(State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan 430071,China;2. School of Civil Engineering,Wuhan University, Wuhan 430072,China;3. Central Southern China Electric Power Design Institute of China Power Engineering Consulting Group Corporation,Wuhan 430071,China)
Abstract:The relation between measured stress of three-dimension pressure sensor(3DPS) and initial stress of surrounding medium plays an important role in rock stress measurement. In order to know the measuring performance of 3DPS for practical applications,calibration test is performed in rock mechanics testing system to investigate the repeatability and linearity of 3DPS and corresponding calibration coefficients are obtained. A cubic cement mortar sample,which side length is 600mm,with 3DPS embedded in the center is poured. It is loaded under different repeated stress states by the developed true-triaxial loading system. Due to pore structure of the cement mortar body,the measured stress curves of 3DPS show a hysteresis phenomenon when loads are applied for the first time. As a result of the pore structures are pressed compact under repeated loads,the measured stress curves tend to be stable. For hydrostatic stress loading,the measured stresses of 3DPS are linear to the loading stresses. For non-hydrostatic stress state loading,the measured stresses of 3DPS are not only linear related to the loading stresses in the same direction but also related to the differential stresses that related to the other two directions. Then,an equation for describing the influence of loading stress on the measured stress of 3DPS in cement mortar body is proposed.
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