EXPERIMENTAL STUDY ON ANISOTROPIC CHARACTERISTICS OF UNDISTURBED Q₃ LOESS FROM DINGXI, GANSU

Through the triaxial test in the laboratory, the anisotropy effect of Q₃ loess from Dingxi, Gansu on the shear strength and deformation parameters was studied. The results show that the anisotropy of undisturbed Q₃ loess has obvious influence on its mechanical properties. The shear strength in vertical direction of the loess is much higher than that in horizontal direction, and with the increase of the confining pressures, the difference between the shearing strengths of the two directions decreases significantly and eventually stabilizes within an error of 10%. When the confining pressure is lower than 100 kPa, the failure strain of the loess in horizontal direction is higher than that in vertical direction, and the difference between the failure strains of the two directions gradually decreases with the confining pressure increases. When the confining pressure is higher than 200 kPa, the failure strains in vertical and horizontal directions tend to be the same. By using Duncan-Chang model, the measured and the calculated deviatoric stresses are compared which indicate that the difference between the vertical direction and the horizontal direction is large in the low strain range, and with the confining pressure increasing, the difference gradually decreases and stabilizes in the error range of 5%. The stress strain curves of the loess samples in both the vertical and horizontal directions show linear relationship with very high regression coefficients when the strain is less than 2%, which can be used to approximately calculate the deformation modulus of the loess samples in both directions, and the corresponding values are 130 MPa and 85 MPa respectively.