Study Of Deformation Effects And Control For High-speed Railway Subgrade Influenced By Active Fault

The safety risk of high-speed railway when crossing active fault is a key scientific and technological problem to be solved urgently.Based on the subgrade engineering of new built Xu-Yan High-speed Railway crossing Tan-Lu Fault,this paper put the deformation effect of high-speed railway subgrade under the influence of active faults and control as the research target,and take in-situ test,laboratory test,theoretical analysis,numerical calculation,large-scale shaking table model test and other research methods,in view of active faults’both creep rupture and stick-slip vibration.The deformation effects and control problems of high-speed railway subgrade engineering under three characteristics of active faults,including creep slip dislocation,superposition of creep slip and vibration and seismic dislocation are studied and analyzed comprehensively.The main research achievements of this paper are as follows:1.Based on the comprehensive analysis of site survey,drilling profile exploration and geophysical exploration information,the structural characteristics,geological characteristics,geometric elements,activity characteristics and motion properties of Xu-Yan high-speed railway spanning the Tan-Lu active fault are determined,which lays the foundation of engineering geology for the subsequent research.2.The three-dimensional numerical analysis model of"bedrock-overburden-subgrade structure"is established,which can take into account the creep slip activity characteristics of faults.The deformation effect and force characteristics of subgrade under the creep slip displacement of faults are analyzed.(1)The specific influence and sensitivity of 7 factors,such as fault motion mode,creep slip momentum,fault dip angle and overburden thickness are clarified.(2)Reveal the stress conduction path in the process of creep slip dislocation development;(3)Under the action of fault creep slip,there are critical creep slip quantityand critical overburden thicknessd_c,which make the subgrade irregular range stable.The critical creep slip quantity and critical overburden thickness under different fault movement conditions are given respectively.(4)According to the different deformation characteristics and stress response of subgrade,the normal fault is divided by 60°dip angle,and the reverse fault is divided by 45°dip angle.(5)The effect of geogrid-reinforced subgrade resistance to such deformation and the influencing factors are analyzed,and the reinforcement design suggestions are put forward.3.A three-dimensional analysis model of high-speed railway subgrade structure with straddle active fault is established,which comprehensively reflects the effect of superposition of creep slip and creep vibration on subgrade deformation and smoothness.The seismic and shear resistance properties of reinforced subgrade and their influencing factors are analyzed.(1)The concept of"active fracture affected section",which reflects the characteristics of high-speed railway subgrade engineering,is put forward;(2)According to the active characteristics of Tan-Lu Fault,the length of"active fault influence section"of Xu-Yan High-speed railway subgrade can be considered as not less than 120m;(3)Determine the seismic and fracture reinforcement range of subgrade and foundation.4.A two-stage vibration model test method for subgrade engineering that can simulate the characteristics of fracture activity is proposed,and a large-scale two-stage vibration model test based on the characteristics of active fracture subgrade of Xu-Yan high-speed railway is carried out to study the vibration response,deformation effect and reinforcement effect of subgrade structure under the influence of fracture activity.(1)The inertial effect characteristics,force deformation characteristics and earthquake-induced failure state of the overlaid and non-overlaid reinforced subgrade and the foundation under the action of fault seismic dislocation are comparatively studied.(2)The seismic and fault resistance differences of related structural measures are compared;(3)It puts forward the strengthening countermeasures of seismic and fracture resistance,such as the overlaying reinforcement type,the appropriate reduction of the reinforcement spacing and the composite foundation of pipe pile.