Engineering Geological Characteristics And The Feedback Of Foundation Rock Of Xiluodu Hydropower Station

The phase of Xiluodu Hydropower foundation excavation has completed. Base surface excavated from the 610m to 324.5m elevation. In the excavation process, the author acquired rock mass structure, the degree of slack rock, rock quality and nature of rock mechanics etc. of base surface rock mass timely and accurately by using advanced equipment and methods under the leadership of the Professor NieDe xin. Then got comprehensive understanding of characteristics of foundation rock mass from the table to the inside. This article studied engineering geological characteristics of foundation rock mass after excavation, and made comparison of early survey results in order to test the accuracy of survey methods of the feasibility study stage. And provided a highly efficient and reliable research methods and ideas for other Station Construction. It means a great deal to reduce the emergence of engineering geology. This paper studied the following aspects:(1) The rock structures were compartmentalized by using precision measuring window with on-site, full crack measurement and the method of combining digital video recording for structural plane of each bench excavation foundation surface, and then got left and right banks spandrel groove and bed base surface distribution of rock mass structure;(2) We compared the rock structure of exploration hole early stage with the one of excavation stage in order to test the similarities and differences of rock structure in same location in two stages;(3) On the base of analysis of sonic drilling of base surface, the studies show that the blast made rock mass of base surface flabby. And different slack depth belongs to different levels rock mass. The statistical depth of impact were in the range of 1.2～1.8m;(4) Weathering degree of shallow and deep of foundation rock was distinguished by using sonic drilling. The weathering boundaries which including the boundary between weak weathering zone upper segment and weak weathering zone lower segment and boundary between weak weathering zone lower segment and very shallow weathered bedrock were almost same.(5) There are more than 70 test points which were accomplished by using a new patent technology-"self-loading" the deformation of test equipment on the both sides of the base surface. The test results covered different situations modulus of deformation which were affected by different lithology and different types of rock. The deformation modulus showed a good correlation with acoustic velocity which were tested at the same time and place.(6) The characteristics of rock mass on Xiluodu base surface were that the lots of random soft interlayer which cut foundation rock into layers and made mechanical properties of foundation rock weak, distributed on the foundation rock. The test was done to determine the mechanical properties of soft interlayer. By using elasticity theory and acoustic conversion formula and modulus, the characters and deformation modulus of rock mass were determined in relaxation and non-relaxation situation.(7) The rock mass quality of foundation has been classified by several indexes which included rock mass structure, integrity factor, velocity ratio and modulus. And compared the resaults between the before and after excavation.(8) The results were given which included rock mass characteristics and the stress range after the rock excavation and the total displacement, maximum principal stress, intermediate principal stress and shear stress distribution in the normal engineering loads by three-dimensional numerical simulation analysis.