The Effect Of Water Content On AE Laws Of Sandstone Under Different Loading Modes

In recent years, with the rapid development of rock mechanics and the need of rock engineering construction, the underground engineering practice has made a huge development. In order to prevent accidents in underground engineering construction, it is necessary to make effective monitoring of engineering rock mass. Taking the necessary method to forecast the stability of rock mass, providing reliable data for the engineering construction. Rock acoustic emission phenomenon as a companion phenomenon in rock failure process, can reveals a lot of information in the process of rock internal damage, So it has a great value to using acoustic emission technique to monitoring engineering rock mass stability. Underground engineering rock mass are often in a state of water, analysis and study the effect of moisture content on acoustic emission characteristics can infer that the internal characteristic changes and invert of the destruction mechanism of rocks under different moisture state and help us to take necessary control measures before the rock mass failure.This paper mainly choose sandstone in Chongqing area as the research object, the acoustic emission experimental studies of three different water content of sandstone under different loading mode which included uniaxial loading, cyclic loading, multi-stage loading are carried out with the equipment of WAW-1000 type electro-hydraulic servo test system and PCI-2 fully digital acoustic emission signal acquisition system.The acoustic emission characteristics of sandstone with different water content under different loading modes had been deeply researched, the main research results are as follows:(1) By sandstone water immersion test and the mechanical property test, obtained the relation curve between water absorption and time, and the effect of water content on the deformation, strength and failure pattern under the different loading modes.(2) Through uniaxial loading acoustic emission test, obtained the acoustic emission parameters of different water content sandstone under different loading rate, drawn the relation curves between acoustic emission parameters and time and stress. Summed up the effect of moisture content on acoustic emission characteristics of sandstone under uniaxial loading condition.(3) Through cyclic loading acoustic emission test, obtained the acoustic emission parameters of different water content sandstone under different loading rate, drawn the relation curves between acoustic emission parameters and time and stress, analyzed the Kaiser effect and the Felicity effect, Summed up the effect of moisture content on acoustic emission characteristics of sandstone under cyclic loading condition.(4) Through multi-stage loading acoustic emission test, obtained the acoustic emission parameters of different water content sandstone under different loading rate, drawn the relation curves between acoustic emission parameters and time and stress,Summed up the effect of moisture content on acoustic emission characteristics of sandstone under multi-stage loading condition.(5) Through acoustic emission test parameters, starting from the microscopic mechanism of rock damage fracture, the uniaxial loading damage model of different moisture content sandstone was built based on AE accumulative ringing count, through the piecewise fitting function of the damage factor-strain curve, proposed the constitutive model of stress-strain which based on the sandstone damage, compared with the stress-strain curve of Weibull distribution which based on microelement statistical strength theory and the curve which actual measured, result shows that, to some extent, this model can reflect the damage evolution process of the different moisture content sandstone under the condition of uniaxial loading.