Study On Surrounding Rock Mass Characteristics And Mechanical Behavior Of Tunnel With Miscellaneous Filling

In the course of the construction of urban underground rail traffic,the problem of tunnels traversal artificial miscellaneous filling layers is inevitable all the time.However,the urban artificial miscellaneous filling soil has several characteristics,including: loose structure,low bearing capacity,high compressibility,collapsibility and deformation of secondary consolidation etc.Not only these undesirable properties will have a negative impact on the project,but also increase uncertainty of excavation and maintenance of the tunnel.This paper aiming the theoretical and technical difficulties of underground cutting with shallow overburden in miscellaneous fill tunnels,and comprehensively uses the methods of theoretical analysis,numerical simulation and indoor test methods to analyze characteristics of surrounding rock of miscellaneous filling layers and the behavior of structure.To be specific,Starting from the engineering characteristics and mechanical properties of miscellaneous filling soil,the constitutive relationship of artificial miscellaneous soils is constructed.Then the secondary development and numerical simulations are used to explore the surrounding rock deformation and internal force evolution law of lining during the entire process from excavation to post-maintenance of artificial miscellaneous filling soil tunnels,and including the effects of rainfall infiltration and secondary consolidation effects on unsaturated miscellaneous filling soil tunnels.Therefore,a set of reasonable theoretical system for miscellaneous filling soil are formed.Simultaneously,the present author hopes that the research result could actively fed back to the actual construction site and have a positive influence in the proceeding of design and construction of artificial miscellaneous filling soil tunnels.The main research results are as follows:1.To construct artificial miscellaneous soil constitutive model.First: based on the double yield surface model,the corrected yield surface and parabolic yield surface of the Cambridge model are introduced,and the hardening function is modified while secondary consolidation effect of the miscellaneous soil is considered.Then a new volumetric yield function and shear yield function are established.Under non-associated conditions,the stress-strain increment relation of artificial miscellaneous soil was deduced,the integrated back-off algorithm and the improved Euler integration algorithm with error control were integrated,and the artificial miscellaneous soil constitutive model was implemented using the user subroutine interface UMAT provided by ABAQUS.In the second development,considering the four possible forms of the stiffness matrix of the double yield surface constitutive model,the elastic-plastic stiffness matrix that introduces the time parameters is deduced.2.Through the numerical simulation study on the artificially-filled underground excavation tunnel,the surrounding rock deformation law and the structure stress characteristics of the miscellaneous filling soil tunnel during the excavation process are explored;To put forward reasonable reinforcement measures,and prove its reinforcement effect,focus on deformation of Surrounding rocks and evolution of internal force of lining in miscellaneous filling soil tunnels under the influence of the secondary consolidation effect.3.Based on the one-dimensional simplification algorithm for unsaturated soil consolidation,the secondary consolidation parameters are introduced to derive a one-dimensional consolidation equation for unsaturated soil which is applied for the primary-secondary consolidation coupling of artificial miscellaneous filling soil.4.Through numerical simulation of unsaturated artificial tunnels under infiltration of rainfall,the effect of rainfall on artificially-filled land layers and tunnel lining structures is explored;Trough study the effect of rainfall infiltration on the secondary consolidation effect of artificial miscellaneous filling soil,and analyze the stability of the artificial miscellaneous filling soil tunnel under the dual effects of rainfall and secondary consolidation effects,this part is purposed to put forward reasonable design and construction suggestions.