An Elasto-Viscoplastic Model for Sand-Structure interface Mehrnoosh Sheikhsaraf m.sheikhsaraf@cv.iut.ac.ir Date of Submission: June 25, 2018 Department of Civil Engineering Isfahan University of Technology, Isfahan 84156-83111, Iran Degree: M.Sc. Language: Farsi Supervisors: Dr. Hamid Hashemolhosseini (hamidh@cc.iut.ac.ir) Dr. Mahdi Abtahi (mabtahi@cc.iut.ac.ir) What in civil engineering is called the soil-structure interface; describes how the deformations are transmitted from the structure to the soil and vice versa. This process, which plays an important role in calculating and designing more accurate, has been the subject of many past and present research. Structures such as shallow foundations and deep piers, retaining walls, pile and tunnels, are all surrounded by a thin crust of peripheral soil, which is relatively different from the adjacent soil mass. Characteristics of this thin layer are the resources determining the behavior of the boundary of the soil-structure. Obviously, the proper simulation of the interaction phenomenon seems to be based on the use of an appropriate constitutive model for the interface. In the final note, by using a constitutive model of soil-structure interface and its modifications, an elasto-viscoplastic model has been extended; therefore, time-dependent behavior of the soil-structure boundary is simulated and, finally, the simulation of the model is compared with and verified by experimental data. The modified model is based on the bounding surface theory; which follows the non-associated flow rule and has the ability to estimate the behavior of sand in contact with the structure under different strain rates. An elasto-viscoplastic model of contact surface can be implemented in FEM and FDM softwares to improve computation and precisely modelling phenomena such as explosion and sedimentation. Key words Soil-Structure interface, Bounding Surface Model, Rate Dependency, Plasticity, Viscosity