This study presents the results of field and numerical investigations of lateral stiffness, capacity, and failure mechanisms for plain piles and reinforced concrete piles in soft clay. A plastic-damage model is used t...This study presents the results of field and numerical investigations of lateral stiffness, capacity, and failure mechanisms for plain piles and reinforced concrete piles in soft clay. A plastic-damage model is used to simulate concrete piles and jet-grouting in the numerical analyses. The field study and numerical investigations show that by applying jet-grouting sur- rounding the upper 7.5D （D = pile diameter） of a pile, lateral stiffness and beating capacity of the pile are increased by about 110% and 100%, respectively. This is partially because the jet-grouting increases the apparent diameter of the pile, so as to en- large the extent of failure wedge and hence passive resistance in front of the reinforced pile. Moreover, the jet-grouting pro- vides a circumferential confinement to the concrete pile, which suppresses development of tensile stress in the pile. Corre- spondingly, tension-induced plastic damage in the concrete pile is reduced, causing less degradation of stiffness and strength of the pile than that of a plain pile. Effectiveness of the circumferential confinement provided by the jet-grouting, however, diminishes once the grouting cracks because of the significant vertical and circumferential tensile stress near its mid-depth. The lateral capacity of the jet-grouting reinforced pile is, therefore, governed by mobilized passive resistance of soil and plastic damage of jet-grouting.展开更多
This paper establishes a lattice Boltzmann equation-discrete element method (LBE-DEM) coupled simulation method under the Eulerian-Lagrangian framework at first, and applies it to simulating a two-dimensional gas-soli...This paper establishes a lattice Boltzmann equation-discrete element method (LBE-DEM) coupled simulation method under the Eulerian-Lagrangian framework at first, and applies it to simulating a two-dimensional gas-solid two-phase cross jet. The gas phase is simulated by the lattice-Boltzmann method via the TD2G9 model; the solid phase is traced by the Lagrangian method and the inter-particle collision is calculated by the DEM method. Three values of the Stokes number St=10, 25, and 50 are simulated under the same mass loading. This paper focuses on the characteristics of vortex structure, particle distribution, and the reverse-flow/rebounding rate in cross jets. We analyze the characteristics of fluid vortex motion, particle cluster distribution, rebounding rate of particles and the influencing factors for them. The results show the existence of joint distribution of discrete clusters and discrete particles in cross jets. Meanwhile, it shows that a larger concentration of particles in the early stage of jet evolution or a smaller Stokes number under the same mass loading can produce a larger rebounding rate. However, the rebounding rate of particles at the late stage, in general, is stable.展开更多
Penetration characteristic(size and shape of penetration craters made in high hardness ARMSTAL 30PM steel) of shaped charge jets formed after detonations of modified PG-7VM warheads was analyzed in the article. Modifi...Penetration characteristic(size and shape of penetration craters made in high hardness ARMSTAL 30PM steel) of shaped charge jets formed after detonations of modified PG-7VM warheads was analyzed in the article. Modifications consisted in removing the frontal part of the grenade(fuse, ballistic cap and conductive cone) and introducing of the liner cavity filling made of polyacetal copolymer POM-C. The filings in the form of solid cones with three different heights(33%, 66% and 100% of H-the height of original PG-7VM liner) were placed inside of the hollow cone shaped charge liner. As opposed to the vast majority of previously published works(in which warhead optimization studies were focused on increasing of the depth of penetration in rolled homogeneous armor steel) the main aim of the presented modifications was to maximize the damage ratio(diameters of craters, inlet and outlet holes) of target perforated by shaped charge jet at the cost of the loss of part of the jet penetration capability. According to the best knowledge of the authors such approach to the use of the old PG-7VM warheads has not been analyzed so far. Taking into consideration high stock levels of PG-7VM warheads, and the fact that they are continuously being replaced by more efficient and more sophisticated high-explosive anti-tank warheads, it seems reasonable to look for alternate applications of the warheads withdrawn from the service. Thanks to the introduction of proposed modifications the warheads could be used by special forces or other assault units as directional mines or statically detonated cutting shaped charges as well as by combat engineers as universal charges used in various types of engineering or sapper works. The research included experimental penetration tests and their numerical reproduction in the LS-Dyna software with the simulation methodology defined and validated in previous works of the authors.Small differences(average error = 10-20%) were identified between the experimental and numerical results(dimensions of crate展开更多
Method of testing for dynamic output forces from jet elements is studied, the handwidth is large in testing with this method. By establishing a model of the test system and simulating it, principles of how inherent fe...Method of testing for dynamic output forces from jet elements is studied, the handwidth is large in testing with this method. By establishing a model of the test system and simulating it, principles of how inherent features of the test system affect the dynamic force test are found out. Thus a theoretical foundation is given for the design and error modification to the actual test system.展开更多
基金supported by the National Science Foundation for Distinguished Young Scholars of China(Grant No.51325901)the International Science and Technology Cooperation Program of China(Grant No.2015DFE72830)State Key Program of National Natural Science of China(Grant No.51338009)
文摘This study presents the results of field and numerical investigations of lateral stiffness, capacity, and failure mechanisms for plain piles and reinforced concrete piles in soft clay. A plastic-damage model is used to simulate concrete piles and jet-grouting in the numerical analyses. The field study and numerical investigations show that by applying jet-grouting sur- rounding the upper 7.5D （D = pile diameter） of a pile, lateral stiffness and beating capacity of the pile are increased by about 110% and 100%, respectively. This is partially because the jet-grouting increases the apparent diameter of the pile, so as to en- large the extent of failure wedge and hence passive resistance in front of the reinforced pile. Moreover, the jet-grouting pro- vides a circumferential confinement to the concrete pile, which suppresses development of tensile stress in the pile. Corre- spondingly, tension-induced plastic damage in the concrete pile is reduced, causing less degradation of stiffness and strength of the pile than that of a plain pile. Effectiveness of the circumferential confinement provided by the jet-grouting, however, diminishes once the grouting cracks because of the significant vertical and circumferential tensile stress near its mid-depth. The lateral capacity of the jet-grouting reinforced pile is, therefore, governed by mobilized passive resistance of soil and plastic damage of jet-grouting.
基金supported by the National Natural Science Foundation of China (Grant No. 51106180)the research funds of China University of Petroleum, Beijing (Grant No. BJ-2010-03)
文摘This paper establishes a lattice Boltzmann equation-discrete element method (LBE-DEM) coupled simulation method under the Eulerian-Lagrangian framework at first, and applies it to simulating a two-dimensional gas-solid two-phase cross jet. The gas phase is simulated by the lattice-Boltzmann method via the TD2G9 model; the solid phase is traced by the Lagrangian method and the inter-particle collision is calculated by the DEM method. Three values of the Stokes number St=10, 25, and 50 are simulated under the same mass loading. This paper focuses on the characteristics of vortex structure, particle distribution, and the reverse-flow/rebounding rate in cross jets. We analyze the characteristics of fluid vortex motion, particle cluster distribution, rebounding rate of particles and the influencing factors for them. The results show the existence of joint distribution of discrete clusters and discrete particles in cross jets. Meanwhile, it shows that a larger concentration of particles in the early stage of jet evolution or a smaller Stokes number under the same mass loading can produce a larger rebounding rate. However, the rebounding rate of particles at the late stage, in general, is stable.
文摘Penetration characteristic(size and shape of penetration craters made in high hardness ARMSTAL 30PM steel) of shaped charge jets formed after detonations of modified PG-7VM warheads was analyzed in the article. Modifications consisted in removing the frontal part of the grenade(fuse, ballistic cap and conductive cone) and introducing of the liner cavity filling made of polyacetal copolymer POM-C. The filings in the form of solid cones with three different heights(33%, 66% and 100% of H-the height of original PG-7VM liner) were placed inside of the hollow cone shaped charge liner. As opposed to the vast majority of previously published works(in which warhead optimization studies were focused on increasing of the depth of penetration in rolled homogeneous armor steel) the main aim of the presented modifications was to maximize the damage ratio(diameters of craters, inlet and outlet holes) of target perforated by shaped charge jet at the cost of the loss of part of the jet penetration capability. According to the best knowledge of the authors such approach to the use of the old PG-7VM warheads has not been analyzed so far. Taking into consideration high stock levels of PG-7VM warheads, and the fact that they are continuously being replaced by more efficient and more sophisticated high-explosive anti-tank warheads, it seems reasonable to look for alternate applications of the warheads withdrawn from the service. Thanks to the introduction of proposed modifications the warheads could be used by special forces or other assault units as directional mines or statically detonated cutting shaped charges as well as by combat engineers as universal charges used in various types of engineering or sapper works. The research included experimental penetration tests and their numerical reproduction in the LS-Dyna software with the simulation methodology defined and validated in previous works of the authors.Small differences(average error = 10-20%) were identified between the experimental and numerical results(dimensions of crate
文摘Method of testing for dynamic output forces from jet elements is studied, the handwidth is large in testing with this method. By establishing a model of the test system and simulating it, principles of how inherent features of the test system affect the dynamic force test are found out. Thus a theoretical foundation is given for the design and error modification to the actual test system.
