Objective The anti-floating stability of metro station structures is one of the key technical issues in the construction of urban rail transit. Therefore, it is necessary to study the distribution characteristics of pore water pressure at the bottom slab of metro station structures (abbreviated as “structure bottom pore water pressure”).

Method Taking a certain metro station project in Xiamen City as an example, field monitoring and laboratory model tests are employed to study the distribution and variation laws of structure bottom pore water pressure under different strata conditions.

Result & Conclusion  The variation process of pore water pressure in the soil below the bottom slab of metro stations can be divided into four typical stages: fluctuation near zero, slight growth, gradual rise, and fluctuation with the ground water level. When with a retaining structure, the pore water pressure is maximum at the center of the station bottom slab, while smaller on the both sides; when without a retaining structure, it is minimum at the center of the station structure bottom slab and larger on the both sides. In typical granite strata, the buoyancy force acting on the metro station structure is less than the hydrostatic pressure. Specifically, the pore water pressure reduction coefficients for residual sandy cohesive soil, completely weathered granite, strongly weathered granite, and moderately weathered granite strata are approximately 0.75~0.87, 0.84~0.94, 0.87~0.90, and 0.82~0.87, respectively.