共查询到20条相似文献，搜索用时 31 毫秒
1.
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
2.
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
3.
G. R. Adhikari A. I. Theresraj R. N. Gupta 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(2):79-92
Various methods of transducer mounting provide varying degrees of coupling between the transducer and the measurement surface. The influence of four of these methods on vibration measurements was studied. For this purpose, the first transducer was placed freely on a horizontal surface, the second one was 'sandbagged', the third one was 'spiked' and the fourth one was completely buried in soil. These transducers were mounted side by side and ground vibrations were monitored for 14 blasts at an opencast coal mine.
Ground vibrations in terms of peak particle velocity, peak vector sum and frequency with different mounting methods were analysed. Assuming the data of the buried transducer as the most acceptable one, relative values of other transducers were determined and plotted. For the given tolerance for instrumental and human errors, anomalous readings were found in some cases. The waveforms of the buried transducer were then compared with those of others. Clear distortion in the waveforms or a very low correlation coefficient between two waveforms was suspected poor coupling.
The results indicate that decoupling is most likely with the surface transducer. However, the sandbagged and spiked transducers are also prone to decoupling. Decoupling can result in higher or lower ground vibration. Therefore, burial should be the preferred method for mounting of transducers in soil. 相似文献
Ground vibrations in terms of peak particle velocity, peak vector sum and frequency with different mounting methods were analysed. Assuming the data of the buried transducer as the most acceptable one, relative values of other transducers were determined and plotted. For the given tolerance for instrumental and human errors, anomalous readings were found in some cases. The waveforms of the buried transducer were then compared with those of others. Clear distortion in the waveforms or a very low correlation coefficient between two waveforms was suspected poor coupling.
The results indicate that decoupling is most likely with the surface transducer. However, the sandbagged and spiked transducers are also prone to decoupling. Decoupling can result in higher or lower ground vibration. Therefore, burial should be the preferred method for mounting of transducers in soil. 相似文献
4.
G. R. Adhikari A. I. Theresraj R. N. Gupta 《Fragblast: International Journal for Blasting and Fragmentation》2004,8(1):41-49
The safety and stability of concrete and masonry dams is a great concern when blasting has to be conducted close to these dams in order to construct small hydro-electric projects. There is a danger of ground vibration amplification to those residential-type buildings that are built close to these dams.
Responses of three concrete and masonry dams were measured directly by conducting a number of blasts and by monitoring vibration in the ground as well as on the dams. The amplitudes and frequencies of the motions were analysed and vibration attenuation relations were derived. These relations were used to compare the vibration levels on the dams with those in the ground.
Because of close-in construction blasts that produced high frequency ground vibrations, there was no amplification of the ground vibrations by these dams. The measured amplitudes of ground vibration were comparable to those of the dams. 相似文献
Responses of three concrete and masonry dams were measured directly by conducting a number of blasts and by monitoring vibration in the ground as well as on the dams. The amplitudes and frequencies of the motions were analysed and vibration attenuation relations were derived. These relations were used to compare the vibration levels on the dams with those in the ground.
Because of close-in construction blasts that produced high frequency ground vibrations, there was no amplification of the ground vibrations by these dams. The measured amplitudes of ground vibration were comparable to those of the dams. 相似文献
5.
H. P. Rossmanith V. Hochholdinger-Arsic K. Uenishi 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(2):93-125
This contribution addresses model blasting and focuses on size and boundary effects on wave propagation, fracture pattern development and fragmentation in small scale laboratory size specimen. Small cylindrical specimens are centre-line loaded by linear high velocity of detonation explosive charges and detonated.
Using elastic wave propagation theory and fracture mechanics it is shown that the type of boundary conditions which prevail at the outer boundary of the cylinder control the extension of bore-hole cracking and fragmentation within the body of the cylinder. In the case of a composite cylinder with dissimilar mantel and core materials, the level of fracturing and fragmentation is controlled by the delamination of the interface. This, in turn, depends on the relative diameters of the core and the mantel. The most important parameter though is the ratio between the length of the pulse (space-wise or time-wise) and the characteristic dimensions of the models, i.e. in this case the diameters of the core and the mantel.
The theoretical basis for a simplified two-dimensional plane treatment is developed. Simple or composite, thin, plate-like specimens are centrally loaded; whereas the core is always a circle, the mantel can be either a circle or a square. 相似文献
Using elastic wave propagation theory and fracture mechanics it is shown that the type of boundary conditions which prevail at the outer boundary of the cylinder control the extension of bore-hole cracking and fragmentation within the body of the cylinder. In the case of a composite cylinder with dissimilar mantel and core materials, the level of fracturing and fragmentation is controlled by the delamination of the interface. This, in turn, depends on the relative diameters of the core and the mantel. The most important parameter though is the ratio between the length of the pulse (space-wise or time-wise) and the characteristic dimensions of the models, i.e. in this case the diameters of the core and the mantel.
The theoretical basis for a simplified two-dimensional plane treatment is developed. Simple or composite, thin, plate-like specimens are centrally loaded; whereas the core is always a circle, the mantel can be either a circle or a square. 相似文献
6.
B. A. Cheeseman S. Wolf C. F. Yen R. Skaggs 《Fragblast: International Journal for Blasting and Fragmentation》2006,10(1):1-8
Shallow buried explosives pose a significant threat to lightweight vehicles and their onboard personnel. To date, designers of lightweight vehicles are limited in their knowledge of what occurs during the blast. The high intensity, short term loading imparted by the explosion is enormously complex and can be significantly affected by a number of parameters including the size, shape, type, detonation point and depth of burial (DOB) of the explosive and the type, density and water content of the soil. Recent advancements in numerical simulations have enabled the complex blast event to be accurately modelled by coupling Eulerian and Lagrangian analyses: the former is well suited to modelling the blast and while the latter, the structural response. Further validation of the modelling technique is considered in the current paper, which details simulations performed utilising the coupled Eulerian-Lagrangian analysis to study the blast output of explosives buried in saturated sand. These experiments varied explosive charge size, its depth of burial, the target stand-off (SO) distance and the dimensions of the target plate. The investigation concludes with a discussion of the accuracy of the numerical simulations when compared with the experimental observations. 相似文献
7.
细砂层埋深对堤基管涌影响的试验研究 总被引：1，自引：0，他引：1
不同土层结构的堤基,其管涌发生和发展的情形不同。以前的研究多集中于双层堤基的情况。事实上,含夹砂层堤基中,位于砂砾石层内的细砂层会对堤基管涌的发生产生重大影响,并且这些影响随细砂层在砂砾石层中的位置不同而不尽相同。利用室内砂槽试验,模拟当细砂层位于砂砾石层内部不同深度时含夹砂层堤基管涌的发展过程,研究细砂层埋深对 堤基管涌的影响。试验结果表明,细砂层埋深存在一个临界深度,当细砂层埋深较浅时,堤基的临界水力梯度较小,易于发生管涌,且管涌发生以后,堤基被侵蚀的速率较大,出砂较多;堤基破坏的临界水力梯度随着细砂层埋深的增加而增大,当细砂层埋深大于临界埋深时,堤基的临界水力梯度基本不变,同时堤基抵抗管涌破坏的能力较强,其破坏形式与双层堤基 相类似。 相似文献
8.
W. L. Fourney U. Leiste R. Bonenberger D. J. Goodings 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(4):205-217
This paper investigates the various mechanisms and parameters that are responsible for delivering impulse to a vehicle that is unfortunate enough to detonate a buried mine. Small scale tests are used to examine the effects of air blast or ejected sand in imparting impulse to a plate that is located above the surface of the saturated soil that contains the explosive. Parameters such as confinement, stand off distance, depth of burial of the explosive, density of the soil, and saturation level of the soil are also examined. 相似文献
9.
断层是控制油气藏形成的重要因素之一;断层的开启及闭合影响到油气运移与聚集的效率。但油气在断层中的运移与在砂层中的充注存在差异性这一问题长期被忽视。一般认为;只要发育断层;其断开的渗透层就会被油气充注;极少关注地层水和石油的压缩特性对充注的影响。本文提出;地下单断层活动时;深部油气在超压作用下以涌流方式难以快速充注进入中浅层被切割的砂体;因此;单砂体至少要存在一条断层作为泄水出口;石油才能通过其余断层充注进入砂体;即单砂体要发育两条及两条以上断层;石油才能注入砂体。在断层静止期;油气通过渗流方式沿特定深度范围断面垂向运移;对油气垂向运移距离影响较小。本文运用4个大型盆地的典型油气藏与断层分布关系讨论了本文观点。该观点对油气成藏规律研究及成藏目标评价有较重要参考意义。 相似文献
10.
砂土中隧道施工对相邻垂直连续管线位移影响的模型试验研究 总被引：1，自引：0，他引：1
隧道施工会对邻近管线造成危害,但目前对土体位移与管线位移两者之间的关系还没有清晰的认识。针对这一问题,设计砂土中考虑不同管线管径、埋深及抗弯刚度的3组隧道施工模型试验,分析垂直下穿隧道施工过程中砂土和管线位移规律。研究结果表明,Vorster修正高斯公式能较好地拟合砂土沉降分布,其控制参数?值在0.2～1.0之间变化,且与地层埋深成正比;土体沉降槽宽度系数i对管线变形有较大影响,埋深相同的条件下管线抗弯刚度与沉降值成反比;深埋管线的变形主要受上拱效应支配,且管径越大上拱效应越明显,而下拉效应主要支配着浅埋管线的位移;Smax /i为影响管土相对位移一个关键参数,在此基础上提出了修正的管土相对刚度计算公式。 相似文献
11.
Empirical approaches for predicting fragmentation from blasting continue to play a significant role in the mining industry in spite of a number of inherent limitations associated with such methods. These methods can be successfully applied provided the users understand or recognize their limitations. Arguably, the most successful empirical based fragmentation models have been those applicable to surface blasting (e.g., Kuz-Ram/Kuznetsov based models). With widespread adoption of fragmentation assessment technologies in underground operations, an opportunity has arisen to extend and further develop these type approaches to underground production blasting.
This paper discusses the development of a new fragmentation modelling framework for underground ring blasting applications. The approach is based on the back-analysis of geotechnical, blasting and fragmentation data gathered at the Ridgeway sub level caving (SLC) operation in conjunction with experiences from a number of surface blasting operations.
The basis of the model are, relating a peak particle velocity (PPV) breakage threshold to a breakage uniformity index; modelling of the coarse end of the size distribution with the Rosin-Rammler distribution; and modelling the generation of fines with a newly developed approach that allows the prediction of the volume of crushing around blastholes.
Preliminary validations of the proposed model have shown encouraging results. Further testing and validation of the proposed model framework continues and the approach is currently being incorporated into an underground blast design and analysis software to facilitate its application. 相似文献
This paper discusses the development of a new fragmentation modelling framework for underground ring blasting applications. The approach is based on the back-analysis of geotechnical, blasting and fragmentation data gathered at the Ridgeway sub level caving (SLC) operation in conjunction with experiences from a number of surface blasting operations.
The basis of the model are, relating a peak particle velocity (PPV) breakage threshold to a breakage uniformity index; modelling of the coarse end of the size distribution with the Rosin-Rammler distribution; and modelling the generation of fines with a newly developed approach that allows the prediction of the volume of crushing around blastholes.
Preliminary validations of the proposed model have shown encouraging results. Further testing and validation of the proposed model framework continues and the approach is currently being incorporated into an underground blast design and analysis software to facilitate its application. 相似文献
12.
13.
The charged sites on soil particles are important for the retention/adsorption of metals. Metallic counterions can neutralize
the intrinsic charges on the surfaces of soil particles by forming complexes. In this study, efforts have been made to determine
the effect of surface potential, pH, and ionic strength on the adsorption of four metal ions, hexavalent chromium Cr(VI),
trivalent chromium Cr(III), nickel Ni(II) and cadmium Cd(II), in glacial till soil. Batch tests were performed to determine
the effect of pH (2–12) and ionic strength (0.001–0.1 M KCl) on zeta potential of the glacial till soil. The point of zero
charge (pH
PZC
) of glacial till was found to be 7.0±2.5. Surface charge experiments revealed the high buffering capacity of the glacial
till. Batch adsorption experiments were conducted at natural pH (8.2) using various concentrations of selected metals. The
adsorption data was described by the Freundlich adsorption model. Overall glacial till shows lower adsorption affinity to
Cr(VI) as compared to cationic metals, Cr(III), Ni(II) and Cd(II). 相似文献
14.
The concept of the equivalent free surface has been extended to determine the seismic horizontal pullout capacity of shallow
vertical strip plate anchors buried in sand. The analysis has been done rigorously by using the method of stress characteristics.
The results have been expressed in the form of non-dimensional charts. The pullout resistance has been found to reduce quite
extensively with increase in the magnitude of horizontal earthquake acceleration. The results were compared with the previously
published data, and it was seen that the computed pullout resistance with the proposed method was found to be lowest.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
砂岩透镜体油气藏成因机理与模式 总被引：1，自引：0，他引：1
泥岩层的幕式压实/压裂现象和砂岩透镜体中沸腾包裹体的发现,证明了该类圈闭成藏过程中超压流体幕式充注机制的存在。综合考虑油气运聚的动力与作用方式、输导格架类型与流体流动样式、成藏特征、运聚机理和成藏模式,将砂岩透镜体动力学成因类型划分为毛细管力-超压联控型和超压单控型。对砂岩透镜体中的流体排放机制进行了探讨,并认为处于强超压状态的砂岩透镜体油气藏可能存在侧向和垂向两种流体排放模式。 相似文献
16.
G. I. Gorchakov A. V. Karpov V. M. Kopeikin A. V. Sokolov D. V. Buntov 《Doklady Earth Sciences》2016,467(1):314-319
Quasi-horizontal trajectories of salting sand grains were found using high-speed video-recording in the desertified territory of the Astrakhan region. The sizes and displacement velocities of the saltating sand grains were determined. A piecewise logarithmic approximation of the wind profile in a quasi-stationary wind–sand flow is suggested, which is consistent with the data of observations and modeling. It was established that, in the regime of stationary saltation, the wind profile in the lower saltation layer of the wind–sand flow depends only slightly on the wind profile variations in the upper saltation layer. The vertical profiles of the horizontal wind component gradient in a quasi-stationary wind–sand flow were calculated and plotted. It was shown using high-speed video recording of the trajectory of a sand grain with an approximate diameter of 95 μm that the weightlessness condition in the desertified territory of the Astrakhan region in a stationary wind–sand flow is satisfied at a height of approximately 0.15 mm. The electric parameters of a wind–sand flow, which can provide for compensation of the force of gravity by the electric force, were estimated. In particular, if the specific charge of a sand grain is 100 μC/kg, the force of gravity applied to the sand grain can be compensated by the electric force if the vertical component of the electric field in a wind–sand flow reaches approximately 100 kV/m. It was shown that the quasi-horizontal transport of sand grains in the lower millimeter saltation layer observed in the desertified territory can be explained by the joint action of the aerodynamic drag, the force of gravity, the Saffman force, the lift force, and the electric force. 相似文献
17.
E. Villaescusa I. Onederra C. Scott 《Fragblast: International Journal for Blasting and Fragmentation》2004,8(1):23-40
This paper presents the results of a comprehensive monitoring program designed to investigate the extent of blast induced damage experienced by rock masses extracted by bench stoping methods. An array of triaxial geophones and extensometers were used to monitor blast vibration attenuation and measure hangingwall deformations during stope extraction. In addition, pre and post surveys of the hangingwall rock mass were conducted using a TV borehole camera and cavity survey instrumentation. These surveys were later used to calibrate damage profiles into the stope hangingwalls.
Peak particle velocity, hangingwall deformation measurements and stope surveys were used to develop a site specific damage model that allowed engineers to asses drilling and blasting configurations to minimise the extent of pre-conditioning and damage. In addition the study included the analysis of the frequency response, displacements and accelerations experienced by the excavation as extraction and mine filling progressed. This work aimed at improving our understanding of the influence of blasting on the dynamic behaviour of stope hangingwalls.
The study demonstrated that estimates of the maximum extent of rock mass pre-conditioning and/or damage made through the application of the Holmberg-Persson approach compared well with measured results. In addition, the study found that dynamic loading imparted on an exposed hangingwall from subsequent stope blasting was also expected to contribute to rock mass weakening and that mine filling was crucial to arrest further deterioration. Hangingwall accelerations were used to demonstrate that larger openings may be more susceptible to dynamic loading. 相似文献
Peak particle velocity, hangingwall deformation measurements and stope surveys were used to develop a site specific damage model that allowed engineers to asses drilling and blasting configurations to minimise the extent of pre-conditioning and damage. In addition the study included the analysis of the frequency response, displacements and accelerations experienced by the excavation as extraction and mine filling progressed. This work aimed at improving our understanding of the influence of blasting on the dynamic behaviour of stope hangingwalls.
The study demonstrated that estimates of the maximum extent of rock mass pre-conditioning and/or damage made through the application of the Holmberg-Persson approach compared well with measured results. In addition, the study found that dynamic loading imparted on an exposed hangingwall from subsequent stope blasting was also expected to contribute to rock mass weakening and that mine filling was crucial to arrest further deterioration. Hangingwall accelerations were used to demonstrate that larger openings may be more susceptible to dynamic loading. 相似文献
18.
土拱效应对考虑拱效应时土压力的计算非常重要,而目前对土拱效应的形成机理认识还不深刻。通过自行设计的室内挡板下落试验对砂土拱效应的问题进行了试验研究。得到了不同的土体埋深情况下,随挡板下移挡板上土体重量、箱内土体的应力和侧压力系数的变化规律。试验结果表明,挡板微小的位移挡板上土体的重量就会快速降低;随着挡板继续下移挡板上土体重量降低的趋势逐渐减缓,认为挡板下移2.5 mm时上部土体达到临界状态;随挡板下移箱底挡板上部中心线上的竖向土压力减小,挡板两侧上部土体的竖向土压力增大;挡板上部中心线上的侧压力系数明显增大。通过土体内的应力变化规律对砂土拱效应的形成机理进行了分析。 相似文献
19.
河道维护、航道开挖及疏浚等一些工程,常常将挖掘的泥沙抛入流动的水体中,利用横流对泥沙颗粒团的对流扩散作用来稀释泥沙浓度.针对这类工程进行水环境质量影响评价时,首先要识别泥沙的运动特性.通过实验手段,研究不同级配的泥沙颗粒团瞬时排放后在横流中迁移扩散混合特性.实验结果表明,泥沙颗粒团进入水体后,在浮力、重力、阻力和横流紊动的综合作用下发生对流扩散;横流是产生泥沙对流运输的主要动力,横流的紊动作用,加强了泥沙颗粒团与水体的混合作用,并且破坏了其在静水中的双漩涡结构,因此大大地增加了垂向前锋位置和纵向扩散宽度.通过分析得出了无量纲泥沙颗粒团垂向前锋位置与时间、纵向扩散宽度与时间以及垂向前锋位置与纵向扩散宽度的3个关系式中的参数(α1、α3和α2)均值及其变化范围,可应用于抛泥对水体环境的影响评价. 相似文献
20.
M. Bali H. Jridi S. Farhat B. Louhichi R. Boukchina 《International Journal of Environmental Science and Technology》2017,14(6):1209-1216
The main purpose of this study was to investigate the ability of sand/granular activated charcoal mixture medium to treat urban wastewater effluents. Several laboratory experiments were conducted to determine the best combination ratio of sand/activated charcoal which would allow the optimum water purification. A comparative study was undertaken to evaluate the effect of the addition of activated charcoal on infiltration-percolation efficiency. Experiments demonstrated that fortifying sand medium with granular activated charcoal improved the pollutants removal efficiencies. Results showed that a combination ratio of 3:1 (by volume) of sand and granular activated charcoal gave the best depuration efficiency regarding organic matter, nitrogen and orthophosphorous. The mean removal rates of COD, NH4–N and PO4–P were 83.29, 95.85 and 65.21%, respectively. Furthermore, experiments demonstrated that a mixture of sand/activated charcoal in a 3:1 ratio resulted in the optimum oxidation capacity. 相似文献