土压平衡盾构施工引起的挤土效应研究

土压平衡盾构施工通常会对周围土体产生挤压作用,导致地面隆起和深层土体向远离隧道方向移动。考虑土体的初始应力场,假定土体是均匀线弹性材料,通过向掘进机周围土体施加向外侧的椭圆形径向位移来模拟盾构挤土过程,在假定小应变情况下,推导了半无限空间中土体位移场的近似解析解。考虑空间效应,给出了修正计算公式,并作了一个算例分析。分析结果表明:过大的支护压力、掘进机偏斜、掘进机与土体的摩阻力以及注浆压力都会引起挤土效应,产生的地面隆起最高点位于轴线两侧,挤土过程会减小施工结束时的沉降值和沉降槽宽度,且所得理论计算结果与实测数据较吻合。

STUDY ON SOIL-COMPACTING EFFECTS INDUCED BY EARTH PRESSURE BALANCE SHIELD CONSTRUCTION

Earth pressure balance(EPB) shield construction often has soil-compacting effects on its surrounding soil.It results in the surface upheaval and moving away of deep soil from the tunnels.The soil is assumed to be a kind of uniform linear-elastic material and the initial stress field of the soil is considered.Through the simulation of soil-compacting process by applying an outward elliptic radial displacement to the surrounding soil of shield,the approximately analytical solutions of soil displacement fields in half space are obtained in small strains.Considering the spatial effectst,he modified calculation formula is presented.Alsot,he analysis of computation for a case by proposed formula is made.It shows that excessive support pressure,deflexion of shield,the friction between shield and soil,and the grout pressure will induce the compacting effects.The maximum surface upheaval is at both sides of axes.In addition,the heaving process will reduce the total magnitude and width of the ground surface settlement troughs after the construction being completed.The calculated results here are in accordance with the measured ones.