ABSTRACT:

This paper introduces the principle and formulas to evaluate the failure behavior of slopes controlled with local discontinuous weaken structures, the decided critical sliding surface and the minimum factor of safely are searched by employing an Optimization process. Finally the laws and behavior of a slope controlled with weaken structure has been numerically analyzed.

I.
INTRODUCTION

At present, the emphasis of slope stability analysis is mainly on two extreme cases, slopes are usually assumed as homogeneous or assumed as absolutely controlled with continuous structures, the relative methods analyzing these slopes are well improved. In practice, certain slope cases are controlled with local discontinuous weaken structures within rockrnass, these local defects play a key role on the stability of the slope. Though these defects usually become the source of slope collapse and decrease the stability of the slope, but the weaken structures cannot form whole sliding surface of the slopes. In analyzing these defects controlled slopes two main problems will arise, that are the determination of the critical sliding surface and the search of the minimum factor of safety of the slope. The determination of the accurate critical sliding surface now depends on the sliding arch in homogeneous rockmass and the key sliding defects. Naturally the key local structures form a segment of the sliding surface of the slope, the sliding arch in homogeneous rock mass has to be searched. Based on kinematics element method, this paper discusses the principle and equation system determining the stability of the slope controlled with local weaken structures, the critical surface, except the key weaken structures, was searched by adopting optimization method to find the minimum factor of safety, and the failure behavior of the slope controlled with local weaken structures has been discussed.

2.
THE FUNDAMENTAL OF KINEMATICAL ELEMENT METHOD

Kinematical element analysis is a numerical method to evaluate ultimate bound problems of Mohr-Columb materials such as rock mass and soil. The method carries out with kinematics analysis, static analysis and optimization analysis. Kinematics analysis determines the kinematics behavior of slope in the critical condition, static analysis calculates the acted forces at boundaries of elements, at last optimization analysis is employed to find the critical sliding surface where there is a minimum factor of safety.

3.
MODELING OF SLOPE CONTROLLED WITH LOCAL STRUCTURES

The critical sliding surface of slope controlled with local defects consists of two parts, the key weaken structures and failure are in rockmass. The nodes of kinematics elements at the key weaken structures are invariable while the position of the nodes at the failure are in rockmass changes in the process finding the decision failure mechanism and the minimum factor of safety.

4.
NUMERICAL EXAMPLE

The stability and behavior of a simple two dimensional slope has been estimated with the above mentioned kinematical element method. The slope is controlled with a key weaken structure, which forms a part of the critical sliding surface of the slope, but the remnant part of the critical sliding surface cannot be predetermined.

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