Using the cross correlation function analysis method, this paper discusses shear wave splitting and crack-inducedanisotropy in the crust beneath Tangshan, North China, by the digital data from Tangshan strong ground m...Using the cross correlation function analysis method, this paper discusses shear wave splitting and crack-inducedanisotropy in the crust beneath Tangshan, North China, by the digital data from Tangshan strong ground monon temporary arrays. Sixteen of twenty-one stations in the arrays recorded earthquake events available forstudying from 1982 to 1984. Having calculated 131 available records, we get slower shear wave time delay r andfaster shear wave polarization azimuth Paz in Tangshan region, and the cracks density s is got further fromthem. The analysis shows that the stress field is very complicated in Tangshan region and has strongly regionalfeature. Because of the complicated distribution of faults, different shear wave splitting characteristics are shownin 16 stations, scattered r and different Paz. And they also were observed that the r and PaZ values were diversewithin the time scale of hours in more than one station. In Tangshan region the average results of r, Paz and Bare 0. 0071 s. km-1, northwest-west near to east-west and 0.022 respectively. Meantime, the standard devia.tions were calculated in this paper.展开更多
We identify two interrelated but independent species of microcracks with different origins and different distributions. One species is the classic high-stress microcracks identified in laboratory stress-cells associat...We identify two interrelated but independent species of microcracks with different origins and different distributions. One species is the classic high-stress microcracks identified in laboratory stress-cells associated with acoustic emissions as microcracks open with increasing stress. The other species is the low-stress distributions of closely-spaced stress-aligned fluid-saturated microcracks that observations of shear-wave splitting(SWS) demonstrate pervade almost all in situ rocks in the upper crust, the lower crust, and the uppermost 400 km of the mantle. On some occasions these two sets of microcracks may be interrelated and similar(hence ‘species') but they typically have fundamentally-different properties, different distributions, and different implications. The importance for hydrocarbon exploration and recovery is that SWS in hydrocarbon reservoirs monitors crack alignments and preferred directions of fluid-flow. The importance for earthquake seismology is that SWS above small earthquakes monitors the effects of increasing stress on the pervasive low-stress microcrack distributions so that stress-accumulation before, possibly distant, earthquakes can be recognised and impending earthquakes stress-forecast.展开更多
In this study, the 3-dimensional discrete element method is firstly introduced to explain the fracturing damage process of the dynamic split experiment of a special brittle glass ZnS. The corresponding dynamic split e...In this study, the 3-dimensional discrete element method is firstly introduced to explain the fracturing damage process of the dynamic split experiment of a special brittle glass ZnS. The corresponding dynamic split experiment is also performed by using the split Hopkinson pressure bar. Then the numerical results correspond closely to those obtained by experiments, and the fracturing damage mode shows that the sample under high strain rate loading would crack along vertical diameter in the band region between two loading edges, which differs from the static damage mode. Furthermore, by comparing a group of contrast numerical tests, the numerical results prove that loading area upon the top side of samples would influence the fracture mode of dynamic split experiments, which indicates that the narrow loading plane is better.展开更多
为研究层理分布对劈裂注浆裂隙扩展的影响,基于离散单元法建立了层理板岩劈裂注浆数值模型。采用平行黏结模型(Parallel Bond Model,PBM)和光滑节理模型(Smooth Joint Model,SJM)建立了层理板岩模型;基于离散元流-固耦合原理建立了浆-...为研究层理分布对劈裂注浆裂隙扩展的影响,基于离散单元法建立了层理板岩劈裂注浆数值模型。采用平行黏结模型(Parallel Bond Model,PBM)和光滑节理模型(Smooth Joint Model,SJM)建立了层理板岩模型;基于离散元流-固耦合原理建立了浆-岩耦合模型,实现了劈裂注浆过程中的浆-岩耦合计算;考虑层理倾角、间距及侧压力系数的影响,分析了层理岩石劈裂注浆裂隙扩展规律。结果表明,层理岩石劈裂注浆过程中产生了沿层理扩展的主裂隙,其扩展方向与层理倾角一致;但其仅存在于临近注浆孔层理,距离较远的层理中无裂隙扩展;层理岩石劈裂注浆初期,裂隙数量增长较快;随后裂隙增长速率逐渐减小,并趋于稳定。层理间距越小,劈裂注浆裂隙更易于沿层理扩展,且裂隙的快速增长阶段越长,微裂隙数量越多;劈裂裂隙在层理中的扩展速率显著高于岩石基质。层理倾角和最大主应力方向控制着劈裂注浆裂隙的扩展和位移场分布,两者相互影响,使层理岩石劈裂注浆裂隙扩展更为复杂。研究结果对层理岩石劈裂注浆施工设计有一定指导作用。展开更多
文摘Using the cross correlation function analysis method, this paper discusses shear wave splitting and crack-inducedanisotropy in the crust beneath Tangshan, North China, by the digital data from Tangshan strong ground monon temporary arrays. Sixteen of twenty-one stations in the arrays recorded earthquake events available forstudying from 1982 to 1984. Having calculated 131 available records, we get slower shear wave time delay r andfaster shear wave polarization azimuth Paz in Tangshan region, and the cracks density s is got further fromthem. The analysis shows that the stress field is very complicated in Tangshan region and has strongly regionalfeature. Because of the complicated distribution of faults, different shear wave splitting characteristics are shownin 16 stations, scattered r and different Paz. And they also were observed that the r and PaZ values were diversewithin the time scale of hours in more than one station. In Tangshan region the average results of r, Paz and Bare 0. 0071 s. km-1, northwest-west near to east-west and 0.022 respectively. Meantime, the standard devia.tions were calculated in this paper.
基金This study was partially supported by the National Natural Science Foundation of China （No. 41174042）.
文摘We identify two interrelated but independent species of microcracks with different origins and different distributions. One species is the classic high-stress microcracks identified in laboratory stress-cells associated with acoustic emissions as microcracks open with increasing stress. The other species is the low-stress distributions of closely-spaced stress-aligned fluid-saturated microcracks that observations of shear-wave splitting(SWS) demonstrate pervade almost all in situ rocks in the upper crust, the lower crust, and the uppermost 400 km of the mantle. On some occasions these two sets of microcracks may be interrelated and similar(hence ‘species') but they typically have fundamentally-different properties, different distributions, and different implications. The importance for hydrocarbon exploration and recovery is that SWS in hydrocarbon reservoirs monitors crack alignments and preferred directions of fluid-flow. The importance for earthquake seismology is that SWS above small earthquakes monitors the effects of increasing stress on the pervasive low-stress microcrack distributions so that stress-accumulation before, possibly distant, earthquakes can be recognised and impending earthquakes stress-forecast.
基金supported by the National Natural Science Foundation of China (10732010,10972010 and 11028206)
文摘In this study, the 3-dimensional discrete element method is firstly introduced to explain the fracturing damage process of the dynamic split experiment of a special brittle glass ZnS. The corresponding dynamic split experiment is also performed by using the split Hopkinson pressure bar. Then the numerical results correspond closely to those obtained by experiments, and the fracturing damage mode shows that the sample under high strain rate loading would crack along vertical diameter in the band region between two loading edges, which differs from the static damage mode. Furthermore, by comparing a group of contrast numerical tests, the numerical results prove that loading area upon the top side of samples would influence the fracture mode of dynamic split experiments, which indicates that the narrow loading plane is better.
文摘为研究层理分布对劈裂注浆裂隙扩展的影响,基于离散单元法建立了层理板岩劈裂注浆数值模型。采用平行黏结模型(Parallel Bond Model,PBM)和光滑节理模型(Smooth Joint Model,SJM)建立了层理板岩模型;基于离散元流-固耦合原理建立了浆-岩耦合模型,实现了劈裂注浆过程中的浆-岩耦合计算;考虑层理倾角、间距及侧压力系数的影响,分析了层理岩石劈裂注浆裂隙扩展规律。结果表明,层理岩石劈裂注浆过程中产生了沿层理扩展的主裂隙,其扩展方向与层理倾角一致;但其仅存在于临近注浆孔层理,距离较远的层理中无裂隙扩展;层理岩石劈裂注浆初期,裂隙数量增长较快;随后裂隙增长速率逐渐减小,并趋于稳定。层理间距越小,劈裂注浆裂隙更易于沿层理扩展,且裂隙的快速增长阶段越长,微裂隙数量越多;劈裂裂隙在层理中的扩展速率显著高于岩石基质。层理倾角和最大主应力方向控制着劈裂注浆裂隙的扩展和位移场分布,两者相互影响,使层理岩石劈裂注浆裂隙扩展更为复杂。研究结果对层理岩石劈裂注浆施工设计有一定指导作用。
