Stability Analysis of Unsaturated Soil Slopes Based on Unified Strength Theory

Abstract:

Based on the unified solution of shear strength in terms of double stress state variables for unsaturated soils, the unified formula of stability coefficient for unsaturated soil slopes under the plane strain condition is derived by Sweden slice method, which considers the effect of the intermediate principal stress rationally. Combining with engineering example, the proposed formula is compared with the one that is on the basis of Fredlund unsaturated soil theory and the influencing characteristics of factors including intermediate principal stress, matric suction, effective internal friction angle and matric suction angle is obtained. The research result indicates that: intermediate principal stress and matric suction have obvious impacts on the stability coefficient for unsaturated soil slopes; the stability coefficient has been increasing with the increase of unified strength theory parameter and matric suction, which proves that the consideration of intermediate principal stress and matric suction can make slopes give full play to their self-stabilities and strength potential, and the yield criterion has great impact on the judgment of slope stability; the stability coefficient also increases nonlinearly with the increase of effective internal friction angle and matric suction angle. The proposed unified formula of stability coefficient for unsaturated soil slopes enjoys a wider application. The stability coefficient for unsaturated soil slopes according to the Fredlund unsaturated soil theory and that for saturated soil slopes are just the special cases. The research result can provide theoretical basis for stability analysis and reinforce design of the unsaturated soil slopes, and it is of great significance to the slope management.

• Periodical: Applied Mechanics and Materials (Volumes 353-356)
• Pages: 946-951
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.353-356.946
• Online since: August 2013
• Authors: Yan Li, Jun Hai Zhao, Qian Zhu, Chang Guang Zhang, Wen Qi Bai, Jian Feng Xu
• Keywords: Slice Method, Slope Stability, Stability Coefficient, Unified Strength Theory, Unsaturated Soil

References

[1] D C Fredlund, N Yang. The mechanical properties and their engineering application to unsaturated soils[J]. Chinese Journal of Geotechnical Engineering, 1991, 13(5): 24-35. (In Chinese).

[2] C G Bao. Behavior of unsaturated soil and stability of expansive soil slope[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(1): 1-15. (In Chinese).

[3] A W Bishop, G E Blight. Some aspects of effective stress in saturated and partly saturated soils[J]. Geotechique, 1963, 13(3): 177-197.

DOI: 10.1680/geot.1963.13.3.177

[4] D C Fredlund, N R Morgenstem, R A Widger. The shear strength of unsaturated soils[J]. Canadian Geotechnical Journal, 1978, 15(3): 313-321.

DOI: 10.1139/t78-029

[5] B R Fisher, J M O Hughes. Cut, slope design and pressuremeter testing in weakly cemented, unsaturated soil[J]. Geotechnical Engineering for Transportation Projects, 2004, 2(126): 2093-2102.

DOI: 10.1061/40744(154)205

[6] A Rahimi, H Rahardjo, E C Leong. Effect of hydraulic properties of soil on rainfall-induced slope failure[J]. Engineering Geology, 2010, 114: 135-143.

DOI: 10.1016/j.enggeo.2010.04.010

[7] R L Ray, J M Jacobs, P de Alba. Impacts of unsaturated zone soil moisture and groundwater table on slope instability[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2010, 136(10): 1448-1458.

DOI: 10.1061/(asce)gt.1943-5606.0000357

[8] Z Z Liu, Z X Yan, N B Peng, et al. Dynamic influence of sustained small-rainfall infiltration on stability of unsaturated soil slope[J]. Journal of Civil, Architectural & Environmental Engineering, 2012, 34(4): 19-23. (In Chinese).

[9] P F Yao. Limit equilibrium method based on ratio of factor of safety for slope stability of unsaturated soils[J]. Chnese Journal of Rock Mechanics and Engineering, 2009, 28(S1): 3250-3256. (In Chinese).

[10] H B Sutherland, M S Mesdary. The influence of the intermediate principal stress on the strength of sand[C]. Proc of 7th Int Conf on Soil Mechanics and Foundation Engineering, 1969, 1: 391-399.

[11] G E Green. Strength and deformation of sand measured in an independent stress control Cell Roscoememorial Symposium' Stress-strain behavior of soils[M]. G. T. Foulis and Co Cambridge, 1972, 285-323.

[12] M H YU. Unified Strength Theory and Its Applications [M]. Berlin: Springer, (2004).

[13] C G Zhang, Y S Hu, J H Zhao. Unified solution of shear strength for unsaturated soil under plane strain condition and its application[J]. Chinese Journal of Geotechnical Engineering, 2011, 33(1): 32-37. (In Chinese).

[14] C G Zhang, Y S Hu, J H Zhao, et al. Elastic-plastic unified solutions for stresses and displacements of a deep buried circular hydraulic tunnel[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(11): 1738-1745. (In Chinese).

[15] Y H Guo, F X Jiang, C G Zhang. Analytical solution for critical rockburst of a circular chamber subjected to high in-situ stress[J]. Engineering Mechanics, 2011, 28(2): 118-122. (In Chinese).

[16] C G Zhang, J H Zhao, Q H Zhang. Convergence-confinement analysis of deep circular rock tunnels based on unified strength theory[J]. Chinese Journal of Geotechnical Engineering, 2012, 34(1): 110-114. (In Chinese).

[17] R J Li, W Zheng, L P Wang, et al. Progress and developing trend on stability analyses of unsaturated soil slope[J]. Northwestern Seismological Journal, 2011, 33(S): 2-9. (In Chinese).

[18] Y W Dong, H Z Guo, Q W Ren. Influence of yield criterion on caculating safety degree of soil slope[J]. Journal of Chongqing Jianzhu University, 2006, 28(3): 51-55. (In Chinese).