| Phyllite is a kind of phyllitic structure of low grade metamorphic rocks.On the one hand,due to the long-term influence of weathering and earthquake,phyllite are generally present broken state.On the other hand,is a layer of phyllite rock,in the construction of tunnel and slope design should pay attention to the occurrence of phyllite especially,phyllite dip on tunnel structure stress and stability will have an important impact.The structure has a significant impact on the integrity,permeability,physical and mechanical properties and stress transfer of engineering rock mass.Therefore,it is of great significance to study the characteristics of the structural plane comprehensively and deeply.In this paper,based on the BOLN passenger line through Qinan County of Gansu Province,Tianshui Zhu Shan Tunnel as the engineering background,in the area of rock,phyllite the mechanical test and the uniaxial compression and measurement of structural surface roughness coefficient JRC,physical and mechanical parameters and the stress-strain curve.Using the 3DEC numerical simulation software,the structure of the surface parameters on the stability of the tunnel effect,simulation of tunnel excavation in thin strata,analysis of tunnel excavation method and support the way through numerical simulation combined with field data partially confirmed the reliability of the calculation results,provide a reference for similar engineering design.Specific research contents are as follows:(1)3DEC discrete element software is used to simulate the tunnel excavation in layered strata.The influence of geometric parameters and mechanical parameters on the stability of tunnel is discussed.For example,the influence of different spacing and dip angle of the structural plane,the deformation characteristics and failure mechanism of the surrounding rock during tunnel excavation are obtained.The results show that the structural plane directly affects the integrity of the rock mass,and the deformation of the surrounding rock is larger when the spacing of the structural plane is small.The inclination of the structural plane affects the failure mode and distribution of surrounding rock.Shear failure of structural plane is the most basicinducing factor of surrounding rock deformation.Analysis of the change of structure of the internal friction and cohesion is the observation of the supporting effect,the increase of internal friction angle and cohesion,the tunnel lining stress to improve the role,which affect the internal friction angle is more obvious.(2)The relationship between the occurrence of rock stratum and the axis of tunnel is obtained through the measurement of the structural surface.Considering the structure parameters on the importance of the stability of surrounding rock,this paper mainly adopts the comprehensive consideration of the geological environment and engineering condition,and low cost,fast speed,and can solve the block structure of the representative experience estimation method.The shear strength of structural plane is estimated by JRC-JCS model,and the shear structure parameters are obtained.On the rock of phyllite uniaxial compression experiments of rock mechanics parameters.(3)Based on the in-situ measurement of rock strata,the geological model is established by using 3DEC discrete element software.Analysis of deformation and failure characteristics of thin wall rock.The tunnel method and the supporting method of simulation.The engineering measures that should be taken during the construction of tunnel are put forward.In order to provide the necessary guidance for the design and construction of the tunnel,and provide technical support for the stability of the tunnel in the design and construction. |
PDF Full Text Request