Preventing Water Outburst in Excavation in Subsea Tunnel

With rapid development of economy and society, many infrastructure of transportation logistics are being constructed all over the world. Xiamen subsea tunnel is an important door which connects Xiamen mainland with Xiang'an district, and is the first heavy section subsea tunnel in Chinese Mainland. Beach cofferdam part in Xiang'an tunnel faces risks of instability inrush of water and water outburst when excavation through rich water sand bed. Water outburst and drift sand happen and big pit appears in ground surface when service tunnel driving to NK12+088, some measurements such as draining, grouting for sealing water and jet grouting pile reinforcement. In order to prevent project from water outburst, in this paper, the minimum impermeable layer thickness which keep tunnel stability is proposed by project analogism and numerical calculation. Furthermore, the feasibility about layout of jet grouting pile reinforcement when encountering above-mentioned risk is also studied. At last, the detailed suggestions for this project are proposed according to the results of numerical simulation.