Study On Prediction Of Curtain Grouting Amount Of Gravity Dam Foundation And Evaluation Of Grouting Effect

Gravity dam curtain grouting is an important method for dam seepage prevention and reduction of dam foundation lifting pressure,and it plays an important role in ensuring the safe and stable operation of dams and hydraulic structures.The grouting project is a concealed project.Due to the complexity of the development law of rock mass fissures,the uncertainty of grouting liquid spreading in the bedrock fissures and the influence of grouting construction conditions,it is often difficult to accurately control the grouting volume and construction quality.At present,grouting projects are mainly constructed according to traditional experience and lack of effective theoretical support.The existing grouting volume prediction related research does not fully consider the geological conditions(permeability),construction conditions(hole depth,section length,grouting time and initial grout injection rate etc.)and the comprehensive influence of factors such as the nature of the slurry(starting and ending water-cement ratio),it is difficult to predict the desired effect.The effect quality evaluation after grouting mostly adopts a single evaluation index,and it is not possible to use multiple indexes to comprehensively evaluate the grouting quality at the same time.Therefore,it is of great significance to carry out research on the grouting ability of the rock mass before grouting,the prediction of grout consumption and the quality effect after grouting in the grouting project.Aiming at the above problems,this paper takes the curtain grouting project of the gravity dam foundation of a certain reservoir as the object,uses theoretical analysis,field test and numerical simulation methods to conduct in-depth research,and obtains the following research results:(1)Based on previous research results and practical experience in curtain grouting design and construction of dam foundation,the influences of grouting construction conditions,bedrock permeability and many other factors on curtain grouting effect of dam foundation are studied.Because the information of influencing factors can not be quantified,which is not conducive to direct comparison,the grey correlation theory is adopted to determine the correlation degree of the influence degree of each influencing factor on grouting quantity.(2)The study of grouting quantity prediction considers the influence of bedrock permeability,construction conditions and slurry water-cement ratio.The algorithm programs of support vector machine regression(SVR)and BP neural network method are compiled,and the grouting quantity and ash injection quantity of grouting engineering are predicted.R~2,MAE,MAPE and RMSE are taken as the evaluation indexes of prediction effect,and good prediction results are obtained.The comparison results of the two methods show that the SVR method has high accuracy and stronger practicability,and can be used as an important support for grouting engineering practice.(3)Evaluation of grouting effect,using a variety of detection methods to comprehensively analyze and evaluate the grouting quality.According to RQD value obtained from drilling and coring of curtain grouting rock mass in gravity dam foundation,the integrity of fractured rock mass after grouting is evaluated Based on the permeability of rock mass determined by the sectional water pressure test of curtain rock mass drilling,the quality of curtain grouting is evaluated whether it meets the requirements of anti-seepage design using the results of borehole acoustic detection,the integrity coefficient of rock mass after grouting is evaluated,and then the curtain grouting effect is evaluated.(4)The finite element analysis software FLAC3D is used to simulate the seepage of dam foundation and stress and strain of dam body under different water levels after grouting.The simulation results show that the seepage of dam foundation has been improved obviously after grouting,which shows that the grouting quality is good and meets the requirements of reservoir water storage and seepage control;And the displacement,stress and strain of the dam under different water levels.The results show that the dam has good stability under different water levels and meets the requirements of reservoir water storage.