The Dynamic Stabitlity Analysis Method Of Block Based On Block Theory And Its Application

Sliding failures of rock blocks along the joint faces are the basic and most important issues in the fields of excavations of underground openings in hydro-projects, minings and slope excavations in the rock engineering. The block theory was firstly proposed for rock block stability analysis in jointed rock mass by Dr. Shi Gen-hua in 1980s of last century. It is rigorious in the theory and is easy to be programmed. It provides the basic method for the stability evaluation of rock mass with blocky structure. The stability of rock block in the static state is studied by utilizing block theory at first, and then the dynamic stability analysis method based on block theory is proposed by couping with earthquake acceleration records in the paper. The main research results include the following respects:(1) It is, at first, a very important issue to have an optimum attitude of joints in rock mass prior to utilization of block theory. So the grouping method of joint faces based on genetic algorithm and fuzzy c-means and another new drawing method of pole contour map are proposed, and its visualization in further analysis with results is carried out in the Quickwin plotting mode of FORTRAN.(2) Some basic programs in the original block theory are recompiled in the FORTRAN platform, and the results can be viewed in the AutoCAD. These calculation codes consist of stereographic projection program, block stability analysis program, block morphology visualization program and londe picture program, etc.(3) The block dynamic stability analysis method based on block theory under the action of earthquake is firstly proposed. It includes the following respects:â‘ dynamic stability analysis of unlocated blocks where only friction angles in sliding faces are considered in the calculation of safety factor.â‘¡dynamic stability analysis of blocks with their boundary faces determined exactly in aspects of orietations and positions and parameters of friction angle and cohesion are inputed simultaneously in the safety calculation. Meanwhile the effects of anchoring force and hydrostatic pressure are considered.â‘¢accumulated slippage concept of Newmark method is introduced to the block stability analysis, and the accumulated sliding displacement concept and its calculation method are proposed, meanwhile the safety calculation considering the loss of shear strength of sliding faces after sliding is proposed. Curves of accumulated sliding displacement and curves of safety factor based seperately on original strength and discounted strength are obtained.â‘£the stability analysis program of blocks based on parameter sensitivity analysis is programmed, which provides a method for overall stability evaluation in the design stage.(4) Applications of the above programs to the dynamo-static stability analysis of the upper stream wall of the surge chamber in Guan-Di hydropower station have been carried out at last.