Study On Rock Kaiser Effect Characteristics Under Multi-factors And In-situ Stress Measurement

With the progress of economic construction and national defense construction, underground space development is going deeper, in-situ stress measurement has become a tecnnical problem that must be solved in the construction of underground engineering. At present, many in-situ stress measurement methods are not applicable to deep rock, and the engineering rock subjected to groundwater and hydraulic pressure, Kaiser Effect method is a feasible method to measure in-situ stress. To analysis the rock Kaiser Effect change rule under water content, pore water pressure and confining pressure is a fundamental frontier issue. In this paper, with the reformed electro-hydraulic servo rock mechanics test system MTS815.02 and acoustic emission equipment AE21 C, taking engineering red sandstone as research sample, study the mechanical properties, AE characteristics and Kaiser Effect under different confining pressure, water content, pore water pressure. A method of selecting Kaiser Point is developed based on the characteristics of energy distribution. The main works and research results are as follow:(1)The electro-hydraulic servo rock mechanics test system MTS815.02 is reformed and the detector is moved inside three axis cylinder from outside, the signal line is lead out based on the device structure. So the AE equipment could collect more accurate and real AE signal without the influence of confining pressure and pore water pressure, and it effectively reduce the impact of environmental noise.(2)Carried out the uniaxial and triaxial compression test of red sandstone under different confining pressure, water content and pore water pressure, we got the change regulations of elastic modulus, peak stress, peak strain, residential stress, ring-down count rate, accumulative ring-down count and accumulative energy of red sandstone under different influence factor, and analyzed the generation mechanism.(3)Based on the red sandstone change curve analysis of AE parameter with time, preliminary determinate Kaiser Point’s range, and analyze all point’s band energy, results show 62.5~93.75 kHz is critical band, Kaiser Point’s energy percentage is biggest in critical band and based on this, we established a method to select Kaiser Point, it’s named as ctitical band energy analysis mentod. And the method is used it to measured the-1000 m in-situ stress of Tang Kou coal mine and the calculation result is similar to the result under stress relieving method.(4)The AE signal of red sandstone cyclic loading and unloading tests under different factors is analyzed to get Kaiser Point and FR, the change regulations of Kaiser memory ability under different confining pressure, water content and pore water pressure is analyzed too. Results show that the Kaiser memory ability is most significant under 10 MPa confining pressure and normal water content.