STUDY OF THE LOADING PATTERN ON CIRCULAR TUNNEL IN SOFT GROUND
软土地层中的圆形隧道载荷模式研究

Abstrct The influencing factors of the loading on the circular tunnel in soft ground, such as tunnel embedment depth from the ground surface, construction techniques, and theoretical calculating approaches, are studied. The analysis of site-measured earth pressure on three tunnels in Shanghai soft ground shows that the earth pressure and magnitude distributions are not only varied with the method of tunnel construction (EPB shield or extruding shield method), but also dependent on constructing and servicing phases. In constructing phase, for extruding shield method, the deformed tunnel lining is like a duck egg standing on end, while for EPB shield, it is like a lying duck egg. According to the Rankin dynamic and static earth pressure theory, the calculated earth pressure magnitudes are less than those measured in site, and the gap between them is fairly big. Based on the presented coefficients of lateral earth pressure and the assumption of cosine function of the earth pressure on circular tunnel in this paper, the calculated magnitudes have good agreement with the site-measured values for the studied three tunnels in Shanghai soft ground.