Stress-strain relationship of unsaturated cohesive soil

Abstract

A moisture-content based constitutive model was proposed based on the hyperbolic model as an attempt to move towards the implementation of unsaturated soil mechanics into routine geotechnical engineering practice. The stress-strain behavior of in-situ soil at a depth of 5 m was investigated by conducting undrained triaxial compression tests using the remolded soil samples. The test results show that the stress-strain relationship of unsaturated cohesive soil is still hyperbolic. The values of parameters a and b given in the model decrease with increasing the confining pressure for soil samples with the same moisture content and increase with increasing the moisture content for soil samples under the same confining pressure. The relationships between parameters a, b and moisture content were studied for confining pressures of 100, 150, 200 and 250 kPa. The comparison between the measured and predicted stress-strain curves for an additional group of soil samples, having a moisture content of 25.4%, shows that the proposed moisture content-dependent hyperbolic model provides a good prediction of stress-strain behavior of unsaturated cohesive soil.

Keywords

unsaturated cohesive soil / moisture content / triaxial compression test / stress-strain relationship

References

[1] FredlundD. G., MorgensternN. R.. Stress state variables for unsaturated soils [J]. Journal of the Geotechnical Engineering Division, 1997, 103(5): 447-466

[2] FredlundD. G., RahardjoH.Soil mechanics for unsaturated soils [M], 1993, New York, John Wiley and Sons: 157-161

[3] ChenZ.-han.. Deformation, strength, yield and moisture change of a remolded unsaturated loess [J]. Chinese Journal of Geotechnical Engineering, 1999, 21(1): 82-90

[4] YangX. L.. Seismic displacement of rock slopes with nonlinear Hoek-Brown failure criterion [J]. International Journal of Rock Mechanics and Mining Sciences, 2007, 44(6): 948-953

[5] YangX. L.. Upper bound limit analysis of active earth pressure with different fracture surface and nonlinear yield criterion [J]. Theoretical and Applied Fracture Mechanics, 2007, 47(1): 46-56

[6] LuanM.-t., LiS.-q., YangQ.. Theoretical soil-water characteristic curve for unsaturated soils [J]. Chinese Journal of Geotechnical Engineering, 2005, 27(6): 611-615

[7] XiongC.-r., LiuB.-c., ZhangJ.-sheng.. Relation of matric suction with moisture state and density state of remolded cohesive soil [J]. Chinese Journal of Rock Mechanics and Engineering, 2005, 24(2): 321-327

[8] GU Bao-he. To talk about science, technology and geotechnical engineering [J]. Journal of Geotechnical Investigation & Surveying, 2006(3): 1–5. (in Chinese)

[9] ShenZ.-jiang.. Exploitation of practical use of unsaturated soil mechanics [J]. Chinese Journal of Geotechnical Engineering, 2006, 28(2): 256-259

[10] BaoC.-g., ZhangL.-tong.. Relationship between unsaturated soil behavior and engineering problems [J]. Chinese Journal of Geotechnical Engineering, 2006, 28(2): 129-136

[11] YinZ.-z., ZhouJ., ZhaoZ.-h., YuanJ.-p., ZhangK.-yong.. Constitutive relations and deformation calculation for unsaturated soils [J]. Chinese Journal of Geotechnical Engineering, 2006, 28(2): 137-146

[12] YangX. L., YinJ. H.. Slope stability analysis with nonlinear failure criterion [J]. Journal of Engineering Mechanics, 2004, 130(3): 267-273

[13] YangX. L., YinJ. H.. Estimation of seismic passive earth pressures with nonlinear failure criterion [J]. Engineering Structures, 2006, 28(3): 342-348

[14] KleinfelterN., ParkM., CushmanJ. H.. Mixture theory and unsaturated flow in swelling soils [J]. Transport in Porous Media, 2007, 68(1): 69-89

[15] SedanoJ. A., VanapalliS. K., GargaV. K.. A simple air pressure gauge for unsaturated soils [J]. Canadian Geotechnical Journal, 2007, 44(8): 1013-1018