Simulation Research Of Concrete Failure On Gravity Dam Foundation Surface Based On Seepage Damage Coupling

In recent years,China has vigorously developed the construction of water conservancy projects and built a number of high concrete gravity dams.The geological conditions of these dams are complex.Under extreme loads such as floods and earthquakes,the concrete at the heel of the dam is prone to damage,and then under the action of high-water head,seepage occurs,resulting in dam instability and damage.In order to better ensure the safety of the dam,this paper adopts the finite element simulation analysis method,taking Poyue Reservoir as the research object,first analyzes the mechanical property distribution and damage evolution process of the cementation surface between concrete and bedrock,reveals its failure mechanism,and then takes the seepage effect into account,analyzes the failure behavior of the gravity dam under the seepage-damage coupling effect,and finally based on the finite element overload method,To explore the damage distribution of the dam body when taking different overload coefficients,and to quantitatively analyze and evaluate its damage and damage degree.The main work of this paper is as follows:(1)Analyze the damage and failure evolution process of the bonding surface and reveal its damage evolution law and failure mechanism.Based on the in-situ direct shear test of Poyue Reservoir,a three-dimensional refined simulation model of the direct shear test on the cementation surface of dam foundation concrete and bedrock is established to simulate the direct shear test under different normal loads.The error of shear strength parameters is less than10%,and its failure mode is in good agreement with the test results,which verifies the validity of the simulation method and the accuracy of the results.The stress at the cementation surface gradually increases with the increase of normal load,the stress distribution is uneven,and the overall trend is large at both ends and small in the middle.The failure modes under different loading conditions can be summarized into three types: cementation surface failure,mixed shear failure and bedrock failure,and the failure mode is mainly related to the size of normal stress.With the increase of normal stress,the shear area along the cementation surface gradually increases,and the fracture surface tends to be flat.(2)Analyze the damage and failure of concrete gravity dams considering seepage effects.A numerical model considering the coupling effect of seepage and damage is established to analyze the seepage,stress,displacement,and damage of the concrete gravity dam of Poyue Reservoir under the coupling and non-coupling effects.The results show that the distribution laws of seepage,stress and displacement of the dam body are basically the same under different calculation schemes.Considering the coupling effect of seepage and seepage and damage,the stress at the dam foundation surface and the displacement of the dam crest are increased.The damage caused by different calculation schemes is concentrated near the dam heel.Under the influence of seepage,the damage area and damage degree at the dam heel will significantly increase,and after considering the coupling effect of seepage damage,the damage value will further increase,from 0.761 to 0.822.When the seepage effect is not considered,the dam body only has local damage,but there is no macroscopic crack;After considering the seepage effect,the dam body damage exceeds the critical value of 0.75,indicating that the dam heel will be partially damaged under the seepage effect,but its damage and damage index is less than 0.2,indicating that the overall stability of the dam body is good.The setting of the zero-pore water pressure boundary increases the effective stress of the dam body,thus reducing the damage degree and scope of the dam foundation concrete.(3)Analyze the degree of damage and failure of the dam body under different overload coefficients.The finite element overload method is used to explore the damage distribution of concrete on the dam foundation surface corresponding to different overload coefficients under the normal water level,and the quantitative analysis and evaluation of its damage and damage degree are carried out.The results show that under seepage,the damage mainly extends along the dam foundation surface,and the damage area gradually increases with the increase of overload coefficient.The damage first occurs near the dam heel.With the gradual increase of the overload coefficient,the damage gradually extends downstream along the dam foundation surface.When K(28)1.0 ～1.4,the damage area expands slowly,and the damage area increases significantly in the range of K(28)1.6 ～ 2.4,indicating that the ability of the dam body to withstand the upstream water pressure is significantly reduced,resulting in rapid expansion of cracks,and thus the expansion rate of the damage area increases.When the overload coefficient K(28)2.4,its corresponding damage and damage index is 0.96,which means that the dam is seriously damaged and loses its bearing capacity.The safety and stability coefficient of the concrete gravity dam is 1.6 based on the results of dam crest displacement change and crack expansion.