Abstract:

In order to solve the influence problem of underpass tunnel construction on existing high filling embankment, a threedimensional finite element model is established based on Dafang Tunnel of ChengduGuiyang Railway crossing underneath HangzhouRuili Expressway project. The influence of tunnel construction on overlying strata displacement, surface longitudinal deformation characteristics and the main influence range of underpass construction on various surface feature positions are studied. The results show that: (1)The significant settlement deformation of the high filling embankment layer is caused by the underpass construction, and the overlying strata produce obvious lateral displacement towards the middle of the tunnel. (2)The surface longitudinal deformation caused by the underpass construction can be divided into three zones: the microdeformation zone (the shallow buried settlement area at tunnel portal), the strong deformation zone (the settlement zone of high filling embankment) and the weak deformation zone (the settlement zone of surface). (3)When the tunnel construction is carried out to the characteristic positions such as tunnel portal, retaining wall and road surface, the longitudinal influence range of the surface is 75, 52 and 65 m in front of the excavation respectively, and the displacement of strata within this influence range changes strongly. (4)The dynamic settlement curves of vaults are all of the inverse "S" shape. Combined with the field monitoring data for comparative analysis, the variation trend of the simulated value and the monitored data is basically consistent, and finally relevant construction suggestions and measures are put forward.

Key words: loose high filling embankment layer, tunnel, underpass construction, numerical simulation, settlement law, influence range