Research on failure modes and strength characteristics of Q(2) loess under true triaxial condition

Based on the true triaxial apparatus of Xi'an University of Technology, the failure modes, intermediate principal stress influence on shear strength parameters and strength surface characteristics on pi plane of Q(2) loess with different water contents was analyzed under the condition of different intermediate principal stress ratio b and different meaning normal stress. It was shown that the failure modes of Q2 loess cubic samples behaved four kinds of failure formation, including of lateral bulge failure, taper failure, trapezoid failure, irregular hexagon failure by true triaxial tests. The shear strength parameters ratio could be got by comparing the strength parameters measured by true triaxial tests with the results of triaxial tests. The coherence ratio changes between 0.9 and 1.9. The friction angle ratio varies between 0.7 and 1.5. The structure property and failure formation of Q(2) loess influence the shape of failure criteria on p plane. The consolidation pressure influence the value of failure surface in p plane. The shapes of Q(2) loess failure criteria on p plane under different water contents and different consolidation pressures include pear-shape and irregular hexagon. With the structure property of Q(2) loess reducing, the shapes of failure surface on p plane changes from pear-shape into irregular hexagon.