Research On Stress Path And Strength Property Of Remolded Loess Under Tensile-shear Stress Zone

Tensile-shear strength is one of the reasons that structural loess slope is steep and upright.Properties of tensile-shear strength and compression-shrear strength,which are important aspects of the mechanical properties of structural loess,are all needed to be studied reasonably.However,research on stress path and strength property of the tensile-shear zone in structural loess is less.A kind of triaxial apparatus based on the coupling of tension shear stress’path and compression shear stress path is invented to study the tensile-shear strength properties of structural loess,and two kinds of tensile-shear stress path tests are conducted.This work studied the regulation of the critical failure fine at p-q plane of structural loess in tensile-shear zone.We further studied the π plane characteristics of structural loess on the basis of the tensile-shear strength characteristics,and compared it with the existing several classic strength criterion.Then the work discussed the applicability on evaluating the tensile-shear strength of structural loess.The conclusions of this work are as followed:(1)There is not an apparatus that can conduct the triaxial tensile-shear stress test at present.In light of this a triaxial apparatus and related equipmerots based on the coupling of the tension shear stress path and compression shear stress path are invented.Through debugging and improvement,we conducted several conventional triaxial tests,and compared results with that of conventional triaxial apparatus test.And the reliability and practicability of the new triaxial apparatus turned out to be well.(2)Eventually we choased the combination of self-adhesive spray and triangle tire rubber as the glue for test through a large number of tests,which solve,d the technical problem that the samples tended to separate with rubber membrane when applying nelpative pressure in the test.Two kinds of shear stress path(the three-axial tensile test with negative confining pressure and traxial compression test with load reduction)are designed.In order to effectively and precisely conduct the test,we studied the impacts of the combined glue on mechanical properties of samples and found a way to scavenge the AB glue on lest socket.(3)This work completed two kinds of tensile-shear stress path tests(the triaxial tensile test and Load-reduction triaxial compression test)of remolded loess under four different moisture content.The relationships between the tensile-shear strength of structural loess with water content and the confining pressure were found out,based on two kinds of stress path tests of shear zone(conventional triaxial test and B true three axis test).And we explored the fitting method of meridional plane strength failure line.Then we obtained the joint strength failure line based on tensile shear stress path tests and compressive shear stress path tests,and compared the joint strength failure line with the M-C strength failure line that based on the compressive shear test.(4)The corresponding three-dimensional surface strength of π plane was obtained,on the basis of the joint strength failure line of tensile and compressive shear stress path test.By comparing the π plane trajectory and corresponding three-dimensional surface based on the pressure and shear stress path test with those calculated by M-C strength criterion theory,it was found that the M-C strength criterion overestimated the tensile-shear strength of soil.(5)On the basis of the cracking trajectories of π plane in tensile shear zone based on several traditional strength theories,this work discussed their applicability on soil considering tensile-shear strength characteristics.