Abstract: Shear deformation gradient near the interfaces of the layered rock mass structure face is very obvious under compression and shear loading. The interfaces boundary layer effect of layered rock mass is studied based on couple stress theory. Numerical calculation is implemented by using the finite element method. The results of the couple stress theory and the classical elasticity theory are compared. The interpolation type functions and displacement interpolation formulae are derived for Serendipity element (S-element). The pre-treatment is put into practice by ANSYS. The computing and the post-treatment programs are writen by Matlab for the typical elasticity theory and the couple stress theory. The results show that the influence of couple stress on the shear strain near interfaces of layered rock mass is remarkable. The scale effect is distinct. Compared with the classical elasticity theory, in couple stress theory, strains decrease and the transition region of shear strain emerges near interfaces boundary layer. The abrupt change of the shear strain is also improved but the shear stress is no longer continuous. The characteristic length affects the size of the transition zone. The second shear modulus, Poisson’s ratio and elastic modulus don’t affect the size of the transition zone.

Key words: couple stress, scale effect, layered rock mass, boundary layer effect, finite element method