盾构下穿河岸开挖面支护压力调整策略

Adjustment of Excavation Face's Support Pressure for Tunneling beneath Banks

对于以盾构施工的隧道工程,开挖面支护压力是控制土体稳定的关键因素之一。在隧道线型及地表起伏平缓的区间推进时,盾构施工参数包括开挖面支护压力有着充分的时间及空间,根据监测数据得到修正,并最终确定最优值。但对于存在较大变化的施工环境,施工参数必须迅速调整以减小对土体原有状态的扰动。盾构下穿河岸即属此类情况,此时盾构覆土急剧减少,根据监测数据调整施工参数往往不能及时反映这一变化情况。而根据覆土调整则可能导致支护压力突变,引起地表变形及周边建构筑物,特别是防汛墙的破坏。本文通过经典弹性力学求解河岸区地下应力场,探讨开挖面支护压力理论值的变化情况,以此作为调整施工参数的理论依据。

For the tunnel constructed by shield machine, the support pressure of excavation face is one of the key factors to control soil stability. When the distance between ground and the centerline of tunnel is relatively stable, the construction parameters, including the support pressure, will have sufficient time and distance, according to monitoring data, to be adjusted, and ultimately the optimal value can be obtained. However, there are big changes for the construction environments usually; the construction parameters must be adjusted timely to reduce the disturbance to soil ＇ s original state. Tunneling beneath a river bank is such a case, and the depths of the tunnel reduce drastically, the monitoring data can not reflect this change in time. The usual practice may lead to mutations in the support pressure, causing surface deformation and damage to the surrounding building structures, especially the flood wall. In this paper, efforts to provide theoretical guidance for the construction are made by solving stress field beneath a bank with classical elasticity theory and discussing the discipline of theoretical changes.