Study Of Macro Mechanical Parameters Of Fractured Rock Mass

Fractured rock mass is often encounted in hydropower,mining and petroleum engineering.The deformation,strength and seepage characteristics of fractured rock mass are critical to design,construction and maintenance of rock engineering.Based on a developed rock mass model considering constitutive models of both intact rock and fracture,scale effects and hydro-mechanical parameters of rock mass are studied by numerical and analytical solutions.The main achievements are as follows:(1)The constitutive models of both intact rock and fracture are developed.Considering the heterogeneity of the rock,cohesions of units throughout the rock are supposed following a three-parameter Weibull distribution,and the cohesions decrease to zero when the units failed according to Mohr-Coulomb criterion.Parameters of the damage model are obtained through triaxial test results.On the other hand,the damage evolution law of fracture is related to magnitudes of shear displacement and normal separation.In addition, the constitutive models of rock and fracture are verified by comparing numerical results with laboratory test results.(2)Scale effects of mechanical and hydraulic properties of rock mass are studied. Firstly,the Monte Carlo simulation approach is used to generate the stochastic fracture network,based on distribution functions of location,orientation,trace-length and density of field fractures.Secondly,a reasonable approach dealing with intersection and end region of fractures is proposed,and a Fortran program is developed to generate rock mass model from the stochastic fracture network.Thirdly,based on the rock mass model,scale effect and anisotropic properties of deformation modulus of rock mass are studied according to elastic anisotropic theory.Furthermore,an analytical method is suggested to study the REV and anisotropic properties of deformation modulus of fractured rock mass.Results obtained from the method show good agreement with numerical simulation results.Finally,by implementing the constitutive models of intact rock and fracture into rock mass model, scale effect and anisotropic properties of compressive strength are evaluated.Equivalent shear strength parameters obtained from numerical simulations coincide well with strength results evaluated by empirical Hoek-Brown criterion and experience analogy.(3) A new laboratory apparatus measuring low permeability of rock in Thermo-Hydro-Mechanical coupled situation is designed and manufactured.Permeabilities of intact marble and fracture are measured under different hydrostatic stresses and temperatures.Test results show that the permeability decreases as hydrostatic stress or test temperature increases. Permeability of fracture can not resume to the previous value when hydrostratic stress returns back because of irreversible deformation.(4) Based on the generated discrete fracture network model,scale effect and anisotropy of seepage properties of rock mass are studied.Equivalent permeability tensor of fractured rock mass is obtained.(5) Based on distribution functions of fractures investigated on site,equivalent compliance matrix,equivalent shear strength parameters and equivalent permeability tensor of rock mass are obtained using the methodology proposed in the previous chapters.The parameters obtained are used to analyze the stability of diversion tunnel of Jinping hydropower station.