The Research On The Method About Tracking The Critical Sliding Surface Of The Slope With The Slip Line Theory

In this paper, finite element method was combined with slip-line theory on the basis ofthe existing achievements. The stress field of the slope was calculated by elastic-plastic finiteelement method, and the stress components of each element were collected. The slip-linefield of the slope was got by using the interpolation function and node stress of the element,and the critical slip surface of the slope was determined in the end. The main contents andresults are as follows.1. The two-dimensional slope model was built and the stress field of the slope wascalculated by the ideal elastic-plastic finite element method, the algorithm of trackingslip-line was composed by FORTRAN program when giving the starting point and fixing thelength of step. The corresponding stability coefficients were calculated by using the normalstress of the slip lines, and the slip line with the smallest stability coefficient is the critical slipsurface.2. The result of elastic-plastic finite element calculation shows that there is stressabnormality near the top and surface of the slope, which can directly affect the orientation ofslip line and the trend of the whole slip line. However, suitably increasing the grid of finiteelement can eliminate the influence of abnormal finite element results on searching for slipline. The elements which are close to the top are sensitive to the deviation because of smallgravity. The quite small deviation still can easily make the orientation of slip lines change.The slip line orientation of the starting point can affect the location of the whole slip line.Thereby, the starting point of slip line should not be set at the top of the slope, but near thetop as possible as it can be.3. By tracking the slip lines under different conditions, the main factors for the locationof slip line should include the step length between two points on the slip line, the grid size offinite elements and flowing rules. The step length has great impact on the shape and locationof slip lines. By reducing the step length gradually, the result of trial shows that when the steplength start to decrease, the location and shape of slip lines changed greatly, butinconspicuously as the step length reduced to a certain value. Therefore, different step lengths should be tested when searching for the slip line field of the slope. Conversely, the grid sizeand flowing rules have less influence on searching slip lines.4. Firstly, the topography before sliding was recovered by the Sanmutai landslidetopographic map measured in the field. Then, the two-dimensional model was built andanalyzed by the elastic-plastic finite element method. Finally, the critical slip surface wasdetermined by the method of tracking slip line proposed in this paper, and the resultindicateds that the sliding surface determined in this paper is basically consistent with the onethat found in field investigation.