土压平衡矩形顶管施工引起的地表沉降探究

顶管施工引起周围土体移动会对路面结构层造成破坏。采用大断面矩形土压平衡顶管顶进工法所引起的地表沉降一直是岩土工程领域技术工作者所关注的热点与难点之一。通过内蒙古科技大学地下过街通道工程,分析了路基变形的实测数据,Peck公式对矩形顶管地表变形预测的适用性,数值模拟不同覆土深度下的顶管施工对地表的变形影响。研究表明:顶进时轴线上的纵向测点变形总趋势是先隆起,后沉降,并趋于稳定状态;横断面上位于轴线10 m左右范围内为主要影响区域,在此范围内沉降槽体积约占总体积的90%;当地层损失率V_l取0.4%,沉降槽宽度参数K取0.4时,实测值与Peck公式法的预测结果曲线拟合较好;当覆土深度增加,地表沉降值逐渐减小,且沉降范围逐渐增大。研究成果为大断面土压平衡矩形顶管与类似工程的施工提供了理论参考及应用借鉴。

Ground Subsidence Caused by Earth Pressure Balanced Rectangular Pipe Jacking Construction

The ground subsidence caused by rectangular soil pressure balanced pipe jacking construction in large section would damage the pavement structure layer, which has always been a difficulty and hot topic in geotechnical engineering. With the underground passage project in the Inner Mongolia University of Science and Technology as a case study, we analyzed the measured data of subgrade deformation and the applicability of Peck’s formula in predicting ground subsidence caused by rectangular pipe jacking, and also simulated the influence of pipe jacking construction in the presence of different soil depths on ground subsidence numerically. We found that, in general, measuring points in longitudinal direction on the jacking axis bulged at first, and then subsided and subsequently tended to be stable; in terms of cross section, pipe jacking affected an area within 10 meters of the axis, where the volume of settling trough occupied 90% of the total volume. When soil strata loss rate equals 0.4% and width parameter K of settling trough equals 0.4, the measured value agrees well with the results predicted by Peck’s formula. With the increase of overburden soil depth, the surface subsidence decreased gradually, and the settlement range gradually increased. The research results provide theoretical reference and application value for the construction of large cross-section soil pressure balanced rectangular pipe jacking and similar projects.