Variation of stress state of foundation soils induced by running subway

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.