Coupled flow-deformation analysis in saturated and unsaturated porous media is important in many geophysics, engineering applications and industrial processes. Typical examples of these problems include rainfall-induced slope failure and landslides, gravity-driven flows such as debris flows, failure of man-made structure (e.g. dykes and embankments) due to internal seepage erosion or overtopping flows during intensive rainfall and flooding events, oil gas extraction in energy sector or carbon dioxide sequestration in geological formations. All of these applications typically involve complex flow patterns and large deformations of the solid phase that require both an advanced theoretical framework and a robust computational platform to capture the salient mechanisms of the complex multiphase interactions. In the past few decades, mesh-based methods such as the finite element method (FEM) has been commonly known as a robust numerical tool for solving such problems. Although giving satisfactory results, FEM or similar mesh-based approaches has some certain limitations. For instance, it is impossible for FEM to simulate complex problems involving large deformation and flow failure of granular materials, such as internal erosion due to seepage flow, piping or transportation of contaminated substances in the subsurface or fractured media, in which the Lagrangian description of fluid flow is explicitly required. In fact, mesh-based approaches are most suitable for the pre-failure regime with small deformation of the porous media. In the post-failure regime involving large deformations (for example catastrophic slope-failure/landslide with rapid progressive failure and long run distance of solid phase), mesh-based approaches suffer from severe mesh distortion issues even when the updated Lagrangian discretisation or adaptive re-meshing is adopted. In these particular problems, mesh-free methods offer an excellent alternative to model large deformation and failure behaviour saturated/unsaturated porous medium. In this talk, Bui will discuss several challenges associated with these types of problems and present recent attempts in his group to advance the mesh-free smoothed particle hydrodynamics (SPH) method to tackle these complex problems.