Abstract: The limitations of the present 3D rock stress measurements are briefly reviewed. A linear elastic model for the determination of the 3D rock stress tensor, based on a special method for stress relief on the local surfaces of a drilled borehole wall, is researched. The six stress tensor components can be calculated from this model. Numerical simulation on the whole stress relief process by side-wall core drilling using FEM was done. The response curves of the strains versus the depth of the annular slot advance are analyzed. Quantitative relationship between the relief depth and the diameter of the rock core to be unloaded is given when the stresses stored in it are completely relieved. Arrangements of strain rosettes attached to the borehole-wall are studied, being free from the influence zone of annular slot resulting from local side-wall core drilling, thus ensuring strain-gauging accuracy. The results obtained from numerical simulation are helpful for designing prototype test or model test and further developing the new stress measuring instrument. This stress measuring method discussed in this paper has a reliable theoretical basis that can not only solve the problem of core-breaking occurring in stress relief with overcoring technique but also overcome the premise of hydraulic fracturing method - one of the principal directions of rock stress tensor should be coincident with the borehole axis. There is also no need for a pilot hole during the stress measurements. It can be anticipated to be a new way and channel for rock stress measurements.

Key words: in situ rock stresses, determination for 3D in situ stress tensor, stress relief, numerical simulation