The detonation of high explosives (HE) in soil generates high intensity stress wave, which may induce soil liquefaction and thus cause damage to surface structures in a larger area. A commonly used criterion for the soil liquefaction is the residual excess pore pressure ratio. In order for such a criterion to be applied directly in a numerical analysis, it will be desirable if the soil is modelled as a multi-phase medium such that the stress and pressure in the individual constituents, namely the solid particles, pore water and air, can be resolved. In this paper, a numerical three-phase soil model is employed for the simulation of the effect of blast-induced soil liquefaction on surface structures. The simulation model uses a full coupled modelling approach, where the HE charge, soil medium and the surface structure are all explicitly included. To tackle the large deformation in the area surrounding the charge, the meshfree SPH model is considered, whereas the remaining domain including the surface structure is modelled by Lagrangian finite elements. Numerical case studies are presented to demonstrate the model implementation and examine the characteristic responses. Results indicate that with the proposed modelling methodology it is possible to reproduce the soil liquefaction process and the subsequent effect on surface structure under blast loading. (C) 2011 Elsevier B.V. All rights reserved.