Analysis And Research Of The Elasto-plastic Damage Characteristics Of Layered Fractured Rock Mass

In engineering,layered rock mass are regarded as compound geological materials composed of fractures system,structural planes and rock,which involves massive geological structures of different genetic:fractures,joints,beddings,faults,weak intercalations,pores,et al.,so exhibit natures of anisotropy,inhomogeneity and non-continuity strongly.At present,elasto-plastic constitutive model of engineering rock mass has been widely recognized,but the effects of damages caused by joints and fractures on the mechanical properties of layered rock mass still can not be estimated quantitatively,as a result its practical application are often limited on many aspects,and the models do not accord with the mechanical behaviors of most engineering rock mass so mcuch.Therefore,in order to understand and characterize the real engineering rock mass better,it is necessary to study damage performance and constitutive model of the layered fractured rock mass.Based on lots of domestic and foreign scholar's research,layered and fractured rock mass are studied in this work.Layered rock mass having structural plane effecting zone can be treated as layered material of transverse isotropy and in which numerous,middle-scale fracture system are considered as initial "damage" of rock mass material.Research methods and principles of damage mechnics are used to analyse the physical and mechanical performance of layered and fractured rock mass quantitatively.At first,according to the conditions of force equilibrium,deformation compatibility and equal stored strain energies,viewpoints and methods of elastic mechanics are introduced and elastic properties of equivalent continuum are characterized with the thickness and elastic coefficients of each layer.In layered fractured rock mass,considering the structural planes and its influence scope,the planes and bilateral rock mass of certain thickness conbine into a sort of 3-layer compound rock mass(which is defined as structural plane affected compound layer) and expressions of equivalent elastic properties of the affected layer can be derived with corresponding theory.Then the affected compound layer can be taken as individual layer combining with other layers in rock mass to achieve the equivalent mechanical behaviour of the representative element volume.On the basis of the theory of damage mechanics and fracture mechanics,considering the influence of the area damage caused by the fractures system on the stress and the damage strain caused by the jump displacement of fractures respectively,damage evolution formula and constitutive relation of the layered and fractured rock mass are established by means of stress and strain volume average and using the Hoek-Brown Strength Criterion as the rock mass damage strength.According to actual situation,detailed numerical simulation of the erecting bay excavation of Shenxigou Hydropower Station is carried out by the theory of this work. The results are reasonable and indicate that,comparing with traditional elasto-plastic constitutive model,this kind of constitutive relation has remarkable optimization, certain universality and better reference value.