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This research include, more than 400 erosion tests performed on coarse and fine grain suspension materials. The purpose of tests was to determine erosion characteristics of mixtures of different materials. Samples of the .same constituents in different groups were cured tit two different setting time of // and 16 !tours before they were subjected to the constant hydraulic heads of 20 and 40 cm for ct time period of 30 urinates. The amount of erosion was measured as the weight loss of the samples offer the test. /n general the lower setting tune and the higher hydraulic head for a large group of samples showed higher erosion. For uniform sand samples when the cement content was 60-70 % the percentage of erosion (PE) was below 2. For the mixture of sand-cement, with the clay content below, 20% the percentage of erosion was below 2 and it increased to 15.5 for the clan, content of 58dc. Die addition of bentonite in the soil-cement mixtures in general did not affect the erosion.

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A study of bearing capacity and compressibility characteristics of cohesive soil, reinforced by geogrid and supporting square footing loads has been conducted. The lack of adequate frictional resistance between clay and reinforcing elements was compensated by using a thin sand layer (lens) encapsulating the geogrid sheet. In this way, tensile forces induced in the geogrid were transferred to the bulk clay medium through the sand particles and soil reinforcement was improved Experiments were conduced on two sets of specimens, one set of 1 x 1 x 1 m dimension and the footing size of 19 x 19 cm (series A), and the other set of 0.15 x 0.15 x 0.15 m dimension and the footing size of 3.7 x 3.7 cm (series B). The loading systems for the above specimens were stress controlled and strain controlled respectively. All specimens were saturated and presumably loaded under an undrained condition. The results qualitatively confirmed the effectiveness of the sand lens in improving the bearing capacity and settlement characteristics of the model footing. In series A, the maximum increase in the bearing capacity due to the presence of the sand lens was 17% whereas in series B, the amount of increase was 24%. The percentage reductions in the settlement for these results were 30% and 46% respectively.

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This paper presents the results of a series of monotonic and post-cyclic triaxial tests carried out on a clay specimen and three types of clay-sand mixed specimens. The focus of the paper is on the post-cyclic mechanical behavior of the mixed specimens, as compared to their monotonic behavior. Analyses of the tests results show that cyclic loading degrade undrained shear strength and deformation modulus of the specimens during the post-cyclic monotonic loading. The degradation depends on the sand content, the cyclic strain level and to some degrees to the consolidation pressure.

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In recent years, soil reinforcement is considered of great importance in many different civil projects. One of the most significant applications of soil reinforcement is in road construction. Sub grade soil and its properties are very important in the design of road pavement structure. Its main function is to give adequate support to the pavement from beneath. Therefore, it should have a sufficient load carrying capacity. The use of geosynthetics in road and airfield construction has shown the potential to increase the soil bearing capacity. One category of geosynthetics to particular, geogrid, has gained increasing acceptance in road construction. A geogrid is a geosynthetic material consisting of connected parallel sets of tensile ribs with apertures of sufficient size to allow strike-through of surrounding soil, stone, or other geotechnical material. Geogrid reinforcement of sub grade soil is achieved through the increase of frictional interaction between the soil and the reinforcement. Geogrid have been successfully used to provide a construction platform over subgrades. In this application, the geogrid improves the ability to obtain compaction in overlying aggregates, while reducing the amount of material required be removing and replacing. Relative agreement exists that substantial benefits can be achieved from the inclusion of geogrids within the pavement systems however, the quantity of the improvement is in relative disagreement. This paper presents the effects of plasticity index and also reinforcing of soft clay on CBR values. Three samples of clay with different plasticity index (PI) values are selected and tested without reinforcement. Then by placing one and two layer of geogrid at certain depth within sample height, the effects of reinforcement and PI on CBR values are investigated in both soaked and unsoaked conditions. The results shows that as the PI increase the CBR value decreases and reinforcing clay with geogrid will increase the CBR value.

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Large size direct shear tests (i.e.300 x 300mm) were conducted to investigate the interaction between clay reinforced with geogrids embedded in thin layers of sand. Test results for the clay, sand, clay-sand, clay-geogrid, sandgeogrid and clay-sand-geogrid are discussed. Thin layers of sand including 4, 6, 8, 10, 12 and 14mm were used to increase the interaction between the clay and the geogrids. Effects of sand layer thickness, normal pressure and transverse geogrid members were studied. All tests were conducted on saturated clay under unconsolidated-undrained (UU) conditions. Test results indicate that provision of thin layers of high strength sand on both sides of the geogrid is very effective in improving the strength and deformation behaviour of reinforced clay under UU loading conditions. Using geogrids embedded in thin layers of sand not only can improve performance of clay backfills but also it can provide drainage paths preventing pore water pressure generations. For the soil, geogrid and the normal pressures used, an optimum sand layer thickness of 10mm was determined which proved to be independent of the magnitude of the normal pressure used. Effect of sand layers combined with the geogrid reinforcement increased with increase in normal pressures. The improvement was more pronounced at higher normal pressures. Total shear resistance provided by the geogrids with transverse members removed was approximately 10% lower than shear resistance of geogrids with transverse members.

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Mixed clayey soils occur as mixtures of sand (or gravel) and clay in widely varying proportions. Their

engineering behavior has not been comprehensively studied yet. An experimental program, comprising monotonic,

cyclic, and post-cyclic triaxial tests was undertaken on compacted clay-granular material mixtures, having different

proportions of clay and sand or gravel. This paper presents the results of cyclic triaxial tests and explains the behavior

of the mixtures based on number of loading cycles, cyclic strain amplitude, granular material content, grain size, and

effective confining pressure. The results indicate an increase in degree of degradation and cyclic loading-induced pore

water pressure as the number of loading cycles, cyclic strain and granular material content increase. Also the results

show that the grain size has no significant effect on the degree of degradation and cyclic loading-induced pore water

pressure in the specimens. The effect of granular material content on pore water pressure during cyclic loading in

equal-stress-level was also examined. The pore water pressure increases with the increase of granular material

content.

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Shear modulus and damping ratio are important input parameters in dynamic analysis. A series of resonant column tests was

carried out on pure clays and sand-clay mixtures prepared at different densities to investigate the effects of aggregate content,

confining stress, void ratio and clay plasticity on the maximum shear modulus and minimum damping ratio. Test results revealed

an increase in the maximum shear modulus of the mixture with the increase in sand content up to 60%, followed by a decrease

beyond this value. It was also found that the maximum shear modulus increases with confining stress, and decreases with void

ratio. In addition, minimum damping ratio increases with sand content and clay plasticity and decreases with confining stress.

Finally, on the basis of the test results, a mathematical model was developed for the maximum shear modulus.

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Soft soil in Hanoi, Vietnam, is mainly originated from lacustrine and shallow-sea sediment. This is the youngest formation with
around 3000 years of age. To serve the research purpose, clayey soil samples at ten areas in Hanoi and some places in the RRD
are prepared. Mineral composition of soils determined by X-ray diffraction analysis shows that clay minerals are predominated
by Illite, Kaolinite, Chlorite, and Montmorillonite respectively. Many previous researches indicated that in saline-saturated
condition, types of cation in saline water and types of clay mineral in soil layers, as well as their predomination decide the
changing process of geotechnical properties in other manner. In this paper, the initial relationship between geotechnical
properties and clay mineral composition of Hanoi soft soils in saline-saturated media is established

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Owing to the proximity of certain locations to the thermal power stations, it has always been efforts of Engineers to enhance

the flyash utilization rate in various Civil Engineering Constructions adopting suitable strategies. In the present study, a soilflyash

interface mechanism has been evolved using different soil-flyash ratios to upgrade significantly stabilization of supporting

medium based on CBR tests. The study confirms soundness of approach when a particular interface arrangement gives high

flyash utilization rate along with many fold increase CBR values. A study was carried out to investigate the interface effect of

soil-flyash layered system in terms of CBR values so that an optimum arrangement can be achieved by using flyash in

combination with soil. In this study, 18 samples of different ratios of soil and flyash (1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3) with three

sets of interfaces N = 2, 4 and 6 were tested to arrive at the most optimized combination of soil and flyash. The results indicate

that the CBR value optimized at soil-flyash ratio 1:2.5 and number of interface N = 4. The present study reveals that soil with

flyash when used in layered system with various numbers of interfaces gives considerable improvement in CBR values. In the

above arrangement about 71 % of flyash and 29 % of soil thus contributing significantly in utilization of flyash in subgrade of

flexible pavements. In the overall study, three equations for number of interfaces N = 2, 4 and 6 have also been developed in

terms of soil-flyash ratio and CBR value, so that CBR value can directly be obtained by substituting the value of soil-flyash ratio

at a particular number of interfaces.

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The use of recycled bassanite, produced from gypsum wastes, in ground improvement projects is initiated recently in Japan to eliminate the huge quantities of gypsum wastes. Meanwhile the use of recycled bassanite has a positive effect on the environment and economy, it has many challenges. These challenges are related to the release of fluorine more than the standard limits results in contaminated fluorine soil. This research investigates the effect of the amount of bassanite, and water content on the release of fluorine from MC-clay soil stabilized with bassanite, taking in consideration their effect on the compressive strength. Recycled bassanite was mixed with furnace cement with a ratio of 1:1 to prevent the solubility of bassanite. Different amounts of this admixture were mixed with the tested soil at different water contents. Unconfined compression test was used to determine the compressive strength while the solubility of fluorine was used to represent the geo-environmental properties in term of the release of fluorine. Scan electron microscopic (SEM) test was done to identify the development of cementation compounds in the matrix of treated-bassanite soil. Test results showed that, the addition of bassanite had a significant effect on the improvement of compressive strength by increasing the amount of bassanite. Curing time had a significant effect on the increase of compressive strength, the strength increases with the increase of curing time, especially in the later curing time. The release of fluorine increases with increasing the amount of bassanite in soil mixture. The increase of water content had an indirect effect on the release of fluorine while it had a negative effect on the improvement of strength and consuming the amount of admixture. The increase of strength is associated with the decrease of the release of fluorine. Recycled bassanite, produced from gypsum wastes, had a potential to be used as a stabilizer material for MC-clay soil and meet the standards of environment.

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This paper investigates the time dependent behaviour of Sunshine embankment on soft clay deposit with and without prefabricated vertical drains. An elasto visco-plastic model was used to investigate the influence of anisotropy and creep effect on the settlement behaviour of the embankment. The constitutive model, namely ACM accounts for combined effects of plastic anisotropy and creep. For comparison, the problem is also analysed with isotropic Modified Cam Clay model which does not consider creep effect. To analyse the PVD-improved subsoil, axisymmetric vertical drains were converted into equivalent plane strain conditions using two different mapping approaches. The results of the numerical analyses are compared with the field measurements. The numerical simulations suggest that the anisotropic creep model is able to give a better representation of soft clay response under an embankment loading. The isotropic model which neglects effects of anisotropy and creep may lead to inaccurate predictions of soft clay response. Additionally, the numerical results show that the mapping method used for PVD improved soft clays can accurately predict the consolidation behaviour of the embankment and provide a useful tool for engineering practice.

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The main objective of present study is to possible use of plastic waste materials for reinforcing clayey soils. An experimental study was planned to investigate compressibility and undrained shear behavior of clayey soil mixed with plastic waste. The mixtures were prepared with various amount of plastic waste (i.e. 0%, 0. 5%, 1.0%, 1.5% and 3.0% in dry weight) and interactive effect of plastic waste, plastic flexibility, confining pressure and initial density on the behavior of clayey soil was studied by performing compaction, consolidated undrained triaxial and oedometer consolidation test. The results show that plastic wastes do not affect compaction characteristics of clayey soil considerably and adding them to the clay more than a specific value (i.e. 1.0% in this research) causes to change undrained behavior of samples from contractive to dilative. In addition, beyond this specific value, it improves shear strength and reduces compressibility of clay. The rate of increase in shear strength and decrease in compressibility depends on the confining pressure, flexibility of plastic and initial density of samples. It is more noticeable when plastic waste in mixtures is relatively rigid and density and confining pressure are high. Moreover, plastic waste has a negative effect on the free swelling, swelling pressure and swelling index of samples, so that these parameters for plastic waste mixed clay are higher than the associated values of plain clay.

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In this study, the relative performance of two soils as a sustainable natural material in retaining the selected heavy metal ions, cadmium (Cd²⁺) and nickel (Ni²⁺), from aqueous solutions has been evaluated. Red earth soil (RS) and black cotton soil (BCS) originating from India, were selected and batch equilibrium tests including sorption kinetics and leaching studies were conducted. The experimental data was used to plot sorption isotherms, Langmuir isotherm was found to be more suitable than Freundlich isotherm for both the soils. Monolayer sorption capacity was calculated from Langmuir isotherm. Kinetic data was fitted on four models namely pseudo first order, second order, Elovich and intraparticle diffusion. Correlation coefficients obtained by all models fitted well in the following ranking: Elovich>Intraparticle diffusion > Pseudo second order> Pseudo first order. Based on extensive experimental data, it is concluded that the ranking on sorption was of the order Cd > Ni for both the soils and BCS exhibited relatively higher retention levels compared to RS.  It is further concluded that, BCS can be used as a substitute to filter material, RS a substitute to main liner material in attenuating Cd²⁺ and Ni²⁺ from an industrial landfill leachate.

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The correlations and relationships between electrical resistivity and geotechnical parameters of soils have become very important for site investigation. However, there is a lack of understanding about the relationships between electrical resistivity and geotechnical parameter values. The resistivity piezocone penetration tests and laboratory tests have been conducted for geotechnical investigations of marine clay in Jiangsu province of China to establish quantitative relationships between electrical and geotechnical data. The geotechnical investigation reveals that electrical resistivity values are very low for marine clay in Jiangsu, ranging from 5 to 10 Ω m. The correlations between electrical resistivity and geotechnical parameters are examined using Spearman’s rank correlation test that is a rank-based test for correlation between two variables without any assumption about the data distribution. It was shown that the electrical resistivity has strong bonds with the moisture content, void ratio, salt content and plasticity index. In terms of quantitative relationships, good fitting relationships between electrical resistivity and selected geotechnical parameters are observed. The statistical analysis indicates that the electrical resistivity is a good indirect predictor of selected geotechnical parameters. The data studied demonstrates the usefulness of the in situ resistivity method in geotechnical investigations, which have an advantage over other geotechnical methods in cost performance.

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In this study, the shear strength parameters of the Kaolinite clay, as the control material, and the Kaolinite clay reinforced by different percentages of two different types of crumb rubber content have been evaluated. The consolidated drained and unconsolidated undrained triaxial and California bearing ratio tests have been conducted on the control and crumb rubber reinforced soils. Addition of crumb rubber would improve shear strength parameters such as cohesion, friction and dilation angles, stiffness and the ductility of the reinforced soil. 5, 10 and 15 % (by the weight of dry soil) of crumb rubber content were used in this study which were undergone confining stress levels of 100, 200 and 300 kPa and an optimum crumb rubber content is found, which results in the maximum bearing capacity of the soil. Also, due to the non-linearity of the failure mode of reinforced soil and inadequacy of Mohr–Columb envelope for describing the behaviour, a failure mode is proposed for the clay soils reinforced by crumb rubber. This failure criterion is useful for failure envelope of clay-rubber matrix.

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This paper proposes a modified strain wedge (MSW) model for nonlinear analysis of laterally loaded single piles in clays. The MSW model is used to calculate the soil resistance under increasing pile deflection. The stress–strain behavior of clays in the MSW, which is needed to calculate the soil resistance, is described in terms of both hyperbolic and bilinear stress–strain relationships. The subgrade reaction modulus of soil below the MSW is assumed to equal the conventional subgrade reaction modulus and to remain constant under the lateral loading of the pile. The applicability of the proposed model was verified by eight case histories. The results indicate that (1) the predicted results are consistent with the measurements for all eight full-scale tested piles; (2) the bilinear stress–strain relationship is not recommended for clays because the clays usually have a large ε50 and, thus, they exhibit a linear behavior in the MSW during loading; (3) the predicted pile response is less sensitive to the effective friction angle than to the undrained shear strength; and (4) the proposed MSW model applies to normally consolidated clays and to overconsolidated clays until they reach their peak strength.