STUDY OF SHEAR STRENGTH OF LOESS UNDER HIGH STRESS STATE

The shear strength envelope is linear in some range of stress. The commonly used 0～400kPa vertical stress for direct shear tests and confining pressure for triaxial tests can meet many engineering soil stress state of interest. And the shear strength envelope can be linear, designated by cohesion c and internal friction angle .In loess area, high loess slope over 100m is common, and the stress state of soil on the potential failure surface varies greatly from the low to the high. It is necessary to consider the shear strength parameters changing with the stress state. The research herein firstly utilizes a linear elastic finite method to figure out the stress field of a high loess slope. It then consolidates soil samples at the stress state of some key point on the potential sliding surface and performs triaxial compression tests(NCTC).Triaxial compression tests with 100kPa, 200kPa, 300kPa, 400kPa confining pressure are also performed for comparison. Results show that when considering the stress state of high loess slope, the shear strength envelope yielded by the total stress Mohr circle is not linear and the linear M-C criterion is not effective. But that yielded by the effective stress Mohr circles is linear, and the strength parameters are higher than CTC tests. In - space, the shear strength envelope(total and effective) of NCTC is higher than that of CTC, which is related to the high consolidated stress.