Theory And Application Research On Displacement Back Analysis Of Transversely Isotropic Rock Mass

On the one hand, transversely isotropic rock mass is widely distributed on the earth surface, therefore there are a large number of stability problems about transversely isotropic rock mass in engineering. On the other hand, rock mass is a extremely complex geological body formed through a long geological evolution, therefore it is very difficult to get its accurate physical and mechanical parameters, and"parameters provided are not accurate"has become a bottleneck problem for theoretical analysis and numerical simulation. So, several theory and application researches on displacement back analysis of transversely isotropic rock mass have been accomplished in this paper to provide new research ideas and methods to ascertain the parameters of transversely isotropic rock mass accurately and quickly.The researches include displacement analytical solution, uniqueness of displacement back analysis, optimization of measurement points layout, shear yield criterion and elastoplastic constitutive model, master-slave parallel genetic algorithm.Based on the equilibrium equation, physics equation and geometry equation of transversely isotropic elasticity mechanics, compatibility equation of transversely isotropic solid is deduced, and then the displacement analytical solution of a deep circular tunnel in transversely isotropic rock mass under non-uniform stress field is derived. Based on the complex function expression of stress function, the complex function expression of displacement components in transversely isotropic solid is deduced, and then the displacement analytical solution of the tunnel with arbitrary cross section in transversely isotropic rock mass is derived by conformal mapping method.The uniqueness of displacement back analysis for the circular, elliptical and complex tunnel in transversely isotropic rock mass is discussed respectively by means of identifiability conditions. The results indicate: all of 6 parameters can't be determined simultaneously no matter how many the measuring points are set; only when there are at least 3 known parameters, may the other parameters be determined simultaneously. In addition, the impact of measurement points layout on the uniqueness of displacement back analysis is analyzed by taking the circular tunnel as an example.The optimization of measurement points layout of displacement back analysis in transversely isotropic rock mass is preliminary studied according to the maximum displacement viewpoint. The results indicate that the range close to the tunnel wall in the direction of major principal stress is optimum for measurement points layout.The shear yield criterion and the elastoplastic constitutive incremental equations of transversely isotropic rock mass are deduced, and then the transversely isotropic elastoplastic constitutive model program is written in C++ in the Visual Studio 2005 environment.By combining the inherent parallelism of genetic algorithm with the high-speed parallelism of cluster system, a back analysis method of geomechanical parameters based on master-slave parallel genetic algorithm is presented. Several improved methods are used: real code is used to shorten the length of individual code and reduce the searching scale; Dynamic task allocation is used to avoid idle resources of some processors; Loose coupling method is used to couple master-slave parallel genetic algorithm with FLAC3D. Besides theoretical analysis, the back analysis program is written in C and MPI(Message Passing Interface).