Based on the mass conservation of fluid

Darcy law and elastic constitutive equation of expansive soil

two-dimensional equations of coupled seepage and deformation in expansive soil are obtained. Combined with the field soaking test on expansive soil foundation under low embankment of Yun-Gui high-speed railway

then both the numerical simulation considering coupling and that without considering coupling are used to analyze the swelling deformation characteristics of expansive soil foundation under low embankment. The study results indicate that the swelling deformation of ground surface can be fitted with hyperbola in the coupled case

but it increases gradually with time in the uncoupled case. The swelling deformation obtained from the numerical simulation which did not consider coupling is less than that obtained from the numerical simulation considering coupling at the same time. The relative expansion ratio decreases along the depth of foundation in the coupled and uncoupled case. In addition

the numerical calculated values are compared with test results in field. It is pointed out that the numerical simulation without considering the effects of coupling is difficult to describe the swelling deformation of expansive soil foundation under the artificial soaking condition. On the other hand

the results from the numerical simulation considering the impacts of coupling agree well with the measured results.