Study On Indoor Test And Numerical Simulation Of Seepage Of Earth-Rock Dam With Core Wall Disease

The risk of earth-rock dam core wall disease is a multi-phase and multi-field coupling phenomenon involving pore water migration,porous medium deformation,temperature transmission,etc.,and most of its occurrence and development are located in the dam body,which has many characteristics such as strong concealment,uncertain spatial and temporal distribution,and fine initial magnitude,which is extremely harmful.If the flow and heat characteristics of earth-rock dams can be accurately simulated under the conditions of disease risk,it can provide a basis for accurate detection of earth-rock dam disease risk and inversion of monitoring data,and provide a basis for the dynamic evaluation of flood prevention and rescue,risk elimination reinforcement and dam safety performance of the project.Based on this,this paper combines the leakage risk test device of earth-rock dam,uses the distributed optical fiber seepage heat monitoring system,uses the waterfall gouge core wall earth-rock dam as the prototype to design the scale-down model,and uses theoretical analysis,indoor physical model test and numerical simulation to carry out research,analyzes the numerical quantitative results of seepage field and temperature field of earth-rock dam under the action of each influencing factor,reveals the intrinsic relationship between each influencing factor and the seepage field and temperature field of dam body,and analyzes the dynamic change mechanism of earth-rock dam flow heat.The main research contents and achievements are as follows:(1)Indoor physical model test.Combined with a large-scale earth-rock dam leakage risk test device,the clay core wall rockfill dam was used as the research object,and the experimental study of indoor seepage heat monitoring of earth-rock dam was carried out.The results show that the leakage risk area will change the double field of flow and heat of the dam body,and become the dominant channel for unstable seepage.With the gradual downward movement of the leakage risk area,the temperature value at the location increased significantly,the fluctuation of the infiltration line and the seepage rate of the dam body also increased,and the unfavorable situation affecting the seepage stability of the dam gradually increased.The temperature and pore water pressure values of each measurement point showed a nonlinear trend with seasonal fluctuations,and the double field change of dam body flow and heat was the most significant when the water infiltration of high temperature reservoir water in summer,while the leakage rate and infiltration line of the dam body fluctuated the most,in contrast,the temperature field of the dam body changed more obviously.The greater the increase in water level or the closer the infiltration head is to the top of the dam,the more obvious the temperature change of the dam core wall and the downstream area,and the significant increase in leakage,the stronger the unfavorable factors affecting the seepage stability of the dam body.(2)Model accuracy evaluation and verification.Based on the indoor physical model test,the constructed earth-rock dam flow thermal coupling model was evaluated and verified,and the model evaluation indicators NSE,RMSE and PCC were introduced to visually analyze the simulation results.The results show that the model simulation effect is good.(3)Numerical simulation study on flow and thermal coupling of earth-rock dams.The method of controlling the index variable of the core wall construction material of the dam body was used to carry out numerical simulation research with the core wall construction factor as the independent variable.The results show that the closer the core wall of the dam body is to the dam heel,the larger the leakage rate of the dam body,the higher the risk area and the surrounding high temperature area,and the more significant the distribution of the dam temperature field.The permeability coefficient of the core wall area increases,which reduces the control effect of the core wall on the hydraulic gradient,and at the same time,the temperature field of the dam body is transmitted backward more obviously,and the overall change trend is slightly greater than the influence of the inclination of the core wall.The permeability coefficient of the risk area increased,so that the infiltration line developed downstream in an arc near the risk area,but had little effect on the temperature field of the lower heart wall part of the risk area,and the overall change trend was slightly less than the influence of the permeability coefficient in the heart wall area.The temperature and pressure changes at the monitoring point show the same trend,and the temperature transmission has a certain hysteresis.(4)Numerical simulation study under the action of disease insurance type.Using the method of controlling variables,a numerical simulation study with the type of disease risk as the independent variable was carried out.The results show that the dam infiltration line develops most significantly downstream in an arc under the condition of curved cross-sectional disease risk channel,the average seepage flow increases the most,and the dam body tends to be more unstable.The influence of different types on the temperature field and the degree of influence on the seepage field were positively correlated,and the penetrating type of disease risk formed a temperature mutation zone with dense isotherms in the upper reaches of the dam core wall.The pressure,flow rate and temperature time series curves of the monitoring points can reflect the risk of disease damage to the core wall of the dam body when the model calculates 60 h,and the existence of the risk area will cause the pressure,flow rate and temperature of each monitoring point to break the balance,and finally the performance is as follows: working conditions B3> B1> B2> B4,the three have a certain correlation.