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Advanced hyperspectral remote sensing technology can identify various clay minerals in the soil. The improved spectral and spatial resolution of the airborne hyperspectral sensor can be used for a better interpretation of clay mineral abundance in the soil. This research utilizes the high-resolution image data acquired from Advanced Visible Infrared Imaging Spectrometer Next Generation (AVIRIS-NG) on an airborne platform to map the abundance of clay minerals in the Udaipur region of Rajasthan (24° 34′ 16.5720′' N, 73° 41′ 29.5584′' E). The representative soil samples for various soil clay minerals, e.g., kaolinite, montmorillonite, and illite, were classified from AVIRIS-NG data using a spectral feature fitting algorithm. A total of thirty sites were selected from agricultural and wastelands for soil sample collection. X-ray diffraction (XRD) analysis of representative soil samples was carried out to find the percentage and type of clay minerals present. Regression analysis between absorption peak depth values estimated from the hyperspectral image of the sampling sites in the spectral region from 2205 to 2214 nm and corresponding clay content value showed a significant relationship. The regression line obtained for the known pixels was used to prepare the mineral abundance map over the study area. This study significantly indicates the dominance of montmorillonite clay mineral over kaolinite and illite in the soils of the Udaipur region. [ABSTRACT FROM AUTHOR]

This study focuses on establishing a robust relationship between Standard Penetration Test-N values (SPT-N), geotechnical parameters and unconfined compressive strength (qu) using regression analysis. The proposed relationship offers a reliable method for estimating qu based on SPT-N values. A comprehensive dataset comprising approximately 200 soil samples collected from various boreholes across Dhaka city was utilized. Multiple Linear Regression (MLR), Rando-forest Regression (RFR) and AdaBoost Regression techniques were employed to develop a unified correlation model. Evaluation metrics including R-squared (R2), Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE), along with Trend-behavior Analysis were employed to assess and compare the performances of the models. Additionally, sensitivity analysis was carried out on the selected model in order to assess the importance of each parameter used to predict qu. Finally, the selected model was compared against the existing empirical models that were published in previous studies. In terms of evaluation metrics and Trend-behavior Analysis, the results showed that the RFR model performed better than the others. Additionally, the selected model outperformed the others, demonstrating the highest R2 score, the smallest RMSE and MAE values and lower residuals compared to the previous models. Hence, the proposed model provides accurate predictions of qu for clayey soil in Bangladesh. Its implementation could ensure more efficient geotechnical designs, specifically adjusted to the geological conditions of the Dhaka region. While previous studies have established regional equations for various parts of the world, our model uniquely has incorporated the Plasticity Index (PI) as a predictor for qu and is specifically calibrated for the geological characteristics of Dhaka city. The findings of this study highlight the effectiveness and applicability of regression analysis in predicting qu for Dhaka's soil properties, thus introducing a valuable tool for enhancing the accuracy and effectiveness of geotechnical assessments and design in the region. [ABSTRACT FROM AUTHOR]

This study investigated the different geotechnical characteristics of soil stabilization with the addition of lime and rice husk ash (RHA) in varying amounts (3%, 5%, 7%, and 9% lime, and 4%, 8%, 12%, and 16% RHA). A series of compaction, unconfined compressive strength (UCS), California bearing ratio (CBR), pH, and X-ray diffraction (XRD) tests were performed in the laboratory to assess the impact of the considered admixtures on the stabilized soil parameters. This study also proposes the successful integration of an artificial neural network (ANN) and a Gaussian process regression (GPR) with the experimental UCS observations. The lime concentration, RHA concentration, and curing period were considered as the input parameters, and UCS was considered as the response. The proposed framework was extended to analyze the compressive behavior of treated soil on the minuscule level. Such coupled machine learning-based experimental investigation can provide deep insight into the soil behavior which otherwise would have remained unexplored due to the prohibitive nature of performing laboratory experiments on a large scale. The findings demonstrated the effectiveness of RHA in addition to lime in stabilizing the considered expansive soil. With the addition of lime and RHA mix, the UCS and CBR values of the treated soil increased significantly. [ABSTRACT FROM AUTHOR]

Several widely used field methods for estimating postliquefaction ground deformation are based on the laboratory data from one series of cyclic simple shear tests performed on one uniform clean sand reconstituted to three relative densities. It is not clear if the trends of this one data set are applicable to other clean sands, nonplastic silty sands, and nonplastic silts. A database of 579 test results on postliquefaction volumetric strain, including 299 test results that relate maximum shear strain to the factor of safety against liquefaction triggering, was compiled and used to examine trends for these soils. The database includes postcyclic test data on 10 clean sands, 2 gravels, 3 silty sands, 5 silts, and 3 clayey soils. The enlarged cyclic testing database was used to develop models that estimate postliquefaction volumetric strain and maximum shear strain as a function of soil type, state, and seismic demand. The models are applicable to uniform nonplastic soil. The state parameter was used in addition to relative density and void ratio to characterize the state of the soil. Correlations between these parameters enable the full data set to inform the models. [ABSTRACT FROM AUTHOR]

This study evaluates the strength behaviors and morphological characteristics of Lianyungang marine clay under the effect of porewater salinity. Soil at higher salinity was found to have increased internal friction angle and undrained shear strength. The difference in undrained shear strength enlarges as the confining pressure increases. Different stress paths were exhibited with soil at different salinities. Soil morphology analysis including scanning electron microscopy (SEM) and Image-Pro Plus (IPP) were employed to investigate the underlying mechanism of the enhanced strength behaviors of soft marine clay with increased salinity. Aggregated soil fabric was observed at higher salinity and contributed to enhanced strength. The results demonstrate that the aggregated soil structure is the primary mechanism responding to the enhanced strength behavior of marine clay under relatively high salinity (6%). Quantitative relationships were developed between the strength parameters and morphological characteristics of soil, i.e., area of particles, roundness of particles, area of pores, pore orientation, and fractal dimension of pore distribution, in the forms of empirical equations, and are expected to serve as the references for prediction in undrained behaviors of soft marine clays with known soil index. [ABSTRACT FROM AUTHOR]

This experimental study examines the efficacy of the inclusion of randomly distributed polypropylene fiber (PP) reinforcement on the engineering properties of expansive clays. The effect of PP fiber inclusions (0%-0.8%) on compaction, unconfined compressive strength (UCS), elastic modulus (E50), California bearing ratio (CBR) and swell-consolidation parameters of test soil were explored. Experimental results showed significant improvement in the strength parameters of treated soils with an optimal fiber content at about 0.4% by weight of soil. The swell-consolidation parameters were also observed to be significantly ameliorated in fiber-reinforced samples. Test results indicate that the use of PP fiber as a reinforced stabilizer for expansive clays not only benefits the sustainable utilization of fiber wastes in soil stabilization, but also reduces the environmental footprint globally. [ABSTRACT FROM AUTHOR]

Soil suction–based analyses are paramount to proper design of foundations in expansive soils, yet availability of field soil suction profiles from direct measurement is limited. A method was developed, using directly measured suction profiles obtained from sites across the US, by which routine geotechnical tests can be used to estimate soil suction to expand the database for estimation of field suction profiles. Herein, the expanded database is used to develop best-estimate clay soil suction envelopes for boundary conditions associated with covered or uncovered ground surface subjected to natural climatic surface flux. Where appropriate for site conditions, the proposed soil suction profile envelopes can be used with any suction-based heave/shrinkage analysis. Key features of the field suction envelopes, consistent with current popular approaches, include climate-dependent estimates for equilibrium suction at depth, depth to equilibrium (stable) suction, and variation in soil suction at the ground surface. Comparisons to existing soil suction envelope recommendations are made. Finally, a limited number of cases of developed/irrigated sites are presented for comparison to soil suction profiles obtained for natural climatic surface flux conditions. [ABSTRACT FROM AUTHOR]

Electrification is done in newer tractors hesitantly. There will be an increase in the need for electrified mounted implements and application units. Semi-liquid manure and degestate from biogas crops are increasingly injected directly into the soil. This technique reduces nutrient losses and ammonia emissions. In the case of loamy soils and clay, a high draft force is needed for slurry deposition into the soil. With the development and testing of an application unit with reduced working width of 3 m, the draft force reduction was found to be lower by nearly one third. The field trials have been performed in two steps: first, a prototype with spiked roller and star packer as a traction element on the roller unit in 3-m working width and second, a final slurry grubber with 6-m working width and cutting coulter on the traction roller. We tested both devices with and without powering the electrified traction roller. These field tests took place on six fields near Freising in Germany. Results showed that firstly, draft force reduction up to 35% was achieved with a powered traction roller on the mounted implement having 20% slippage on the traction roller. These values were obtained by pulling a tractor with the electrified implement by another tractor in a horizontal ground level. Second, we observed a different variation range of the values among the three test fields. This results from differences in the soil structure on the test fields having pebbles and stones near the soil surface or bigger stones down the working depth of 22.5 cm. The presented results show new kinds of working scenarios and operation modes for agriculture. Electrification can be an advantage in taking care of nutrient losses and ammonia emissions as it leads to a draft force reduction on heavy soils. [ABSTRACT FROM AUTHOR]

Soil compaction causes negative effects on crop yield and its mechanical response analysis has recently gained relevance for research through numerical methods. In this work, Finite Element Method (FEM) using the Mohr-Coulomb (MC) and Hardening Soil (HS) constitutive models were employed to simulate the mechanical response of a Vertisol agricultural soil. First, an experimental study of the unconsolidated-undrained (UU) triaxial compression test with different moisture contents (w = 10%, 20% and 34%) and confining pressures (σ3 = σc = 0.05 MPa, 0.10 MPa and 0.15 MPa) was carried out, to obtain the shear strength parameters cohesion (c) and friction angle (φ), as well as the Young's modulus (E) of the soil. The experimental study was conducted through a 32 factorial design with three replicates that it was used to evaluate the influence of the w and σc on E of the studied soil. Also, an analysis of the behavior of the φ and c parameters at each w was performed. Numerical simulations were done with similar conditions as the experimental tests with respect to loading and boundary conditions. A comparison of the mechanical response between numerical results and physical experiments was carried out. As a result, the MC model allowed to estimate satisfactorily the stress-strain relationship of the soil for w of 10% and 20%, while HS model exhibited a better approximation for w of 34% in comparison with the MC model. Finally, the methodology and the adjusted parameters of the agricultural soil obtained in this work, can be used in the study of soil compaction produced by the agricultural machinery. [ABSTRACT FROM AUTHOR]

Three extractions were used to assess the availability of micronutrients in different soil collections. The suitability of some extractions under the conditions of Egyptian soils will be discussed. Three extraction methods (Mehlic 3, Soltanpour and Kelowna) were used for the determination of available Fe, Zn, Mn, Cu and B content of the soil samples (sand, calcareous and clay) during 2020 season. Surface soil samples (0-30 cm) were collected from three sites of Al Boston area in the new Nobaria, Governorate, Egypt, during 2020 season. From each selected plot, ten points were selected in a zig-zag path. The results revealed that the highest values of available Fe, Zn and Cu were given with the extraction solution of Soltanpour, while the highest values of available Mn and B were given with the extraction solution of Mehlic 3. On the other hand, the results showed that clay soil recorded the maximum available Fe, Zn, Mn and Cu, while calcareous soil recorded the maximum available boron content. The interaction between different extraction methods and soil samples was highly significant during 2020 season. [ABSTRACT FROM AUTHOR]

A useful method for the disposal of waste from an incineration plant is to reuse it for geotechnical and civil engineering applications. The primary objective of this study concerns the reuse of local incinerated ash from municipal solid wastes in soil stabilization. Municipal Solid Waste Incinerated Ash (MSWIA) is blended with soil in various combinations and tested for its Atterberg limits, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and Free Swell Index (FSI). A 1-D Consolidation Test was conducted, and changes in the soil during the test were examined by a scanning electron microscopic (SEM) analysis. The test results showed that there are increments in the UCS and CBR values with the reductions in the FSI, swell pressure, and swell potential of the treated soils. [ABSTRACT FROM AUTHOR]

The use of in-situ soil testing has become popular in many geotechnical projects because of its high measurement accuracy and low disturbance of the soil sample during the testing process. Pressuremeter Test (PMT) and standard penetration test (SPT) are two important in-situ tests in geotechnical engineering. The former is an expensive and time-consuming experiment that can measure some detailed mechanical properties of soil while the latter is low-cost and can estimate some basic soil specifications. Thus, identifying the relationship between PMT and SPT parameters can help improve the mechanical characterization of soil samples through a cost-saving methodology. In this research, 47 SPT and 47 PMT were performed on very stiff and hard silty clay and clay soil samples. The variation range of EPMT and the N60 are in the range of 16.55-75.95 MPa and 16-51, respectively. Empirical equations were proposed between EPMT-N60, PL-N60, and Epmt-PL with R² ≥ 0.65. Regression analysis by determining 'R²', 'Sig.', and 'F' values demonstrated that the proposed models are highly significant and strongly meaningful. The Mean Square Error (MSE) and Root Mean Square Error (RMSE) values for each relation showed that the estimation error is very small, and the relationships are acceptable. The equations proposed in this research can be used for very stiff and hard silty clay and clay soil types. Also, by comparing the N60 and EPMT/PL values, silty clay and clay soil were classified in terms of consistency according to EPMT/PL ratio. Finally, the results from this study were grouped and compared with those reported earlier, leading to a practical advisory methodology for the estimation of PMT parameters from the SPT data applicable to a wide range of soil samples. [ABSTRACT FROM AUTHOR]

Abstract Tensile strength is one of the most important mechanical parameters controlling the development of cracks in soil. However, it is frequently neglected in conventional geotechnical practice, because its magnitude is small and difficult to measure relative to other soil strength parameters. In this paper, a newly designed direct tensile test apparatus was employed to measure the tensile strength of an unsaturated clayey soil. A digital image acquisition and analysis system was developed for tensile strain analysis with the help of Particle Image Velocimetry (PIV) and Digital Image Correlation (DIC) techniques. Six groups of samples were compacted at a dry density of 1.7 Mg/m3 and different water contents (6.5%, 8.5%, 10.5%, 12.5%, 16.5% and 20.5%). Test results show that the tensile strength characteristic curve (tensile strength versus water content) of the compacted unsaturated soil exhibits mono-peak feature. When water content is relatively low, the tensile strength increases with increasing water content and reaches the maximum value at a critical water content of about 9.3%. Then, it declines with further increase in water content. The evolution of tensile strength with water content depends on both suction and microstructure. Based on plotted tensile load-displacement curves, the tensile failure process can be divided into three typical stages which are: stress increasing stage (I), failure developing stage (II) and post-failure stage (III). It is found that the overall tensile failure process presents different patterns controlled by water content. Generally, the failure developing stage (II) lasts longer and the failure ductility is more pronounced when the sample is compacted at higher water content. Using PIV and DIC techniques, the development of displacement direction and strain concentration during tension can be well captured for appreciation of the soil failure mechanism. Based on the strain concentration information, the tensile fracture location and direction can be pre-determined for soil samples. Graphical abstract Unlabelled Image Highlights • New direct tensile test apparatus with image capture system is designed. • Tensile curve shows three typical stages which strongly depend on water content. • TSCC of compacted soil shows mono-peak feature related to both suction and fabric. • Tensile stiffness and failure brittleness decrease with increasing water content. • PIV/DIC is valuable to get deformation and strain concentration characteristics. [ABSTRACT FROM AUTHOR]

The research included a standard study of the age of the which tires are (80%) and (50%) of standard condition and the inflation of the rear tire of the boat are (32) psi and (27) psi and the affect in both of the following properties(draft force, loss power to slippage, fuel consumption, effective field capacity, energy utilization efficiency, volume of soil disturbed, soil penetration resistance, dry bulk density) The experiment was carried out in a global experiment by using the Duncan test with experimental design (RCBD) was used to show the significance of the differences between the average transactions. The result showed a significant effect of the age of the tires in all the studied traits except for the description of the apparent density and showed a significant effect of the pressure factor of the tire bulge in all studied traits except of effective field capacity, volume of soil disturbed, dry bulk density. All the studied traits were significantly affected by the dual interference between the age of tires and pressure of bulge except for the dry bulk density which did not affect significantly. [ABSTRACT FROM AUTHOR]

Volume changes of soil associated with soil moisture changes are caused by the presence of clay minerals from illite and montmorillonite groups. Clay minerals are found in the so-called clay soil component which can be quantified by laboratory analysis of the soil particle-size distribution. Consequently, the potential for volume changes in soil can be assessed from soil texture. In our study, 172 soil samples with different textures were used to measure dependencies between volume changes in soil and changes in soil moisture under laboratory conditions. The samples were collected from 11 sites in the Eastern Slovak Lowland. On the basis of the measurements, 10 mathematical models were created to compute the correlation between volume changes of soil and soil moisture content and texture. The highest accuracy was obtained with the model which assumes the content of particles < 0.002 mm. When comparing the clay particles < 0.001 mm (colloidal clay) with the particles < 0.002 mm (colloidal + physical clay) it was also found that the particles < 0.002 mm have a larger impact on the volume changes of soil than the particles < 0.001. The inclusion of particles > 0.002 mm (silt + sand) into the models resulted in either no or only negligible refinement of the soil volume change calculations. [ABSTRACT FROM AUTHOR]

Volume changes of soil associated with soil moisture changes are caused by the presence of clay minerals from illite and montmorillonite groups. Clay minerals are found in the so-called clay soil component which can be quantified by laboratory analysis of the soil particle-size distribution. Consequently, the potential for volume changes in soil can be assessed from soil texture. In our study, 172 soil samples with different textures were used to measure dependencies between volume changes in soil and changes in soil moisture under laboratory conditions. The samples were collected from 11 sites in the Eastern Slovak Lowland. On the basis of the measurements, 10 mathematical models were created to compute the correlation between volume changes of soil and soil moisture content and texture. The highest accuracy was obtained with the model which assumes the content of particles < 0.002 mm. When comparing the clay particles < 0.001 mm (colloidal clay) with the particles < 0.002 mm (colloidal + physical clay) it was also found that the particles < 0.002 mm have a larger impact on the volume changes of soil than the particles < 0.001. The inclusion of particles > 0.002 mm (silt + sand) into the models resulted in either no or only negligible refinement of the soil volume change calculations. [ABSTRACT FROM AUTHOR]

Mechanized tunneling through clayey formations is threatened by encountering the clogging problem. Adhesion stress, as the tendency between clay and a metal surface, leads to clogging between TBM and excavated materials. Some empirical clogging classification charts were prepared based on the experienced clogging problems. Moreover, experimental attempts have been made to evaluate clogging potential. The relation between available empirical charts with laboratory measurements has not been fully defined. This research was conducted to clarify the relationship between measured adhesion values and to propose empirical charts to support a laboratory assessment method. In this regard, 35 clayey soil samples (assumed to have different levels of clogging potential) were selected using the main existing empirical evaluation charts. The clayey soil samples were tested at two different consistency indexes using the piston pullout test, as a highly qualified adhesion assessment tool. The performance of available classifications was examined by laboratory test results. For this purpose, distribution of the measured adhesion values and levels of clogging potential with classification charts were compared. Among the examined classification charts, one of them showed a high match with adhesion values. Using the resulting relationship, a new experimental method was proposed to evaluate clogging potential using laboratory data. [ABSTRACT FROM AUTHOR]

Abstract: A specific swelling clayey strongly alkaline soil with gilgai microtopography is characterized. The profile of this soil displays diagnostic features of both Solonetzes and Vertisols. In the Russian soil classification system, it is classified as a crusty quasigley slitic (vertic) sulfate-sodic clayey dark solonetz. In the WRB-2015 system, it can be defined as a Nudinatric Vertic Stagnic Protosalic Solonetz (Clayic, Columnic, Cutanic, Humic, Hypernatric). The area with this soil is found on the northern spurs of the Kalach Upland in the Kamennaya Steppe (Talovskii district of Voronezh oblast). Data on the particle-size distribution, soil density, composition of extracts from water-saturated pastes, and the content of exchangeable cations in the soil profile are analyzed. The 2D distribution of the morphological features indicated by symbols of the soil diagnostic horizons and features is presented. Data on the contents of organic carbon and calcium carbonates; the activities of sodium, calcium, and chloride ions and their ratios; the contents of oxalate- and dithionite-soluble iron compounds and their ratios, and the swelling capacity of ground samples are also presented. Three levels of morphologically manifested deformation structures are identified in the soil profile. Their impact on the spatial distribution of the physical and chemical properties is discussed. [ABSTRACT FROM AUTHOR]

Abstract: It is shown that deep ameliorative plowing with destruction and disintegration of solonetzic horizons changes the morphology of the profile and water-physical properties of soils in solonetzic soil complexes of the dry-steppe zone. This results in a more active migration of calcium salts and dissolution and recrystallization of carbonate and gypsum pedofeatures. Data on the tendencies of changes in the contents of carbonates and gypsum and the morphology of carbonate and gypsum pedofeatures at the macro- and mesolevels are given for the reclaimed high-carbonate deep-gypsum solonetzic soils and light chestnut soils (Protosalic Solonetzes (Loamic, Columnic, Cutanic, Differentic, Ochric); Eutric Cambisols (Loamic, Protocalcic, Ochric)). Reclaimed solonetzes and light chestnut soils are characterized by an increase in the carbonate content of the plow horizon. This attests to the accumulation of carbonates in the plow layer of these soils, which is a new elementary pedogenic process for them. The mechanism of this process is described. It includes dissolution of carbonates in the carbonate-accumulative horizon in spring followed by the upward migration of dissolved carbonates upon the soil drying in summer. [ABSTRACT FROM AUTHOR]

Constant rate of strain (CRS) and incremental loading (IL) consolidation tests are extensively used to measure consolidation properties of clayey soils. However, results of CRS test are usually strain rate dependent. In this study, a finite differences simulation of CRS test based on Terzaghi's theory of consolidation is performed. The numerical simulation permits to evaluate a strain rates range satisfying a preset relative pressure criterion. Results of simulation show that the required relative pressure criterion can be verified, during the steady state stage of CRS test, only for particular types of soils and particular range of strain rates. Subsequently, a simple method is proposed to select, for a soil sample defined by its initial height, initial void ratio and liquid limit, an appropriate strain rates range satisfying the ASTM 4186-06 criterion. Comparison of previsions and experimental results reported in literature shows good agreement. [ABSTRACT FROM AUTHOR]

Clay soils can exhibit excessive swelling due to changes in water content. The clay swelling threatens the long-term stability of structures and foundations, thus an accurate prediction of clay swelling properties is essential in many geotechnical projects. We present feed-forward and cascade-forward neural network models trained with the Levenberg–Marquardt and Bayesian optimization algorithms to determine the swelling potential of natural and artificial clayey soils. The compiled experimental dataset includes various types of soils covering a wide span of swelling potential, ranging from 0.01 to 168.6%. The activity, water content, dry unit weight, liquid limit, plastic limit, plasticity index, and clay content were considered as the input parameters of the models as they are commonly measured during the experimental testing of soil behaviour. The results show that the feed-forward neural network trained with the Levenberg–Marquardt algorithm is the most accurate model for the prediction task. The performance of the model is satisfactory, showing an acceptable agreement with experimental data. The developed model showed substantial improvements over previous empirical and semi-empirical correlations in determining the swelling potentials of both natural and artificial soils. • Developing a feed-forward neural network model to determine swelling potential of clayey soils • The effectiveness of the model was compared with empirical and semi-empirical correlations • The model determines swelling potential of clayey soils with sufficient degree accuracy [ABSTRACT FROM AUTHOR]

The original paper explicitly reports that large direct shear tests were performed to quantify the shear strength of geotextile-reinforced expansive soil subgrade. The writers agree with the discusser about the critical soil mechanics of geotextile-reinforced and unreinforced expansive soil; however, in the original scope of work was limited to and focused on assessing the interface efficiency of geotextile-reinforced expansive soil. 6(b-d), which compared different configurations of the geotextile layer test sections with the unreinforced expansive soil test section. [Extracted from the article]

Under traffic loading, the soil elements in subgrade are subjected to a cyclic cardioid-shaped stress path in the 2 τ vh ~ ( σ v − σ h ) stress plane. This significantly differs from the conventional stress paths that have been simulated using the cyclic triaxial and simple shear apparatuses, as widely reported in the literature. To date, the influence of shear stress level on cyclic deformation behaviour of intact soft clay subjected to cyclic traffic loading were rarely considered in the existing experimental investigation. For this reason, a series of cyclic hollow cylinder experiments that mimic cardioid-shaped stress paths are carried out on intact samples of Wenzhou soft clay. A wide range of vertical stress levels combined with different shear stress levels (i.e., different cardioid-shaped stress paths) are simulated in the experiments. The results show that the shear stress level significantly influences the cyclic straining and exacerbates the potential of cyclic shear failure. The difference of cyclic tests with variable shear stress level increases as the vertical cyclic stress ratio value increases. Based on the test results, an allowable cyclic stress ratio is determined to be about 0.22, which may serve as the upper bound limit of cyclic traffic loadings on soft clayey deposit. For the hollow cylinder specimens used in this study, a resilient axial strain of 3% could be a proper failure criteria value. A simplified permanent strain model that considers shear stress is proposed for the deformation behaviour of soft clay under cyclic traffic loading. [ABSTRACT FROM AUTHOR]

Effective pretreatment of spectral reflectance is vital to model accuracy in soil parameter estimation. However, the classic integer derivative has some disadvantages, including spectral information loss and the introduction of high-frequency noise. In this paper, the fractional order derivative algorithm was applied to the pretreatment and partial least squares regression (PLSR) was used to assess the clay content of desert soils. Overall, 103 soil samples were collected from the Ebinur Lake basin in the Xinjiang Uighur Autonomous Region of China, and used as data sets for calibration and validation. Following laboratory measurements of spectral reflectance and clay content, the raw spectral reflectance and absorbance data were treated using the fractional derivative order from the 0.0 to the 2.0 order (order interval: 0.2). The ratio of performance to deviation (RPD), determinant coefficients of calibration (), root mean square errors of calibration (RMSEC), determinant coefficients of prediction (), and root mean square errors of prediction (RMSEP) were applied to assess the performance of predicting models. The results showed that models built on the fractional derivative order performed better than when using the classic integer derivative. Comparison of the predictive effects of 22 models for estimating clay content, calibrated by PLSR, showed that those models based on the fractional derivative 1.8 order of spectral reflectance ( = 0.907, RMSEC = 0.425%, = 0.916, RMSEP = 0.364%, and RPD = 2.484 ≥ 2.000) and absorbance ( = 0.888, RMSEC = 0.446%, = 0.918, RMSEP = 0.383% and RPD = 2.511 ≥ 2.000) were most effective. Furthermore, they performed well in quantitative estimations of the clay content of soils in the study area. [ABSTRACT FROM AUTHOR]

To study effect of plasticity on shear behavior of low-plasticity fine-grained soil, a Mississippi River Valley (MRV) silt with a plasticity index (PI) of 5.8 was treated with different dosages of sodium bentonite to modify its plasticity up to a PI of 13.5. The naturally occurring material originated from the MRV exhibited dilative behavior under normally consolidated conditions. The silt-bentonite mixtures tend to lose quasi-steady-state strength and dilative characteristics as the plasticity increased. At a PI of 13.5, the silt-bentonite mixture had plastic stress-strain clay-like behavior. Overconsolidation did not influence the friction angle of the natural silt, but for silt-bentonite mixtures with Pis of 6.2 and 9.4 the influence of prestress was evident. The normalized shear strength was significantly reduced with an increase in PI from 5.8 (natural MRV silt) to 6.0 (natural MRV silt with 2.5% bentonite added). Compared to the predictive relationships proposed by other researchers, the normalized shear strength of the natural silt was clearly higher. The critical PI was about 6 to differentiate clay-like soil and intermediate soil for the subject silt. The PI was found not to be an ideal parameter to identify the transformation of the shear behavior of the MRV silt, because the shear behavior had a big change with a slight change of PI. [ABSTRACT FROM AUTHOR]

A full-flow ball penetrometer is now routinely used in centrifuge testing for characterizing single-layer clay, silt, sand, and stratified soil samples. The behavior of the standard ball penetrometer (including the shaft) used in the field, penetrating through single and two-layer uniform clays, has recently been investigated. However, the ball penetrometers used in centrifuge testing has either a similar or higher area ratio (of the shaft to the ball) and significantly greater equivalent prototype diameter compared with the standard one used in the field. The thickness of the soil layers, however, are scaled accurately mimicking strength profiles in the field, leading to lower relative thickness of the soil layers. Large deformation finite element (LDFE) analyses were, therefore, carried out for the centrifuge ball penetrometers to investigate its performance in characterization of single- and double-layer clays. The results were validated against plasticity solutions and other previously published finite element (FE) results prior to undertaking a detailed parametric study, exploring a range of normalized soil properties and layer thickness. Three commonly used centrifuge balls were studied. For single-layer uniform clay, the area ratio of shaft to ball was shown to have significant influence on the deep bearing factors and the critical penetration depth of attaining that factor. For two-layer uniform clays, the undrained shear strength of the top layer was mostly underestimated because of the lower thickness of that layer relative to the centrifuge ball diameter. In addition, the shear strength of the bottom layer was mostly overestimated because of trapping of stiff clay at the base of the ball, advancing in stiff-over-soft clay deposits. To interpret a reference undrained strength profile, taking into account the scale effects of the penetrometer relative to layer thickness, a framework has been proposed accounting for these effects, with the LDFE data used to calibrate the framework. [ABSTRACT FROM AUTHOR]

The responses of soil moisture to rainfall are of great significance for watershed hydrological modeling. However, few studies have been done to investigate these responds on hillslope in a typical semi-arid grassland region. This study used high temporal resolution soil moisture data to explore the soil moisture dynamics, response conditions and its controls of 0–40 cm soil profile in the upslope (14°), midslope (9°), and downslope (4°) of a typical grassland inland river basin under bare ground (BG), stubble (SG), and natural grassland (CK) treatments. The results showed that soil water content and water storage increased in the downslope direction, and all showed as BG > SG > CK. The dry and wet changes in fast-changing layer (5 cm) and active layer (10 cm) were rapid, while soil moisture below 20 cm was relatively stable and fluctuated only in heavy or continuous rainfalls. The soil moisture response process varied greatly under different rainfall, rainfall intensity and antecedent soil moisture conditions, which explained 41.1% of the total difference. The rainfall replenishment threshold and the required initial soil profile water content of soil moisture response in 5 cm, 10 cm and 20 cm soil layers were 5.8 mm, 8.0 mm, 11.4 mm and 8.7 vol%, 9.4 vol%, 10.8 vol%, respectively. Soil properties, vegetation characteristics and topography could explain 38.8%, 14.5% and 5.6% of the soil moisture variation on the hillslope. In addition, under the comprehensive influence of environmental factors, changes in soil moisture of the upslope were significantly affected by soil sand content, the differences in the midslope were mainly due to soil clay content and belowground biomass, whereas the vegetation characteristics were the main factors in the downslope. This study can contribute to the further understanding of slope-scale ecohydrological processes and hydrological simulation of semi-arid grassland watersheds. • The response of soil moisture to rainfall under different vegetation treatments at different hillslope positions was investigated. • Rainfall recharge thresholds and initial soil profile water content for soil moisture responses at different soil depths were determined. • The effects of water condition, vegetation characteristics and soil properties on soil water responses at different hillslope locations were quantified. [ABSTRACT FROM AUTHOR]

The identification of clayey soil desiccation cracks is an important practical issue in geotechnical engineering and engineering geology. The desiccation cracks can dramatically increase the hydraulic conductivity and deteriorate the mechanical performances of clayey soils. Traditionally, the analysis of soil desiccation cracks relies on visual inspection and image processing techniques, which lack automation and intelligence. Therefore, there is an increasing need for an automated algorithm to meet accuracy and efficiency requirements for various engineering scenarios. In this study, a state-of-the-art deep-learning algorithm, Mask R-CNN, was utilized for the clayey soil crack detection, localization and segmentation. A comprehensive dataset including 1200 annotated crack images of 256 × 256 resolution was prepared for the algorithm training and validation. The proposed Mask R-CNN algorithm achieved precision, recall and F1 score of 73.29%, 82.76% and 77.74%, respectively. Besides, the algorithm gained a mean localization accuracy (APbb) of 64.14% and a mean segmentation accuracy (APm) of 47.59%. The detection performance of the Mask R-CNN was also compared with that of the U-Net under three different scenarios. The test results have demonstrated the superiority of the Mask R-CNN over the U-Net algorithm in crack detection, localization and segmentation. [ABSTRACT FROM AUTHOR]

• Application of asymmetric SCB (ASCB) specimen for investigating mixed mode I/II fracture of compacted soil. • Obtaining critical mode mixity corresponding to the lowest fracture resistance for the tested soil. • Nearly the same values were obtained for pure modes I and II fracture toughness (KIc and KIIc). • Ability of maximum tangential stress criterion was examined for prediction of soil fracture data. Soil is a common material for constructing the sub-grade layer in multi-layer pavement systems, buried pipelines and embankment dams. Failure and fracture of this material may result in undesired deformation and bad effect on the long-term performance of such structures. So far a number of testing methods and data are available for tensile type fracture (or mode I fracture) of soil materials. However, soil materials can experience mixed mode tensile-shear deformations in real situations due to external applied loads. Hence, a suitable testing method called asymmetric semi-circular bend (ASCB) specimen was proposed and utilized in this paper for characterizing the mixed mode tensile-shear cracking behavior of compacted soil materials. Full mode mixities ranging from pure mode I to pure mode II were tested on a clay soil material using the ASCB specimen. Depending on the mode mixity, the soil fracture toughness value was varied between 0.025 and 0.035 MPa.m0.5. The lowest fracture toughness was obtained at mixed mode I/II with nearly the same contribution of tensile and shear deformations. In this loading situation the effective fracture toughness (K eff) was approximately 30% less than K Ic and K IIc (i.e. pure modes I and II fracture toughness values, respectively). The fracture toughness values under pure mode I and pure mode II were almost equal. The maximum tangential stress criterion was also able to predict well the experimental mixed mode I/II soil fracture toughness results. [ABSTRACT FROM AUTHOR]

Laboratory experiments were carried out to investigate the effect of operating pressure on wetting pattern in layered soil for subsurface point water source. This study helps to determine a suitable operating pressure and appropriate spacing between emitters and drip lateral pipes. The layered soil profiles were prepared using two types of soil (clay and loam) in two combinations (clay over loam and loam over clay) . Three operation pressures (4.99, 9.99 and 16.14, m) with a nominal dripper discharge rate (2 l/hr) were used. The experimental results showed that positive back pressure around dripper outlet develops, when the water application rate is larger than the soil infiltration capacity , and the actual dripper discharges were less than the rated dripper discharges by about (10%-28%) due to back pressure effect . Furthermore, it has been observed that water start rising up to the soil surface (Chimney Effect) when the operating pressure is (16.14m) for the loam over clay soil profile, which occurs when water application rate exceeds the soil capability to spread the water. It is found that the total wetted area for both layers was not affected by the operation pressure for the same volume of applied water. In the relationship of the wetting advance (a tb) , it is found that , the constant (b) is not effected by operation pressure while the constant (a) increased with increased operation pressure . [ABSTRACT FROM AUTHOR]

Soil compaction caused by machinery traffic on agricultural soil is becoming a problem in all parts of the world. In this experiment, vertical distribution of machinery-induced compaction on clay soil was investigated. The weights of the machineries used during the experiment were 82.80 kN (light vehicle or L) and 132.34 kN (heavy vehicle or H). Both machines passed repeatedly (1, 2, 4, 8 times) on the same track of the soil at two different moisture contents known as dry and wet plots of the farmland. The different parameters measured during the experiment were dry bulk density, vehicle axle load, and track width of the wheel traffic. The results showed that in a wet soil profile the dry bulk density of the soil taken to a depth of 0.30 m showed a statistically significant difference (p < 0.05) relative to the control (zero traffic zone). But it requires at least two passes by the same vehicles to obtain a statistically significant difference (p < 0.05) on the dry soil. [ABSTRACT FROM AUTHOR]

A special inverse analysis method is established in order to calibrate soil constitutive models. Taguchi method as a systematic sensitivity analysis is conducted to determine the real values of mechanical parameters. This technique was applied on the hardening soil (as an elastoplastic constitutive model) which is calibrated using the results from pressuremeter test performed on "Le Rheu" clayey sand. Meanwhile, a genetic algorithm (GA) as a well-known optimization technique is used to fit the computed numerical results and observed data of the soilmodel. This study indicates that the Taguchimethod can reasonably calibrate the soil parameters with minimum number of numerical analyses in comparison with GA which needs plenty of analyses. In addition, the contribution of each parameter on mechanical behavior of soil during the test can be determined through the Taguchi method. [ABSTRACT FROM AUTHOR]

Abstract: The effect of soil properties on the transport of silver nanoparticles (AgNPs) was studied in a set of laboratory column experiments, using different combinations of size fractions of a Mediterranean sandy clay soil. The AgNPs with average size of ∼30nm yielded a stable suspension in water with zeta potential of −39mV. Early breakthrough of AgNPs in soil was observed in column transport experiments. AgNPs were found to have high mobility in soil with outlet relative concentrations ranging from 30% to 70%, depending on experimental conditions. AgNP mobility through the column decreased when the fraction of smaller soil aggregates was larger. The early breakthrough pattern was not observed for AgNPs in pure quartz columns nor for bromide tracer in soil columns, suggesting that early breakthrough is related to the nature of AgNP transport in natural soils. Micro-CT and image analysis used to investigate structural features of the soil, suggest that soil aggregate size strongly affects AgNP transport in natural soil. The retention of AgNPs in the soil column was reduced when humic acid was added to the leaching solution, while a lower flow rate (Darcy velocity of 0.17cm/min versus 0.66cm/min) resulted in higher retention of AgNPs in the soil. When soil residual chloride was exchanged by nitrate prior to column experiments, significantly improved mobility of AgNPs was observed in the soil column. These findings point to the importance of AgNP–soil chemical interactions as a retention mechanism, and demonstrate the need to employ natural soils rather than glass beads or quartz in representative experimental investigations. [Copyright &y& Elsevier]

The effects of two soil datasets on planetary boundary layer (PBL) height are analyzed, using model simulations. Simulations are performed with the MM5 weather prediction system over the Carpathian Basin, with 6 km horizontal resolution, investigating three summer days, two autumn, and one winter day of similar synoptic conditions. Two soil datasets include that of the United States Department of Agriculture, which is globally used, and a regional Hungarian called Hungarian unsaturated soil database. It is shown that some hydraulic parameter values between the two datasets can differ up to 5-50%. These differences resulted in 10% deviations in the space-time-averaged PBL height (averaged over Hungary and over 12 h in the daytime period). Over smaller areas, these relative deviations could reach 25%. Daytime course changes in the PBL height for reference run conditions were significant ( p < 0.01) in ≈70% of the grid points covering Hungary. Ensemble runs using different atmospheric parameterizations and soil moisture initialization setups are also performed to analyze the sensitivity under changed conditions. In these cases, the sensitivity test showed that irrespective of the radiation and PBL scheme, the effect of different soil datasets on PBL height is roughly the same. PBL height is also sensitive to field capacity (Θ) and wilting point (Θ) changes. Θ changes seem to be more important for loamy sand, while Θ changes for the clay soil textural class. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the potential manufacture, and the engineering properties, of producing an economical, ecological and sustainable building material using a Spanish clay soil. Cylindrical clay soil test specimens incorporating three types of commercials stabilizer additives i) Portland cement (PC), ii) Natural Hydraulic Lime (NHL-5) and iii) Hydrated Lime (CL-90-S) were used, on similar mix compositions for brick production. The investigations were carried out using a clay soil supplied by a rural bricks manufacturer. The laboratory results demonstrated that compaction effort, compressive strength, moisture content, rate of water absorption, density and durability (repeated 48-hours of freezing/thawing cycles) were all within acceptable engineering standards typical for clay masonry bricks. This paper has demonstrated that with the mix formulations tested, unfired masonry bricks can be manufactured at the appropriate optimal compaction and optimum additive content depending on the desired engineering properties and any other desirable brick characteristics. [Copyright &y& Elsevier]

The undrained shear strength of clays is an important geotechnical parameter used during construction processes. Several laboratory tests were performed on kaolinite and smectite mixed with pore fluids with different pH values. Vane shear tests were carried out and it was found that the undrained shear resistance for clays increased considerably if the pore fluid had a high or a low pH. A possible explanation could be the dissolution of Al which acts as a coagulant, increasing the internal shear resistance. Geochemical computations, Al measurements and ζ-potential experiments were performed to confirm this theory. The research suggests varying the pH may make a useful contribution to soil improvement techniques. [ABSTRACT FROM AUTHOR]

Soil clay content is an important soil attribute and has been used to classification of phosphorus status in the soil in order to determinate the needing of phosphorus amounts to be applied to crops production. The aim of this research was to adjust the method for soil clay content determination, adopted by the laboratories of Southern Brazil (ROLAS-RS/SC), for soil clay content evaluation in Rondônia soils. The study was conducted using 50 soil samples from Rondônia State with wide range clay content. It was tested shaking periods (1.5, 2.0 and 2.5h) associated with periods for soil particles decantation (1.5 and 2.0h) to correlate with the standard method for soil texture testing, known as the pipette method. Clay content determined through this method was significantly correlated with pipette method. The better treatment was the combination of 2.0h of shaking and 1.5h of decantation, resulted in total period of 3.5h, which reduced the period to determine the soil clay content without loss of accuracy. [ABSTRACT FROM AUTHOR]

A fundamental study of pile-soil systems subjected to lateral loads in clay soil was conducted by using experimental tests and a lateral load-transfer approach. The emphasis was on an improved wedge failure model developed by considering three-dimensional combination forces and a new hyperbolic p-y criterion. A framework for determining the p-y curve on the basis of both theoretical analysis and experimental load test results is proposed. The proposed p-y method is shown to be capable of predicting the behavior of a large-diameter pile under lateral loading. The proposed p-y curves with an improved wedge model are more appropriate and realistic for representing a pile-soil interaction for laterally loaded piles in clay than the existing p-y method. [ABSTRACT FROM AUTHOR]

Résumé  Une étude expérimentale des cycles de drainage-humidification a été réalisée sur les Argiles vertes de Romainville du bassin de Paris, afin de caractériser leur aptitude au retrait-gonflement par l’analyse de courbes de rétention, par la mesure de paramètres mécaniques (pression et taux de gonflement), et par une étude microstructurale (MEB, porosimétrie). Les résultats expérimentaux montrent que les déformations volumiques les plus grandes se produisent dans le domaine où le potentiel de l’eau est inférieur à 15 MPa, avec des valeurs de pression et de taux de gonflement élevées. Par ailleurs, au cours des cycles successifs de sollicitations hydriques, alors que les échantillons présentent une augmentation du taux de gonflement cumulé, une stabilisation des déformations de gonflement s’amorce à partir du troisième cycle, en rapport avec une réorganisation de la microstructure du sol mise en évidence par l’analyse microstructurale. Enfin, l’étude menée sur la prévision du taux et de la pression de gonflement montre que les modèles de prévision ne sont pas systématiquement applicables à tous les sols. [ABSTRACT FROM AUTHOR]

This article presents a research program developed for the evaluation and determination of the Morh-Coulomb model parameters and the Hardening Soil model parameters in clay soils. The methodology includes the analysis of some correlations, basic characterization soil tests and undrained compression triaxial tests carried out on reconstituted soil samples in laboratory (kaolin). From the obtained parameters the behavior stress-strain was simulated in the element finite software PLAXIS, examining the performance of the models by comparing the numeric calculation results with the experimental soil behavior. For the sets of considered model parameters, the analysis shows that the computational results have a reasonable agreement with the experimental results, appreciating a better approximation to the behavior described by the tests in the simulations performed with the Hardening Soil model, whose results evidence a better grade of adjustment to the typical hyperbolic relationship of the soil tested. In addition, the concluding results represent an important validation of the methodology program developed. [ABSTRACT FROM AUTHOR]

The studies focused on fragmented clayey soils, which are classified as second-type fragmented substances characterized by a multistorey structure and double porosity. The unstable structure of this substance makes it highly vulnerable to the influence of external factors, particularly changes of water content. The studies enabled the author to evaluate the influence of water content on changes of compressibility parameters and on the character of stress-strain relationships. Differences were emphasized in the behaviour of fragmented clayey soils in comparison to local soils. In author's opinion, the studied samples are a good representation of overburdened soils (dump soils), and the regularities found in this study can be readily applied to them. [ABSTRACT FROM AUTHOR]

Small angle neutron scattering (SANS) data are reported from a system that models the contamination of a clay - organic matter soil from a fuel spillage. The soil was represented as an aqueous dispersion of the synthetic clay mineral Laponite coated with lysine, and the contaminant was a representative jet fuel, quadricyclane, mixed with the detergent cetyltrimethylammonium bromide (CTAB). The adsorbed surface coverage on the clay was estimated. It is shown that the presence of adsorbed lysine considerably enhances the subsequent adsorption of both CTAB and quadricyclane. It is demonstrated that the SANS technique can contribute to the general problem of environmental remediation and retention by probing the interactions of pollutants and clay surfaces. [ABSTRACT FROM AUTHOR]

It is well accepted that the quality of soft clay samples obtained using standard fixed piston samplers can be relatively poor and that block samples are necessary to yield very high quality samples. However, for many practical projects it is not economically viable or physically practical to obtain block samples. In this project, the quality of standard 54 mm composite piston samples of soft clay is examined by comparing six separate sets of 54 mm samples to parallel block sampling. Sampling and laboratory testing was carried out by three different organizations at a well characterized highly uniform soft clay site in Norway. As expected, the work showed that the block samples behaved significantly differently from those obtained using the 54 mm sampler and were of higher quality. Block sample-derived parameters were considerably different from those obtained from the 54 mm sample tests. However, significant differences were also found between the different sets of 54 mm samples. Although the differences are less than when compared with block samples, the consequences of poor quality 54 mm sampling will be significant in engineering design. It is concluded that the differences are due to small details in the sampling operation such as the need to keep the piston effectively stationary at all times, to avoid overcoring and to handle the recovered sample carefully. If a well trained driller follows good quality practice, then relatively good samples can be obtained by the fixed piston sampler, which are suitable for analysis and design of routine engineering works. [ABSTRACT FROM AUTHOR]

A new method of estimating the permeability of soils using an acoustic technique is proposed in this technical note. Biot’s coupled theory of mixtures from the mid-1950s, which addresses the relationship between the permeability of saturated soils and the characteristic frequency of elastic waves, is used. The characteristic frequency is determined from the attenuation versus frequency curves obtained by acoustic sweep tests. This study presents the experimental technique for measuring the characteristic frequency of soils and calculation procedure for estimating the permeability of sandy soils. This technical note holds discussion for silty or clayey soils. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) can form symbiotic relationships with roots of plants and potentially affect nitrogen (N) cycling in cropping systems. However, it is unclear how AMF influence N 2 O emissions and crop N assimilation, two key N cycling steps which are closely related to climate change and food production, under different soil management regimes. A microcosm experiment was conducted to test the effects of AMF on N 2 O emission and plant N assimilation, with wheat as a model crop, under organic (straw) amendment in soils with different textures. We found that AMF suppressed N 2 O emissions, promoted mycorrhizal N uptake and remobilization to grains and increase grain biomass under organic amendment in the sandy soil. However, AMF did not affect N 2 O emission, although increased plant N uptake, but inhibited mycorrhizal N remobilization to grains under organic amendment in the clay soil. These findings highlight that AMF have different effects on N 2 O emission and N translocation between sandy and clay soils. Appropriate soil management for mycorrhizal symbiosis in the cropping system can combat climate change and ensure food production. • AMF only reduced N 2 O in sandy soils, but not for clay soils. • AMF could promote N uptake irrespective of soil texture. • Organic amendment could promote N foraging from mycorrhizae remobilized to grains. [ABSTRACT FROM AUTHOR]

A viscoplastic cap model of the Perzyna type was developed for simulating high strain rate behaviors of soils. An associative viscous flow rule was used to represent time-dependent soil behaviors. The viscoplastic cap model was validated against experimental data from static and dynamic soil tests. The model was also compared with soil behaviors under creep and stress relaxation with good agreement. However, the model was unable to represent tertiary creep where strain softening became significant. The model was subsequently integrated into LS-DYNA for finite-element simulations of high strain rate behaviors of sandy and clayey soils in explosive tests. The significance of strain rate effect on the soil responses is presented herein. It is concluded that the viscoplastic cap model is adequate for simulations of soil behaviors under high strain rate loading, creep, and stress relaxation, covering a wide range of time-dependent problems. [ABSTRACT FROM AUTHOR]

The potential of woodash to stabilize clay soil was evaluated. The evaluation involved the determination of the geotechnical properties of clay soil in its natural state as well as when mixed with varying proportions of woodash. The parameters tested included the particle size distribution, specific gravity, Atterberg limits, compaction characteristics, California bearing ratio (CBR) and the compressive strength. The CBR and strength tests were repeated after 28-day curing of the treated samples. Results showed that the geotechnical parameters of clay soil are improved substantially by the addition of woodash; plasticity was reduced by 35% and CBR and strength increased by 23–50% and 49–67%, respectively, depending on the compactive energy used. The highest CBR and strength values were achieved at 10% woodash. Results also showed that curing improved the strength of the woodash-treated clay. However, the strength gain was short lived as the strength quickly decreased after 7–14 days of curing. These results imply that although woodash provides some of the beneficial effects of lime in soil stabilization, such as plasticity and swell reduction, improved workability, and strength increase, it is unlikely to be a substitute for lime as strength gain is short lived. [ABSTRACT FROM AUTHOR]

Lime continues to be one of the most popular chemical admixtures used to modify expansive clays despite the associated mixing and pulverization problems. In the present investigation, the efficacy of CaCl2 in place of conventionally used lime is studied by conducting laboratory and field tests. These investigations were carried out on the slopes of a trapezoidal trench made in expansive clay bed. Heave measurements were taken on the lime and CaCl2 treated slopes and also on untreated slopes for four consecutive cycles of wetting and drying. The field cyclic seasonal movements and the subsequent laboratory tests on undisturbed and disturbed soil samples revealed that the CaCl2 could be a promising chemical modifier instead of conventionally used lime, not only due to its multifold influence on heave control, plasticity reduction, and swell properties but also its easy application in the form of solution without any need for pulverization and mixing. Though an apparent reduction in unconfined compressive strength of treated samples is observed, the drained triaxial tests on treated and untreated samples revealed that there is an increase in the angle of internal friction of treated samples. [ABSTRACT FROM AUTHOR]