The Evaluation Of Long-term Stability At Right Dam Abutmet Slope Of Miaowei Hydro Power Station In Lancang River

The under construction Miaowei Hydropower station in Lancang river is located near the JiuZhou Town Miao Village in Yunlong County.It is in the Mountain range Rift Valley region of Lancang river. Planning is the most downstream Lancang River upstream of a cascade hydropower stations. The proposed dam is rockfill dam, the maximum height of 139.80m, reservoir normal water level 1408.0m, corresponding storage capacity 660 million m3, dead water level 1398m, corresponding storage capacity of 501 million m3.The geological environment of Dam Area is complex, in the process of excavation,There comes a series of deformation and partial collapse phenomenon at right dam abutmet slope. After emergency reinforcement, slope deformation has been some control, but the long-term slope stability problems after process of reservoir water during operation,is become an important engineering geological problems which concern the construction sector. Therefore, the long-term stability studies on the right bank dam abutment after the impoundment during operations has very important significance.In this paper, by the basis of a large number of on-site geological survey and indoor rheological the mechanical properties experiments analysis, analysis the causes of slope toppling deformation mechanism to simulate the process of deformation and failure of slope partial collapse; The use of general physical and mechanical tests and triaxial compression rheological test analyzes the physical and mechanical properties, rheological equations and long-term strength of rock slope; Using three-dimensional finite element numerical simulation analysis of the deformation behavior of the slope in the process of impoundment; based on fluid-solid coupling theory to analysis the slope seepage field and deformation field characteristics each time while water level changed; Finally Based on the above findings, make a long-term stability evaluation.on the right bank abutment slope during the operation of hydropower. More systematic study by the above analysis, this paper has made the following findings and basic understanding:(1)In the right abutment slope exposed strata of MiaoWei hydropower mainly are J2h1, J2h2 medium to thin-bedded sand slate, slate, phyllite and metamorphic quartz sandstone. Internal slope mainly developed Ⅲ～Ⅴ grade structural surface, the shallow of rock slope mostly in sub-massive-massive structure, the local structure was broken, somewhat less rock engineering properties.(2)Using discrete element of slope deformation and failure process analysis showed that if carried out excavation support, the slope will likely face deformation process in three phases:① Rock bent-dumping deformation stage, ② Toppling of sustainable development-broken destruction stage, ③ Rock buckling-Slip shear failure stage;(3)Mechanical properties of rock mass trials show:quartz sandstone, slate, sandy slate, schist, the mean tensile strength was 6.22 MPa,2.17 MPa,0.907 MPa,0.31 MPa. Interlaminar shear strength index of natural fracture zone c is 105KPa,(?) is 47°, saturated shear strength index c is 49KPa,(?) is 30°. Soft rock of slope stress-strain curve can be divided into four stages::compaction stage, the elastic deformation stage, the stage of plastic deformation, damage phase. Unsaturated shear strength index of schist:c is 5.54MPa, (?) is 46.4°.(4)The rheological experimental studies of schist at toe of slope shows that, schist creep deformation characteristics consistent with Burgeers rheological models, the creep constitutive equation is: Schist enter rheological stages long-term shear strength index:c is 4.92MPa,(?) is 38°.(5)The three-dimensional numerical simulation study of slope stability after impoundment shows that:if impoundment while no dams, slope overall appear very large deformation, deformation mainly concentrated in the top of the slope strong deformation zone A dump site, the variable value up to 60cm; On the basis of the excavation and backfill on shoring build the dam, slope deformation significantly reduced after the impoundment, the largest part of the deformation is still a strong deformation zone A dumping slope at the top of the top and free face steeper the rock, the magnitude of maximum 8cm.(6)Based on the theory of fluid-solid coupling analysis the slope seepage field and deformation field characteristics under the change of water level at the right bank abutment slope shows that:The initial slope of the water line is consistent with the actual diving position, with the upgrading of water level, the saturation line slope is also rising, Maximum deformation magnitude and scope of the slope is further increased, the largest regional deformation occurs in the vicinity of the slope and the fault intersects the saturation line in rock; As the water level dips, saturation line is also rapid decline, Y direction displacement did not change significantly, the total value X direction displacement is unchanged, but the increasing range.(7)The long-term stability calculation by the theory of fluid-structure coupling results shows that:Long-term stability of the fluid-structure coupling calculation results showed Slope:After impounding natural conditions, storm conditions and natural conditions+ earthquake slope stability coefficient exceeds 2.0, all in a steady state; Only in the stability coefficient storm+earthquake conditions, slippery surface two somewhat smaller, but also reached the lowest 1.577, in line with stability criteria.