基于透明土的盾构隧道突水涌砂灾变发展试验研究

针对饱和砂土地层盾构隧道施工中的突水涌砂灾害问题，以上海市轨道交通某盾构区间为研究背景，将自主研制的灾变可视化试验模型与透明土技术相结合，对砂土地层隧道顶部结构破损灾变过程的土体流动形态、土颗粒位移速度场进行试验研究。结果表明： 1)盾构隧道突水涌砂灾害发生后，隧道裂隙孔口上方部分区域的土颗粒密实度减小，砂土发生剪切破坏。2)在灾变前期，土颗粒竖向位移场呈椭圆状等值线分布，颗粒位移速度随与隧道中心水平距离的增加而非线性地衰减，当隧道埋深为2D（D为隧道直径）时，水平向影响范围为3D。3)随着灾变的发展，土颗粒位移速度先增大后减小，涌入隧道内的砂水混合物中土颗粒的体积分数占比持续减少，最大程度地还原了隧道突水涌砂后期的灾变现象。

Experimental Study on Water Gushing Sand Burstingin Shield Tunnels Based on Transparent Soil

A case study is conducted on a shield section of Shanghai rail transit to address the problem of water gushing and sand bursting during shield tunneling in saturated sandy stratum. To investigate the flow pattern of soil and velocity field of particle displacement in the soil layer during damage of the top tunnel structure in the sandy stratum, a self developed disaster visualization test model is established, which incorporates transparent soil technology. The results reveal the following: (1) After water gushing sand bursting in shield tunnels, the density of the soil particles at some regions above the tunnel fissure orifice reduces, and shear damage occurs to the soil. (2) In the early stage of the water gushing sand bursting disaster, the vertical displacement field of soil particles shows an elliptical contour distribution; the particle displacement velocity decreases nonlinearly with increasing distance from the tunnel center; when the tunnel burial depth is 2〖WT５《TNR#I》〗D (D〖WT５《TNR》〗 is tunnel diameter), the horizontal impact range is 3〖WT５《TNR#I》〗D.〖WT５《TNR》〗 (3) With the development of the water gushing sand bursting disaster, the displacement velocity of soil particles increases and then decreases, and the proportion of soil particles in the sand water mixture flooding into the tunnel continues to decrease, which is almost similar to the actual water gushing and sand bursting phenomenon in tunnels.