盾构施工影响下砂土地层变形规律模型试验研究

为了研究盾构施工影响下隧道埋深、地层损失率、颗粒级配对砂土地层变形规律的影响，设计由试验模型箱、隧道开挖模拟装置以及非接触试验监测系统组成的模型试验系统，利用该试验系统对10种试验工况进行研究。试验模型箱是由钢化玻璃板、底部钢板以及刚框架组合而成的开口箱体，砂性地层采用完全烘干的砂土来制作，盾构开挖过程通过一种能够精确控制地层损失率大小的小型圆筒状传动装置来模拟，试验过程中的地层变化利用视频测量系统进行监测。研究结果表明：随着隧道埋深增加，土体扰动范围逐渐向两侧扩展，地表最大沉降值逐渐减小；当隧道埋深临近土拱形成深度时，沉降槽宽度显著增加，隧道上方核心沉降区逐渐减小。地层损失率与沉降槽宽度之间存在明显的线性关系。砂土粒径越大，地表最大沉降值越小，沉降槽宽度越大；当最大粒径与最小粒径比一定时，地层沉降范围内的最大沉降量随着砂土粒径的增大而减小；当最大粒径一定时，地层沉降范围内的最大沉降量随着粒径范围的增大而增大。不同隧道埋深、地层损失率和砂土颗粒级配下的地表沉降曲线均具有类似高斯分布函数的形态特征，向隧道中线处急剧下降，向远处逐渐变缓，与地层变形规律相似。

Model Experimental Study on Stratum Deformation of Shield Tunnelling in Sand

To study the influence of cover depth, ground loss ratio, and particle gradation on the stratum deformation of shield tunnelling in sand, a model test system was designed, which consisted of a test model box, tunnel excavation simulation, and non-contact measurement system. This test system was used to research 10 experimental conditions. The test model box was an open box, which was made up of a tempered glass, bottom steel plate, and rigid frame while the sandy layer was made of completely dried sand. The shield excavation process was simulated by a small cylindrical transmission, which could precisely control the ground loss ratio. The formation changes were monitored by a video measurement system during the test process. First, the results show that with an increase in cover depth, the soil disturbance range gradually expands to both sides, and the maximum settlement value of the ground surface gradually decreases. Settlement through the width increases significantly and the core settlement area above the tunnel decreases gradually as it approaches the depth of the arch. Secondly, there is an obvious linear relationship between stratum deformation and ground loss ratio. Thirdly, the larger the sand particle size, the smaller the maximum settlement value of the ground surface, and the larger the settlement through width. When the ratio of maximum particle size to minimum particle size is constant, the maximum settlement decreases with the increase of particle size of sand. When the maximum particle size is constant, maximum settlement increases with the increase of particle size range in the range of stratum settlement. Finally, the results show the surface settlement curves under different cover depths, ground loss ratios, and particle gradations have similar Gaussian distribution, which drops sharply toward the middle line of the tunnel and gradually becomes slower toward the distance, similar to the law of stratum deformation.