Abstract:

The stability of surrounding rock in soilsand strata in Yangcheng Tunnel on Menghua Railway is studied by field test, laboratory test and numerical simulation; and the influences of strata types and thicknesses on surrounding rock deformation, plastic zone and supporting structure stress are emphatically discussed. The results show that: （1） Compared to single stratum, the soilsand strata would affect the distribution of stress around the tunnel, the plastic zone is easier to appear in surrounding rock around soilsand interface, and the deformation properties of the soilsand strata are much closer to soft and weak sand stratum. （2） There is a larger horizontal convergence and tensile stress at the interface of soilsand strata. （3） As increase of the proportion of sand, the settlement of tunnel crown top and surrounding increases, and the stress of supporting structure of bench at the interface would develop to a higher peak in advance. （4） When the interface locates in top heading, large plastic deformation would occur to surrounding rock, and the support structure would bear much larger stress, which is the worst situation.

Key words: railway tunnel, interface of soilsand strata, surrounding rock stability, field test, laboratory test, numerical simulation