The results confirmed the validity and reliability of the improved interface model. A zone may belong to many groups in different slots, up to a maximum of 128. Use of the group logic is described in Groups.This command may take the form zone group 'slotname groupname' quotation marks required, spaces at equals sign ignored where slotname is the slot assignment and groupname is the group name. Results of the numerical tests show good agreement with the results obtained from theoretical calculations, indicating that the model incorporated into FLAC3D can simulate the nonlinear strain-softening behavior of interfaces involving geosynthetic materials. Add group name s to the zones in the range. A numerical simulation of a direct shear test for geosynthetic interfaces was conducted to verify that the interface model was implemented correctly. XSite is a powerful three-dimensional hydraulic fracturing numerical simulation program based on the Synthetic Rock Mass (SRM) and Lattice methods.XSite is capable of modeling multiple wellbores with multiple stages and clusters, including open-hole completions and perforation tunnels. In order to simulate the strain-softening characteristics of interfaces, a nonlinear strain-softening interface constitutive model was incorporated into fast Lagrange analysis of continua in three dimensions (FLAC 3D) through a user-defined program in the FISH environment. Due to the complexity of soil-structure interaction, simple constitutive models typically used for interface elements in general computer programs cannot satisfy the requirements of discontinuous deformation analysis of structures that contain different interfaces.