The mechanical behavior evolution characteristics of sandstone are important to the application and practice of rock engineering.Therefore,a new method and concept of deep rock mechanics testing are proposed to reveal...The mechanical behavior evolution characteristics of sandstone are important to the application and practice of rock engineering.Therefore,a new method and concept of deep rock mechanics testing are proposed to reveal the mechanical behavior evolution mechanism of deep roadway surrounding rock after excavation with a depth over 1000 m.High stress-seepage coupling experiments of deep sandstone under various confining pressures are conducted using GCTS.Stress−strain and permeability curves are obtained.The three-stage mechanical behavior of deep sandstone is better characterized.A platform and secondary compaction phenomena are observed.With the confining pressure increasing,the platform length gradually decreases,even disappears.In the stade I,the rigid effect of deep sandstone is remarkable.In the stage II,radial deformation of deep sandstone dominates.The transient strain of confining pressure compliance is defined,which shows three-stage evolution characteristics.In the stage III,the radial deformation is greater than the axial deformation in the pre-peak stage,but the opposite trend is observed in the post-peak stage.It is found that the dynamic permeability can be more accurately characterized by the radial strain.The relations between the permeability and stress−strain curves in various stages are revealed.展开更多
Based on the Typhoon Yearbook data(1980-2000),some wind-pressure fitting relationships were established for different typhoon intensity at the different latitudes of the western North Pacific.As shown in validations w...Based on the Typhoon Yearbook data(1980-2000),some wind-pressure fitting relationships were established for different typhoon intensity at the different latitudes of the western North Pacific.As shown in validations with the 2001-2005 data,the relationships(namely,those between minimum sea level pressure(SLP) and maximum sustained wind near a typhoon center) are stable.They may be applied to correct the overestimated typhoon wind speeds in earlier years(1950-1979).Statistical analysis showed that the stronger the typhoon,the more stable this wind-pressure relationship is.Moreover,it is more stable at the lower latitude belt(10°N-30°N).On the basis of this result,a methodology of correcting typhoon's wind speeds and frequency in these years was put forward,and the climatological series were reconstructed of yearly total typhoon frequencies over the western North Pacific in 1950-1979 and indices were determined of destructive power of typhoons in the offshore regions of China.展开更多
Shear wave splitting is studied based on the digital waveforms of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MS5.7 earthquake of November 26, 2005 around the epicenter area....Shear wave splitting is studied based on the digital waveforms of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MS5.7 earthquake of November 26, 2005 around the epicenter area. The result shows that the time delays of slow shear waves of the DJS station, which is not far from the epicenter and where the distribution of faults is complex near the station, are relatively larger and the polarization directions of fast shear waves are not concentrated; the predominant polarization direction of fast shear waves of WUJ station, with single fault distributed nearby, has a difference of 35° to the strike of the fault and is inconsistent with the direction of regional principal compressive stress. The predominant polarization direction of fast shear waves of SZD station with no faults nearby is in accordance with regional principal compressive stress. There is no obvious regular relationshipship between the delay time and the focal depth.展开更多
Cryogenic propellants LOx/H2 are used at very high pressure in rocket engine combustion. The description of the combustion process in such application is very complex due essentially to the supercritical regime. Ideal...Cryogenic propellants LOx/H2 are used at very high pressure in rocket engine combustion. The description of the combustion process in such application is very complex due essentially to the supercritical regime. Ideal gas law becomes invalid. In order to try to capture the average characteristics of this combustion process, numerical computations are performed using a model based on a one-phase multi-component approach. Such work requires fluid properties and a correct definition of the mixture behavior generally described by cubic equations of state with appropriated thermodynamic relations validated against the NIST data. In this study we consider an alternative way to get the effect of real gas by testing the volume-weighted-mixing-law with association of the component transport properties using directly the NIST library data fitting including the supercritical regime range. The numerical simulations are carried out using 3D RANS approach associated with two tested turbulence models, the standard k-Epsilon model and the realizable k-Epsilon one. The combustion model is also associated with two chemical reaction mechanisms. The first one is a one-step generic chemical reaction and the second one is a two-step chemical reaction. The obtained results like temperature profiles, recirculation zones, visible flame lengths and distributions of OH species are discussed.展开更多
基金Projects(51974319,52034009)supported by the National Natural Science Foundation of ChinaProject(2020JCB01)supported by the China University of Mining and Technology(Beijing)。
文摘The mechanical behavior evolution characteristics of sandstone are important to the application and practice of rock engineering.Therefore,a new method and concept of deep rock mechanics testing are proposed to reveal the mechanical behavior evolution mechanism of deep roadway surrounding rock after excavation with a depth over 1000 m.High stress-seepage coupling experiments of deep sandstone under various confining pressures are conducted using GCTS.Stress−strain and permeability curves are obtained.The three-stage mechanical behavior of deep sandstone is better characterized.A platform and secondary compaction phenomena are observed.With the confining pressure increasing,the platform length gradually decreases,even disappears.In the stade I,the rigid effect of deep sandstone is remarkable.In the stage II,radial deformation of deep sandstone dominates.The transient strain of confining pressure compliance is defined,which shows three-stage evolution characteristics.In the stage III,the radial deformation is greater than the axial deformation in the pre-peak stage,but the opposite trend is observed in the post-peak stage.It is found that the dynamic permeability can be more accurately characterized by the radial strain.The relations between the permeability and stress−strain curves in various stages are revealed.
基金Youth project from Science & Technology Office of the Fujian Province (2007F3019)
文摘Based on the Typhoon Yearbook data(1980-2000),some wind-pressure fitting relationships were established for different typhoon intensity at the different latitudes of the western North Pacific.As shown in validations with the 2001-2005 data,the relationships(namely,those between minimum sea level pressure(SLP) and maximum sustained wind near a typhoon center) are stable.They may be applied to correct the overestimated typhoon wind speeds in earlier years(1950-1979).Statistical analysis showed that the stronger the typhoon,the more stable this wind-pressure relationship is.Moreover,it is more stable at the lower latitude belt(10°N-30°N).On the basis of this result,a methodology of correcting typhoon's wind speeds and frequency in these years was put forward,and the climatological series were reconstructed of yearly total typhoon frequencies over the western North Pacific in 1950-1979 and indices were determined of destructive power of typhoons in the offshore regions of China.
基金sponsored by the China Spark Program of Earthquake Science and Technology(XH12027)the Three-Combination Topics of China Earthquake Administration of"Research on the Crustal Medium Anisotropy in the Jiujiang-Ruichang Earthquake Area"the Special Fund of Seismic Industry Research(201008007)
文摘Shear wave splitting is studied based on the digital waveforms of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MS5.7 earthquake of November 26, 2005 around the epicenter area. The result shows that the time delays of slow shear waves of the DJS station, which is not far from the epicenter and where the distribution of faults is complex near the station, are relatively larger and the polarization directions of fast shear waves are not concentrated; the predominant polarization direction of fast shear waves of WUJ station, with single fault distributed nearby, has a difference of 35° to the strike of the fault and is inconsistent with the direction of regional principal compressive stress. The predominant polarization direction of fast shear waves of SZD station with no faults nearby is in accordance with regional principal compressive stress. There is no obvious regular relationshipship between the delay time and the focal depth.
文摘Cryogenic propellants LOx/H2 are used at very high pressure in rocket engine combustion. The description of the combustion process in such application is very complex due essentially to the supercritical regime. Ideal gas law becomes invalid. In order to try to capture the average characteristics of this combustion process, numerical computations are performed using a model based on a one-phase multi-component approach. Such work requires fluid properties and a correct definition of the mixture behavior generally described by cubic equations of state with appropriated thermodynamic relations validated against the NIST data. In this study we consider an alternative way to get the effect of real gas by testing the volume-weighted-mixing-law with association of the component transport properties using directly the NIST library data fitting including the supercritical regime range. The numerical simulations are carried out using 3D RANS approach associated with two tested turbulence models, the standard k-Epsilon model and the realizable k-Epsilon one. The combustion model is also associated with two chemical reaction mechanisms. The first one is a one-step generic chemical reaction and the second one is a two-step chemical reaction. The obtained results like temperature profiles, recirculation zones, visible flame lengths and distributions of OH species are discussed.
