盾构在软土深部地层进行主动开挖时，开挖所采取的地层损失率差异，会使得深部地层土体产生不同的位移以及应力变化，从而对软土深部地层的主动土拱效应产生差异影响。通过调整计算模型中的主动开挖土体范围，设定7种不同的地层损失率，建立地层损失与软土主动土拱效应比例之间的对应关系。通过分析可得： 1）盾构在4倍直径埋深条件下进行主动开挖时，在隧道上方1~2倍直径范围内形成主动土拱作用区域； 2）主动开挖所采取的地层损失率越大，开挖后拱顶处所受到的主动土压力荷载越小，土拱效应发挥越充分，且当地层损失率到达一定值时，盾构开挖所产生的主动土拱效应比例逐渐趋近于稳定临界值。

During shield construction in deep soft soil, different ground loss rates bring various displacement and stress change, and cause impacts on soil arching effect. By adjusting the radius of the excavation area in calculation model, seven kinds of ground loss rate are set, which can establish the corresponding relationship between ground loss and soil arching effect. Through analysis, the results show that: (1) When the shield excavation is carried out in depth with 4 times the diameter, the active areas of arching effect are formed in the range of 1-2 times the diameter above tunnel; (2) With the ground loss rate increasing, the earth pressure load at crown reduced greatly, and the soil arching effect is more obvious. When the ground loss rate reaches a certain value, the soil arching effect of shield tunneling is close to the critical value.