Finite Difference Simulation For Progressive Failure Of Over-Consolidated Fissured Clay Slope

Over-consolidated fissured clay is one kind of special clay which has two characteristics: fissured and over-consolidated. First, at one point, the clay is weakened in some direction by fissures; at the other point, these fissures make the clay stress concentrated more easily when some forces act on it. Second, consolidation and heavy consolidation make the clay had strong structure. When this structure is destroyed, the strength of the clay will fall sharply. Because of fissures and overconsolidation, the over-consolidated fissured clay is strain-softening. This feature and stress concentration make the slope of this special clay has progressive failure characteristic. Traditional limit equilibrium method can not be used to simulate and analyze the process and mechanism of the slope progressive failure, and the judgment for long-term stability of slope is also not accurate.FlAC(Fast Lagrangian Analysis of Continua) is a two-dimensional explicit finite difference program. The explicit, time-marching solution of the full equations of motion permits the analysis of progressive failure and collapse in large-strain mode. Furthermore it has strain hardening/softening ubiquitous-joint model which just match the strength characteristics of over-consolidated fissured clay and progressive failure characteristic of this clay slope. In this paper, the progressive failure process of over-consolidated fissured clay slope is simulated and the stability of slope is analyzed with FLAC code.First, the whole development process of shear band for the gentle slope whose failure is always due to shear failure and connecting process of the shear band and cracks for the vertical slope are simulated and their stability are analyzed. By the study we can find that there may be more than one shear bands in one failure process of a slope and the forms of the shear bands are not always arcs. Besides, through tracing the changing of the cohesion in different parts of the slope, the softening of the clay is clearly exhibited. Simulating of this failure process, obviously, is very important for understanding the progressive failure of the over-consolidated fissured clay slope.Second, to study the influence of fissures and over-consolidation respectively, different cases are designed. Through studying of these case, we can find that the influence of fissures is the main reason for the changing so much of the shear band forms and of connection ways of shear bands and cracks during their developing process. Besides, softening is one reason of stress concentration and it has great influence on the form of the shear band.At last, different mesh forms and physical mode sizes are studied to get more accurate result.