Abstract:
The long-term structural safety issues of water-rich tunnels under complex hydrogeological conditions during operation period and their mutual interaction mechanism with groundwater environment are receiving increasing attention. To study the evolution process of seepage and stress field of urban tunnels with small interval and propose reasonable waterproof-drainage methods, the model tests and numerical studies on seepage are carried out based on the Kexuecheng Tunnel in Chongqing City. The evolution process of water and earth pressure on the lining structures is revealed. Subsequently, a proactive control technology for groundwater environmental protection based on the collaborative regulation of drainage and structural safety is proposed. The results indicate that the precipitation funnels formed by the left and right holes of urba tunnels with a small interval partially overlap and affect each other in space. The water pressure exhibits a W-shaped distribution in the horizontal direction, gradually evolving into a concave arc shape as the burial depth increases or decreases. The horizontal influence range of the seepage field and stress field exceeds 80 meters. The reduction effects of grouting circle on water pressure and surrounding rock pressure decrease with the increase of water head height. When the water head height is 30~50 m, the reduction ratio of grouting circle to the total load is about 18.6%~40%. The distribution of earth and water pressure of tunnels with small interval shows significant asymmetry. Under heavy rainfall conditions, the evolution process of the total load on the lining can be divided into three stages: slow growth, rapid growth and gradual stability phase. The secondary lining cracking and water inrush disasters caused by high water pressure are mainly concentrated at the haunch, arch foot and bottom of tunnel. For high water pressure sections of urban tunnels with small interval, it is recommended to add drainage blind pipes at the inverted arch. In ecologically sensitive areas, the active regulation technology should be adopted for groundwater discharge in tunnels to protect the ecological balance of groundwater environment.