Study On Analysis Methods Of Tunnel In Jointed Rock Mass

In recent years, study on jointed rock mass had been paid close attention, manyscholars mainly studies respectively from aspects such as theory and experiment and thenumerical analysis, etc. Although the aspects of theory and experiment had madeconsiderable progress, with the complexity of rock mass numerical analysis has been apractical and effective method of solving the problem of jointed rock mass. At present,study on tunnel in jointed rock mass for numerical analysis method, generally idealizedjointed rock masses as continuous media, and considered the impact of the joints byreducing the mechanical parameters of rock mass. Although the treated method had acertain degree of rationality, it was not consistent severely with practice. Other,numerical analysis of jointed rock mass using the model of distinct media simulatedrespectively rock blocks and joints by the reduced values of given material parameters,which was more consistent with material properties of the rock mass. Although themethod had been applied widely in a foreign country, the domestic application was less.In this paper, the tunnel of jointed rock mass was analyzed by using the model of bothdistinct and continuous media. The model of distinct media employed the theory basedon distinct element method, taking a jointed tunnel for example, analyzed the influenceon the displacement of the tunnel surrounding rock and the internal forces of the supportthrough the mechanical parameters of the joints (cohesion, internal friction angle andstiffness). The model of continuum media employed the theory based on Hoek-Brownstrength criterion, which took jointed rock mass to be equivalent to continuoushomogeneous rock of Mohr-Coulomb strength criterion, then it was numericallyanalyzed. Hoek-Brown strength criterion used the geological strength index GSI toconsider, and GSI value of was reflected the jointed rock mass quality by the specificparameters of the joints, so the method takes into account the impact of the joints on theanalysis results and was equivalent to homogeneous continuous rock based onHoek-Brown strength criterion, This could make it widely used in numerical analysissoftware based on the Mohr-Coulomb strength criterion.Internal force of the support was compared and analyzed by using continuum anddiscontinuum approaches in rock mass including two cross joints, and safety factorbased on continuum model was bigger than based on discontinuum model, that is, safetyreserve of using continuum approach was lower than using discontinuum approach. Inorder to further analysis, this conclusion is still valid through multiple comparison andanalysis of the effect of joint orientation and spacing on the tunnel. According to Shitang tunnel engineering, internal force of the support was analyzed by usingrespectively two approaches, which verified further that the above conclusions. Usingnon-continuous method to analyze the stability of the tunnel surrounding rock, receivedthat tunnel surrounding rock was unstable, which had collapsed at the vault of the tunnel,the surrounding rock of the tunnel was stable after the advance of anchorage forprocessing. In summary, because simulation of jointed rock mass of non-continuousmethod was coincidence with the actual situation, not only computed the internal forceof the support with better security, but also had the more obvious advantages in theanalysis of the stability of surrounding rock, the method could accurately find theunstable blocks, and thus pre-reinforce and further analyzed the reinforcement effect.