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1.
Blast damage control in jointed rock mass 总被引：2，自引：0，他引：2
Highly jointed rocks often cause problems associated with blast damage and the stability of the back and/or walls of the excavation. A field study was performed to understand the role played by the joint parameters in inducing blast damage. The field work included blasting of small scale models, drift rounds and monitoring of blast damage at several operating mines. The damage was assessed by blast vibration monitoring, half cast factor, overbreak measurement and visual inspection.
The effect of spacing, orientation, aperture, condition, filling material and wall strength of joints on blast damage is described. The interaction between the joint planes and explosive energy has been discussed and the overbreak control measures have been suggested. 相似文献
The effect of spacing, orientation, aperture, condition, filling material and wall strength of joints on blast damage is described. The interaction between the joint planes and explosive energy has been discussed and the overbreak control measures have been suggested. 相似文献
2.
Mei Jie Zhang Wanzhi Xu Bangshu Zhu Yongxue Wang Bingkun 《Geotechnical and Geological Engineering》2021,39(7):5309-5323
For large cross-section tunnel in horizontal layered rock mass, blasting excavation often causes serious overbreak and underbreak. In this study, blasting excavation tests of tunnel upper face were conducted, blast-induced excavation damage and the influence mechanisms of weak beddings and joints were analyzed based on the Panlongshan tunnel. In order to achieve fine excavation, the cut mode of “center holes and four-wedge cutting holes”, the blasthole pattern of “empty holes, long holes, short holes and additional relief holes”, the maximum single-hole charge and the air-deck charge structure were proposed. Compared with the damage characteristics, overbreak and underbreak, and deformations of surrounding rock before and after optimization, the latter was better in tunnel contour formation and surrounding rock stability. The results show that after optimization, the large-area separation of vault rock mass is solved, the step-like overbreak of spandrel rock mass is reduced and the large-size rock block and underbreak are avoided. The maximum linear overbreak of vault, spandrel, and haunch surrounding rock is decreased by 42.3%, 53.7% and 45.1%, respectively. The underbreak at the bottom of the upper face is reduced from ??111.5 to ??16.5 cm. The average overbreak area is decreased by 61.1%. The surrounding rock displacement after optimization finally converges to the smaller value. The arch crown settlement and the horizontal convergence of haunch are reduced by about 21.6% and 18.3%, respectively. Furthermore, from the completion of blasting excavation to the stabilization of surrounding rock, it takes less time by using the optimized blasting scheme.
相似文献3.
Tunnel blasting techniques in difficult ground conditions 总被引：1，自引：0，他引：1
Summary The quality of tunnelling can be improved by proper blast design which takes into account the rock mass conditions. The effects of different rock mass properties on tunnel blast performance need to be assessed. The strength of the formation and joint orientation critically affected fragmentation and overbreak in a model study of blasting. Similar effects were noted in situ when the performance of a blast pattern in different rock mass conditions in the Tandsi inclines (Bihar, India) were analysed. Accordingly, the on-going blast pattern was modified for the poor ground conditions prevailing in the rest of the inclines. Improved fragmentation and smooth profile were obtained as a result; the rate of drivage improved considerably and the cost of excavation was reduced. Based on the observations in the model studies and the investigations at Tandsi, some guidelines for optimum blast design in difficult ground conditions are suggested. 相似文献
4.
V. M. S. R. Murthy Kaushik Dey 《Fragblast: International Journal for Blasting and Fragmentation》2003,7(3):149-166
Tunnels are required to be constructed for meeting different human needs such as power generation, transportation, underground storage, sewage etc. The predominant method of excavation, world over, is drilling and blasting owing to its capability to meet changing geo-technical conditions. Irrespective of the purpose for which the tunnels are driven, all are plagued by overbreak problems. Tunnels driven for water conveyance in hydroelectric power projects, in particular, need to be excavated with minimum overbreak to minimise cost of permanent concrete lining. Thus, predicting overbreak assumes significant importance to design site-specific blasts for minimizing rock damage. This paper presents a brief review of existing PPV (Peak Particle Velocity) based blast-induced rock damage estimation criteria and attempts to outline the ground vibration threshold levels for overbreak/rock damage in a tunnel driven through compact basalt. Rock damage manifested as overbreak is measured and correlated with the possible threshold levels of PPV. Also, the PPV levels for crack initiation and widening are proposed. The case pertains to a lake tap horizontal tunnel of Koyna Hydro-electric Power Project, India which is a water feeder tunnel for a fully underground hydroelectric power project. The tunnel was driven under a shallow rock cover of average depth ranging from 20 to 25m beneath a fully charged water body. The parting rock is mainly compact basalt. Blasting was carried out in two rounds in a controlled manner, i.e., by limiting the maximum charge per delay based on ground vibration monitoring. Ground vibration generated with free face (in second round) has been modeled and a new ground vibration propagation equation is proposed for tunnel blasting including the effect of an extra free face. The threshold limits of PPV for different degrees of overbreak/rock damage are proposed from extrapolated vibration predictor equation. The actual overbreak in the tunnel, measured using a Planimeter, varied from 2.45 per cent to 17.75 per cent of the finished tunnel area. The predicted overbreak from extrapolated PPV measurements is compared against the measured overbreak to validate the proposed blast-induced rock damage (BIRD) assessment model. The PPV level for overbreak was found to exceed 2050 mm/s in compact basalt. A linear relationship between the overbreak and maximum charge per delay is also established to design a tunnel blast in similar formations. 相似文献
5.
E. Widzyk-Capehart P. Lilly 《Fragblast: International Journal for Blasting and Fragmentation》2002,6(2):151-168
Blasting is the primary comminution process in most mining operations. This process involves the highly complex and dynamic interaction between two main components. The first is the detonating explosive and the second is the rock mass into which the explosive is loaded. The mechanical properties of the rock material (such as dynamic strength, tensile strength, dynamic modulus and fracture toughness) are important considerations in understanding the blasting process. However, it is the characteristics of the geological defects (joints, foliation planes, bedding planes) within the rock mass that ultimately determine how effectively a blast performs in terms of fragmentation, all else being equal. The defect characteristics include, but are not limited to, their orientation, spacing, and mechanical properties. During the blasting process, some of the geotechnical characteristics of the rock mass are substantially changed. From the blasting outcome point of view, the most notable and important is the change in fragment size distribution that the rock mass undergoes. The pre-blast in situ defect-bounded block size distribution is transformed into the post-blast muckpile fragment size distribution. Consequently, it is fundamental to our understanding of and ability to predict the blasting process that both the blastability of a rock mass and its transformation into the fragment size distribution can be appropriately quantified. 相似文献
6.
Considering different mechanical cutting tools for excavation of rock, drilling and blasting is said to be inexpensive and
at the same time most acceptable and compatible to any geo-excavation condition. Depending upon strength properties of in-situ
rock mass, characteristics of joint pattern and required quality of blasting, control blasting techniques viz., pre-split
and smooth blasting are commonly implemented to achieve an undamaged periphery rock-wall. To minimize magnitude of damage
or overbreak, the paper emphasized that in-situ stresses and re-distribution of stresses during the process of excavation
should be considered prior to selection of explosive parameters and implementation of any suitable blast pattern. Rock structure
being not massive in nature, the paper firstly explains the influence of discontinuities and design parameters on smooth-wall
blasting. Considering the empirical equations for estimation of stress wave’s magnitude and its attenuation characteristics
through transmitting medium, the paper has put forward a mathematical model for smooth blasting pattern. The model firstly
illustrates that rock burden for each hole should be sub-divided into thin micro strips/slabs to understand the characteristics
of wave transmission through the medium and lastly with the help of beam theory of structural dynamics have put forward a
mathematical model to analyze and design an effective smooth blasting pattern to achieve an undamaged periphery rock-wall. 相似文献
7.
节理的存在是岩体明显区别于岩石的一个重要特征,也是导致岩体具有非均质性及各向异性的一个重要因素。节理岩体在爆炸冲击荷载作用下的破坏特征不仅是岩体力学研究的一个热点问题,也是岩石爆破领域经常遇到的一个工程问题。目前,常用的有限元和离散元等数值方法都不能很客观地反映岩体中节理分布的实际规律,而最新出现的数值流形方法则完全能够按照岩体中节理的实际分布规律进行建模,并能够很好地模拟岩体在外力作用下新裂纹的产生及已有节理的开裂。对3种不同节理岩体,即无节理岩体、均布水平节理岩体、均布垂直节理岩体等在均布垂直于圆周方向上的冲击荷载作用下的破坏过程进行了模拟。由模拟结果可以明显看出,节理的存在对岩体的破坏型式起到了关键性的控制作用。对于完整岩体,其破坏型式呈现出了很好的对称性;而对于水平及垂直节理岩体,其破坏型式在很大程度上受到节理分布的控制。研究结果对岩石爆破工程设计具有一定的指导意义。 相似文献
8.
预裂爆破的现场实践表明,诸如节理、软弱夹层和断层等地质不连续面是影响预裂爆破效果的一个重要因素。运用LS-DYNA 3D程序研究了不同角度的节理对预裂爆破效果的影响。通过数值模拟发现,岩体中节理的存在对预裂爆破效果影响显著,其吸收应力波能量并阻碍应力波的传播,且影响预裂缝产状。研究结果表明,节理附近的预裂缝大多沿节理垂直方向开裂,逐渐与被破坏节理连接,节理夹角较小时,易形成锯齿状裂缝,且较难贯通。随着节理与炮孔连线夹角的增大,应力波在节理处的透射率越大,节理附近位置上的质点振速也越大,预裂缝更趋于平直且更易贯通。当节理垂直炮孔连线时透射率最大,所形成的预裂缝与炮孔连线基本重合,不会出现锯齿形裂缝,相对成缝效果最佳。 相似文献
9.
Agne P. Rustan 《Engineering Geology》1998,49(3-4):303-313
The optimal delay time between the contour holes in rock blasting has been studied by theoretical and empirical research in Sweden, regarding ground vibrations, increase in crack frequency, radial crack length and finally overbreak (half cast factor). The model test presented in this paper concerns controlled contour blasting in tunnelling and the full-scale blasts concern tunnelling, road cutting, and dimensional stone quarrying. The results indicate that the microsequential contour blasting technique (contour holes fired in sequence and with a delay in the order of 1–2 ms) is superior to simultaneous initiation both regarding blast-induced ground vibrations and crack frequency increase in the rock mass. Both these evaluation methods reflects the conditions deeper in the remaining rock mass. Simultaneous initiation, however, is superior to micro-sequential contour blasting both regarding the half cast factor and the length of radial cracks emanating from the blastholes. These two parameters are more related to the surface conditions after blasting. The industrial applications of this new knowledge are the use of micro-sequential contour blasting when ground vibrations are of greater concern than the contour, for example, in trench blasting or quarrying in urban areas, and the use of simultaneous initiation when an even rock surface is of high priority. 相似文献
10.
Rock mass characterization using photoanalysis 总被引：3，自引：0，他引：3
John A. Franklin Norbert H. Maerz Caralyn P. Bennett 《Geotechnical and Geological Engineering》1988,6(2):97-112
Summary Rock formations are distinguished from each other by measuring first the properties of the intact rock, and second those of the jointing. Whereas simple methods are available for measuring intact rock properties, those available for measuring jointing remain slow, expensive, and sometimes dangerous. Digitized photographs (photoanalysis) may provide a solution. In this paper, the new techniques of photoanalysis are reviewed together with applications, promising areas for research, and also some obstacles that remain to be overcome. Aspects of the rock mass that lend themselves to photoanalytical measurement include those of individual joints, such as persistence, orientation and roughness, and those relating to the mass as a whole, such as block size and the spacing or intensity of jointing. Photoanalysis can also be applied to measurement of blasting. It allows characterization of the rock about to be blasted, helping the engineer to predict fragmentation and to design an appropriate blasting pattern. Afterwards, the same methods can be used to measure fragmentation, overbreak and backbreak, for quality control and for diagnosis of problems.Presented at the 28th US ROck Mechanics Symposium, Tucson, Arizon, 29 June–1 July 1987. 相似文献
11.
Summary Quick, simple, reliable, and inexpensive measurements of overbreak and underbreak are needed for proper evaluation of tunnelling by the drill and blast method. Problems causing rock damage can be identified and remedied while the work is still in progress. The measurements are also useful in identifying causes of overbreak and overbreak, and in helping to settle contractual disputes relating to payment for replacement concrete and secondary blasting of tights (zones of underbreak). A newly developed method to measure underbreak and overbreak is presented here. The light sectioning method (LSM) uses a radial sheet of light to define the tunnel profile. An image of the final tunnel profile is acquired and digitized, using digital image analysis. This profile is superimposed over the design profile, and from this zones of overbreak and underbreak are identified, quantified, and presented graphically. 相似文献
12.
J.C. Jhanwar A.K. Cakraborty H.N. Anireddy J.L. Jethwa 《Geotechnical and Geological Engineering》1999,17(1):37-57
In blasting with air decks, repeated oscillation of shock waves within the air gap increases the time over which it acts on the surrounding rock mass by a factor at between 2 and 5. The ultimate effect lies in increasing the crack network in the surrounding rock and reducing the burden movement. Trials of air deck blasting in the structurally unfavourable footwall side of an open pit manganese mine has resulted in substantial improvements in fragmentation and blast economics. Better fragmentation resulted in improved shovel loading efficiency by 50–60%. Secondary blasting was almost eliminated. Use of ANFO explosive with this technique reduced explosive cost by 31.6%. Other benefits included reductions in overbreak, throw and ground vibration of the order of 60–70, 65–85 and 44% respectively. This paper reviews the theory of air deck blasting and describes in detail the air deck blast trials conducted in a manganese open pit mine in India. The blast performance data have been analysed to evaluate the benefits of air decking over conventional blasting. 相似文献
13.
Modelling Rock Blasting Considering Explosion Gas Penetration Using Discontinuous Deformation Analysis 总被引：1，自引：0，他引：1
Explosion gas plays an important role in rock mass fragmentation and cast in rock blasting. In this technical note, the discontinuous deformation analysis method is extended for bench rock blasting by coupling the rock mass failure process and the penetration effect of the explosion gas based on a generalized artificial joint concept to model rock mass fracturing. By tracking the blast chamber evolution dynamically, instant explosion gas pressure is derived from the blast chamber volume using a simple polytropic gas pressure equation of state and loaded on the blast chamber wall. A bench blasting example is carried out. The blast chamber volume and pressure time histories are obtained. The rock failure and movement process in bench rock blasting is reproduced and analysed. 相似文献
14.
15.
金丽温高速公路连拱隧道超挖预测及原因分析 总被引：3，自引：0，他引：3
通过对金丽温高速公路连拱隧道的地质特征进行现场调查,经分析得出隧道区岩体结构面的特征参数,利用分析出的结构面特征参数值,结合隧道超挖预测中的神经网络理论及结构面网络模拟理论,对连拱隧道的超挖情况进行预测。从分析结果看,超挖问题在连拱隧道的施工过程中不可避免,其产生部位主要集中在中导洞与隧道的连接部位,通过预测得出的结果与现场开挖情况进行对比分析说明,隧道的超挖预测理论预测结果与实际有较好的一致性,文中最后针对隧道的特点,分析了产生超挖的基本原因,为确保隧道开挖过程中减少超挖提供依据。 相似文献
16.
Wu Li Chen Jianping Engineering Faculty China University of Geosciences Wuhan 《中国地质大学学报(英文版)》2001,12(2)
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17.
光面爆破质量直接关系到隧道施工的质量、安全及成本等,牛角山隧道凿岩爆破开挖施工过程中,采用PD—CA循环质量管理方法,根据TM隧道断面测量系统采集的断面超欠挖数据,进行现场检查、讨论分析,找出影响光面爆破质量的主要因素,通过制定有针对性的改进措施并监督执行,较好地提高了光面爆破效果,一次循环进尺平均光面爆破合格率达到95％,炮眼残留率达到85％,不仅保证了隧道施工质量,而且降低了施工成本,加快了施工进度,获得了良好的质量效果和经济效益。 相似文献
18.
One of the most important problems during tunneling in soft rock is deformation and fracturing of the rock during tunneling. The problem was successfully explored by using a transparent rock surrogate to simulate the behavior of soft rock, which permitted visualizing conditions within the rock. Synthetic soft rock was made using consolidated fused quartz saturated with a blend of two mineral oils that have the same refractive index as the quartz. The tunnel was simulated using a smooth aluminum tube and two tunneling methods representing machining and blasting were considered. Two observation planes made of seeding particles were pre-placed within the model and used to track soil movements and crack propagation. Images of both planes were captured simultaneously using two orthogonal cameras. Rock deformations were concentrated in the vicinity of the tunnel face, and deformation rates behind the tunnel face were significantly greater than those ahead of the face. However, deformation rates and patterns varied considerably depending on the excavation method/rate. Fracturing mechanisms exhibited similar differences, for machining deformations occurred higher above the crown and propagated toward the tunnel face. Conversely for blasting deformations sprang from the crown upwards. These observations can assist with numerical simulations and in planning tunnel support systems.
相似文献19.
安塞区主城区范围内的基岩地层发育一以延河为枢纽线、走向约330°的背斜构造,在基岩地层中普遍发育走向与褶皱轴面平行（320°～340°）和垂直（40°～60°）两个方位的两组张性节理,还发育有两组与褶皱轴斜交的共轭剪切节理,第一组共轭剪切节理面走向为近南北（0°～10°）和近东西（80°～90°）,第二组共轭剪切节理面走向为100°～120°和200°～210°。上述基岩中发育的、不同走向的多组节理面对研究区内具相同走向分布特征的崩塌结构控制面的发育有较强控制作用。第一组共轭剪节理中走向近东西（80°～90°）的节理面控制着研究区内发育程度最高的崩塌结构控制面,它与区内岩质崩塌的发育相关程度最高;其次是两组张性节理面分别控制着走向相同且发育程度较高的两组岩质崩塌结构控制面,第二组共轭剪节理面则控制着区内发育程度相对较低的、走向与共轭节理面相同的两组崩塌结构控制面。 相似文献
20.
S. P. Singh 《Geotechnical and Geological Engineering》1996,14(1):41-50
Summary A variety of overbreak control techniques are used during excavation with the drill and blast system. Tracer blasting is used in Canadian underground mines to minimize blast damage and involves placing a low-strength detonating cord along the length of a blast hole prior to charging with ammonium nitrate-fuel oil (ANFO). The results of tracer blasting are not always consistent and its mechanism is only hazily comprehended. In the absence of a clearly defined mechanism, it is difficult to analyse the results of tracer blasting and to identify the factors responsible for the inconsistency of results.A series of bench blasts and pipe tests were carried out to investigate the mechanism of tracer blasting. The evidence indicated partial deflagration and desensitization of ANFO, thus reducing the total available explosive energy. The rock mass surrounding the traced blasthole experienced a low level of ground vibrations. As a result of the continuous side initiation of ANFO, energy partitioning was more in favour of gas energy. A mechanism of tracer blasting has been proposed and the factors responsible for the inconsistency of the results have been identified in this paper. 相似文献