| This thesis takes Shiquan reservoir in zhongjiang county as the research object.Based on the regional data and the detailed field geological survey and laboratory test analysis,this thesis studies the structural stability of the reservoir area,the dam engineering geological conditions,the selection of dam line and the possible engineering geological problems.Tectonically,the study area is located in the northeast part of the Longmenshan tectonic zone,on the west edge of the Yangtze platform,which belongs to weakly active area of the Sichuan basin.Reservoir field ground motion peak acceleration of 0.10 g and the degree of corresponding basic earthquake intensity is Ⅶ,indicating that regional tectonic stability is poorer.Line 2 and line 4 in right dam possess the similar geological structure,stratigraphy,engineering geological conditions.However,considering the micro topography,quaternary thickness,tectonic fracture,rock mass permeability characteristics,weathering thickness and weak intercalated ways,line 4 is slightly better than line 2 in right dam.The reservoir exhibit two leakages through thin ridge and along the Jinjisi fault.The leakage volume along the fault is 98.4 m3/d,and the perennial average flow rate is 0.182 m3/s.The leakage volume accounts for about 1.21%of the perennial average flow rate.The leakage volume of the thin ridge is 188 m3/d,and the reservoir leakage will have a infiltration effect on the farmland and housing foundation downstream.The stability analysis of slope in the reservoir area shows that the overburden accumulation body is in a stable state under various working conditions,and the collapse body is located at the tail of the branch reservoir,so it has little influence on the normal operation of the reservoir.When the reservoir is filled with water,the overlying sandstone is cut into blocks due to cracks.Under the impacts of gravity,local small-scaled collapse may occur,which has no important impact on the normal operation of the reservoir.Simulation calculation shows that after impounding the reservoir,the problems of submersion may occur in Tianjiawan and Xiangjiawan,the width of which is about 40～70 m,the length of which is about 0.75 km,and the submersion area is about 70 mu.The width and length of the yard into the house are about 30～50 m,0.45 km and 32 mu respectively.There are no houses in the two submerged areas,and only farmland is submerged.Based on the numerical simulation results of ABAQUS,it is shown that the maximum position of flow flow on the section of the dam site after the reservoir is full of water is concentrated at the connection position between the front and rear sides of the dam body and surrounding rock,and the flow vector distribution is uneven,and the flow near the dam body is larger than that far away.The distribution of pore water pressure in the section of the dam site shows that the water pressure decreases gradually from the upstream to the downstream,and the change rate of pore water pressure is concentrated at the bottom of the dam site.After the reservoir begins to fill,the rock layer of the dam body is in a saturated stateThe velocity vector diagram of the dam site section after the reservoir is full shows that in saturated unsaturated seepage,water can flow through the infiltration line,and on the right side of the section,water flows across the infiltration line from the saturated zone to the unsaturated zone,and continues to flow in the unsaturated zone.At the same time,the velocity vector is not evenly distributed,the velocity near the dam body is larger than that far away,and the maximum velocity is concentrated in the connection between the front and rear sides of the dam body and surrounding rocks.The seepage of the dam body is closely related to the dam body material,bedrock material,and the water-stopping curtain at the junction of the dam body and bedrock.According to the results of the numerical simulation,the seepage flow of the water level at the toe of the dam downstream under different water storage levels should be monitored.This simulation takes into account the situation of the most unfavorable condition(when the dam body water level reaches the designed maximum).It can be seen that the seepage is mainly concerned with the seepage at the bottom of the reservoir.According to the permeability coefficient measured above and the selection of the dam site,the weakly permeable bedrock can effectively constrain the overall seepage flow,and the prevention and control of seepage should focus on the location of the water curtain.Dam site of pore water pressure distribution can be seen that water pressure is from the upstream to downstream of the law of diminishing,it is worth noting that the position in the bottom of the dam site is concentrated and the condition of changing rate of pore water pressure due to concrete and bedrock two contact interface position is discontinuous,so the location of pore water pressure there is a big change,global existence this moisture surface pore water pressure value shift to the left of the phenomenon.At the same time,it can be seen that the isobaric line with zero pore pressure is located on the right side of the section map,where is the position of the infiltration surface.The oozing surface gradually moves to the left with the decrease of the upstream water level,which conforms to the general law of the continuous deep flow-oozing processThe seepage field and rock saturation cloud map of the three sections of the dam site on the left and right sides show that the seepage mainly concentrates on the stratigraphic turning and contact positions of the two sides of the slope.The uniform distribution of bedrock saturation along the whole oozing surface is consistent with the actual situation.And from the quantity value,permeability is very low,belongs to the appropriate dam site... |
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