粉细砂地层对地铁列车荷载的动力响应及长期变形研究

DYNAMIC RESPONSE AND LONG-TERM CUMULATIVE DEFORMATION OF SILTY SAND STRATUM INDUCED BY METRO TRAIN VIBRATION LOADS

为探明地铁列车荷载作用下粉细砂地层的动力响应特征及长期累积变形发展规律,首先基于南京地铁2号线沉降监测数据,分析了位于粉细砂地层中某区段隧道结构的沉降发展规律;然后采用2.5维数值方法,模拟分析了地铁列车荷载作用下粉细砂地层的振动响应特征;最后,基于振动荷载作用下粉细砂的累积变形经验公式,采用分层总和法研究了粉细砂地层由列车荷载诱发长期累积变形的发展规律。研究结果表明:(1)列车运行引发地铁隧道地基粉细砂地层的动偏应力随着深度的增加呈先增大后减小的变化趋势,其最大值通常出现在隧道底部以下1 m处,最大值约为3.5kPa;(2)列车振动荷载诱发粉细砂地层的长期变形在运营初期发展较快,并在运营1年左右达到稳定,随后缓慢增长,其稳定后的地基总变形量约为15.1mm;(3)由列车振动荷载长期作用诱发的隧道粉细砂地基沉降量约占运营7年后总沉降量值的26%。

The dynamic response characteristics and long-term cumulative deformation development law of silty sand stratum under the metro train load are important engineering topics.In order to study them,the following works are carried out.At first,we analyze the long-term settlement monitoring data of Nanjing Metro Line 2 in typical silty sand stratum.Then,based on two-and-a-half-dimensional(2.5D)numerical method,we analyze the vibration characteristics of silty sand stratum under the train vibration load.Finally,we sum up the cumulative deformation formula of silty sand under vibration load,and use the stratified summation method to study the long-term cumulative deformation development law of silty sand.We have the following results.(1)With the increase of the depth,the dynamic deviator stress of the silty sand layer under the tunnel increases at first and then decreases.Its maximum value usually appears at 1m below the bottom of the tunnel and is about 3.5kPa.(2)The long-term deformation of the silty sand stratum induced by the train vibration load develops rapidly at the initial stage of the metro operation.However,it can reach a stable stage in about one year,then the deformation increases slowly.The total deformation value after stabilization is about 15.1mm.(3)After 7 years of metro operation,the settlement value of the tunnel silty sand foundation induced by the long-term metro vibration loads takes up about 26%of its total settlement value.