“…For SPH, EFG, MPM, and CEL, applying boundary conditions is difficult and, moreover, is always inaccurate when solving small-deformation problems or during the early stages of large-deformation problems. By contrast, PFEM that is developed to solve fluid-structure interaction problems (Oñate et al 17,21,22 ) and fluid only problems 23,24 can be employed as an ideal method for avoiding the aforementioned problems and has recently been used to solve problems in geomechanics [25][26][27][28][29][30][31][32][33] . The key feature of PFEM is that nodes are regarded as "particles" and the continuum medium as a cloud of these particles, which transport all the information of the continuum medium (eg, displacements, strains, stresses, material properties, and state variables), allow free movement and even separation from the continuum to which they originally belong.…”