Self-stability Quantitative Method Of Bearing Surrounding Rock And Support Optimization Research For Underground Structures

Modern underground structure supporting principle thought surrounding rock is not only the source of the load pressure, but also the main part of the bearing, and artificial support is the auxiliary bearing. However, according to this concept, Industry standards only provided the qualitative description of the all levels of surrounding rock supporting, whose specific type and parameters were dependent on engineering experience of the decision makers, which caused the unnecessary waste of materials. Therefore, in order to make the supporting design to develop in the quantitative direction, based on the self-stability of the surrounding rock as the research object, tasks was carried out by the following aspects:Firstly, discussed the application of intensity reduction numerical method in stability calculation of geotechnical engineering and the working principle as well as the advantages and disadvantages of the finite software FLAC. Then, the M-C correction value with plastic stress was derived by using the incremental elastic theory and the established flow rule.Then, divided the state of surrounding rock into stable and unstable state according to dynamic equilibrium and put forwards a method to lock in the critical failure point of surrounding rock by matching elastic-plastic deformation and plastic flow phase curve equation of surrounding rock according to the plastic zone and the displacement variation characteristics of the key points.After that, identified the limit state of the surrounding rock intensity which is able to withstand all the destructive effects based on a large number of rules and derived the surrounding rock stability coefficient k0(using FLAC3 D and intensity reduction method) to act as the constant stability criterion. Then, the paper identified the condition of II~IV class surrounding rock to maintain long-term stability according to a large number of numerical simulations and the role of the surrounding rock self bearing structure in maintaining the stability of the tunnel.Again, primarily made stability calculation of the four section forms with the equal area and satisfied the requirement of internal limit of tunnel engineering construction to correct k0; next made strength weakening simulation of a tunnel surrounding rock by different Poisson’s ratio and elastic modulus, finding that Poisson’s ratio and elastic modulus have little effect on the stability coefficient, which overcomes the defect of traditional criterion of the plastic zone and displacement not uniform for their measuring error; then carry out indoor similar model experiment to test the results of numerical simulation thus verify the correctness of the steady coefficient k0.Further more, analysed the function mechanism and mechanical properties of the different support type, combined with the survey data and highway tunnel design specifications, and gave an optimization scheme for the Guangxi province Mensa tunnel block(1) level III by applying our method.Finally, in view of the existing bolt which was low elongation and couldn’t adapt to the problems of large deformation of roadway surrounding rock, the paper devised a new increasing resistance pressure component and carried out related work.