为研究砂卵石隧道开挖过程中洞顶上覆土体的应力变化规律，以某市轨道交通1号线砂卵石地层中地铁隧道开挖为研究背景，采用PFC2D颗粒流程序，建立隧道-土体颗粒流模型，对台阶法隧道开挖全过程引起的洞顶上覆土层的应力扰动规律进行细观数值模拟研究。研究结果表明： 1）开挖初期，隧道上覆土层的应力扰动作用明显，上覆土体有一个明显的应力重新分配到再平衡过程； 2）环形开挖对洞顶上覆土层产生的应力扰动最为明显； 3）开挖对竖向应力产生的扰动作用强于水平应力。本文研究结果与实际工程较为吻合，分析结果可为今后砂粒卵石地层隧道施工提供指导。

The tunnelsoil particle flow model of a metro tunnel on a rail transit line No. 1 in sandcobble strata is established by particle flow code 2D (PFC2D); the stress variation laws of overlying soil induced by bench method tunnel excavated are studied and numerically simulated. The study results show that: 1) During the initial excavation phase, the stress disturbance and redistribution of the overlying soil are obvious. 2) The annular excavation affects the stress distribution of the overlying soil most obviously. 3) The excavation disturbance effect on the vertical stress is stronger than that on the horizontal one. The results coincide with the actual monitoring results and can provide theoretical guidance for tunnel excavation in sandycobble strata.