| Face rockfill dam is a common and important hydraulic structure at present.Seepage is one of the important factors causing the failure of face rockfill dam.The leakage of concrete faced rockfill dam in different degrees during operation has aroused great concern in scientific research circles.Once the seepage problem reaches a relatively serious level,it needs to be analyzed again.This paper takes Bachi reservoir as an engineering example.After normal water storage,the leakage amount is too large.After two grouting treatments,certain results have been achieved.But there is still a large leakage phenomenon.It is necessary to carry out seepage analysis on the face rockfill dam of Bachi reservoir.The hydrogeological conditions of the dam foundation of Bachi reservoir are complicated,which can be considered as complex leakage.In order to reduce the construction workload of plugging and save the construction cost,this paper studies the plugging optimization based on various information(geophysical exploration,seepage calculation and grouting construction progress information).The main research work and results are as follows:(1)Preliminary determination of concentrated leakage area based on geophysical prospecting.The pseudo random flow field method is used for geophysical exploration analysis.By comparing the potential difference of the seepage field,the concentrated leakage points on the left and right banks of the upstream are determined,so as to determine the concentrated leakage area.It is inferred that there is a connection between the right leakage area and the mountain of the right bank.It is concluded that the leakage area on the left is caused by the leakage at the bottom of the reservoir.(2)Determining the seepage area based on analytical seepage calculation.The seepage calculation and analysis of the curtain,the bedrock below the bottom line of the curtain and the dam body of Bachi reservoir are carried out by analytical method,and the calculation results are compared with the allowable seepage value.Then,the mean value of the permeability of the unknown area is obtained through the inversion analysis.The results show that the mean value of the permeability of the unknown area is much higher than the impervious standard 5Lu,indicating the existence of seepage channels,and the results are consistent with the geophysical results.(3)Determining the seepage area based on finite element seepage calculation.The seepage of Bachi reservoir is calculated and analyzed based on the finite element software ANSYS.Through inversion analysis,the influence degree of rainfall factors on the measured leakage behind the dam is calculated.Then,the influence law of the water head on the measured leakage after the dam is analyzed.By comparing the seepage calculation results of the analytical method with the finite element method,it is found that there is a seepage channel.(4)Dynamic optimization based on grouting construction schedule.According to the actual seepage amount of the downstream after formal construction combined with the seepage calculation of analytical method and finite element method,the predicted seepage value of the reservoir after impounding to the normal water level is 6.42L/s.Comparing the process of downstream measured seepage reduction,the grouting seepage control progress is combined with seepage calculation for dynamic optimization of leakage plugging.The above conclusions are of certain engineering significance,and the research work of seepage analysis provides some theoretical data to support for the subsequent construction. |
