Hydromechanical behaviour of expansive soils with different suctions and suction histories

2016 ◽  
Vol 53 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Junran Zhang ◽  
De’an Sun ◽  
Annan Zhou ◽  
Tong Jiang
Keyword(s):  
Expansive Soils ◽  
Volumetric Strain ◽  
Expansive Soil ◽  
Experimental Results ◽  
Triaxial Tests ◽  
Test Results ◽  
Soil Water Retention ◽  
Suction Control ◽  
Vapor Equilibrium ◽  
High Suction

This paper presents a number of experimental results of suction-controlled triaxial tests on a compacted weakly expansive soil with different suctions and suction histories. In terms of suction control methods, the high suction level (from 3.29 to 38 MPa) was realized by the vapor equilibrium technique and the low suction level (from 0 to 800 kPa) was controlled by the axis translation technique. Results of the triaxial tests indicate that the specimen with higher suction shows higher strength and lower contractive and higher dilative volumetric strains, and the average skeleton stress ratio (q/p′) at failure decreases with increasing suction in the high suction range (3.29∼38 MPa). Given that suction during shearing is constant (e.g., 200 kPa), the specimen dried to a higher suction and the history shows higher strength and lower contractive volumetric strain. Experimental results also show that high pre-applied suction (i.e., the maximum suction in the history) can lead to peak strength, post-peak softening, and shear dilation. Three different methods (pressure plate, filter paper, and vapor equilibrium) were employed to study the soil-water retention behaviour of the unsaturated expansive soil. Test results indicate that by combining these three different methods, it is possible to determine the SWCC in the entire suction range (0∼367 MPa). Test results of the expansive soil also show that the void ratio keeps decreasing with increasing suction in the entire suction range.

scholarly journals Experimental Study on Dynamic Resilient Modulus of Lime-Treated Expansive Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zheng Lu ◽  
Yang Zhao ◽  
Shaohua Xian ◽  
Hailin Yao
Keyword(s):  
Moisture Content ◽  
Environmental Changes ◽  
Resilient Modulus ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
The Stability ◽  
Compaction Degree

Dynamic resilient modulus is the design index of highway subgrade design code in China, which is significantly affected by the traffic loads and environmental changes. In this study, dynamic triaxial tests were conducted to investigate the influence of moisture content, compaction degree, cyclic deviator stress, and confining pressure on lime-treated expansive soil. The suitability of UT-Austin model to lime-treated expansive soils was verified. The results indicate that the dynamic resilient modulus of lime-treated expansive soils increases nonlinearly with the increase of compaction degree, while decreases nonlinearly with the increase of dynamic stress level. The dynamic resilient modulus decreases linearly with the increase of moisture content and increases linearly with the increase of confining pressure. Moreover, the moisture content has a more significant effect on the dynamic resilient modulus of lime-treated expansive soil. Therefore, it is necessary to ensure the stability of soil humidity state and its excellent mechanical properties under long-term cyclic loading for the course of subgrade filling and service. Finally, the calculated results of the UT-Austin model for dynamic resilient modulus show a good agreement with the test results.

scholarly journals Studi Regangan Axial dan Lateral pada Tanah Ekspansif

2017 ◽  
Vol 19 (2) ◽  
pp. 121-127
Author(s):  
Lisa Fitriyana ◽  
Abdul Rochim
Keyword(s):  
Water Content ◽  
Expansive Soils ◽  
Retaining Wall ◽  
Expansive Soil ◽  
Axial Direction ◽  
Lateral Strain ◽  
Membrane Thickness ◽  
Test Results ◽  
Measurement Tools ◽  
Digital Caliper

Swelling and shrinkage abilities of soils are dangerous for buildings. According to Hardiyatmo (2014) There are two types of swelling in expansive soils that are the movement of lateral (horizontal) and axial (vertical). Oftentimes the deformation of soils cannot be supported by building stiffness. This damage can be seen in retaining walls, tunnel walls, and etc. With the aims to identify an expansive soil and to know its lateral and axial strains, an experimental study was performed. Swelling tests were conducted in a specimen having diameter (d) of 4,5 cm and height (h0) of 2 cm with the variations in : 1) water content wopt = 31% and 18%; 2) vertical pressure (pv) 1 kPa, 3.5 kPa and 6.9 kPa; and 3) membrane thickness (t) 0.7 mm and 0.5 mm. The strain in the axial direction was measured with a dial gauge that was set vertically parallel whereas the lateral strain is by measuring changes in diameter of the specimen with a digital caliper measurement tools. Based on the analysis on the identification results, the observed soil is classified as expansive soil with the expansion potential is high average. The test results show the same potential for the occurrence of lateral and lateral strain if the lateral retention (e.g. retaining wall) is weak. The largest lateral and axial soil development occurred at water content w0 = 18% are 15.7% and 15.8% respectively.

scholarly journals Characterization of the Undrained Shear Strength of Expansive Soils of High Water Content

2018 ◽  
Vol 206 ◽  
pp. 01002
Author(s):  
Zheng Su ◽  
Daokun Qi ◽  
Xinju Guo ◽  
Xiaojuan Xi ◽  
Liang Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Friction Angle ◽  
High Water ◽  
Ease Of Use ◽  
Triaxial Tests ◽  
High Water Content

In recent years, engineering constructions increase rapidly in western and central areas of China, where expansive soil widely distributes. Since expansive soil is sensitive to water content, the characterization of its shear strength should be carefully conducted. For simplicity and ease of use, the Mohr-Coulomb criterion is often adopted to describe the shear strength of expansive soil. In this paper, the physical meaning of the cohesion and frictional strength of expansive soil are explained, and the variations of the strength parameters with water content are investigated. By fitting to the experimental results from direct shear test and triaxial tests, the changing characteristics of cohesion and friction angle with water content are obtained.

Study on Algorithm of Improved Modified Cambridge Model Calculation Accuracy

2014 ◽  
Vol 1065-1069 ◽  
pp. 204-207
Author(s):  
Yan Hua Guo ◽  
Xiao Yan Zhang ◽  
Xue Zhong
Keyword(s):  
Least Squares ◽  
Shear Strain ◽  
Model Calculation ◽  
Yield Surface ◽  
Theoretical Calculations ◽  
Volumetric Strain ◽  
Experimental Results ◽  
Triaxial Tests ◽  
Elastic Plastic ◽  
Plastic Matrix

Roscoe and Burland set the yield surface of the Cambridge model to elliptic and concluded modified Cambridge model. In this paper, the model has been improved and got the accuracy of the elastic-plastic matrix improvement model, by using the Cambridge model to calculate the volumetric strain and shear strain of soil theoreically and inculcating CU triaxial tests to measure the corresponding soil volumetric strain and shear strain and applying least squares theory to simulate the ratio of theoretical calculations and experimental results.

scholarly journals Experimental Testing and Numerical Modelling of Mechanical Behaviors of Silty Clay under Freezing-Thawing Cycles

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Tianfei Hu ◽  
Dawei Liu ◽  
Hui Wu
Keyword(s):  
Numerical Modelling ◽  
Experimental Testing ◽  
Axial Strain ◽  
Volumetric Strain ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Silty Clay ◽  
Test Results ◽  
Mechanical Behaviors ◽  
Physical Weathering

Seasonal freezing-thawing cycle is one of the most common physical weathering processes in cold regions, which can significantly affect the mechanical behaviors of soil. In this paper, a series of freezing-thawing (F-T) cycle and consolidated drained triaxial tests have been carried out on silty clay samples collected from Tibetan Plateau. To do so, a modified numerical model was developed taking into F-T effect. Test results showed that the stress-strain curves of original soil specimens presented strain hardening characteristics, accompanied with shear shrinkage. In F-T experienced specimens, volumetric strain in triaxial loading stage was gradually increased, while failure strength was decreased. Elliptic and parabolic functions were selected in numerical modelling to describe volume and shear yield surfaces on a p-q plane, respectively. Moreover, a double-yield surface constitutive model was developed to describe relationships among deviatoric stress, axial strain, and volumetric strain. Furthermore, equations for model parameters with the number of F-T cycles as variable were derived based on the triaxial test results which were then substituted into the established model to take into account the effects of F-T cycles. Finally, numerical results were validated with experimental findings.

scholarly journals Prediction of final settlements of buildings constructed on expansive soils

2015 ◽  
Vol 4 (3) ◽  
pp. 424
Author(s):  
María-de-la-Luz Pérez-Rea ◽  
Tania Ayala ◽  
Victor Castano
Keyword(s):  
Soil Structure ◽  
Expansive Soils ◽  
Volumetric Strain ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Soil Structure Interaction ◽  
Soil Behavior ◽  
Building Conditions ◽  
Structure Interaction ◽  
Strain Coefficient

Because the action of the swelling pressure, the settlements caused by the transmitted load from the structure on expansive soils, and the settlements calculated by classic theories of soils mechanics are different. This swelling pressure acts in opposite direction to the weight of the building. In this paper, the authors propose the use of a volumetric strain coefficient by settlements exp, in a soil-structure interaction algorithm taking into account the expansive soil behavior in the reduction of the settlement magnitude when a building is placed above soil. It’s necessary to know the initial properties of the expansive unsaturated soil and the load building conditions. A laboratory process is described for determining the aexpcoefficient.

scholarly journals Creep Properties of Expansive Soils under Triaxial Drained Conditions and its Nonlinear Constitutive Model

2021 ◽  
Author(s):  
Jingjing Li ◽  
Lingwei Kong
Keyword(s):  
Expansive Soils ◽  
Creep Property ◽  
Volumetric Strain ◽  
Failure Stress ◽  
Creep Model ◽  
Creep Process ◽  
Triaxial Tests ◽  
Nonlinear Creep ◽  
Deviator Stress ◽  
Accelerated Creep

The creep behaviors of expansive soils play an important role in landslide prediction and long-term stability analysis. In this paper, triaxial drained compression creep tests of expansive soils were conducted on the improved stress-controlled triaxial apparatus. The test results show that only transient deformation and attenuation creep occur with low deviator stress, and the increment of axial strain increases exponentially with deviator stress increasing; while deviator stress reaches a certain value, attenuation creep, steady creep and accelerated creep all occur in a creep curve. Meanwhile, the volumetric strain presents the shear shrinkage characteristic at the initial stage of loading, and the shear shrinkage is small. With the extension of loading time, the volumetric strain gradually varies from shear contraction to dilatancy. When entering the accelerated creep stage, the development rate of volumetric strain increases sharply. Besides, isochronous stress-strain curves of expansive soils indicate that their creep process possesses nonlinear characteristics, and the nonlinear degree is related to creep time and stress level. Imitating the empirical formula of cyclic cumulative deformation of clay, a new nonlinear creep model is presented, which may well describe the creep property of expansive soils. Furthermore, critical failure stress could be obtained based on the proposed creep model. The ratio of the critical failure stress to conventional shear failure stress ranges from 70% to 80%, with average of 75.56%, therefore, critical failure stress may be estimated by conventional triaxial tests with the margin of error 5.5% within.

scholarly journals Identification of Anisotropic Criteria for Stratified Soil Based on Triaxial Tests Results

2017 ◽  
Vol 39 (3) ◽  
pp. 59-65 ◽  
Author(s):  
Matylda Tankiewicz ◽  
Marek Kawa
Keyword(s):  
Least Squares Method ◽  
Experimental Results ◽  
Triaxial Tests ◽  
Test Results ◽  
Optimal Parameters ◽  
Identification Procedure ◽  
Wide Range ◽  
Confining Pressures ◽  
Optimal Values ◽  
Varved Clay

Abstract The paper presents the identification methodology of anisotropic criteria based on triaxial test results. The considered material is varved clay – a sedimentary soil occurring in central Poland which is characterized by the so-called “layered microstructure”. The strength examination outcomes were identified by standard triaxial tests. The results include the estimated peak strength obtained for a wide range of orientations and confining pressures. Two models were chosen as potentially adequate for the description of the tested material, namely Pariseau and its conjunction with the Jaeger weakness plane. Material constants were obtained by fitting the model to the experimental results. The identification procedure is based on the least squares method. The optimal values of parameters are searched for between specified bounds by sequentially decreasing the distance between points and reducing the length of the searched range. For both considered models the optimal parameters have been obtained. The comparison of theoretical and experimental results as well as the assessment of the suitability of selected criteria for the specified range of confining pressures are presented.

scholarly journals Post Stabilization Performance of Lime Stabilized Soil Admixed with Press Mud

2019 ◽  
Vol 8 (4) ◽  
pp. 9198-9202 ◽  
Keyword(s):  
Soil Stabilization ◽  
Expansive Soils ◽  
Low Cost ◽  
Expansive Soil ◽  
Liquid Limit ◽  
Test Results ◽  
Unconfined Compression Test ◽  
Press Mud ◽  
Expansive Clays ◽  
Stabilized Soil

In this study the investigational results obtained in the laboratory on expansive soils treated with low-cost materials i.e, lime and press mud are used. It is conducted to check the signs of progress in the properties of expansive soil with Press Mud and lime in varying percentages. The test results such as the Unconfined compression test, liquid limit, plastic limit, shrinkage limit, hydrometer analysis and pH obtained on expansive clays mixed with different proportions of lime and press mud are presented and discussed in this work. From the demonstrated result the addition of Press mud with lime in soil stabilization improves the Unconfined Compressive strength of the soil when compared to lime stabilization alone. The index properties of the soil have also been marginally improved due to the addition of Press mud as an admixture.

FRACTAL CHARACTER OF GRAIN-SIZE DISTRIBUTION OF EXPANSIVE SOILS

Fractals ◽  
1999 ◽  
Vol 07 (04) ◽  
pp. 359-366 ◽  
Author(s):  
YONGFU XU ◽  
SONGYU LIU
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mass Distribution ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Fractal Character

Fractal mass distribution of expansive soil grains is studied in this paper. It is found that there is different fractal mass distribution exponent of the grain-size distribution for different genesis of expansive soils. The expansiveness, physical properties and mechanical properties of expansive soils can be quantitatively described by the fractal mass distribution exponent of grain-size distribution of expansive soils. In consolidated tests, the fractal mass distribution exponent increases with increases in consolidated pressure, as well as increases in confining pressure in triaxial tests.

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