Papers by Author: Chun Guang Li

Abstract: There are a large number of cracks, joints and layers with different scales and orientations in the rock masses. With the structural formation in it, the rock mass is unlike the isotropic and homogenous materials in physics and mechanics characteristics, and the failure of the rock mass is controlled by those discontinuities. This paper studies the stability of a jointed rock slope with bedding-planes. Universal Distinct Element Code (UDEC) is used to carry out the numerical analysis. The factor of safety (FOS) and failure mode are obtained by strength reduction technique before and after the steel bolts are installed in the slope. In addition, the forces along the bolts indicate that they reaches the maximum value in the potential slip surface of the slope.

Abstract: There are several different yield surfaces of Drucker-Prager yield criterion which corresponds to Mohr-Coulomb yield criterion in principal stress space. The different yield surfaces are determined by parameters in Drucker-Prager criterion. The influence of the different parameters on computational results is discussed in the paper, and the use of the equivalent Drucker-Prager criterion to Mohr-Coulomb criterion is suggested when elastoplastic analysis is performed in engineering problems.

Abstract: A numerical technique based on using manifold elements in finite element method, for modeling propagation of arbitrary cracks in solids, is described. When the region with crack(s)is subjected to external loading and the crack(s) starts to extend, the crack growth may intersect boundaries of nearby finite elements. Those intersected finite elements are replaced by manifold elements. The technique, by which the initial finite element mesh can be kept unchanged during the processes of crack propagation, is called manifold elements in finite element method. The crack growth is governed by the theories of linear elastic fracture mechanics. The stress intensity factors are computed by a contour integral technique and crack trajectory is determined by applying the maximum tangential stress criterion. Finally, test examples are given to verify the new method and the predicted trajectories are compared to experimentally obtained crack growth paths with good agreements

Abstract: A series of formulas about two-parameter parabolic Mohr strength criterion(2-PP Mohr criterion) are derived. Based on the results of uniaxial tension and uniaxial compression tests, the parameters involved in the criterion can be easily determined, then the criterion in terms of the major principal stress and the minor principal stress is derived, and the damage pattern is also discussed. At last, the formulas about the rupture angle and the friction angle are presented, and their relationship is also given. 2-PP Mohr criterion can describe not only shear but also tensile failure. In this criterion the ratio of the uniaxial compression strength and the uniaxial tension strength is not confined as in Griffith criterion. The formula about the rupture angle provides steady theoretical foundation for determining the direction of crack faces and damage patterns in the computation of macro crack propagation. In fact, Griffith criterion is only a special case of the two-parameter parabolic Mohr strength criterion proposed in this present paper.