Physical Model Test And Numerical Simulation Study On Seepage Field Of Complex Landslide In Reservoir Environment

In the reservoir environment,the fundamental reason for the slope stability change is the change of the seepage field on the bank slope caused by the reservoir water level fluctuation.Under the condition of uniform slope material,the variation law of reservoir bank slope seepage field with reservoir water level fluctuation has been extensively studied by the predecessors.However,when the material composition and structure of the slopes on the reservoir bank are complex,how the changes of the seepage field in the slopes have not been discussed by previous studies.The large old landslides in the reservoir area are the most complicated bank slopes in terms of material composition and structure.The revival of old landslides is the most frequent geological hazard in the reservoir environment.Based on this,this paper takes the Chaiwan landslide,which has three layers of sliding belts and three layers of sliding bodies in the Three Gorges reservoir area and the material permeability of each layer is significantly different,as a prototype,using similar material physical model tests and numerical simulation methods to explore the reservoir water level fluctuations Under the condition of complex structural landslides,the groundwater seepage field changes.The physical model test is completed.The reservoir water level rise and fall rate and the landslide level permeability are different.The landslide model has 3 groups and 3 reservoir water level rise and fall conditions.27 points in the real-time model using a micro-osmometer are used to monitor different depths on three longitudinal and two cross sections.Variation characteristics of pore water pressure and infiltration surface;on the basis of verification and comparison with model test results,the SEEP/W module in GeoStudio software was used to explore the variation law of landslide seepage field and its relationship with the permeability of landslide and the rise and fall rate of reservoir water level.Thesis research found:(1)Under the condition of the same reservoir water level rise and fall rate,when the reservoir water level rises,the magnitude of the dynamic water pressure pointing to the slope is negatively related to the permeability coefficient of the sliding body,and the magnitude of the buoyancy force is positively related to the permeability coefficient of the sliding body;when the reservoir water level drops,The dynamic water pressure pointing out of the slope is inversely related to the permeability coefficient of the sliding body.(2)The rate of rise and fall of the reservoir water level affects the effect of the dynamic water pressure and buoyancy force.The inward dynamic water pressure when the water level rises and the outward dynamic water pressure when the water level falls are the most significant.When the combined structure of landslide permeability is fixed(K1<K2<K3 from top to bottom),the hysteresis effect of the response of the sliding body to the fluctuation of groundwater increases with the increase of the rate,which has the most significant effect on the sliding body with weak permeability.The water level rise process can be divided into synchronous type,lag type and transition type;the water level fall process can be divided into synchronous type,slow fall type and sudden fall type.(3)At the same location in the upper,middle and lower layers of the same section of the landslide,the response law of the groundwater level to the reservoir water level fluctuations in the complex landslide with three-layer structure differs from the weakly permeable sliding body at different levels,mainly showing the permeability of the upper sliding body When the reservoir is at its weakest level,when the reservoir water level rises,and the permeability of the upper,middle and lower layers of the sliding body increases in sequence,it will be sequentially affected by the dynamic water pressure in the slope and the buoyancy of the groundwater in the sliding body with relatively strong permeability in the middle and lower layers Function: When the water level of the reservoir drops,the upper-layer sliding body with weak permeability is subjected to dynamic water pressure pointing out of the slope.When the permeability of the intermediate sliding body is the weakest,the weaker intermediate sliding body during the rise of the reservoir water level is successively subjected to the action of dynamic water pressure in the slope and the buoyancy of groundwater in the sliding body with relatively strong permeability in the lower layer;When the water level drops,the weakly penetrating mid-level sliding body is subject to dynamic water pressure pointing out of the slope.When the permeability of the lower layer is the weakest,when the reservoir water level rises,the lower sliding body is subjected to the dynamic water pressure directed inside the slope;when the reservoir water level decreases,the weaker lower sliding body is subjected to the dynamic water pressure pointing outside the slope.