软土地区矩形顶管施工地表变形控制措施探讨

通过上海软土地层中3个大截面矩形顶管施工实例结果分析,发现矩形顶管推进引起地表变形具有一般规律性。笔者对地表隆沉及局部变形的机理进行了深入分析,并对变形控制措施进行了详细探讨。变形一般规律:地表隆起越大,则相应地表沉降量越小;最大沉降均发生在距始发井5~10 m的范围;当顶管机经过测点后推进约25 m左右时,监测断面上各测点的沉降值已趋于稳定。掘进面的地表隆起主要受顶进推力影响,地表沉降则受土体损失控制。顶管中段的土体损失沉降比较稳定,可通过调整掘进面上方的隆起与最终沉降的量值占比来达到最优变形控制目的。

Discussion on Control Methods of Ground Surface Settlement Caused by Rectangular Pipe Jacking Construction in Soft Soils

Through the analysis on three projects of large cross section rectangular pipe jacking construction in Shanghai soft soil, some general regularity of the earth surface deformation are found. The author makes a deep analysis on the mechanism of surface heave and local deformation,also carries out a detailed study on the deformation control measures . The general rule of ground deformation is as follows: the more ground surface heave induced by pipe jacking, the smaller is corresponding ground surface settlement; the largest settlement occurred in the range of 5~10 m from starting well; when the pipeline machine advanced by measuring point about 25 m, the settlement value of each measuring point on monitoring section has been stabilized. The surface uplift at tunneling surface is mainly controlled by the thrust force and the surface subsidence is affected by the soil loss. The ground loss settlement is stable at middle part of pipe jacking, the optimal deformation controlling can be realized through the adjustment of upper surface uplift and the final settlement value.