Parameter Back Analysis For Fluid-Solid Coupled Analysis In Fractured Rock Masses

At present, the domestic and foreign scholars have done the massive research work on the selection of fluid-solid coupling model in the fissured rock mass, and they proposed many good simulation coupling models, but the corresponding parameters of these models often could not accurately reflects the real seepage and mechanics characteristics of rock masses. And the exactly selection of parameters is the key of numerical simulation. The coupling model could simulate the deformation mechanism and seepage characteristic better, but there contains many parameters that could not be easy directly mensurated. Therefore, back analysis on the coupling of seepage and mechanics parameters based on observation of water head and displacement could not only enhance the result reliability of the traditional parameter back analysis, but also could supply powerful tool for determination these parameters that could not be easy directly mensurated.In this paper, on the basis of reviewing the research advances in the fields of seepage parameter back analysis, numerical simulation and parameter back analysis of the fluid-solid coupling in the fissured rock mass are unfolded, the primary work and the major results of this paper are as follows:1) The variational inequality formulation is applied to resolve the seepage problems with free surfaces, on the basis of a united mixed media model, the seepage parameter inverse problem about fracture rock masses is studied systematically and some effective measures are presented to decrease the ill-posed property and improve the reliability of parameter identification. The indirect method widely used in parameter identification fields is applied to solve the seepage parameter inverse problem.2) The sensitivity of the seepage coefficient is analyzed by use of the difference method, and a new weight function for the objective function is developed. With the application of the weight function, the effects of monitored water heads with high sensitivity against objective parameters can be strengthen to decrease the ill-posed property of the inverse problem.3) The original population is created by use of the method of netlike distribution, primary genetic algorithm is improved by the construction of individual self-adapting cross and mutation probabilities, and a hybrid genetic algorithm with high efficiency is presented to decrease several limitations of primary genetic algorithm in practice, such as poor local search ability, premature convergent, excessive computational cost and bad adaptability to large search space, and applied successfully to the seepage parameter back analysis in the stratum of a pumped-storage power station.4) Because of the strong interaction between the fluid-flow and stress in fracture rock masses, the parameter inverse problem for the coupled analysis is further studied in which both water heads and displacements are regarded as monitored information. In the back analysis of the couple problem, the sensitivity analysis of displacements against mechanical parameters is made firstly with the mathematical statistics method, and on the basis of the sensitivity analysis, the objective mechanical parameters are determined. Then the hybrid genetic algorithm is applied to solve the parameter inverse problem. And a typical dam case is carried out to prove that the theory of this paper is correct.