Abstract
In recent years, subway has developed rapidly in many cities of China. However, the environmental problems caused by train vibration load, such as the large settlement of surrounding ground around tunnels, can’t be ignored. The subway tunnels in shanghai mainly lie in the 3rd layer of muddy-silty clay or the 4th layer of muddy clay. These two layers of clay were especially soft and sensitive to vibration load. In this paper, a numerical study on long-time deformation characteristics of soft clay around the tunnel of Shanghai Metro Line 9 under train vibration load was presented. The numerical simulation adopted an elasticplastic constitutive model that can take into account the long-term accumulation of soil deformation and excess pore water pressure under a huge number of cyclic loadings. The simulated results, including long-time displacement of soils around the tunnel, ground surface subsidence, and the variation of excess pore water pressure, were analyzed and discussed. The final settlement of surrounding ground was predicted through analyzing the variation tendency of maximum vertical displacement of soil. By comparing the simulated results and the measured data, it was proved that the simulated results were consistent with the measured data. Therefore, the long-term deformation of soil around subway tunnels under vibration load can be evaluated and predicted by the numerical method presented in this paper.
1. INTRODUCTION
Metro has become an important part of urban public traffic because of the less occupation of land and space, fast speed and little pollution. Subway effectively eases the pressure on increasingly overloaded urban traffic and expands the available space in the city. According to statistics, the total length of metro lines has reached 1200km in China. In addition, a large number of city’s metro construction projects have been approved. With the rapid development of city rail traffic, a new round of metro construction boom will inevitably be set off. But the environmental problems caused by city rail traffic construction cannot be ignored. Among the problems, environmental impact of vibration induced by metro is particularly significant
