Study On Seepage Characteristic And Stability Of Mengdigou Deposit

The stability of Mengdigou deposit body ditch the dam has played a important role in Mengdigou Hydropower Station construction and operational security。 According to detailed geological site investigation, engineering geology survey of the project area,and the analysis of the spatial distribution,structural characteristics,geological origin, and then tomake qualitative judgment to Mengdigou deposit body from global aspect。 On the basis of the overall knowledge on Mengdigou deposit body, the author use of laboratory tests to obtain basic physical and mechanical parameters。Rainfall and reservoir water levelchanges are main factor that affect on deposit bodystability due to the deposit of body engineering properties。This thesis takes application of saturated-unsaturated theory to analys seepage characteristic comprehensivly under different rainfall scheme and reservoir water level rise rate, and then abtain variation of the pore water pressure, volumetric water content。Afterwards, the author calculate and analysMengdigou deposit body stability effected byrainfall and reservoir water level changes through limit equilibrium method。Around the deposit bodypenetration characteristics and stability, the thesis obtained the following cognition:1. Through investigation of geological history, topography features, deposit body composition and structural characteristics of the project area, the author is convinced that Mengdigou deposit bodyis glacier moraine left bywestern China last glaciation。2. Using laboratory tests, like snip、large scaletriaxial tests、permeability test and saturation experiment to obtain shear strength index, permeability of deposit body, and propos soil strength parameters recommended value。3. Under the rainfall through different programs, taking into account the flow characteristics of the deposit body under different permeability overall performance, the total rainfall maintain the same, when the rainfall intensity is smaller and the rainfall duration islonger, then amount of rainfall infiltration is grater, infiltration depthsis deeper, scope of influence is grater; As same time, because of gravity, rainfall presents "toe pooling effect", comparatively speaking, infiltration depth and rate of deposit body toeis larger than upper; Comparedwith the permeability coefficient, the bigger the permeability is, the greater the infiltration capacity is, but they are non-linear proportional relationship.4. As the reservoir water level rising at a certain rate, the leading edge of the deposit was flooded, reservoir water infiltration, pore water pressure increases, Volumetric water contentincrease to saturated until reservoir water level rise to elevation2254m and water table is stable. In this process, the water table elevation relative to the rise in the water level of a significant lag, showing that the faster reservoir level rise, the smaller the coefficient of permeability, hysteresis effect is more obvious.5. According to the changes of stability,deposity stability depends on strength of the most dangerous sliding surface with rainfall infiltration, deposit stability is almost stable at1.51under three different rainfall program; only if penetration of soil is50ko, rainfall with less intensity and greater scheme will reduce the deposit stability, and showing rule thatlonger rains lasted, the greater stability reduces; At the process of reservoirlevel rising, as the leading edge gradually have been submerged, stability coefficient decreases from1.151to about1.06, until the water table get stable, magnitude of the stability reduce is only about elevation the reservoir level rise, and has no significant relationship with permeability coefficient or reservoir water level rise rate which has effect on thetiming of stability coefficient began to decline and rate of stability coefficient decline, in general, when reservior level rise faster and permeability coefficient is greater then the stability coefficient begins to drop earlier anddrop more quickly。...