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袋装砂井爆夯法处理软土地基是利用炸药在设置有排水通道的软土中爆炸产生冲击和振动而使土体加固的方法。针对该法进行理论研究,提出了一种将袋装砂井爆夯处理软土地基的三维问题转化为二维平面应变问题的数值模拟方法：袋装砂井转化为等价砂墙;利用等效冲量原理,炮孔爆炸压力则转化为等效压力墙。数值模拟中考虑了土体骨架变形与孔隙水非达西渗流的耦合。对数值模拟的现场试验验证分析表明,沉降数值分析的结果与铁路宁启线软基处理现场测试结果具有很好的可比性。所提出的数值分析方法可模拟袋装砂井爆夯处理软土地基的超静孔隙水压产生和消散以及土体沉降变形的动态过程。 相似文献
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LC Taylor RR Skaggs W. Gault 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(1):19-28
The ultimate aim of our overall task, of which the effort described in this paper is a part, is to be able to model the impulsive output of buried charges and the response of targets of interest. It is not practical or cost-effective to determine the response of all targets of interest to buried charges of all sizes by testing them. In order to have confidence in our models, however, they must be validated by a modest number of tests. A critical element in modelling the response of a target is the ability to model the loading function. The load a buried charge applies to a target above it when the charge detonates can be characterized in terms of the vertical impulse. The vertical impulse is a function of the size of the charge, its depth of burial, and the properties of the soil in which it is buried. The primary objective of the effort described in this paper is to determine the load a known charge places on a non-responding target so the data can be used to validate our models.
For model validation, a large number of detonator-scale experiments have been conducted by the University of Maryland (Fourney et al. [1]). It was also necessary to conduct a modest number of experiments at a larger scale, nine in total, to ensure that the results of the detonator-scale tests can be satisfactorily scaled up. Of the nine large-scale experiments conducted, seven were conducted with 5 or 10 lb cast TNT charges. All experiments were conducted in sand that was as nearly fully water-saturated as possible. The objective of the experiments was to determine the vertical impulse applied to a non-deforming target plate above the charge.
The large-scale experiments were conducted using the Vertical Impulse Measurement Fixture (VIMF) at the Army Research Laboratory, Aberdeen, MD. The VIMF is a unique facility that has been designed specifically to measure accurately the vertical impulse from buried charges weighing up to 8 kg.
This paper describes the VIMF and its instrumentation, test methods and test results. The results obtained demonstrate that in some cases, when the soil is saturated sand, explosive 'bubble' effects similar to those encountered in shallow water are encountered. 相似文献
For model validation, a large number of detonator-scale experiments have been conducted by the University of Maryland (Fourney et al. [1]). It was also necessary to conduct a modest number of experiments at a larger scale, nine in total, to ensure that the results of the detonator-scale tests can be satisfactorily scaled up. Of the nine large-scale experiments conducted, seven were conducted with 5 or 10 lb cast TNT charges. All experiments were conducted in sand that was as nearly fully water-saturated as possible. The objective of the experiments was to determine the vertical impulse applied to a non-deforming target plate above the charge.
The large-scale experiments were conducted using the Vertical Impulse Measurement Fixture (VIMF) at the Army Research Laboratory, Aberdeen, MD. The VIMF is a unique facility that has been designed specifically to measure accurately the vertical impulse from buried charges weighing up to 8 kg.
This paper describes the VIMF and its instrumentation, test methods and test results. The results obtained demonstrate that in some cases, when the soil is saturated sand, explosive 'bubble' effects similar to those encountered in shallow water are encountered. 相似文献
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爆炸荷载作用下的堤坝破坏形态研究在国防以及工程应用中都具有重要意义。为了研究堤坝在不同爆炸工况下产生的破坏形态,在LS-DYNA软件框架内,建立了适合于爆炸荷载作用下土体动力分析的实用模型,并基于多物质ALE法,对均质土坝遭受爆炸袭击开展了仿真分析,得到了不同炸药埋深以及不同孔隙水压力上升程度下的堤坝爆炸弹坑形态。结果表明,随着炸药埋深的增加,堤坝弹坑尺寸具有增大的趋势,但当埋深超过一定范围,则无法形成弹坑;同时,爆炸荷载作用下含水土体的孔隙水压力发展对弹坑的形成具有重要影响,孔隙水压力上升程度越强,产生的弹坑尺寸就越大。研究结果可以为堤坝抗爆安全设计以及爆破拆除堰塞坝等工程提供参考。 相似文献
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Rohit Tiwari Tanusree Chakraborty Vasant Matsagar 《Geotechnical and Geological Engineering》2017,35(4):1491-1512
The present work deals with the three-dimensional nonlinear finite element (FE) analyses of the tunnel in soil subjected to internal blast loading. The analyses are performed using the coupled Eulerian–Lagrangian analysis tool in FE software Abaqus/Explicit. The soil and reinforced concrete lining are modeled using the Lagrangian elements. The explosive Trinitrotoluene (TNT) is modeled using the Eulerian elements. The stress–strain response of soil, concrete, and reinforcement are simulated using strain rate dependent Drucker–Prager plasticity, concrete damaged plasticity and Johnson–Cook (J–C) plasticity models, respectively. The pressure–volume relationship of the TNT explosive is simulated using the Jones-Wilkins-Lee equation of state. Parametric sensitivity studies have been performed for different (1) tunnel lining thicknesses, (2) explosive charge weights and (3) angles of internal friction of soil. It is observed from the results that blast induced pressure on the tunnel lining increases with the increase in charge weight. Both the lining and the surrounding soil undergo significant deformation. The deformation of the tunnel lining increases with increasing charge weight and decreases with increasing lining thickness and increasing the angle of internal friction of soil. Blast-induced velocity in soil attenuates with increasing distance from the source of the blast. 相似文献
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覆盖型岩溶塌陷的塌陷机制分析 总被引：2，自引：2，他引：0
以覆盖型岩溶塌陷为研究对象,首先分析了覆盖型岩溶塌陷的演化机制,然后考虑土体自重、真空负压、降雨和爆破等因素的共同作用,并基于极限平衡理论建立了覆盖型岩溶塌陷土体稳定系数及塌陷范围的计算方法,以重庆市南岸区涂山湖二外桥梁左侧塌陷为例,发现计算出的塌陷范围与现场塌陷范围基本一致,并分析出该处土体在爆破、真空负压、自重和渗透等因素作用下的稳定系数和塌陷范围变化规律为:稳定系数在土层厚度增加时可增大46%,而当水深从0.1 m增加到1 m和真空负压由0 kPa增大到50 kPa时,可降低30%～35%。最后考虑爆破的时效性,探讨了土柱稳定系数随着爆破振动的变化规律,在考虑爆破荷载作用后,土柱稳定系数将降低4%,爆破对土柱的作用时间约为6 s。 相似文献
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爆炸固结法是软土地基处理的新方法。为了分析爆炸作用在土中的变化规律,通过有限元方法对单孔条形药包在土中爆炸的数值模拟,在验证计算结果与实测数据的基础上,对地基中单孔条形药包在上覆压力和药量两组爆炸参数下进行模拟对比分析,以解决在不同上覆压力和药量条件下条形药包爆炸作用在土中的显著影响范围。针对条形药包土中爆炸问题,运用ALE算法解决了炸药网格的畸变问题。研究结果表明,上覆压力发挥作用的主要时间不是在爆炸瞬间,而是在爆炸以后的时间段,主要的贡献是对爆炸产生的孔隙水压的消散作用。而炸药的药量对于布置爆炸孔和竖向排水通道的间距影响具有较大影响。 相似文献
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A set of experiments were conducted at the Aberdeen Proving Grounds 1 (Taylor, L.C., Skaggs, R.R. and Gault, W., 2005. Vertical impulse measurements of mines buried in saturated sand. Proceedings of the 31st Annual Conference on Explosives and Blasting Technique, Orlando, FL, 6 - 9 February, 2.) in which explosive charges were buried in saturated sand beneath a suspended rigid platform. The goal of these experiments was to measure the dependence of the impulse transmitted to the platform on the standoff distance and the charge burial depth. Simulations of these experiments were performed using the BUB2D axi-symmetric code using a frictional-cohesive visco-plastic model to describe the response of the saturated sand. This code solves a constrained set of conservation laws in which the liquid region (in this case saturated sand) is assumed incompressible. The explosion is initialized as a high pressure gas bubble (void) within the fluid. Comparisons of the simulations to the experiments are presented together with a study of the physical phenomenology associated with the loading process. In particular, it is shown that the force imparted to the platform is a combination of the impact of the sand on top of the explosion gas bubble and the pressure of the bubble as it expands before venting into the atmosphere. Under certain conditions, when the platform standoff is sufficiently small and the platform is sufficiently large, the bubble can over-expand before venting and pull the platform downward. This phenomenon was studied further through carefully measured and photographed small-scale experiments performed at the University of Maryland 2 (Fourney, W., Leiste, U., Bonenberger, R. and Goodings, D., 2005, Predicting explosive impulse by means of small scale tests. Proceedings of the 31st Annual Conference on Explosives and Blasting Technique, Orlando, FL, 6 - 9 February, 2.). The small-scale experiments provide additional important validation benchmarks for our model. 相似文献
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Dynamic Analysis of Subway Structures Under Blast Loading 总被引：3，自引：1，他引：2
Huabei Liu 《Geotechnical and Geological Engineering》2009,27(6):699-711
Public transit systems have become one of the targets of terrorist attacks using explosives, examples of which are the 1995
attack on Paris subway and the 2004 attack on Moscow subway. Considering the intense threats of terrorist attacks on subway
systems in metropolitan areas, explicit three-dimensional Finite Element method was used to investigate the dynamic response
and damage of subway structures under internal blast loading. The study was motivated by the fact that explosion in subway
structure may not only cause direct life loss, but also damage the subway structure and lead to further loss of lives and
properties. The study based on the New York subway system, and investigated the influences of various factors on the possible
damage of subway tunnel, including weight of explosive, ground media, burial depth and characteristics of blast pressure.
A mitigation measure using grouting to improve ground stiffness and strength was also analyzed. Considering the amount of
explosive terrorists may use, the present study focused on small-diameter single-track tunnels, which are more vulnerable
to internal blast loading and are common in New York City. Blast pressure from explosion was applied to lining surface assuming
triangle pressure–time diagram, and the elasto-plasticity of ground and lining as well as their nonlinear interaction was
taken into account in the numerical model. It is found from the numerical study that maximum lining stress occurred right
after explosion, before the blast air pressure reduced to the atmospheric one, and it was more dependent on the maximum magnitude
of air pressure than on the specific impulse, which is the area below the pressure–time curve. Small tunnels embedded in soft
soil, with small burial depth, might be permanently damaged even by modest internal explosion that may be perpetuated by terrorists. 相似文献
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This paper describes a soil‐structure coupling method to simulate blast loading in soil and structure response. For the last decade, simulation of soil behavior under blast loading and its interaction with semi buried structure in soil becomes the focus of computational engineering in civil and mechanical engineering communities. In current design practice, soil‐structure interaction analysis often assumes linear elastic properties of the soil and uses small displacement theory. However, there are numerous problems, which require a more advanced approach that account for soil‐structure interaction and appropriate constitutive models for soil. In simplified approaches, the effect of soil on structure is considered using spring‐dashpot‐mass system, and the blast loading is modeled using linearly decaying pressure–time history based on equivalent trinitrotoluene and standoff distance, using ConWep, a computer program based on semi‐empirical equations. This strategy is very efficient from a CPU time computing point of view but may not provide accurate results for the dynamic response of the structure, because of its significant limitations, mainly when soil behavior is strongly nonlinear and when the buried charge is close to the structure. In this paper, both soil and explosive are modeled using solid elements with a constitutive material law for soil, and a Jones–Wilkins–Lee equation of state for explosive. One of the problems we have encountered when solving fluid structure interaction problems is the high mesh distortion at the contact interface because of high fluid nodal displacements and velocities. Similar problems have been encountered in soil structure interaction problems. To prevent high mesh distortion for soil, a new coupling algorithm is performed at the soil structure interface for structure loading. The coupling method is commonly used for fluid structure interaction problems in automotive and aerospace industry for fuel sloshing tank, and bird impact problems, but rarely used for soil structure interaction problems, where Lagrangian contact type algorithms are still dominant. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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旁孔透射波法检测既有建筑物桩基的三维有限元分析 总被引：3，自引：0，他引：3
介绍了旁孔透射波法的原理和测试步骤,对这种无损检测方法在既有建筑物桩基础检测中的应用进行了三维有限元分析。建立了三维桩-土模型并计算动力响应,分别给出了饱和土、非饱和土地基中完整桩和缺陷桩的旁孔透射波信号,并分析了P波时间-深度特征与桩身的相关性。研究表明,旁孔透射波法具有简单易行、无损等优点,可以有效地检测既有建筑物的基础。 相似文献
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WL Fourney U. Leiste R. Bonenberger D. Goodings 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(1):1-17
This paper describes a series of very small scale model tests that were conducted in support of a full scale test program conducted by the Army Research Laboratory at Aberdeen, Maryland for the US Navy to investigate the impulse delivered to a military vehicle by a buried land mine. The full scale tests were conducted in July of 2004 and investigated the effect of various parameters on the impulse delivered. The vehicle was represented by a steel plate and depth of burial, standoff distance, and explosive size (up to 10 pounds of TNT) were changed in the seven tests conducted for the Navy. The full scale tests were conducted in saturated sand. The tests described in this paper used a maximum charge size of 3.3 gm of RDX and PETN. Each of the tests conducted for the Navy were simulated by the small scale tests and a prediction of the impulse that would be measured for each of the tests was made. The small scale tests (as well as the full scale tests results) were also used by the developers of various numerical codes that were also used to predict the impuse that would be measured in the full scale test series.This paper is accompanied by a paper by Taylor et al. (Taylor, L. C., Skaggs, R. R. and Gault, W., 2005, Vertical impulse measurement of mines buried in saturated sand, Fragblast, International Journal for Blasting and Fragmentation, 9, 19-28) in this issue of FRAGBLAST. In the next issue of FRAGBLAST several additional papers will be published. These will be the results of the numerical codes that were used to predict the impulse. 相似文献
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通过数值模拟分析地基的强夯加固效果,把夯后地基土的体应变与工程要求的干密度联系起来,用控制体应变作为评价加固范围的标准。通过对数值模拟及试验数据的分析发现,夯击冲量越大,加固效果越好。相同夯击能可以产生不同加固效果的规律,得出了用夯击冲量替代夯击能作为施工参数的控制标准更为合理的结论。改进了夯锤尺寸影响强夯加固效果的研究方法,分析时固定夯锤厚度比固定夯锤质量更具归一性。研究表明,在土性参数相同的条件下,夯击沉降量仅与单位面积夯击冲量有关,而加固深度不仅与单位面积夯击冲量有关,还与夯锤半径有关。在以控制体应变作为加固范围的评价标准、研究各参数影响规律的基础上,采用量纲分析法得到了加固范围的计算公式,并与工程实例进行对比分析,得到了强夯作用下土的干密度分布特征。所得结论对类似工程具有一定的参考价值。 相似文献
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滑坡-涌浪灾害威胁沿河两岸居民生产生活安全和航道安全。当前尚缺乏同步提供流固两相运动矢量的相关物理试验分析系统,以深刻分析滑坡-涌浪产生机制。文章提出了基于流固两相识别的粒子图像测速（PIV）技术和试验实现方法。利用2560×1024像素的工业相机,该PIV技术可实现在3 m×1.5 m视窗下最小1.17 mm的空间分辨率和0.01 s内最小0.117 m/s的观测速度。同时,提出了与该系统方法有关的误差来源和克服相关问题的解决方法。利用相关硬件设施示范性构建了滑坡-涌浪两相运动观测平台,并编制了专门的解算软件。对三维柱体颗粒崩塌、二维柱体颗粒崩塌及其涌浪和水下崩塌-涌浪进行了展示性试验,取得了良好效果。该系统可以揭示广泛的岩土体及水体运动全过程,具有很好的应用前景;将为滑坡-涌浪及相关动力学领域研究提供强有力的研究工具。 相似文献
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爆炸成腔后土体物理力学性能的变化规律 总被引：1，自引：0，他引：1
在6块不同的土质场地完成了21次爆炸成腔试验,试验用炸药埋深为1.20～12.5 cm,起爆药量为0.05～51 kg。对其中的5个腔体进行了土工试验。对爆后土体的天然密度、孔隙比、饱和度、压缩系数、压缩模量、内摩擦角、黏聚力的分布规律进行了实测。试验结果表明,爆炸作用对土体的影响半径是爆炸成腔半径的4～6倍。土体的天然密度、干密度、饱和度、压缩模量和黏聚力等指标随土体距爆炸中心距离的增大而降低。土体的孔隙比、压缩系数和渗透系数等指标随土体距爆炸中心距离的增大而提高。未在腔壁附近发现密度低于原状土的低密度区。爆炸冲击作用对土体内摩擦角的影响规律不明显。 相似文献
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选取东南沿海某建筑工程地基浅层残积土为试样,运用超声波岩土损伤检测技术,测试计算在不同冲击荷载作用下试样纵波波速。选用纵波波速为损伤变量进行损伤度计算,分析了冲击荷载冲击频率、冲量等参数对试样损伤度的影响关系。同时结合试样试验破坏实际情况,分析了冲击荷载作用下试样损伤演化破坏特性。结果表明,随着冲击频率和冲量的增大,残积土试样损伤度都有增大上升趋势;随着损伤度的增加,残积土冲击损伤演化过程可分为小变形、端部出现裂纹、前端1/3处鼓胀或出现裂纹、前端裂纹扩展与表面剥落等几个不同破坏阶段。研究结论为揭示动荷载作用下残积土动力损伤演化规律提供科学依据和量化参数。 相似文献
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开展饱和钙质砂爆炸密实动力特性试验研究,探索饱和钙质砂爆炸密实机制和密实效果,对钙质砂地层中进行的工程建设有重要的理论意义和工程实用价值。通过控制爆炸参数,测试不同参数作用时钙质砂爆炸前后声波特性和表面沉降规律,揭示饱和钙质砂爆炸密实动力特性。试验结果表明：钙质砂高孔隙比和颗粒破碎特性对爆炸密实效果有重要影响。爆炸密实作用后,在爆炸近区,钙质砂颗粒受到较强爆炸冲击作用,导致钙质砂颗粒破碎而形成破碎区和压缩区,压缩区随着时间的推移有松弛的趋势,钙质砂颗粒结构重新固结过程在爆炸后2 h内基本完成。 相似文献