Vibration Characteristics of Permafrost Embankment Induced by Passing Trains in Qinghai-Tibet Railway in Winter

Abstract

The vibration characteristics of embankment induced by passing trains in the Qinghai-Tibet railway were investigated, and the effects of vibratory load of train on soil-in-ice layer were quantitatively evaluated, based on the self-programming software of vehicle-track-embankment dynamic coupled system. The results indicate that: (1) the maximum dynamic compressive stress induced by locomotives is apparently higher than that by trailers. (2) Vibrational energy of the embankment top surface concentrates on the interval from 0.5Hz to 10Hz, and dominant frequency of soil-in-ice layer top surface is within 3Hz; (3) The phenomenon of stress concentration emerging in ballast at rail supporting position is apparent, and the distribution of maximum dynamic compressive stress of roadbed surface is in the shape of saddle. (4) Vibratory load of train has main effect on embankment in an ellipse-shaped zone about 6m under sleeper. (5) The maximum dynamic compressive stress level of soil-in-ice layer top surface induced by trailers is about 16.7~19.8% that of embankment top surface, and negative exponential function is used to fit the attenuation relationship of embankment dynamic compressive stress versus depth. (6) Embankment vibration displacement is predominant in the vertical direction, and the dynamic displacement of soil-in-ice layer top surface can be neglected. The conclusions are the reliable theoretical basis for engineering design and safety analysis of Qinghai-Tibet railway operation. INTRODUCTION With the opening to traffic of Qinghai-Tibet Railway, China scientific academia has made significant progress in the world problem of road building engineering in permafrost regions. Currently, dynamic performance of embankment with frozen layers and simulation of geothermal field mechanism have been further researched by domestic and foreign scholars, and great achievements has been ICCTP 2009: Critical Issues in Transportation Systems Planning, Development, and Management ©2009 ASCE 973