Quality Evaluation Of Rock Mass And Prediction Of Shear Strength Parameters For Dam Foundation Of A Reservoir In Shaanxi Province

The determination of rock mass mechanical parameters has always been one of the hot issues in rock mass mechanics research.The selection of mechanical parameters directly affects the design scheme and the stability of engineering rock mass.Most of the problems in rock mass engineering arise from the deviation of the estimation of rock mass mechanical parameters.In water resources and Hydropower projects,the selection of mechanical parameters of dam foundation rock mass directly affects the safe operation and cost of the project,which is one of the most important and difficult problems in engineering investigation and design.For large-scale projects with large investment and long construction period,the most direct and effective method to obtain rock mechanics parameters is in-situ testing of rock mass.However,in-situ testing of rock mass is difficult and expensive,and the test results will be affected by size effect.A large number of engineering practices show that there is an implicit relationship between rock mass strength and rock mass strength.In engineering application,rock mass mechanical parameters can be estimated by using rock test results,in-situ test and field mapping data,and parameters estimation values close to the actual situation of rock mass can be obtained.In this paper,the Ordovician Majiagou Formation limestone exposed in the dam foundation of a reservoir in Shaanxi Province is taken as the research object,and combined with the rock test and in situ test results in the dam site area,the characteristics of rock mass structural plane are analyzed and the quality of the foundation rock mass is evaluated;the relevant data of rock mass mechanical parameters are collected,and the prediction model of rock mass mechanical parameters is established by using machine learning method,which is applied to the estimation of rock mass mechanical parameters in the dam foundation.The dam body construction of reservoir engineering provides reasonable and accurate recommended values of rock mass mechanics parameters.The conclusions are as follows(1)Based on the analysis of the development scale and characteristics of rock mass structural planes in dam site area,the classification criteria for rock mass structural planes in dam site area are put forward by using the indexes of width,spacing,filling state and extension length of structural planes and combining with the current engineering geological survey criteria The rock mass structural planes in dam site area are divided into four levels,namely,grade ?,?,? and ?.(2)The rock mass quality of dam foundation is classified into four grades,i.e.?-?,and mainly ?-?,by selecting the representative indexes of rock mass structure,P-wave velocity integrity coefficient,deformation modulus and compressive strength,and the availability of rock mass at all levels is judged(3)A support vector machine model for predicting shear strength parameters of rock mass is established,and the model is used to predict shear strength parameters of rock mass of reservoir dam foundation.The model accuracy test results show that the prediction error is small and meets the needs of engineering application accuracy.