The Ageing Characteristics And Performance Evaluation Of Anti-seepage Curtain For High Pressure Waterway

In order to alleviate the shortage of electric energy in China and realize the sustainable development of renewable energy,a large number of pumped storage power stations have emerged.The design water head of the pumped storage power station is generally high.Under the unfavorable operating conditions such as high head seepage for a long time,the seepage and abnormal seepage pressure caused by the deterioration of the material properties of the anti-seepage curtain often occur.Therefore,the service performance of the anti-seepage curtain is a major research topic related to the success of engineering seepage prevention and operation safety.Taking the anti-seepage curtain of high-pressure waterway as the research object,based on the study of the complex physical-chemical process of fluid flow and mineral dissolution of anti-seepage curtain under the coupling action of high-pressure water seepage and chemistry,and taking the time-dependent characteristics and anti-seepage performance evaluation of anti-seepage curtain as the research goal,this paper carries out the numerical simulation of anti-seepage corrosion of anti-seepage curtain and multi index comprehensive evaluation of anti-seepage performance,Systematic research is carried out by closely focusing on the core scientific problem of seepage and dissolution effect of high pressure hydropower tunnel of Xianyou pumped storage power station.The main research results are as follows:（1）In order to study the deterioration law of the seepage resistance of the high-pressure water channel anti-seepage curtain in the pumped storage power station,based on the principles of continuum dynamics,solute migration and chemical kinetics,combined with the characteristics of grouting materials and anti-seepage curtain materials,from the seepage field,chemical field The seepage control equation,solute migration control equation and parameter evolution equation of the anti-seepage curtain are simultaneously analyzed from three perspectives and the microstructure of the anti-seepage curtain,and the seepage-corrosion coupling model of the anti-seepage curtain is established.The numerical solution of the model is obtained,and the rationality and correctness of the model and the solution program are verified through the approximate calculation example of the anti-seepage curtain of the dam foundation.（2）Based on the engineering geology,hydrological environment and anti-seepage drainage design of Xianyou Pumped Storage Power Station,a three-dimensional finite element model of anti-seepage curtain for high-pressure waterway is constructed.The visual dynamic process of seepage corrosion of anti-seepage curtain is realized by multi-physics coupling calculation software.The results show that the internalCa²⁺precipitates continuously under the action of seepage corrosion of anti-seepage curtain with high water head for 30 years.The solid phase calcium in the deepest corrosion degree of anti-seepage curtain is dissolved by17.76%,and its porosity increases by 29.38%compared with the initial porosity.The permeability coefficient increases by 2.49 times,and the impermeability and durability continue to decay.The direction of groundwater seepage affects the process of horizontal and vertical dispersion ofCa²⁺produced by seepage-dissolution of the anti-seepage curtain,which is the main factor leading to the migration and enrichment ofCa²⁺.The seepage-corrosion damage of anti-seepage curtain of high pressure hydropower tunnel has the characteristics of temporal and spatial variation.The corrosion area of the contact part between the middle of the anti-seepage curtain and the high-pressure bifurcated pipe is the largest,while the top and bottom dissolution are mainly encircling dissolution,and the dissolution area is smaller than that on both sides of the middle.The erosion area on the upstream side is significantly larger than that on the downstream side.3)The anti-seepage performance of the anti-seepage curtain is comprehensively analyzed by combining the monitoring data of the seepage pressure and seepage flow of the macroscopic dynamic characteristics of groundwater,the acidity and alkalinity（p H）,salinity,water chemical composition and precipitation composition characteristics and sources of the water behind the groundwater microscopic dynamic characteristics.The research results are as follows:The general trend of the correlation between the macro dynamic quantity of groundwater and the water level of the reservoir is that the anti-seepage curtain has a relatively weakened period from2014 to 2016,and it is a stable period until 2017.Although the p H of the water quality behind the scenes is weakly acidic,the anti-seepage performance of the anti-seepage curtains in the adjacent parts is attenuated to a certain extent,but most of the water quality behind the scenes is alkaline and strongly alkaline,and the anti-seepage performance of the anti-seepage curtains is still complete and effective.The ion content of water behind the scenes is generally higher than that of reservoir water,especiallyCa²⁺andHCO₃^-（10）CO₃^2-.It shows that the main hydrochemical action of the evolution of leakage water quality behind the scenes is the dissolution between liquid-solid series,that is,osmotic dissolution Through the physical and chemical analysis of the precipitates,it is found that the main chemical composition of the precipitates is Ca O and the proportion is the largest,followed bySi O₂.Compared with the composition of bedrock,it is analyzed that the cement stones in the anti-seepage curtain account for the main material source,which shows that the precipitates are the result of seepage dissolution of the anti-seepage curtain.A multi-index system was established to evaluate its anti-seepage performance,and it was found that the anti-seepage curtain at the position of Shanglang-01 was weakened,and anti-seepage reinforcement measures should be taken in time.