Experimental research on micro-pore and macro-deformation characteristics of soils considering stress paths#br#
WU Yuntao1，YE Wanjun1，YANG Gengshe1，DUAN Zhao2
(1. College of Architecture and Civil Engineering，Xi'an University of Science and Technology，Xi'an，Shaanxi 710054，China；
2. College of Geology and Environment，Xi'an University of Science and Technology，Xi?an，Shaanxi 710054，China)
Abstract：To confirm the mechanisms of different deformation and failure patterns of rock and soil masses in engineering constructions under complicated stress paths，taking the typical pale soil and surrounding rock in Zaosheng channel No. 3 of Yinchuan-Xi?an high-speed rail as the objects，triaxial shear test was done on soil samples under different stress paths using multi-stress path triaxial apparatus，and the pore size distribution characteristics of soils were acquired by low-field scanning MRI. Macroscopic and microscopic methods were integrated to make sure the soil mass deformation and failure mechanisms under different stress paths. The test results show that，under the conditions of both axial-loading and side-discharging stress paths，the stress-strain curves of the soil present a strain-hardening pattern，and that the initial confining pressure directly affects the variation trend of the stress-strain curve of the soil. Based on the normalization curve，the stress-strain relationships of the soil under the two kinds of stress path conditions conform to the hyperbola model，The p-q (average shear stress-generalized shear stress)curve of the soil shows a good linear relationship，and under the same stress path，the variation trends of the curves are tend to be identical with a parallel correlation in spatial position. However，the initial solidification confining pressure directly decides the position of p-q curve. The initial confining pressure plays a significant role on the improvement of the shearing strength of the soil. The cohesion and internal friction angle of the soil under axial loading are both larger than those under side-discharge in the same condition，especially for the cohesion. The initial confining pressure and the deformation of the soil have a good correlativity. Under the same deviatoric stress，the smaller the initial confining pressure is，the larger the deformation of the soil mass would be. The larger the peak strength of T2 is，the larger the scope of the relaxation time would be. It is observed that the content of small and medium pores of the soil is low while that of large pores is high. Under side-discharging with the same initial confining pressure，the peak strength of T2 is high and the relaxation time is long，which indicates that the content of medium and large pores in the soil mass is high. Under the same deviatoric stress，the deformation due to side-discharging would be larger. In addition，for the same axial strain condition，the samples show different pore information with different stress paths and initial confining pressures.
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2019, Vol. 38 
