Further Research On Dam Abutment Resisting Force Body During Construction Period Of Dagangshan Hydropower Station On Dadu River

The constructing Dagangshan hydropower station is one of the large-scalehydropower stations planned on Dadu River. It`s a Concrete hyperbolic arch dam,with210m height,7.42×108m3reservoir storage and2600MW equipped capacitor.The main lithology exposed in the dam site mainly is black mica adamellite granite ofJining-Chengjiang periods. Influenced by long term tectonic, the rock mass structureis complex, which controls engineering geology problems in the dam area, especiallythe anti-sliding stability of the dam abutment resistance force body.Through the former research results of Dagangshan abutment resistance forcebody boundary, which is limited in the construction phase, the rock structurecharacteristics collected by the adits and surface expression have limits. And now,based on the excavation of foundation rock already been completed, it is meaningfulof discussing resistance force body again based on the new revealed rock massstructure characteristcs.Based on lots of the field investigation, the statistics and the laboratory analysis,this paper systematicly studies the rock mass structure revealed by the excavation ofthe dam abutment foundation base, as follows: describing the main structural planesand7group matrix fissures traits of the foundation base on both left and right bank,then calculating the connecting rate of two groups rock mass fissures in each elevationwhich may most probably consist the boundary of dam abutment resistance forcebody, confirming the boundary conditions of the dam abutment resistance force body,whose main research object is the sliding surface and side prespliting surface, andconfirming the mechanical parameters of each boundary. And then the combinationforms of all boundaries and the space distributions of blocks are discussed. At last, theabutment resistance body of the anti-sliding stability is evaluated by the rigid bodylimit equilibrium method.The conclusions are as follows: both some Ⅲ~Ⅳ structural planes and the fourth and sixth advantage fractures meet the conditions of constituting the boundary of thedam abutment resistance. There are21pieces of potential sliding block in both sidesof the Dagangshan foundation rock mass, among which there are12blocks on the leftbank and9on the right one, which shows that the blocks distribution of space are notuniformity. The sideslip planes of block in the left bank are mainly controlled by somelarge structure planes of dikes such as β21、β28、β41and so on, but the sliding surfacesare consisted of low-angle faults (f145) and the sixth advantage fractures. The largefaults f231with inclination angle in right bank meets the requirement of constitutinglateral fissure, it also meets the requirement of constituting end of slide surface in aspecific height, and the sixth set of matrix crack in right bank is main structuralsurface constituting end of slide surface too. Through calculation by limit equilibriummethod, I found that the stability against sliding of blocks basically meets therequirement of code for design of arch dam. But to the blocks which end of slidesurface is constituted by large faults, it is suggested to make slip-resistantreinforcement on construction.