Study On Tunnel Alteration Surrounding Rock Classification And Mesoscopic Characteristics Of Soil-rock Mixture

Tunnel engineering construction project because of its complex geological conditions,and in the construction phase of the geological conditions in front of the face of the survey is not detailed,many engineering risk factors complex easy to cause serious consequences.This study based on national highway 111 line for paying town to poplar under section of the scenic mountain highway tunnel engineering renovation,based on the matter-element extension method of combining the theory with practice to identify the level of surrounding rock,indoor experiment combined with numerical simulation on the earth-rock aggregate macro-mesoscopic mechanical properties research,the main results as follows:?1?Study the related theory of matter-element extension theory and entropy weight method,and select five indicators that reflect the nature of altered surrounding rock:rock uniaxial compressive strength?Rc?,alteration coefficient?Ja?,rock quality index?RQD?,Groundwater???,rock mass integrity coefficient?Kv?,using the matter-element extension model and the entropy weight method to establish a model for calculation,the results are compared with the site surrounding rock grades,and the accuracy of the results reaches 90.9%.?2?The soil-rock mixture was collected by on-site sampling,the density,moisture content and gradation of soil and block stone were measured indoors,and a cylindrical sample of 50 mm×100 mm was remade.Through the uniaxial test and the triaxial compression test,the physical and mechanical parameters under different stone contents are obtained.Based on the uniaxial and the triaxial test,the compressive strength of the earth-rock mixture and the crack development rules and influencing factors were obtained.?3?PFC^2D was used to model the soil-rock mixture,and the evolution law and influencing factors of the shear zone were studied.At the same time,the macro-microscopic characteristics of the soil-rock mixture were studied based on the micromechanical parameters.The research results show that:Compared with the angle of the long axis of the block stone,the weak surface plays a dominant role in determining the location of the shear zone,and the main fracture surface appears near the weak surface;under the same loading condition,as the stone content increases,The morphology of the shear zone gradually became single,and the fracture analysis of the soil-rock mixture based on crack analysis was a cumulative failure;according to the difference in the stiffness ratio of the block stone and the soil particles,it showed that the specimens with large stiffness ratio had shearing and dilatant effects Decrease,but has little effect on the strain softening before the peak and the residual strength after the failure;based on the evolution of the force chain on the contact force,it is concluded that the transmission of the contact force is the root cause of the inconsistent curve after the peak;based on the force chain group According to the study of the porosity of the structure,the analysis shows that the formation of the shear band and the change of the porosity mainly come from the high-order“Loop”,and when the specimen fails,the high-order“Loop”??plays a dominant role.The determination of the altered surrounding rock grade of the tunnel and the study of the macro-micromechanical properties of the soil-rock mixture have certain significance for the smooth progress of the tunnel construction and the reduction of the tunnel engineering risk,and have reference significance for similar studies.