考虑渣土特征的盾构施工力学动态耦合仿真研究

Dynamic coupling simulation of shield construction mechanics considering characteristics of soils

土压平衡盾构渣土作为开挖面支护力与土仓压力之间的传递介质,其力学性能直接影响到土仓压力的控制、开挖面支护力大小和地层变形等。通过编制离散元和有限差分耦合程序,模拟了土压平衡盾构机动态掘进过程,分析了渣土改良对土仓压力传递性和开挖面地层响应的影响。研究结果表明:盾构掘进过程中土仓压力会出现一定的波动幅度,越靠近刀盘,压力的波动幅度越大。刀盘转动角度对土仓压力有一定的影响。刀盘面板转至监测点水平线上时土压力较大,刀盘开口转至监测点水平线上时土压力较小。渣土改良能增大土仓压力传递系数,降低土仓压力的离散性。压力传递系数不是一个稳定值,而是一个受刀盘转动角度影响的变化值。

The soils are a transfer medium between supporting force of excavation face and earth pressure of soil chamber, and their performance directly affect the control of earth pressure of soil chamber, the supporting force of excavation faces, and the deformation of soil stratum, and subsequently the stability of surrounding buildings. Through the preparation of coupling procedures between discrete element and finite difference element, the dynamic excavation process of earth pressure balance shield is realized, and the effects of soil conditioning on transfer of earth pressure and response of excavation surface formation are analyzed. The results show that the earth pressure of soil chamber is not a stable value, which is a certain range of fluctuations, and the closer its distance to the cutterhead, the greater the pressure fluctuations in the process of shield tunneling. Under the excavation of shield machine, the rotation angle of cutterhead has certain influences on the internal and external earth pressures of soil chamber. The pressures are relatively large when the panel of cutterhead goes to the horizontal line of the monitoring point, whereas they are relatively small when the opening of cutterhead goes to the horizontal line of the monitoring point. The soil conditioning increases the transfer coefficient, which is not a constant, but a variable value affected by the rotation angle of cutterhead, and it reduces dispersion of earth pressures.