Analysis On Large Deformation Of Surrounding Rock Mass Squeezed By High Ground Stress

The large deformation of surrounding rock mass squeezed by high ground stress is the most popular problem in deeply-lying underground works, and it often occurres in engineering rock mass with great discontinuities, the systemic theoretic study on the problem is imperfect. The induction, summarization or engineering analogical method is usually used to solve the problem, there is no reliable one. With the development of underground construction, more and more underground engineering meet the trouble of this problem. In order to search effectual engineering countermeasures, it is very necessary to study the engineering characteristics and mechanism of deformation and failure of surrounding rock mass squeezed by high ground stress.Firstly, researchs on large deformation of surrounding rock mass squeezed by high ground stress are reviewed. Current study on high stress area, large deformation and stability analysis of the fractured rock are summarized. Character and process of large squeezed deformation are generalized. Secondly, based on the similarity test designed to imitate the process of large squeezed deformation, the damage evolution of rock is described with the weibull probability distribution, and then a strain-softening model is developed which is more suit to simulate softening behavior of rock. Large deformation nonlinear finite element method and strain-softening models are used to do the emulational calculation on surrounding rock mass squeezed by high ground stress, the formation and development of squeezing large deformation is represented, and the basic condition, controlling factors and mechanism of squeezing large deformation also are investigated. The result of analysis by theoretical and numerical method demonstrates it important to consider rock softening behavior during solving the large deformation problem, and the most suitable one of the several strain-softening model presented in thesis is selected. Finally, following the example of jiazhuqing tunnel, formation and development of squeezing large deformation of surrounding rock corrsponding to two construction schemes are reappeared by the large deformation nonlinear finite element method and the optimum strain-softening model selected above and the effect of several supporting methods is compared, the mechanical response, dynamic characteristic, stability and engineering countermeasures of surrounding rock mass squeezed by high ground stress in deeply-lying underground works are also discussed.