Research For Multi-Complicated Rock Mass As Gravity Dam Foundation Located In The Wide River-bed With Deep Overburden Layer

There are Triassic dolostone in left and Carboniferous basalt in right and fault belt rock mass between dolostone and basalt in Saige Hydropower Station. The research region have many fault and Rock mass integrality be effected because of the NuJiang deep and major fault. The RQD of basalt is only 33% and RQD of dolostone even under 10%. The dolostone that the space of discontinuities is universal several centimeter even under 1cm is very cataclastic apparently because there are many discontinuities in rock mass. The size of fault belt rock mass between dolostone and basalt is large. There are many fault gouge in fault belt rock mass with thickness of 35-40m in borehole. Can these rock mass that surface textures so cataclastic will be as foundation of high concrete gravity dam. It will be important theory and project significance. Therefore, the main contents of this dissertation are:①According to position of fault belt rock mass by borehole disclosing, getting the distribution, thickness and orientation of main fault belt rock mass make use of three-dimensional model and method of tectonic geology.②According to field and indoor investigations and analysis, found out especial formation mechanism of dolostone. According to result of research, dolostone with small space between discontinuities is differs from the common cataclastic rock mass because the discontinuities are filled and cemented with calcium, make the dolostone from discontinuous medium features to continuous medium features. In this dissertation, these new special structure rock masses were named filling cementation cataclastic rock mass.③Rock mass structure and rock mass quality of dolostone and basalt are evaluated under overburden layer. Demonstrate these quantifiable indexes have the perfect correlativity. ④According to field and indoor investigations and tests, under the conditions of non-disturbance or slight disturbance, basalt and filling cementation cataclastic dolostone have high longitudinal wave velocities, high modulus of deformation, high sound degree coefficient, high shear strength and low osmosis. Rock mass mechanical parameters of basalt and dolostone achieve or exceed criterion of grade III enter into weakly weathering belt. But mechanical parameters of fault belt rock mass in river-bed are low, and need to be treated.⑤By making the rock mass mechanical parameters as kernel, select the rock mass of dam foundation by index of rock mass quality, rock mass weathering and rock mass osmosis, and broke through the limitation of dam foundation rock mass selection only based on weathering zones. At last made sure the lowest of selected dam foundation rock mass to bed rock roof is 646.74m in the position of ZK115 without regard to the fault belt rock mass in river-bed.⑥According to result of three-dimensional FEM analysis, stability of dam 11 is low because of unequal settlement when don't treat the fault belt rock mass in river-bed. Stability coefficient of Dam 11 can be achieved 2.3-2.4 and reduce unequal settlement effectively by making use of integrative prevention measures that are board of concrete with steel, plug of concrete and increase of modulus of deformation of fault belt rock mass.