Analysis And FEM Stimulation Of The Dilatancy And The Plastic Softening Deformation In Soft Rock Tunnel

More than 70 percent of energy is coal which occupies a pivotal position in construction of national economy in our country. With the development of coal mining's depth, the problem of supporting and maintaining for soft rock tunnel becomes more and more conspicuous. Whether we can solve it properly is a key-point for coal mining's development in depth and safety in production. So the thorough studying and exploring is urgent. The deformation and displacement of the soft rock tunnel has an important influence on the stability of the whole structure. It is vital for us to calculate and stimulate exactly the deformation conduct of the surrounding rock to choose the time and program of the supporting.This paper makes a systematic exposition for the characteristics and mechanics property of soft rock, characteristics of broken soft rock tunnel, influencing factors of surrounding rock's deformation. The characteristics of dilatancy and softening during the rock mass damage influence the displacement of the tunnel greatly. In this thesis, the characteristic of the dilatancy is discussed under the state of loading as well as unloading. The relationship between the dilatancy and the stress status of the rock, the generation mechanism of the dilatancy expanding of the rock are analyzed.Proceeding from the mechanism of deformation damage mechanism of the soft rock tunnel, this paper analyses the principle of interaction between soft rock tunnel supporting and surrounding rock. Under the condition of the dilatancy and the plastic softening, introducing the dilatancy gradient and softening modulus and using the theory of the elastic-plastic and the rock mechanics, the new analytic solution of the stress, deformation and the radius of the plastic zone and the broken zone of the round soft rock tunnel. Through the calculation of the example, the influence of the dilatancy gradient and softening modulus on the deformation and pressure of the surrounding rock is analyzed. Comparing the result with the results from the other theory models, the model established in this thesis is proved proper.