Study On The Deformation Control Of High Speed Railway Subgrade Under The Active Faults

The high-speed railway infrastructure is an important guarantee for the train operation safety.As an important part of the high-speed railway infrastructure,the subgrade plays a great role in crossing the active fault zone.The eastern part of China is in the junction of Eurasian plate and Pacific plate,located on the circum-Pacific seismic belt,where active faults are widely distributed.In the previous research results of the interactions between the active fault and the railway subgrade,in general,the researches on the general speed railway are more than that on the high-speed railway,and that qualitatively stating the treatment measures according to the construction experience are more than that quantitatively pointing out the scope of influence and the scope of destruction.In view of contents mentioned above,this paper is based on the project of "the research on the seismic performances of high railway subgrade crossing active fault zone and foundation",and has its background on the newly-built project of Xu-Su-Huai-Yan high speed railway(design speed is 250km/h)which is across the Tanlu active fault zone.By combined technology means of theoretical analysis and numerical simulation,a three-dimensional finite element model with considering the characteristics of active fault zone is established by adopting the ABAQUS finite element analysis software.Studying and analyzing the deformation characteristics and change rules of high-speed railway subgrade under different fracture activities,and on this basis,discussing the effect of geogrids on the deformation control of high-speed railway subgrade located on the active fault zone.The main research works and results are as follows:(1)Analysed the types of the high-speed railway subgrade crossing the active fault zone,and classifying the active faults according to factors such as the mechanical properties,the slipping rate,the overlying soil thickness and the fault dip.(2)Established the subgrade-soil-rock three-dimensional finite element model,which has considered the characteristics of active faults;confirmed the relationships between the influence scope of the deformation of the high-speed railway subgrade under the action of different types of active faults and the thickness of overlying soil,the fault dip as well as the displacement of the fault;investigated the distribution features of the deformation of the ground to the horizontal direction and the vertical direction;made clear the propagation direction of the fault activity in the soil body and the subgrade;analysed the loading deformation response and disaster-causing mechanism of the high-speed railway subgrade structure under the action of active faults;and put forward the quantitative relation formula between the maximum displacement of the subgrade under the action of translational displacement fault,the thickness of the overlying soil layer and the radius of the circular curve formed by lines under the action of the strike-slip fault.(3)Established the three-dimensional finite element model of reinforced subgrade under the action of active fault,and compared and analysed the optimization effect of subgrade deformation under the action of strike-slip fault,normal fault and reverse fault.Discussed the optimization effect of subgrade deformation under the effect of different laying length,different laying distance and different laying position;and on this basis,proposed the subgrade construction design scheme of the newly-built project of Xu-Su-Huai-Yan high speed railway(design speed is 250km/h)which is across the Tanlu active fault zone,and finally,gave the design proposals for high-speed railway subgrade in the active fault zone.