Abstract: It is a basic problem that obtainment of the local stress field from the large stress field. The usual methods consist of two steps including interpolation of stress field or boundary conditions and calculation of the local stress field once again. But the previous methods are too complex, high calculation cost or special for a class of problems to being applied. From the engineering angle of view, it is unessential for the high degree of accuracy as to stress field interpolation affected by the complicated geology construction. So, the improved IDW (inverse distance to a power) method which considers the volume effect is presented aiming to the above problems. Based on this method, the obtainment methods of local stress field, in which two kinds of boundary conditions are proposed, are presented for solving the corresponding plane problems, 3-D ground problems and 3-D underground problems. Their rationalities are verified through the settlement of several cases. Finally, the methods are applied to the stability analysis of high rock slope in Nuozhadu Hydropower Project. The results indicate that the improved IDW method is simple and practical; the corresponding solving methods for local stress field are efficient and of satisfied accuracy.

Key words: in situ stress, IDW(inverse distance to a power), boundary condition, local stress field, slope, tunnel