Search

In this work, a series of unconfined compression tests at different water contents were performed to investigate the mechanical behaviour of clay–sand mixtures compacted in standard Proctor conditions. For studying the effect of water content and suction on unconfined compressive strength (UCS) and on strain secant modulus (E50 modulus) of these mixtures, drying–wetting paths were defined by measuring the soil–water characteristic curves (SWCCs) using osmotic and salt solution techniques and filter paper method. The results highlighted that an increase in sand content of the mixture leads to an increase in the maximum dry densities and a decrease in the optimum water content of the materials. However, at the given state, when clay is mixed with 25% of sand, the UCS and E50 modulus increase to 37% and 70%, respectively, compared to those of clayey samples. But when clay is mixed with 50% of sand, the UCS and E50 modulus decrease to 38% and 46%, respectively, compared to those of clayey samples. The results also indicate that the UCS and E50 increase with a decrease in the water content and an increase in suction, irrespective of the sand content.

Many geotechnical problems involve pavements in Algerian arid regions; the main among them being related to the scarcity of standard materials. Recently, numerous studies were carried out on the va...

This article presents the results of experimental work carried out both in situ (coring; pressuremeter test) and in the laboratory (drying-wetting and oedometric tests) to describe the volumetric behavior on drying-wetting path of a swelling clayey soil of eastern Algeria. In order to perform drying-wetting tests the osmotic technique and saturated salts solutions were used. These suction-imposed methods have gained widespread acceptance as reliable methods for imposing suction on soil specimens. They allowed to sweep a wide range of suctions between 0 and 500 MPa. The ability to impose suction on soil specimens allows for drying and wetting stress paths to be applied to evaluate resulting changes in state parameters (void ratio, degree of saturation and water content). These paths were carried out on specimens with different initial states. Slurries of soil were used to characterize the reference behavior, while the undisturbed soil samples allow to describe the behavior of material under in situ conditions. In the last part of this article and to specify the behavior observed in the saturated domain, a comparison between the resulting deformations of the drying-wetting test and those resulting from the oedometric test was made.

The current experimental research aims to valorise two Saharan soils (dune sand and tuff) for pavement purposes in arid zones. A mixture of 65 % tuff and 35 % dune sand (named TDSopt) was previously studied and exhibited optimum geotechnical characteristics that were suitable for low-traffic pavements. However, the rise of groundwater level with aggressive sulphate in the Ouargla region, Algeria, weakened the mechanical properties of this TDSopt. Further treatment with sulphate-resistant binders was therefore proposed to remedy this defect. In this research, laboratory testing was performed to define the optimum treatment for the TDSopt, followed by the hydromechanical characterisation of the treated TDSopt. Experimental results validated the following observations. First, the treatment of TDSopt with cement and/or lime resulted in decreased dry density, but an increased California Bearing Ratio (CBR) index. Also notably improved were unconfined compressive strength (UCS), secant modulus (E50) and resistance to immersion (Rimm). More specifically, the defined optimum recipe – TDSopt plus 1.33 % cement and 2.66 % lime – increased the CBR index by 75 % and 35 % for the soaked and unsoaked specimens, respectively. UCS, E50 and Rimm increased by 65 %, 75 % and 65 %, respectively. The optimum treatment also increases the shrinkage limit void ratio of compacted TDSopt from 0.39 to 0.46. Finally, the strength parameters (UCS, cohesion and friction angle) of optimum treated specimens were larger than those of untreated material regardless of water content. At Modified Proctor Optimum, the UCS, cohesion and friction angle increase from 0.54 to 2.46 MPa, 167 to 800 kPa and 23° to 40°, respectively.

International audience; Nowadays, raw earth construction is an area of growing interest, both for its eco-friendly characteristics and very interesting thermo-hygroscopic properties. Nevertheless, this type of construction exhibits a weakness related to cracking due to the shrinkage strains caused by desiccation. In this context, this paper presents an experimental study of restrained drying-shrinkage, carried out on a fine clayey soil. Several amounts of soil reinforcement with orderly layout patterns using vegetal flax fibers have been investigated in order to enhance soil properties. The new feature of this work is the analyzing of crack initiation and propagation by coupling the Digital Image Correlation (DIC) method with the Clay-Ring-Test (CRT) technique, using an innovative device called DIC-CRT. Suction measurements in clay samples are performed during desiccation using tensiometers. A good agreement is noticed between suction and strain evolution until cracking revealing the direct influence of suction on clay shrinkage. Through the two techniques, DIC and CRT, a relevant parameter to quantify crack intensity in materials is proposed. A significant decrease of crack ratio, by a factor of about 8, highlights the impact of soil reinforcement on the level of crack opening. Likewise, a significant decrease, by a factor of about 20, is observed in the analysis of DIC and CRT slopes, highlighting the impact of reinforcement on the kinetic of crack opening.

In the context of valorizing local materials at Saharan region for road constructions, a mixture composed of 65% tuff and 35% dune sand (named 65T35DS) was previously studied. The 65T35DS was shown to have the optimum geotechnical and mechanical properties. As an extension, this study consists in investigating the behavior of the 65T35DS mixture under coupled hydro-mechanical loadings. Suction-controlled drying-wetting tests were performed on the 65T35DS statically compacted at the modified Proctor optimum (MPO) state. A series of small-strain cyclic triaxial tests under constant water content condition was then followed. Key findings of this paper include i) the 65T35DS prepared at MPO state is able to resist severe drought condition without inducing significant shrinkage. However, it swells during wetting and the swelling indices are quantified by correlations; ii) the elastic modulus under small-strains is governed by suction and the applied confining stress. The effect of confining stress becomes dominantat lower suction level and negligible when suction increases; iii) at failure, the apparent cohesion drops quickly on the dry side of the MPO, on wet side, it decreases a little. The apparent friction angle decreases for the specimens with water content larger than 5.5%, i.e. wMPO - 5. The studied mixture satisfies the design standards of Saharan pavements and seems to be a good compromise for the valorization of local materials.

The ecological and environmental issues today encourage the use of eco-geo-materials that consume less «grey energy» , such as raw earth building material. This raw earth material is inexpensive and is generally available on the construction site. The compressive strength and ductility have a major role on its mechanical behavior. However, few studies are effectively dedicated to estimate both the compressive strength and the ductility property of raw earth materials. Treated with a very low percentage of binders, the raw earth is transformed into an eco-material suitable for use in the construction. However, the experimental study of the raw earth concrete mechanical properties presents uncertainties related to the bio-sourced nature of its components, such as plant fibers and raw earth. In this study, the raw earth samples of 25 different formulations were casted and tested for 90 days of curing time. The samples were tested for unconfined compressive strength through which ductility index were inferred. In order to optimize the formulation of this raw earth material, a «Design of Experiments» was conducted to study the effect of the various components on these two mechanical properties. A multivariate statistical regression technique of PLS, Partial Least Square, was performed to evaluate the design. This PLS technique was selected because of the complicated experimental design data along with different constraints on model based on the two responses. The obtained results show this technique could be a helpful tool to improve and optimize a raw earth concrete formulation.

International audience; This article presents a new osmotic oedometer that is able to measure changes in the degree of saturation (Sr) during suction-controlled drying-wetting and oedometric tests. A circular four-electrode cell made of polyvinyl chloride was developed. The geometric factor of the cell was determined by numerical simulation and validated by calibration tests. A total of 29 samples was statically compacted in the oedometric cell at different moisture contents and dry densities. Based on these measurements, the normalized electrical resistivity was defined and correlated with the Sr. After that, three suction-controlled drying-wetting and oedometric tests were performed on the samples statically compacted at the water content of 21 % and dry density of 1.62 g/cm3, which corresponds to the standard Proctor optimum conditions. The results show (i) the potential of the new oedometer for the study of the hydromechanical behavior of unsaturated soils, (ii) the ability of the electrical resistivity technique to estimate the variation of the Sr in unsaturated oedometric tests, with a relative error smaller than 5 %, and (iii) the coupled effect of vertical stress and suction on the change in void ratio (e) and Sr shown in the (e - suction pressure [s] - vertical total stress [σv]) and (Sr - s - σv) state surfaces.

Building construction technology by raw earth materials is already known and used since ancient times. The raw earth material is abundant, low cost, requires very low energy to manufacture and does not generate waste. Ductility is required for earth building materials in the areas of seismic risks where the earth buildings are particularly vulnerable to earthquakes. Hence, a raw earth treatment by binders and vegetal fibers is one of the techniques applied to improve its strength and ductility. This paper presents the use of mixture design as a tool to evaluate and analyze the plastic behavior of the raw earth material. The ductility is quantified through two ductility indices. The results indicate that an alternative ductility index based on the post-peak behavior of the material could be used to define a ductility criterion to meet specific requirements of the seismic regions.

To overcome water scarcity issues in arid and semi-arid regions, Managed Aquifer Recharge (MAR) remains a viable and suitable solution to manage and restore aquifers. However, clogging represents a major issue that can affect the durability and efficiency of MAR structures. The aim of this study was to evaluate the extent of clogging in MAR sites (Berrechid, Morocco). To achieve this objective, two field-based studies were undertaken: the first one consists of implantation of sand-filled columns in the recharge sites to evaluate the surface and subsurface clogging. The second one consists of the implantation of pickets over a 750 m2 area in each recharge site to measure the extent of deposit thickness on the surface of the wadi bed. Results show that, despite the low rainfall (

Several geotechnical structures constructed with fine soils submitted to wetting and drying (W-D) cycles face a variety of disorders. This is the case of some roads and slopes in the North of Tunis...

The present paper focuses on the effect of the addition of dune sand on the physical and mechanical properties of the tuff. The percentage of sand added to tuff ranged between 0 and 100%. The geotechnical characteristics of sand and tuff as well as those of their different mixtures were first determined. Then, a series of mechanical tests (unconfined compressive strength UCS and triaxial shear test) were performed on compacted samples at modified proctor optimum (MPO). The results showed that the tuff–dune sand mixtures are denser than the basic materials with lower optimum water content at MPO. It was noticeable that the plasticity index decreased with the increasing percentage of sand added, due to the contribution of the fine particles of the sand. However, Californian Bearing Ratio, suction, UCS, maximum deviatory strength and secant modulus increased with the increasing percentage of sand added. They reach their maximum value when the portion of sand incorporated ranged between 25 and 35%. The optimal formulation of 65% tuff and 35% dune sand was selected to meet economic and environmental constraints. This analysis showed that the dune sand incorporation improved the geotechnical characteristics and the mechanical behavior of the tuff. It provided a better elaborated material; satisfying the standards requirements, which could be exploited for the construction of Saharan roads.

The silting of dams requires periodic dredging campaigns to maintain their functional capabilities. In Algeria, more than 32 million m 3 of sediment are deposited every year. In this paper, we investigate the case of the Bakhadda dam in western Algeria, whose dredged sediments can be valorised as an eco-geo-material for building construction in the form of compressed earth blocks (CEB). Preliminary hydro-mechanical study showed the need to amend the natural sediment with sand fraction up to 30% to reach the recommended characteristics of the standards, as granulometry, plasticity and mechanical properties. To achieve high mechanical strength, compaction energy equivalent to modified optimum proctor + 25 blows was required. The hydro-mechanical properties of the manufactured CEB were then studied. Water content effect on their mechanical properties was highlighted. In fact, the strength increases when water content decreases due to an increase in suction. Using the measured drying-wetting paths, relations were established between small strains modulus and water content and suction. Results of this study have led to the valorisation of natural dredged sediments in CEB which respond to the recommendations. Based on the hydric and mechanical tests carried out, the behaviour of CEB in situ was determined.

Managed aquifer recharge is an efficient approach using surface water for groundwater recharge. However, soil clogging in the infiltration systems represents a critical problem that reduces the efficiency of recharge systems. In recent years, much research has been conducted to investigate clogging in subsurface and surface soil (cake). Cake prevents infiltration into the water table and can drastically reduce the recharge rate. In arid and semi-arid areas, alternation of humid and dry seasons has an effect on cake cracking. In the present research, the propagation of desiccation cracking and self-healing of unconsolidated soil (cake), placed in Plexiglas columns, was investigated using X-ray computed tomography (CT) during drying–wetting (D W) paths. The results showed that during the drying path, cracks initiated at the base of the soil by friction with the bottom of the column and then propagated to the top surface of the cake. As the drying time increased, evaporation at the top surface led to more cracks growing from the surface than from the bottom of the cake. However, the cracks at the bottom tended to stabilize because the water content was greater than at the top surface. The initiation, propagation, and expansion of the cracks developed in the saturated condition of the cake. During the wetting path, some cracks were closed while others appeared. The cracks tended to close progressively with wetting time, highlighting the self-healing phenomenon, probably due to the high plasticity index of cake soil. The results showed that cake swelling is mainly related to an increase of the void ratio due to a decrease in suction between particles. The results demonstrate the capacity of the X-ray CT technique to investigate the evolution of cracks during D W paths.

In this paper, a new osmotic oedometer with double flux is developed. The results on loading–unloading stress path with constant suction, for a high plastic marl (wL = 54%, Ip = 28%), are presented...

International audience; The main goal of this research was to try, experimentally, to identify the cause of initiation and propagation of cracks network related to desiccation. The work may provide a better understanding of the drying behavior in clayey soils. Kaolin, which is a little swelling “nearly pure” kaolinite, was studied in this context. The experimental method is based on the determination of the local two-dimensional strains and displacements fields using the softwares Vic-2D and Vic-3D on thin layers of the initially saturated clay. Using digital image correlation technique at the macroscopic level, the analyses of strain fields during drying allow to clearly identify and characterize different phenomena such as: shrinkage, stress concentration, initiation, and propagation of cracks.

International audience; Clay fine soils are characterised by an ability to change volume when subjected to suction. Soil cracking due to desiccation is a phenomenon of great importance in the environmental geotechnical engineering domain. Aiming to understand shrinkage mechanism, and conditions that lead to appearance of drying cracks, a new experimental testing coupled device digital image correlation- clay ring test (DIC-CRT) was developed to investigate fine soils shrinkage and cracking. The new feature of this paper is to link both measurement techniques, based on 2D/3D-DIC and an innovative CRT, in order to assess stress and strain in soils during desiccation. Tests were carried out on a kaolinite having a liquid limit of wL = 40%, and prepared as a slurry with w = 1.5 wL of water content. The results highlight the relevance in combining these two techniques, particularly to assess internal stresses developed in the material using CRT and link them to strains leading to cracking measured by DIC method.

This paper aims to study the behaviour of dense RF Hostun sand subjected to dynamic loading in the triaxial cell. The wet tamping method was used to prepare the samples with the same initial conditions including water content and void ratio. The samples were firstly saturated to dissolve the remaining air bubbles inside the samples. After that, all the samples were consolidated isotropically then the cyclic deviator stress was applied to study liquefaction. All tests show that, saturation affects significantly to the cyclic stress ratio needed to liquefy the sample. The samples having an equal degree of saturation were liquefied by the same level of deviator stress; however, there is a great difference in the load cycles causing liquefaction. This consequence suggests that besides the void ratio and the saturation degree, the different soil fabrics (caused by sample preparation technique) can effect on the sand liquefaction susceptibility and as well the triggering time of liquefaction in situ or in the laboratory.

This work is part of a program for the development of a Compressed Earth Block (CEB) from a material that is readily available, and in large quantities, in the region of Beni-Saf, a town in northwestern Algeria. In this paper, an experimental study has been carried out on the influence of lime treatment on the mechanical behaviour of a compressed earth block. The first step has consisted of carrying out a complete identification process to check the eligibility criteria of the material for earth construction. The next step has intended to examine the influence of 4% and 6% lime treatment on the compaction characteristics (optimum moisture content and maximum dry density). Besides, the drying process of the material, which is characterized by variations in the moisture content and suction values, has been examined. Finally, the influence of these variations on the unconfined compressive strength and elastic modulus has been studied as well.

The paper presents an experimental study of the hydromechanical behavior of a compacted clay used in the design of the core of the Boughrara dam (western Algeria). The influence of compaction energy level (CEL) is explored using three different energies: Standard Proctor energy (SP), reduced Proctor energy (SP-20 blows) and enhanced Proctor energy (SP+ 20 blows). The resulting compaction curves are supplemented by measurements of suction, which is a very important parameter in the behavior of compacted unsaturated soils. In addition to the compaction curves, elastic modulus and immediate bearing capacity ratio (IBCR) are measured, and related to suction and compaction energy level (CEL). Mechanical compaction paths following the SP curve and drying-wetting paths starting from SPO are compared. Mechanical properties such as E-modulus and IBCR are related to the two independent major parameters γd and Sr. Measuring these mechanical properties in the field allows to evaluate the compaction state regardless of the CEL. The results are compared with those of the literature.

The main objective of this paper is to examine how different engineering soils react to environmental variations and to provide correlations to characterize their behaviour under null external mechanical stress. Two French and two Algerian soils with liquid limits ranging from 36 to 112 were prepared under both slurry and Proctor compaction conditions, and then subjected to drying–wetting paths with suction controlled from several kPa to several hundreds of MPa. Experimental results are presented in five diagrams to show globally and simultaneously the shrinkage–swelling, saturation–desaturation and water retention characteristics. A reasonable consistency was observed between the oedometric and drying curves of slurry, confirming the equivalence between hydraulic loading (suction) and mechanical loading (consolidation stress) on the volume change behaviour of different soils. As an intrinsic parameter of soil nature, liquid limit was found to have a significant influence on the shrinkage limit, air-entry suction and compressibility of both slurry and compacted samples. For that reason, correlations between these characteristics and liquid limit were set up, providing a good basis for a first estimation of the drying–wetting curves. At the micro-scale, new experimental results were obtained: either on drying or wetting path, the micro-pores were almost unaffected, whereas, when matrix suction increased from 0.1 to 8 MPa, the volume of macro-pores decreased to quasi-closure. At last, the analogy between the compaction and drying–wetting curves, and the comparison of different methods to determine the water retention curve were addressed. Such analogies and comparisons contribute to a better understanding of the mechanisms of mechanical stress and suction.

This paper presents an experimental investigation of the hydro-mechanical behaviour of two compacted non-standard soils with respect to the French standards GTR 92 in the framework of embankment construction (a low plasticity silt and a high plasticity marl). The aim is to establish relationships between the mechanical parameters (small-strain stiffness, bearing capacity index IBCR …) and hydraulic parameters (water and air permeabilities, and suction). Results show that, for water content lower than the optimum water content, the small-strain stiffness, IBCR index, air permeability and suction change little with water content, whereas for water content larger than the optimum, there is a sharp drop of all the parameters.

The study investigates shrinkage behaviour of a new earth concrete amended with various volume percentages of recycled concrete aggregates (RCA). Two preparations techniques, in situ (industrial) and laboratory (manual), were used. Shrinkage was evaluated using a one-dimensional method and a 2D image analysis. Shrinkage decreases with RCA percentages. Industrial vibration has also an impact on shrinkage. Adding superplasticizer reduces crack appearance without affecting the global shrinkage. Mechanical tests were performed to evaluate the impact of RCA. Compressive strength increases with the addition of RCA, and the bending tensile strength remains quasi constant. Keywords: Recycled concrete aggregates, Earth concrete, Superplasticizer, Shrinkage, Cracks, Image analysis

International audience; Desiccation cracking in drying clays is a common problem with a severe impact on the performance of clayey soils in various geotechnical engineering applications. This article highlights different methods to analyze the formation and propagation of cracks related to desiccation in clays. The research is based on an experimental study of different clays subjected to drying and a phenomenological study of cracking during free desiccation tests on thin clay layers. The approach consists, on one hand, in analyzing the characteristics of cracks with the Image-J software and, on the other hand, in determining the local two-dimensional strains and displacements fields using the digital image correlation (DIC) method. Various tests were carried out to verify the accuracy of the DIC method. Plotting the mechanical strain tensors results in a better understanding of the drying mechanisms of the studied clays. The results show that the combination of two image processing methods, associated to fracture mechanics, is a powerful tool to investigate the mechanisms of cracking in drying soils.

International audience; Reinforcement feasibility of a new ecological earth concrete was examined. Steel rebar corrosion, when in contact with three different types of clayey soil, was investigated using electrochemical methods, potentiodynamic voltammetry and impedance spectroscopy (EIS). Results have shown that the voltammetry method overestimates the corrosion rate while EIS supplies the most reliable results. Corrosion rate decreased and a steady state was reached after four months of contact. The type of clay does not have a significant influence on the corrosion rate of the steel rebar, and the average value of 3 µm/year was considered acceptable for the lifetime of the structure.

Nowadays, structures are mainly constructed using natural aggregates as sand and gravels. In the future, we would increasingly have to consider replacing them by more abundant and ecological natural materials such as raw earth. However, despite its many qualities (low gray energy, thermal and hygrometric isolation), this eco-material has some defects: cracking by desiccation. The later prevent its widespread diffusion. This study aims to understand the mechanisms of appearance and propagation of cracks in order to try to either prevent or repair it. To carry out this study, digital image correlation technique is used. It consists in performing free desiccation tests to follow the initiation and propagation of cracks, from the beginning of homogeneous strain until the appearance of discontinuity, in order to determine the strains tensor in the massif. In order to understand the origin of cracking, desiccation is studied for different boundary conditions and according to different intrinsic characteristics of the material.

This article presents the results of the volumetric behaviour of an Algiers clayey soil. An experimental work was carried out both in situ (core drilling; pressuremeter testing) and in the laboratory (drying–wetting and oedometric tests). Drying–wetting paths of soil samples were obtained using vapour equilibrium method and osmotic technique. These suction-controlled methods have gained widespread acceptance as reliable methods for imposing suction on soil specimens. They allowed for tests to be performed in the range of suction comprised between 0 and 300 MPa. The ability to impose suction on soil specimens allows for drying and wetting stress paths to be imposed to evaluate resulting changes in void ratio, degree of saturation and water content. These paths were explored at different initial states of clay. Slurries of soil were used to characterise the reference behaviour, whereas undisturbed soil samples allow characterising the material under in situ conditions.

Summary Granular materials like sand are widely used in civil engineering. They are composed of different sizes of grains, which generate a complex behaviour, difficult to assess experimentally. Internal instability of a granular material is its inability to prevent the loss of its fine particles under flow effect. It is geometrically possible if the fine particles can migrate through the pores of the coarse soil matrix and results in a change in its mechanical properties. This paper uses the three-dimensional Particle Flow Code (PFC3D/DEM) to study the stability/instability of granular materials and their mechanical behaviour after suffusion. Stability properties of widely graded materials are analysed by simulating the transport of smaller particles through the constrictions formed by the coarse particles under the effect of a downward flow with uniform pressure gradient. A sample made by an initially stable material according to the Kenney & Lau geometrical criterion was divided into five equal layers. The classification of these layers by this criterion before and after the test shows that even stable granular materials can lose fine particles and present local instability. The failure criterion of eroded samples, in which erosion is simulated by progressive removal of fine particles, evolves in an unexpected way. Internal friction angle increases with the initial porosity, the rate of lost fine particles and the average diameter D50. Copyright © 2016 John Wiley & Sons, Ltd.

International audience; Series of drying tests are carried out on natural silt intended for the preparation of new raw earth concrete. This technique is different from rammed earth. The study treats the drying of various formulations of the natural silt with and without reinforcement. No binders were added to highlight the impact of reinforcement. Global and local deformation around a single crack are analysed using image processing. Adding reinforcements to natural silt reduces the percentage of cracking by a factor around 10. The suction is derived from water content corresponding to crack appearance and correlated to the ultimate resistance of the material. (C) 2015 Elsevier Ltd. All rights reserved.

The paper presents an experimental study on the volumetric behavior of two compacted soils (Boughrara and Châtaignier clays) through suction-controlled drying-wetting and oedometric tests. During hydraulic loading (drying-wetting tests), the changes in void ratio, degree of saturation, and water content of both materials are plotted against the logarithm of suction, providing relatively comprehensive experimental results to validate recent empirical correlations on the wetting path and to derive the suction yield curve on the drying path. For mechanical loading (oedometric tests), volumetric changes are presented in the log10 (σv)-e plane, and an increase in yield stress and a monotonic decrease in compressibility coefficient λ(s) with suction are observed. These results show the suction hardening effect on soil stiffness, which is further illustrated by the analysis of the pore-size distribution curve. In addition, a new osmotic oedometric cell which takes advantage of the electrical resistivity technique is developed and used to measure the variation of degree of saturation and volumetric water content in oedometric tests, highlighting in particular how the hydraulic parameters change in a different way from the mechanical parameters (void ratio). The Barcelona Basic Model is examined and a new empirical correlation is proposed to determine the yield stress.

A study was undertaken to characterise the evolution of the clogging of various porous media during filtration experiments. Long-term tracer tests were carried out at various flow velocities. To highlight the effects of intraporosity on transport and retention mechanisms, both single porosity and double porosity media (DPM) were used. The presence of matrix porosity in the two investigated DPM provided additional sites, promoting retention of suspended particles (SP). The particle size distribution (PSD) of the recovered particles increased with time. However, and due to the additional retention sites in intraporosity, the changes in PSD with time were slower for tests on DPM. Ultrasonic transmission was used to detect modifications to the properties of the porous media induced by particle retention. The results demonstrate the capacity of ultrasound for detecting the evolution of physical clogging as a consequence of particle deposition.

The present study focuses on a theoretical model for unsaturated soils based on elastic spherical particle arrangement, which can be considered to be a simplified Discrete Element Method. As a first step, a uniform model is introduced with a single soil particle diameter. This approach follows a new research methodology so that the physical relations between soil particles, interstitial water and air are used. With such a model, the number of experimental parameters needed will be limited. The theoretical model takes into account the different arrangement of soil particles so that the entire voids ratio scale is covered. The wetting and drying paths are modelled. A comparison with previous theoretical model and the proposed new theory is achieved on experimental results with two uniform glass samples. It shows that this new theory improves the precision of the prediction, using only simple physical parameters.

Granular soil in construction of earth works can be solicited by hydrodynamic and mechanical forces. Fine particles constituting these soils may be eroded by the flow leading to a modificat...

A Spray Test and the first test results on soil-cement mixture in the laboratory were presented in this paper. This device simulates the impact of rains on the walls or earthen walls. The results show a resistance to erosion by a rain of the soil-cement mixture, while the other materials were eroded by rains under the same precipitations.

In Algeria, the siltation phenomenon affects all dams. Million cubic meters of sediments are deposited annually. A research program is developed for a rational use of dredged sediments.

International audience; Non-cohesive soils subjected to a flow may have a behavior in which fine particles migrate through the interstices of the solid skeleton formed by the large particles. This phenomenon is termed internal instability, internal erosion or suffusion, and can occur both in natural soil deposits and also in geotechnical structures such as dams, dikes or barrages. Internal instability of a granular material is its inability to prevent the loss of its fine particles under flow effect. It is geometrically possible if the fine particles can migrate through the pores of the coarse soil matrix and results in a change in its mechanical properties. In this work, we uses the three-dimensional Particle Flow Code (PFC3D/DEM) to study the stability/instability of granular materials and their mechanical behavior. Kenney and Lau criterion sets a safe boundary for engineering design. However, it tends to identify stable soils as unstable ones. The effects of instability and erosion, simulated by clipping fine particles from the grading distribution, on the mechanical behaviour of glass ball samples were analysed. The mechanical properties of eroded samples, in which erosion is simulated and gives a new approach for internal stability. A proposal for a new internal stability criterion is established, it is deduced from the analysis of relations between the mechanical behaviour and internal stability, including material contractance.

The present study is focused on a theoretical model of unsaturated soil based on elastic spherical particle arrangement, which can be considered to be a simplified DEM method. The model is presented with a large graded soil. This approach follows a new research method so that the physical phenomena are explained and the number of experimental parameters is limited. The theoretical model takes into account the different arrangements of soil particles so that the entire void ratio scale is covered. The wetting and drying paths are modelled. A comparison with the Brooks and Corey (1962) theory and the new theory is achieved on experimental results with a sample of glass micro-sphere and two natural soils, the Livet-Gavet sandy-loam and the Livet-Gavet loam. It shows that this new theory improves precision of the prediction using only simple physical parameters.

Different approaches have been used for modeling retention curves. The experimental correlation was first proposed [1-3]. The physical modelling of unsaturated soils is used for this study. The shape of the retention curve is a consequence of physical assumptions. The paper presents a theoretical model based on elastic spherical particle arrangement. Firstly, a uniform model is presented with a single diameter of soil particle. The second step extends the use of the model to graded soils. The model uses only physical parameters easy to measure. The model is compared with the experimental retention curve of two different samples, the Livet-Gavet loam (1.61m-3mm) as paste and the Gavet sandy loam compacted with 85 falls per layer of Proctor weight. It shows its ability to model the experimental curves. It is of great interest for engineers as it uses only physical parameters. It gives a direct determination of the retention curve along the wetting path and along the drying path. It shows also the importance of adsorbed water to describe the retention curve.