基于PIV技术的隧道施工引起的地层变形规律试验研究

Experimental Study on Deformation Law of Stratum Caused by Tunnel Construction Based on Particle Image Velocimetry Technique

为研究隧道施工引起的地层变形规律,设计由试验台架和非接触式图像测量系统组成的模型试验系统。利用该系统,以干砂为填料,通过电机牵引隧道使其下沉来模拟盾构掘进过程中因停滞时间过长引起的仰拱变形进而导致的隧道上方地层的沉降变形。通过对不同隧道埋深、地层损失率、土体相对密实度等工况下的地层沉降模式展开研究,得出以下结论:1)不同隧道埋深、地层损失率和土体相对密实度工况下,地层内部的破坏模式和变形规律大致相似,形状类似“漏斗”。距离隧道越远,地表沉降值越小;不同工况下的地表沉降曲线均符合高斯分布。2)地表沉降槽宽度系数与隧道半径、土体抗剪强度参数以及隧道埋深等因素相关。通过对试验结果进行量化分析得出沉降槽宽度系数的修正公式。最后,将修正后的公式与目前已有的研究结果以及工程实测数据进行对比,验证了修正公式的合理性。该公式可用于砂土地区隧道施工引起的地表沉降预测。

A model test system comprising a model rig and a non-contact measurement system is designed for investigating the deformation law of the stratum caused by tunnel construction.In this system,dry sand is used as a filler.The stratum deformation and settlement upon the tunnel,which is due to the invert arch deformation caused by a long stop time of shield,is simulated by motor towing.The results of investigating the settlement pattern of the stratum under various buried depths of the tunnel,stratum loss rates,and soil compactness conditions show that:(1)The failure modes of the stratum are roughly similar,but exactly similar to the shape of a funnel under various conditions;the ground settlement decreases as the distance from the tunnel increases,but the ground settlement curves under various conditions are consistent with the Gaussian distribution function.(2)The width coefficient of the ground settlement trough is related to the tunnel radius,shear strength parameters of soil,and buried depth of the tunnel.The modified formula of the settlement trough width coefficient is obtained by a quantitative analysis of the test results.Finally,the modified formula is compared with that in current research and the measured data to verify its reasonableness.In conclusion,the formula can be used to predict the ground settlement in sandy soil areas.