By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then incr...By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then increased.The variation in velocity was influenced by the sandstone’s porosity.The commonly used Gassmann equation based on fluid substitution theory was studied.Comparing the calculated results with the measured data,it was found that the Gassmann equation agreed well with the measured data at high water saturation,but it could not explain the bending phenomenon of P-wave velocity at low saturation.This indicated that these equations could not accurately describe the relationship between fluid content and rock acoustic velocity.The reasons for this phenomenon were discussed through Taylor’s expansion.The coefficients of the fitting formula were calculated and verified by fitting the measured acoustic velocity changes of the cores.The relationship between P-wave velocity and saturation was discussed,which provides experimental support for calculating saturation using seismic and acoustic logging data.展开更多
Radon is a polluting and radioactive gas released by rock fracture. Shear fracture is widely developed in surrounding rock mass of deep engineering. Nevertheless, the correlation between radon release and the shear fr...Radon is a polluting and radioactive gas released by rock fracture. Shear fracture is widely developed in surrounding rock mass of deep engineering. Nevertheless, the correlation between radon release and the shear fracture is undefined. In this study, the intact Jinping marble and Baihetan basalt were adopted as samples. Based on radionuclide content analysis, the intrinsic characteristics of radon emission were analyzed. Then a direct shear testing system was designed to synchronously measure radon release during rock fracture. The direct shear tests were carried out under different normal stresses. The relationship between shear fracture process and cumulative radon concentration was explored. The results indicated that radon release varied with the increase of shear displacement under the same normal stress. The general pattern showed a slight increase and fell in the initial loading phase, then increased rapidly to the peak release approximately corresponding to the peak of shear stress, and finally decreased to a stable level with the development of shear displacement after sample failure. The initial and peak radon concentrations increased linearly with the increase of normal stress. The same trend was found in shear failure surface area and cumulative radon concentration according to the rise angle(RA) value-average frequency(AF) distribution.展开更多
文摘By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then increased.The variation in velocity was influenced by the sandstone’s porosity.The commonly used Gassmann equation based on fluid substitution theory was studied.Comparing the calculated results with the measured data,it was found that the Gassmann equation agreed well with the measured data at high water saturation,but it could not explain the bending phenomenon of P-wave velocity at low saturation.This indicated that these equations could not accurately describe the relationship between fluid content and rock acoustic velocity.The reasons for this phenomenon were discussed through Taylor’s expansion.The coefficients of the fitting formula were calculated and verified by fitting the measured acoustic velocity changes of the cores.The relationship between P-wave velocity and saturation was discussed,which provides experimental support for calculating saturation using seismic and acoustic logging data.
基金Project(U1865203) supported by the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of ChinaProject(Z020007) supported by the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of SciencesProjects(41941018, 52109142) supported by the National Natural Science Foundation of China。
文摘Radon is a polluting and radioactive gas released by rock fracture. Shear fracture is widely developed in surrounding rock mass of deep engineering. Nevertheless, the correlation between radon release and the shear fracture is undefined. In this study, the intact Jinping marble and Baihetan basalt were adopted as samples. Based on radionuclide content analysis, the intrinsic characteristics of radon emission were analyzed. Then a direct shear testing system was designed to synchronously measure radon release during rock fracture. The direct shear tests were carried out under different normal stresses. The relationship between shear fracture process and cumulative radon concentration was explored. The results indicated that radon release varied with the increase of shear displacement under the same normal stress. The general pattern showed a slight increase and fell in the initial loading phase, then increased rapidly to the peak release approximately corresponding to the peak of shear stress, and finally decreased to a stable level with the development of shear displacement after sample failure. The initial and peak radon concentrations increased linearly with the increase of normal stress. The same trend was found in shear failure surface area and cumulative radon concentration according to the rise angle(RA) value-average frequency(AF) distribution.
