Study On Soft Rock Characteristics And Its Sensitive Analysis To The Slope Of Zi Pingpu Hydroelectric Project

Zipingpu hydraulic project is located at Shajinba reach, upriver of Minjiang River, Sichuan, being built for agricultural irrigation and civil water supply. It also has integrative benefits such as preventing flood, generating power, environmental protection and tourism. Minjiang River benches almost conversely in Shajinba reach and makes the right bank being a thin and weak ridge, which is a syncline geo-structure. All of the hydraulic structures are arranged in the right bank. According to the project design, a lot of high steep slopes are formed during excavating period in dam. The soft rock distribut very widely, and can be divide into four typical groups as follows: argillized seam, coal, carbonaceous shale, pelitic siltstone and so on. Based on the researches of the excavated slopes, the slopes are controlled by multiple factors such as rock stratum, geo-structure, geomorphic etc.. In addition, the indirect influence of the strongly unloaded slope rock mass, relatively poor quality of rock mass, interbedded shearing belts, existing of F₃ fault and a series of thrust structure inclined to northwest, produced the bad complex of rock mass structure. The characteristics of soft rock's development and distribution directly affect the slope stability and the design of support measure. Influced by these factors, the problems of slope stability are quite obvious.The characteristics of soft rock and the slope sensitiveness are researched in this paper. Starting from the geological condition investigations, a series of the researches on soft rock characteristics were conducted. Based on the further investigation of geo-environmental condition, the characteristics of soft rock are studied. Particularly, the water quality and physics mechanics characteristics of soft rock are researched. The characteristics of rocky texture and mineral composition of soft rock are systematically analyzed by mineral and rock identifications and X-ray diffraction, and microcosmic identifications also appear particularity of physics mechanics characteristics to a certain extent. When falling across water, soft rock is easy to absorb water, and then argillize, intenerate, slake. Through the study of mechanical experiment, the uniaxial compression strength indices and shear strength parameters are put forward, which indicate that several typical soft rocks have strong aeolotropy, and that strength parameters are all very low. The results of long-term direct shear rheological test indicate that time effects of soft rock is also obvious and would be the potential factor to make the excavated slope creep-ripredly destructed along the soft rock and to play a mainly controlling role to the long-term stability. The possible destruction styles of intake slope is influenced by the soft zones to a certain extent. Taking the 4^# hydropower tunnel intake slope as an example, by elastoplastic finite element compution, the sensitivity of soft rock to excavated slope is analyzed. Simultaneously, the long-term stability of the slope is predicted after sluicing. Finally, the reasonable engineering suggestions are put forward in terms of the computing results.