Abstract：Different loading rates on rock samples may lead to considerable differences among the cumulative AE hit-stress curves. Kaiser stress values of sandstone，gritstone and mudstone increase with relatively faster loading rate，while for brittle rock-like limestone，loading rate has hardly any influence on Kaiser effect. Hence，a more in-depth analysis of the influence of loading rate on Kaiser effect of different lithological rock is very necessary. On one hand，all cracks in rock samples，regardless of their sizes，slip and propagate when loading rate is relatively smaller，which leads to a clearer acoustic emission signal. As a result，a smaller stress value is achieved. On the other hand，only larger cracks slip and propagate when loading rate is speeding up，which results in larger stress value. As for different lithological rocks，distinct loading rates are needed during the tests. In addition，the research shows that Kaiser effect point of the core below 2 500 m appears after its collapse point，which demonstrates that the measurement of Kaiser effect under confining pressure is needed in order to simulate formation situation to achieve corresponding stress value. The results of the test are applied to oilfield tests. The experimental results in laboratory test are in largely accordance with those in oilfield. It provides theoretical basis and reference for testing in-situ stress by Kaiser effect laboratory tests.
