Abstract：The Kaiser effect of rock can be employed to measure the in-situ stresses. The stresses corresponding to Kaiser effect of rock will approach and even exceed the uniaxial strength of rock with increment of strata depth. And when this happens，the rock collapses，then it is impossible to use the conventional Kaiser effect to measure the in-situ stresses. So under the above conditions the conventional Kaiser effect of rock becomes ineffective. The in-situ stress measurement using Kaiser effect of rock samples under confining pressures is carried out，in order to offset the unsatisfactory property of the uniaxial Kaiser effect measurement of rock sample stresses. The influence of the confining pressure on the Kaiser effect of rock is systematically studied by applying a group of varied confining pressures to the rock samples with the same depth. And an experimental measuring method of in-situ stresses with Kaiser effect of rock samples under confining pressure is proposed，as well as the experimental principles. The conclusion is that the relationship between the stresses corresponding to Kaiser effect of rock and the confining pressures is linear，and the statistical regression relationship is obtained. The calculated results based on the experiments are in good accordance with the hydro-fracture results.
