Abstract:The internal friction character is one of the basic properties of geomaterial,and the internal friction exists in mechanical elements all the time. However,until now the internal friction is only considered in limit analysis and plastic mechanics,but not included in elastic mechanics and energy theory. It is considered that the internal friction exists whether in plastic state or elastic state,and the mechanical elements of friction material are constituted based on this cognition. According to the research of soil tests,it is presented that the cohesion takes effect firstly,and then the internal friction increases gradually with the increment of deformation. By assuming that the friction factor is proportional to the strain,the internal friction is computed. At last,by imitating the linear elastic mechanics,the nonlinear elastic mechanical model of friction material is established,where the shear modular G is not a constant. The new model and the traditional elastic model are used simultaneously to analyze an elastic foundation. The results indicate that the displacement and the shear stress computed by the new model are smaller than those of the traditional model,which is in agreement with the fact. So it is suitable for geomaterial to adopt the mechanical elements of friction material.