Abstract The correlation between rock mass quality indices and shear strength parameters are investigated by means of analyzing the specimens tested in-situ of gently weathered marble rock mass in Jinping I hydropower station. Taking the advantage of Copula theory that the marginal distribution and dependence structure can be studied separately;the marginal distributions of variables under small sample conditions are established. The optimal fitting Copula functions of Q-f and Q-c are selected on basis of researching on the dependence structure between rock mass quality Q and shear strength parameters f and c. For similar rock mass,the guaranteed rates of estimated f and c by other methods can be obtained;and the estimate of f and c can be calculated with a certain guaranteed rates with known Q system by solving the conditional probability of the optimal fitting Copula functions. Then the guaranteed rates of estimated f and c by the predominant slope method and least-squares method are calculated;the estimation of f and c with a certain guaranteed rates are compared to the estimation by Hoek-Brown criterion. The results show that,Q has a positive correlation with f,while Q has a negative correlation with c,the symmetric structured Copula functions Nelsen NO 1 and Nelsen NO 2 are the optimal fitting Copula functions of Q-f and Q-c. The estimation of f and c by the predominant slope method and least-squares methods are skewed because the correlation between rock mass quality and shear strength parameters are ignored;and the rock mass shear strength derived from this paper?s method with guaranteed rates 0.8 is more coincident with practical situation than by Hoek-Brown criterion. This paper's method takes full use of the limited in-situ information,the shear strength parameters with a guaranteed rate can be estimated,it can be used for rock mass shear strength parameter estimation.
|
Received: 25 December 2012
|
|
|
|