地铁列车运营引起的地基土应力状态变化分析

Variation of stress state of foundation soils induced by running subway

将地铁列车移动荷载简化为多个移动轮轴荷载,基于弹性半空间内Mindlin解,分别以单个轮轴荷载和列车移动荷载为例,研究了地铁列车荷载作用线正下方地基土中的动应力特征、应力路径变化及主应力轴旋转,分析了不同隧道埋深下荷载作用线正下方土单元应力状态变化。结果表明,单个轮载移动线正下方计算土单元的主应力轴旋转了180°且方向始终为顺时针。荷载向土单元移动时,隧道埋深越大,下方土单元应力增长也越快。在多个轮载作用下,土单元的动应力和主应力轴旋转具有持续循环特性,循环次数与列车车厢节数有关,由于相邻轮载的影响,一个循环内主应力轴旋转角度并非单调递增或递减,而是具有来回震荡过程的特性。

The moving load of subway train is simplified as a plurality of moving wheel loads. Based on the Mindlin solution in elastic half-space, taking one moving load and one moving train load as examples, in which the characteristics of dynamic stress, stress path and principal stress axis rotation of soil elements under the load-moving line are analyzed. The variation of stress state of soil elements under the load-moving line is studied when the tunnel is at different depths. It is found that the principal stress axis rotates 180° clockwise for the soil elements under the load moving line during one load-moving, when the tunnel is deeper, the stress of soils grows faster. Under multiple wheel load moving, the dynamic stress and principal stress axis rotation of the soil elements perform circulation characteristics continuously. The circulation number relates to the number of train carriages. Because of the effect of the adjacent load, the angle of principal stress axis rotation does not monotonically increase or decrease in one circulation, but it is characterized by a back and forth oscillation process.