silt loam, and under dry conditions. For both species, limitations to growth and survival at medium and high compaction levels were consistent with expectations based on the least limiting water range. Our results, however, are also consistent with a continuously declining growth response due to increasing compaction. The RBD was a good predictor of limiting soil conditions for both soil types and species, and substantially reduced survival and growth was observed at RBD levels higher than 0.80. Abbreviations: AWSC, available water storage capacity; LLWR, Least limiting water range; MBD, maximum bulk density; RBD, relative bulk density. doi: 10.2136/sssaj2009.0458

The objective of the study was to investigate the effects of (i) wheel load (3.3, 6.3, and 7.5 Mg), (ii) tire inflation pressure, and (iii) tillage treatment (conventional vs. conservation) on stress propagation in Luvisols derived from loess and glacial till and to assess the compressibility risk of these soils under different stress situations. Stress and its distribution in the soil were determined with wheel track experiments using a tractor-pulled load frame and stress-state transducer stress sensors. The soil stability with respect to the soil mechanical parameter precompression stress (Pc, -6 kPa) was analyzed on undisturbed soil samples using the oedometer test. Wheel track experiments pointed out no significant differences in stress distribution between the two parent materials and higher stress ([[sigma].sub.1]) with heavier wheel load, whereby [[sigma].sub.1]) more than doubled with a load increase from 3.3 to 7.5 Mg. Conservation tillage showed a greater attenuation ofv1 and lower stress in the topsoil and subsoil (~26%). A reduction in tire inflation pressure decreased [[sigma].sub.1]) in the topsoil for all loads. In the subsoil, [[sigma].sub.1]) decreased for 3.3- and 6.3-Mg loads, whereas the 7.5-Mg wheel load resulted in a trend of increasing stress and propagation into depth with lower inflation pressure. The ratio Pc/[[sigma].sub.1] (the Pc concept), which specifies the transition between plastic and elastic deformation behavior of the soil, indicated that regardless of the tillage treatment, the stress of wheel loads >6.3 Mg exceeded the Pc of the Luvisols down into the subsoil. doi: 10.2136/sssaj2009.0336

Dynamic compaction (DC) is an economical approach for mitigating the hazard posed by collapsible soils particularly when they are deeper than 3-4 m. In this paper, case histories are provided for 15 projects at 10 locations in the United States where collapsible soils were treated with DC. For each site the soil properties, compaction procedures, and subsequent improvement are summarized. Although cohesionless and low-plasticity collapsible soils were successfully compacted, clay layers in the profile appeared to absorb energy and severely reduced compaction effectiveness. Correlations are presented for estimating the maximum depth of improvement, the degree of improvement versus depth, the depth of craters, and the level of vibration based on measurements made at the various sites. The compactive energy per volume was typically higher than for noncollapsible soils because collapsible soils are usually loose but relatively stiff. The maximum depth of improvement was similar to that for noncollapsible soils; however, significant scatter was observed about the best-fit line. Improvement was nonuniform with nearly 80% of the total improvement occurring within the top 60% of the improvement zone. The crater depth was related to a number of factors besides the drop energy including the number of drops, drop spacing, and contact pressure. The peak particle velocities were typically lower than those for noncollapsible soils at shorter distances, but the vibrations attenuated more slowly with distance. DOI: 10.1061/(ASCE)GT.1943-5606.0000331 CE Database subject headings: Collapsible soils; Soil stabilization; Soil compaction; Vibration; United States; Case studies. Author keywords: Collapsible soils; Compaction; Dynamic compaction; Soil improvement; Vibration.

An approach to quantify nonuniformity of compacted earth materials using spatially referenced roller-integrated compaction measurements and geostatistical analysis is discussed. Measurements from two detailed case studies are presented in which univariate statistical parameters are discussed and compared to geostatistical semivariogram modeling parameters and analysis. The univariate and geostatistical parameter values calculated from the roller-integrated measurements are also compared to traditional spot test acceptance criteria. Univariate statistical parameter values based on roller-integrated measurement values provide significantly more information than traditional point measurements, while geostatistics can be used to identify regions of noncompliance and prioritize areas for rework. DOI: 10.1061/(ASCE)GT.1943-5606.0000285 CE Database subject headings: Statistics; Soil compaction; Quality control; Earthwork; Measurement. Author keywords: Geostatistics; Semivariogram; Soil compaction; Quality control; Earthwork; Intelligent compaction.

Abstract: For successful designs of geotechnical structures, rational determination of the engineering properties of soils is an important process. In this context, compaction parameters, maximum dry unit weight ([γ.sub.dmax]), and [...]

Integrated crop-livestock systems directly link crop and livestock production together to generate positive economic and environmental outcomes. Some methods used in integrated systems, like winter grazing on cropland, could negatively affect soil properties and crop productivity. We compared soil compaction, corn (Zea mays L.) yield, and soil nutrient pools between an integrated crop-livestock system and continuous corn system to address this issue. The study was conducted near Pana, IL, between 2002 and 2006. Soil compaction was evaluated indirectly by measuring soil penetration resistance (PR) and surface C[O.sub.2] effluxes. Total soil C, N, and microbial biomass C, were measured from 2002 to 2005. Soil PR and C[O.sub.2] effluxes showed inconsistent trends related to soil compaction and cattle presence. Corn yield from 2004 to 2006 was higher (P = 0.01) in the integrated system (11.6 Mg [ha.sup.-1]) compared with continuous corn (10.6 Mg [ha.sup.-1]). Total soil C concentration increased significantly from 2002 to 2005 within components of the integrated system but remained unchanged in continuous corn. Microbial biomass C was also higher in the integrated system but only in 2005. The study determined that integration of crops with livestock had generally positive effects on crop yield and soil organic matter despite the potential for livestock to compact soil during winter grazing.

Soil surface sealing is one of the main causes for low infiltration rate (IR) and high runoff and soil loss under raindrop impact conditions in arid and semiarid regions. Many studies have focused on the effects of soil properties on seal formation under fast wetting conditions. However, in the field, soils can be exposed to different wetting conditions, before an intense rainfall event, which can affect the role of the soil properties on seal formation. The present paper reviews the effects of different initial wetting conditions and their interactions with soil properties on seal formation, IR, runoff, and soil loss in smectitic soils. Fast wetting of soil causes aggregate slaking, which enhances seal formation, runoff, and soil loss under rainfall, mainly in soils with > 40% clay content. An increase in clay content of the soil increases aggregate strength, but at the same time increases the slaking forces. Hence, in soils with low clay content (40% clay content and high aggregate stability, slaking plays an important role in aggregate breakdown and seal formation. An increase of raindrop kinetic energy, from 8 to 15.9 kJ/[m.sup.3], decreased the effect of the slaking forces on seal formation and runoff. It was suggested that the effects of raindrop kinetic energy and of the slaking forces on aggregate disintegration and seal formation are complementary. An increase in soil exchangeable sodium percentage (ESP), from 0.9 to 20.4%, decreased the effect of slaking forces on seal formation and runoff production under rainfall with 15.9kJ/[m.sup.3] kinetic energy. Probably, increasing the ESP increased the soil dispersivity, and therefore diminished the effect of the slaking forces on aggregate disintegration and seal formation. Aging (the time since wetting) of soil increased the stability of soil structure, decreased the seal formation, maintained high IR, and diminished soil loss amounts. These effects of soil aging depend on both the prewetting rate of the soil and soil texture., Introduction Arid and semiarid regions are characterised by water scarcity and highly variable precipitation. In addition, the water resources in some parts of these regions are expected to decrease as [...]

The acceleration of consolidation rate by stone columns was mostly analyzed within the framework of a basic unit cell (i.e., a cylindrical soil body around a column). A method of converting the axisymmetric unit cell into the equivalent plane-strain model would be required for two-dimensional numerical modeling of multicolumn field applications. This paper proposes two simplified conversion methods to obtain the equivalent plane-strain model of the unit cell, and investigates their applicability to multicolumn reinforced ground. In the first conversion method, the soil permeability is matched according to an analytical equation, whereas in the second method, the column width is matched based on the equivalence of column area. The validity of these methods is tested by comparison with the numerical results of unit-cell simulations and with the field data from an embankment case history. The results show that for the case of linear-elastic material modeling, both methods produce reasonably accurate long-term consolidation settlements, whereas for the case of elastoplastic material modeling, the second method is preferable as the first one gives erroneously lower long-term settlements. DOI: 10.1061/(ASCE)1090-0241(2008)134:2(185) CE Database subject headings: Plane strain; Columns; Stones; Soil consolidation; Numerical models; Constitutive models; Plastic deformation; Embankments.

Thermal-chemical-hydraulic separation process is used to extract bitumen from surface mined oil sands ores. Huge amounts of oil sands fine tailings are produced from the extraction process. The most fundamentally challenging issue facing the geoenvironmental community is containment, long-term storage, and volume reduction of oil sands fine tailings. One of the fine tailings disposal techniques is to homogenize fine tailings with coarse tailings forming nonsegregating tailings (NST). NST exhibits enhanced performance in consolidation and strength, and reduction in water retention as compared to fine tailings. This paper examines onedimensional consolidation behavior of NST with varying fine and coarse tailings compositions. A mechanistic model based on theory of mixture is developed and proposed to predict consolidation behavior of NST. This model is demonstrated to achieve an optimum design of NST for accelerated consolidation rate and water recovery. DOI: 10.1061/(ASCE) 1090-0241(2008)134:2(195) CE Database subject headings: Soil consolidation; Permeability; Compression; Mixtures; Tailings.

Abandoned coal ash ponds cover up vast stretches of precious land and cause environmental problems. Application of suitable in situ stabilization methods may bring about improvement in the geotechnical properties of the ash deposit as a whole, converting it to a usable site. In this study, a technique of in-place stabilization by hydrated lime columns was applied to large-scale laboratory models of ash ponds. Samples collected from different radial distances and different depths of the ash deposit were tested to study the improvements in the water content, dry density, particle size distribution, unconfined compressive strength, pH, hydraulic conductivity, and leachate characteristics over a period of one year. The in-place stabilization by lime column technique has been found effective in increasing the unconfined compressive strength and reducing hydraulic conductivity of pond ash deposits in addition to modifying other geotechnical parameters. The method has also proved to be useful in reducing the contamination potential of the ash leachates, thus mitigating the adverse environmental effects of ash deposits. CE Database subject headings: Fly coal; Ponds; Lime; Columns; Stabilization.

This paper is the first of a two-part series investigating the mechanical behavior of rammed aggregate pier (RAP) groups supporting isolated rigid footings. The first paper presents the experimental test results from instrumented load tests performed on two different 2.3 m square reinforced concrete footings supported by four 0.76 m diameter RAPs of two different pier lengths--2.8 and 5.1 m. Comparisons are made to load tests performed on three isolated RAPs of the same diameter and lengths. Instrumentation consisted of total stress cells, inclinometers, and tell-tale reference plates. Soil conditions at the test site were evaluated using various in situ testing techniques and consist of relafively uniform soft alluvial clay overlain by a 1-m-thick desiccated layer. Interpretations of the test results focused on load-deformation behaviors of the isolated piers and pier groups, group efficiencies in terms of settlement and bearing capacity, stress concentrations as a function of applied load at the top of the piers, and stress transfer with depth. CE Database subject headings: Piers; Bearing capacity; Soil-structure interaction; Soil stabilization; Load tests; Instrumentation.

The favorable effects of the environmentally friendly, nontoxic, anionic polyacrylamide (PAM) as a soil conditioner have long been established. Some uncertainties exist, however, regarding the effects of PAM molecular weight (MW) on its performance as a soil amendment and its ability to penetrate into aggregates and stabilize interior surfaces. We studied the effects of two anionic polymers, a high-MW (12 x [10.sup.6] Da) and a medium-MW (2 x [10.sup.5] Da) PAM, using deionized water (electrical conductivity of 0.004 dS [m.sup.-1]) or a 15 mmol [L.sup.-1] gypsum solution, on the stability of aggregates from four smectitic soils varying in clay content. Penetration of PAM into the aggregates was estimated from treating 0.5- to 1.0- and 1.0- to 2.0-mm aggregates with PAM and thereafter comparing the stability of the small aggregates to that of the large aggregates after the latter had been crushed and sieved to 0.5- to 1.0-mm size. The stability ratio (SR) ranged from 0.090 to 0.900 and tended to (i) increase with the increase in soil clay content, (ii) maintain, in the absence of PAM, a greater level with electrolyte solution than deionized water, and (iii) be greater for the PAM-treated aggregates than the control. In the finer textured soils, the SR of the initially small aggregates was generally greater than that of the initially large aggregates, indicating that most of the PAM was adsorbed on the exterior surfaces and only a small fraction of the PAM added, if any, entered into pores. A significant interaction among the treatments tested (PAM MW, aggregate size, and solution ionic strength), with respect to their effect on the SR, was identified. Consequently, neither of the two PAM polymers tested could have been singled out as preferable. Abbreviations: DW, deionized water; GS, gypsum solution; MC, moisture content; MW, molecular weight; PAM, polyacrylamide; SR, stability ratio; VDP, volume of drainable pores.

No-tillage (NT) farming is a proven technology for soil and water conservation, but its impacts on soil compaction and structure development are soil- and site-specific. We conducted a regional assessment of long-term (>5-yr) NT farming impacts on soil compaction, structure, and aggregate-associated soil organic carbon (SOC) concentration across 13 contrasting but representative soils in the eastern USA, each within a Major Land Resource Area (MLRA: 111C, 98, 114B, and 122 in Indiana; 111A, 111B, 111B2, 99, 111D, 124, and 126 in Ohio; and 147 and 127 in Pennsylvania). Each MLRA comprised NT, chisel plow (CP), and woodlot (WL) land uses. Impacts of NT management were moderate on soil compaction, small on soil structural properties, and nonsignificant on aggregate-associated SOC concentration. No-tillage soils had higher cone index (CI) and shear strength than CP in nine out of the 13 MLRAs, and they had the highest CI (~2 MPa) and shear strength (>180 kPa) within MLRAs 122 and 124. Bulk density ([[rho].sub.b]) in NT was higher than in CP soils only in 111B (1.31 vs. 1.18 Mg [m.sup.-3]) and 127 (1.37 vs. 1.17 Mg [m.sup.-3]). No-tillage farming increased the mean weight diameter (MWD) of aggregates by a factor of 1.6 in MLRA 99, by 3.0 in 124, and by 5.3 in 111A, and reduced their tensile strength (TS) in l14B, 126, and 111 B by a factor of ~2.5. Macroaggregates (> 1 mm) contained 15 to 100% more SOC than microaggregates. Woodlot soils had the lowest [[rho].sub.b] and TS and the highest MWD and aggregate-associated SOC concentration. The MWD increased with increasing SOC concentration. Overall, the impacts of no-tillage farming on soil compaction and structure were small compared with plow tillage. Abbreviations: CI; cone index; CP, chisel plow; MLRA, Major Land Resource Area; MWD, mean weight diameter; NT, no-tillage; SOC, soil organic carbon; TS, tensile strength; WL, woodlot.

The San Jacinto Monument was built in 1936 to commemorate the 100-year anniversary of the victory of the Texan army over the Mexican army. The victory at the battle of San Jacinto followed the defeat at the battle of the Alamo and secured the independence of Texas, as well as several other states along the Mexican border. The monument consists of a 176.5-m-high column resting on a large square mat with each side=37.8 m. The mat foundation was designed by Raymond Dawson who chose an average pressure of 223.8 kPa under the mat. Dawson had settlement points placed on the mat foundation together with benchmarks away from the monument. The settlement of the monument has been recorded over the last 70 years and shows a total settlement to date of 0.329 m. The settlement appears to be almost complete. This remarkable case history is used to evaluate current practice of calculating consolidation settlement and a best approach is suggested for such structures. Other issues addressed include the depth of influence, the time rate of settlement, the elastic-modulus approach, and the ultimate bearing capacity. DOI: 10.1061/(ASCE)1090-0241 (2007) 133: 11(1337) CE Database subject headings: Mat foundations; Foundation settlement; Soil consolidation; Case reports; Monuments; Texas.

Low plasticity silts are liquefiable and the dissipation of pore pressures after an earthquake will be accompanied by densification and compression of the soil skeleton. Anisotropic rather than isotropic stress distributions are commonly found to exist in slopes or silty fills placed under [K.sub.0] conditions and this can be enhanced further by the weight of overlying structures. Compression after an earthquake generally increases soil resistance but it can still be liquefied by aftershocks. The postcyclic recompression of silt, and postdrainage monotonic and cyclic strength and stiffness have therefore been investigated with respect to the effect of initial anisotropic consolidation. The compressibilities during postcyclic recompression were similar to those for isotropic consolidation. Samples with a greater initial anisotropy had less volumetric strain but larger axial strains during postcyclic drainage. Under stress reversal conditions failure occurred as a result of the development of double amplitude cyclic strains, whereas under nonreversal conditions compressive axial plastic strain was accumulated. Postdrainage second loading cyclic strength increased with increasing anisotropy. For isotropically consolidated samples failure under reversal cyclic loading resulted in a weaker soil structure even after postcyclic reconsolidation. DOI: 10.1061/(ASCE)1090-0241(2007)133:4(416) CE Database subject headings: Compression; Stiffness; Silts; Cyclic strength.

A field investigation was carried out with an instrumented vibratory roller compactor to explore the relationship between vibration characteristics and underlying soil properties, namely soil stiffness. The roller was outfitted with instrumentation to monitor drum and frame acceleration, as well as eccentric excitation force. Multiple consecutive passes were performed over six test beds on an active earthwork construction site to capture changes in roller vibration during compaction. Using lumped parameter vibration theory, soil stiffness was extracted from the roller data (drum and frame acceleration and drum phase lag). Both drum acceleration and drum phase lag were found to be very sensitive to changes in underlying soil stiffness. The drum-soil natural frequency of the coupled roller-soil system varied considerably and increased with compaction-induced soil stiffening. Phase lag always decreased with increasing soil stiffness, whereas drum acceleration trends depended on whether the excitation frequency was less than or greater than resonance. Roller-determined soil stiffness was found to be a function of the eccentric force, and heterogeneity in moisture, lift thickness, and underlying stiffness has a considerable affect on roller vibration behavior. When used as a proof roller, the instrumented roller identified soft areas in the embankment that were not identified by a static proof roll test. DOI: 10.1061/(ASCE)1090-0241(2007)133:3(257) CE Database subject headings: Earthwork; Soil compaction; Soil dynamics; Quality control; Subgrades; Monitoring; Vibration.

This paper focuses on the mechanisms occurring in a granular earth platform over soft ground improved by rigid piles. Two-dimensional physical model experiments were performed using the Schneebeli's analogical soil to investigate the load transfer mechanisms by arching and the settlement reduction and homogenization. Experimental outputs are compared to results obtained on a numerical model using a plane strain continuum approach. The impact of the constitutive model complexity to simulate the platform material behavior was first assessed, but no large difference was recorded. As lar as the proposed model, which takes the main features of the observed behavior satisfactorily into account, the numerical procedure could be validated and the parametric studies extended numerically. Both approaches of this study underlined the main geometrical and geotechnical parameters which should inevitably be taken into account in a simplified design method, namely the capping ratio, the platform height, and the platform material shear strength. DOI: 10.1061/(ASCE)1090-0241(2007)133:3(295) CE Database subject headings: Piles; Soil stabilization; Granular materials; Numerical models; Scale models; Two-dimensional models: Soft soils.

The standard and modified Proctor compaction tests have been widely used for evaluation of design properties and compaction characteristics of subgrade soils. However, different types of compaction roller equipment, each producing a different level of soil compaction, are used in the field for compaction of subgrade soils. The purpose of this paper is to evaluate the design properties of compacted subgrade soils using the gyratory compactor made by Servopac to simulate field compaction conditions. Field compaction data were collected from a road construction site in Pusan, Korea. After compaction of the subgrade soil in the field using a vibratory roller was concluded, block samples of the subgrade material were collected. Disturbed soil samples were collected for preparation of specimens in the laboratory using the Proctor compaction and gyratory compaction methods. Unconfined compression test results show that the peak strength, cohesion, and elastic modulus values of the specimens prepared from the field block samples and that of the specimens prepared using the Superpave gyratory compactor with a 600 kPa vertical pressure are similar. On the other hand, much higher values were obtained for these quantities for the laboratory specimens prepared using the modified Proctor method. Our test results indicate that the evaluation of design properties of subgrade soils based solely on the Proctor compaction tests may not be appropriate. DOI: 10.1061/(ASCE)0733-947X(2007)133:2(82) CE Database subject headings: Subgrades; Soil compaction; Compression strength; Creep; Parameters; Sampling.

Large numbers of soil-cement block masonry buildings exist in India and many other countries. The paper deals with an experimental study on the influence of soil grading on the characteristics of soil-cement blocks and shear-bond strength of soil-cement block masonry triplets. Influence of clay content of the soil-cement block on strength, absorption and durability characteristics, and interfacial mortar-block bond strength has been examined. Some of the major conclusions of the study are: (1) optimum clay content leading to maximum strength is in the range of 14-16%; (2) saturated water content of the blocks increases with increase in clay content of the block; (3) initial rate of absorption decreases with increase in clay content of the block; (4) weight loss after ASTM wire scratch test is minimum when the clay content of the block is about 16%; and (5) optimum clay content for the highest modulus for the blocks and for highest shear-bond strength is about 16%. DOI: 10.1061/(ASCE)0899-1561(2007)19:2(139) CE Database subject headings: Soil-cement; Compressive strength; Durability; Soil stabilization; Bonding strength; Stress strain relations.

Measuring root biomass is time consuming and prone to sampling error. We compared three different methods of measuring root biomass in six northern hardwood stands at the Bartlett Experimental Forest. We found that root coring, the most common method of root sampling, yields estimates of fine root biomass about 27% greater than the estimates based on roots sampled in soil pits. Soil compaction contributes about 10% to this difference; the other contributing factor is that cores cannot be taken through obstructions such as rocks and coarse roots. Pits are the only method allowing characterization of root distribution by depth in rocky soil. If the depth and diameter distribution of roots are not required, allometric equations, if available, provide the easiest method of estimating total root biomass. Equations developed at the nearby Hubbard Brook Experimental Forest predicted root mass measured in soil pits with a mean absolute error of 32%. Allometric equations systematically underpredicted observed soil pit root mass in the young stands, presumably because of mature root systems remaining from the previous cohort, and systematically overpredicted observed root mass in the oldest stands. Soil pits can accurately characterize roots up to about 2 cm; coarser roots are encountered too rarely to be estimated by this method. Soil cores sample only fine roots (up to 1-2-mm diameter) but are much less work than excavating soil pits. Root mass estimates made using cores are more accurate if larger diameter corers are used (5 cm rather than 2.5 cm); subsampling before picking roots can help to control labor costs in the face of larger sample sizes. Abbreviations: dbh, diameter at breast height.

For the purpose of understanding the influence of stabilizing agents on the internal structure of aggregates in treated soils, seven soil samples were prepared for tests according to type and quantity of stabilization agents, as well as sampling location. In nitrogen adsorption and desorption tests, HK and BJH methods are, respectively, adopted to analyze the diameter distributions of micropores and mesopores within aggregates in samples with diverse treatment. The results indicate that: (1) micropores with the diaineter of approximately 8.4 A in aggregates are prominent in both untreated and treated expansive soil samples; (2) mesopores with the diameter of greater than 30 [Angstrom] are mainly distributed in four ranges of 30-40, 70-75, 90-95, and 450-500 [Angstrom], and the stabilization agent has significant effect on the structure of mesopores with the diameter of greater than 200 [Angstrom]; and (3) both lime and cement are able to decrease the volumes of micropores while increasing those of mesopores and macropores in expansive soils. The scanning electron microscope images of the samples were presented to interpret the difference in micropore structure between lime-treated soils and cement-treated soils and further validate the results from adsorption tests. In addition, energy-dispersive X-ray spectrometer (EDX) analysis was employed to determine the composition of some points on the individual aggregate and migration of calcium ions in the aggregates in lime treated soils. Through the EDX analysis, it is shown that lime usually concentrates in pores or on the surface of aggregates and has few effects on the inner of aggregates with size ranging from 5 to 10 mm. DOI: 10.1061/(ASCE)0899-1561(2007)19:1(99) CE Database subject headings: Aggregates; Structures; Soil stabilization.

Physicochemical interactions between polymer molecules and clay particles affect the swelling rate and magnitude of expansive clay soils. The effectiveness of aqueous solutions of three polymers: Sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), polyethylene oxide (PEO) ranging in concentration from 0.5 to 10 g/L, as soil stabilization agents against Na-montmorillonite swelling was analyzed. Rates of volumetric swelling of Na-montmorillonite upon hydration were recorded over durations ranging from 120 to 200 h, and data were used to compute the volumetric swelling ratio (VSR), an expression of the clay volume at any time relative to the initial volume of clay in the immersion tube. The results show that PAM, the cationic polymer reduces the VSR by as much as 40% relative to distilled water. PAM molecular weight and concentration have minimal effects on VSR although sorption of PAM of higher molecular weight (PAM B) is favored at aqueous concentration below 2 g/L. Data from x-ray diffraction and batch sorption tests on dried Na-montmorillonite samples indicate that postsorption/swelling interlayer spacings of 0.74 and 0.78 nm for PALM A (molecular weight =4 X [10.sup.6]) and PAM B (molecular weight=7 x [10.sup.6]) respectively, are attained through fixation of PAM molecules in clay interlayer space during sorption at an aqueous concentration of 4 g/L. Test results for CMC (the anionic polymer) and PEO (the neutral polymer) show that swelling is not significantly reduced relative to that of distilled water. PAM can be used at aqueous concentrations between 0.5 and 4 g/L as an effective stabilization agent for expansive soils. DOI: 10.1061/(ASCE)0899-1561(2007)19:1(84) CE Database subject headings: Soil stabilization; Swelling; Polymers; Expansive soils; Clays.

Three relatively new applications for controlling wind and water erosion using polyacrylamide copolymers are described that take advantage of their ability to stabilize and add structure to soil. In the first application, low concentrations of anionic, high purity polyacrylamide (PAM) eliminates sediment in runoff water by more than 90% when added to irrigation water at 10 ppm, or at a rate of 1 to 2 kg [ha.sup.-1] per irrigation. Lab-furrow tests were utilized to characterize the role of molecular weight, charge, and ion concentrations in applying PAM during irrigation. In the second application, PAM is applied at construction sites and road cuts at rates of 22.5 kg [ha.sup.-2] (tenfold higher rates than in irrigation control) resulting in reduction in sediment runoff by 60-85% during (simulated) heavy rains. Finally, a formulation of PAM mixed with aluminum chlorohydrate and cross-linked poly(acrylic acid) superabsorbent at a ratio of (6:1:1) has been applied to create helicopter landing pads that minimize dust clouds during helicopter operation. This formulation was specifically developed to minimize dust clouds during landing of helicopters in fine, arid soils such as those potentially encountered in the Middle East. A biodegradable alternative to PAM, acid-hydrolyzed cellulose microfibrils, was tested in lab-scale furrows and was less effective than PAM at similar concentrations, but show promises. Microfibrils reduce sediment run-off in lab-furrow tests by 88% when applied at eight- to tenfold the concentration of PAM. DOI: 10.1061/(ASCE)0899-1561(2007)19:1(58) CE Database subject headings: Erosion; Runoff; Polymers; Soil stabilization.

Efficacy of stabilizing Ce, Co, and Pb by adding apatite and zero-valent Fe(Fe(0)) to contaminated wetland sediments was quantified under oxidizing and reducing conditions. The redox status and the general water chemistry of the oxidized and reduced treatments differed greatly, yet the influences of the amendments on contaminant stabilization were quite similar; both amendments significantly (p [less than or equal to] 0.05) reduced aqueous contaminant concentrations. Based on resin sorption studies and thermodynamic calculations, Ce is believed to exist primarily as cationic species and Co as cationic, neutral, and organically complexed species. Based on a series of selective extractions, almost 50% by weight of the Co and Pb were already strongly bound to the sediment, thereby limiting the potential (and need) of affecting additional immobilization through the use of amendments. Fe(0) and combined Fe(0) and apatite additions tended to increase the in situ desorption [K.sub.d] values more than apatite-only additions. DOI: 10.1061/(ASCE)0899-1561(2007)19:1(49) CE Database subject headings: Contamination; Lead; Coefficients; Soil pollution.

Passive site stabilization is a new technology proposed for nondisruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction. It is based on the concept of slowly injecting colloidal silica at the edge of a site with subsequent delivery to the target location using natural or augmented groundwater flow. Colloidal silica is an aqueous dispersion of silica nanoparticles that can be made to gel by adjusting the pH or salt concentration of the dispersion. It stabilizes liquefiable soils by cementing individual grains together in addition to reducing the hydraulic conductivity of the formation. Centrifuge modeling was used to investigate the effect of colloidal silica treatment on the liquefaction and deformation resistance of loose, liquefiable sands during centrifuge in-flight shaking. Loose sand was successfully saturated with colloidal silica grout and subsequently subjected to two shaking events to evaluate the response of the treated sand layer. The treated soil did not liquefy during either shaking event. In addition, a box model was used to investigate the ability to uniformly deliver colloidal silica to loose sands using low-head injection wells. Five injection and two extraction wells were used to deliver stabilizer in a fairly uniform pattern to the loose sand formation. The results of the box model testing will be used to design future centrifuge model tests modeling other delivery methods of the grout. DOI: 10.1061/(ASCE)0899-1561(2007)19:1(33) CE Database subject headings: Liquefaction; Soil stabilization; Grouting; Colloids.

It is well known that Ca[Cl.sub.2] and Mg[Cl.sub.2] can been used for dust control and soil stabilization in many fields. However, solutions of Ca[Cl.sub.2] and Mg[Cl.sub.2] are slightly acidic and their application is often forbidden in the area where acid is restricted. Furthermore, in wet seasons, Ca[Cl.sub.2] and Mg[Cl.sub.2] can be partly leached away by water and result in other pollution. In order to solve such problems, CaO, MgO and sodium silicate were individually mixed to the chlorides to reduce their acidity in the investigation. Based on a large number of experiments, the principal results are as follows: CaO, MgO, and sodium silicate cannot only reduce effectively the acidity of the solutions but also decrease greatly the water absorption capacity of the chlorides. The more CaO, MgO, and sodium silicate are added, the less its water absorption rate of the chlorides will be. At the same time, CaO, MgO, and sodium silicate can react with the chlorides, some ions on the surface of soil and dust particles, water and C[O.sub.2] in atmosphere, and their formation products can also bind dust and soil effectively. The binding principles of dust and soil are also explained in detail in this paper. DOI: 10.1061/(ASCE)0899-1561 (2007) 19:1 (10) CE Database subject headings: Chlorides; Dust; Absorption; Soil stabilization.

To determine the effect of wheel traffic and two different management practices on soil compaction and its consequences on physical and chemical soil properties, we measured penetration resistance, water infiltration, bulk density, macroporosity, chemical mobility, air permeability, and soil strength in a conventional orchard (integrated fruit-production program) with bare (sprayed with herbicides) rows and an organic apple orchard with grassed rows. Resistance measurements were taken both within the tree row and the wheel track, down to a depth of 0.35 to 0.40 m. The results indicate that compaction is greater in the wheel tracks under both management methods. Compaction in the wheel track was higher under organic than conventional management. Organic management resulted in a higher macroporosity in both the row and the wheel-track than conventional management. The 'close-to-saturation' infiltration rate was significantly greater within the row of the organic orchard (0.06 m/h) compared with the row of the conventional orchard (0.02 m/h), and compared with the wheel tracks (0.01 m/h). The precompression stress value in the top 100 mm, a measure of the soil strength, was low on all sites. The chemical mobilities were 57 and 50% in the organic orchard, and 86 and 93% in the conventional orchard, respectively, for wheel track and row. Apart from the compaction in the wheel track of the organic orchard, physical and chemical soil characteristics were in a better condition compared with the conventional orchard. Additional keywords: penetrometer, infiltration, chemical mobility, precompression stress, wheel track., Introduction Intensive trafficking in orchards by heavy machinery can cause soil compaction. This can change the soil structure and pore system (Peng et al. 2004), both pore size distribution and [...]