砂土层注浆引起地表隆起机制分析及试验研究

隧道穿越砂土层易发生涌水涌沙、塌方等灾害,注浆是软弱砂土地层常用的加固方式,但浅埋隧道的预注浆极易引起地表隆起。笔者采用数值仿真、模拟实验与现场试验系统研究了注浆抬升效应的机制,结果表明,砂土层注浆引起地层抬升的体积由于地层压缩而逐步耗散,地表显现部分按高斯函数的形状分布。依据砂土层抬升模拟试验与现场监测数据,将抬升过程分为砂土体压缩、裂缝产生与发展、圆台抬升3个阶段,通过试验研究砂土层抬升过程压力、位移变化规律,得到地表隆起曲线与注浆量、加固宽度、地层埋深、地层力学参数之间的定量关系,给出了估算公式,并依托青岛地铁2号线开展现场试验进行验证,希望能够对类似工程提供借鉴。

Experimental Study on Ground Surface Heave Affected by Grouting in Sandy Soil Layer

Tunnel through the sandy soil layer is apt to cause the disaster like gushing water, sand disasters and landslide, as grouting is the common reinforcing method in soft sandy soil layer. However, Pre-grouting in shallow tunnel easily causes ground surface heave. Adopting numerical simulation, analogue signal and field investigation, the mechanism of pre-grouting lifting effect is studied. The results show that pre-grouting in sandy soil layer can lead to ground surface heave, some of volume dissipate because of formation compression, the rest of the volume distributing on ground surface as shape of Gaussian function. Conduct uplifting in sandy soil layer simulation test, divide uplifting process to three phases: sandy soil layer compression, formation and expansion of cracks, uplifting as a circular truncated cone. Through the experimental study on the variation of pressure and displacement during uplift in sandy soil layer, obtain quantitative relation of surface uplift curve related to grouting amount、grouting range width、grouting formation depth、sandy soil mechanics parameters, and the quantitative relation is verified and apply to pre-grouting engineering in Qingdao metro line 2, with the hope to provide reference for similar projects.