FINITE ELEMENT ANALYSIS OF EFFECTS OF STICK-SLIP MOVEMENT OF THE SEISMOGENIC FAULT ON THE DEFORMATION OF THE QINGHAI-TIBET RAILWAY——A CASE STUDY OF THE EAST KUNLUN ACTIVE FAULT

The East Kunlun fault(EKF) is one of the present-day most active,left-lateral strike-slip seismogenic faults in the northern Qinghai-Tibet Plateau.Future seismic activities or abrupt strike-slip movement of the EKF will cause serious engineering-geological problems to the Qinghai-Tibet Railway.On the basis of the geometric and kinematic characteristics of the EKF,the deformation effects of the rails occurring when the epicenter of a future earthquake is located near the railway were simulated,with 8 m horizontal left-lateral displacement added.The results show that the bedrock moves 8 m en masse when the epicenter is located near the railway,while the Quaternary loose sediments and groundsill are deformed.The horizontal diaplacement of the Quaternary close to the fault is obviously smaller from above downward,while the rails and groundsill show successive left-lateral crooked deformation for about 25 m.There occur a NE-trending tensional graben and a NW-trending seismic drumlin on the east and west sides of the railway respectively.The rails are seriously distorted near the fault and the stress of the rails is reduced toward both sidess of the fault and the maximum shear stress plane of the rails is perpendicular to the direction of elongation of the rails;therefore the rails are most likely to be subjected to shear once an earthquake happens.On the basis of the simulation,the paper puts forward such countermeasures as widening of the groundsill and replacement of the soil layer near the fault.