Study On Numerical Simulation Method Of Reinforcement Effect Of Rock Bolt To Intermittent Jointed Rock Mass

The demand of underground cavern development increases rapidly with the sustained stable growth of the national economy. These underground caverns include urban subway, submarine tunnel, underground shopping mall and garage, large-scale air-raid shelter structure, municipal underground engineering, underground workshop of hydropower station, super-long hydraulic tunnel, multiple line tunnel of highway and railway, mineral engineering, momentous national defense projects and military engineering, underground storage of fuel and nuclear waste. Geotechnical anchoring technology which can ensure the project smooth progress and normal operation also can control the deformation of surrounding rockmass has become an irreplaceable reinforcement measures in geotechnical engineering safety.Joint which is the most significant property of rock as a kind of engineering material distribute universally in natural rockmass. In all kinds of joints, intermittent joints are most universal. The mechanics characteristics and failure style if the entire rockmass are determined directly by the quantity, distribution, feature and properties of the joints. The failure of the rockmass is usually caused by initiation, development, expand, transfixion of the cracks under the external load. As the most widely used reinforcement structure, anchoring effect of the bolts is significant. The mechanism of anchoring effect is not explicit yet. Taking bolted intermittent jointed rockmass as the research object, through the damage theory and numerical simulation, this dissertation is dedicated to obtained a simple, efficient, propagable, engineering-usable technology which is capable of simulating the anchorage effect of bolt to intermittent jointed rockmass.A FEM model is established to compute stress intensity factor (SIF) of winged-crack in bolted rockmass, contact effect of crack surfaces is also considered in this model. A comparison is conducted between method in this paper and virtual spring method. From the result of this model, the anchoring effect of bolt is embodied by bending resistance. The most fatal defect of virtual spring method which is very popular is that bending can not be expressed from virtual spring.Geometrical damage tensor of intermittent jointed rockmass is defined and derived. A singular Dirac function is introduced to describe the orientation distribution of crack density and Damage tensor is obtained by integrating the Dirac function. The accuracy of the Damage tensor in crack density description is determined by the order of the tensor. Low order tensor can be adequately derived from high order tensor. Orientation distribution of crack density can not be wholly described by second order tensor while two or more family of crack exist.Based on the imitation to existing definition of Damage, the increase of bearing area or stiffness caused by reinforcement (bolt, grout, geotechnical grille) is defined as Anti-Damage. In fact this is an extension to existing definition of damage. The definition, special distribution, operational rule of Anti-Damage is just same as Damage tensor.On the base of quasi-phenomenology damage mechanics and non-location theory, from the calculation result of FEM model, it is found that the attenuation of SIF accord with Gaussian distribution. The parameters of Gaussian distribution vary with the scale and stiffness of bolt. So Gaussian distribution is chosen to fit the attenuation of SIF.The statement expounded above is programmed via FORTRAN programming language whose version is 6.5.The calculation result of program is capable of expressing the anisotropic weaken effect caused by existence of joints and anisotropic and non-local anchoring effect caused by existence of bolts.