To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain ...To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground Laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth.展开更多
Effective depth of dynamic compaction was summarized, and the advantages of dynamic compaction technology of effective depth were analyzed elaborately. The formula determining the reinforcement depth was deduced by us...Effective depth of dynamic compaction was summarized, and the advantages of dynamic compaction technology of effective depth were analyzed elaborately. The formula determining the reinforcement depth was deduced by using dimensional analysis method. The influential factors of hammer weight, hammer area, dry density of filling materials and filling materials types were comprehensively investigated. The formula of effective depth was established based on the definition of the dimensions analysis. Based on experimental results of in-situ dynamic compaction, the technology was applied to highway embankment filled with soils and rocks. From the comparison between the theoretical calculations and the experimental results, it is found that the theoretical results using the developed formula are close to experimental results.展开更多
Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn: Fir...Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn: First, the damage depth of suspended pipe is smaller than that of the bare pipe in case of the same fall energy, and with the increase of fall energy, the difference grows; Second, with the falling object's speed and mass rising, the deformation of pipeline intensifies at the impact site and the maximum vibration amplitude of submarine pipeline increases; Third, when the fall energy is equal, the smaller the contact area of falling objects and pipeline is, the greater the damage depth of pipeline becomes; Fourth, changes of seabed soil parameters (shear elastic modulus, internal friction angle, density) have less influence on the suspended pipeline's dent depths and maximum vibration amplitude,展开更多
Dynamic compaction is a cost-effective method commonly used for improvement of sandy soils. Anumber of researchers have investigated experimentally and numerically the improvement parametersof soils using dynamic comp...Dynamic compaction is a cost-effective method commonly used for improvement of sandy soils. Anumber of researchers have investigated experimentally and numerically the improvement parametersof soils using dynamic compaction, such as crater depth, improvement depth, and radial improvement,however, these parameters are not studied for improvement adjacent to the slopes or trenches. In thisresearch, four different slopes with different inclinations are modeled numerically using the finiteelement code ABAQUS, and impact loads of dynamic compaction are applied. The static factors of safetyare kept similar for all trenches and determined numerically by application of gravity loads to the slopeusing strength reduction method (SRM). The analysis focuses on crater depth and improvement regionwhich are compared to the state of flat ground. It can be observed that compacted area adjacent to theslopes is narrower and slightly away from the slope compared to the flat state. Moreover, crater depthincreases with increase in slope inclination.2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
Development and expansion of cities in one hand and increasing transport needs on the other hand have been causing underground constructions. So understanding the behavior of these structures is essential. Ground disp...Development and expansion of cities in one hand and increasing transport needs on the other hand have been causing underground constructions. So understanding the behavior of these structures is essential. Ground displacement around the tunneling area is one of the most important issues which have been studied by many researchers, while the effects of the slope behavior of the ground on the tunnel is paid less attention. This study will have analyzed the effects of frequency and surface slope on the surface subsidence caused by tunneling under dynamic loads (without structure). The results show that the frequency and surface slope have significant effects on the land displacements and the area surrounded by a tunnel.展开更多
基金supported by the National Natural Science Foundation of China(No.U1965203).
文摘To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground Laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth.
文摘Effective depth of dynamic compaction was summarized, and the advantages of dynamic compaction technology of effective depth were analyzed elaborately. The formula determining the reinforcement depth was deduced by using dimensional analysis method. The influential factors of hammer weight, hammer area, dry density of filling materials and filling materials types were comprehensively investigated. The formula of effective depth was established based on the definition of the dimensions analysis. Based on experimental results of in-situ dynamic compaction, the technology was applied to highway embankment filled with soils and rocks. From the comparison between the theoretical calculations and the experimental results, it is found that the theoretical results using the developed formula are close to experimental results.
文摘Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn: First, the damage depth of suspended pipe is smaller than that of the bare pipe in case of the same fall energy, and with the increase of fall energy, the difference grows; Second, with the falling object's speed and mass rising, the deformation of pipeline intensifies at the impact site and the maximum vibration amplitude of submarine pipeline increases; Third, when the fall energy is equal, the smaller the contact area of falling objects and pipeline is, the greater the damage depth of pipeline becomes; Fourth, changes of seabed soil parameters (shear elastic modulus, internal friction angle, density) have less influence on the suspended pipeline's dent depths and maximum vibration amplitude,
文摘Dynamic compaction is a cost-effective method commonly used for improvement of sandy soils. Anumber of researchers have investigated experimentally and numerically the improvement parametersof soils using dynamic compaction, such as crater depth, improvement depth, and radial improvement,however, these parameters are not studied for improvement adjacent to the slopes or trenches. In thisresearch, four different slopes with different inclinations are modeled numerically using the finiteelement code ABAQUS, and impact loads of dynamic compaction are applied. The static factors of safetyare kept similar for all trenches and determined numerically by application of gravity loads to the slopeusing strength reduction method (SRM). The analysis focuses on crater depth and improvement regionwhich are compared to the state of flat ground. It can be observed that compacted area adjacent to theslopes is narrower and slightly away from the slope compared to the flat state. Moreover, crater depthincreases with increase in slope inclination.2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
文摘Development and expansion of cities in one hand and increasing transport needs on the other hand have been causing underground constructions. So understanding the behavior of these structures is essential. Ground displacement around the tunneling area is one of the most important issues which have been studied by many researchers, while the effects of the slope behavior of the ground on the tunnel is paid less attention. This study will have analyzed the effects of frequency and surface slope on the surface subsidence caused by tunneling under dynamic loads (without structure). The results show that the frequency and surface slope have significant effects on the land displacements and the area surrounded by a tunnel.