Simulatiomn And Analysis On Dynamic Responses Of Soils Around Sole-hole Double-track Tunnel Induced By Subway Train During Operation

Subway trains can cause the surrounding soils dynamic responses including acceleration, stress, strain, displacement, and pore water pressure, etc. The stratum, which the subway tunnel passes through. has complicated engineering geological condition, so the above mentioned dynamic responses probably caused by subway train operation to the engineering property of the surrounding soils cannot be ignored. At present, systematic research hast not yet been carried out at home and abroad for the dynamic responses of the soils around sole-hole double-track tunnel. In this article, the levee section near the north of the Yangtze River in this area is taken as an example to simulate the above mentioned dynamic responses caused by subway train operation through PLAXIS 2D finite element analysis and meanwhile analyze the liquefiable property of the sandy soil of the tunnel substratum. The following conclusions are obtained:(1) The dynamic effect of the train can cause the surrounding soils to have periodically changed dynamic responses. During the train passing period, there are 24 peak values respectively corresponding to the effects of 12 bogies and 24 wheel sets of a single train during the wheel-track contacting process.(2) During the train passing period, at the substratum and the waist part of the tunnel, the acceleration is attenuated along with the increase of the distance away from the tunnel center. During the propagation process, the surface acceleration has a maximum value at the horizontal place 10m away from the tunnel center.(3) The dynamic stress peak of the basement in single-track working condition is about 3.6kPa while that in double-track working condition is about 7.2kPa, so the dynamic stress generated in double-track working condition to the surrounding soils is two times of that generated in single-track working condition. Meanwhile, such dynamic stress has a fast attenuation speed within the range 5m below the tunnel basement.And the dynamic stress decreased in exponential type with the distance of the basement of tunnel.(4) The compressive strain of the surrounding soils in single-track working condition is obviously less than that in double-track working condition, and the resilience strain of the surrounding soils in double-track working condition is greater than that in single-track working condition.(5) The excess static pore water pressure peak of the basement in single-track working condition is about 2.5kPa while that in double-track working condition is about 5kPa, and the excess static pore water pressure peak decreased in exponential type with the distance of the basement of tunnel.(6) The specific value of the pore water pressure of the tunnel substratum and the total stress fluctuates around 0.6, and the silty sand layer of the substratum has a weak liquefiable property.