Abstract:

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.

Key words:

shield tunnel, sandy stratum, water gushingsand bursting, transparent soil, model test