坑探工程技术讲座

二、爆破爆破作业在整个掘进循环中所占的时间不超过10％，但其重要性却大大超过其他工序，舍此而无传统的钻眼爆破法可言。因此，炸药的爆炸过程、炸药在岩石中爆破作用以及钻眼爆破参数等方面的研究，引起人们的关注。     

硝铵炸药包的腊液防水加工法

我队在涌水井巷爆破岩石时应用硝铵炸药,曾多次发生误炸或炸药爆炸不完全现象,严重影响爆破效     

突变理论在层状岩体破碎分析中的应用

本文简要介绍突变理论的尖点突变模型。在分析层状岩体在爆炸冲击荷载作用下破碎程度主要受控因素的基础上,运用拟合的途径建立了岩石破碎分析的尖点突变控制方程。该方程可以被用来直接定量计算岩石破碎块度发生明显变化点的炸药单耗(q)或炮孔与层状结构面间的夹角(α),实践证明是可行的。     

复杂环境下框架结构大楼的爆破拆除

爆破拆除的钢筋混凝土框架结构大楼的周围环境比较复杂。通过试爆确定多种承重立柱的合理炸药单耗和相应的爆破参数。在保证安全的前提下,对有可能影响楼房倒塌的非承重结构做了必要的预处理。对爆破切口层的主次梁、楼梯梁以及梁柱交接处布置炮眼,采用松动控制爆破,随楼层起爆,充分保证楼房倒塌过程中结构的解体和破碎。爆破中设计了非电交叉复式起爆网络,并利用洒水车降尘,实践中取得了预期的效果。     

舟山灌门水道海底隧道钻爆法施工稳定性分析

以舟山灌门水道海底隧道为背景,依据地质资料,选取隧道典型横断面来研究钻爆法施工时围岩的稳定性。由典型横断面的几何参数和地质资料构建数值计算模型,采用国际上常用的计算模式模拟爆破荷载,根据FLAC3D动态计算的特点,将爆破荷载以等效应力的方式加载于模拟炮孔之上。数值计算结果表明,各关键点的位移、振动速度、加速度-时程曲线均满足隧道爆破变形规律,且振动速度峰值均小于规范要求临界值,爆破作用影响范围小于岩石覆盖层建议厚度,验证了岩层覆盖厚度建议值和爆破方案的合理性。最后,为了弄清岩石覆盖厚度和炸药量对围岩稳定性的影响,给出了不同岩石覆盖厚度和炸药量情况下的计算结果。所得结论对后续施工和类似工程具有一定的指导意义。     

水平巷道中棱柱形掏槽炮眼布置的基本研究

在炸药爆破作用下不易塑性变形的脆硬岩石中应用棱柱形掏槽效率最高。在国外许多采矿企业中进行了确定棱柱形掏槽合理参数的实验和理论研究。在白云石化的石灰岩层中进行了各种结构的棱柱形掏槽的研究。破碎岩石所消耗的能量按破碎岩石体积和爆破后形成的掏槽孔大小或掏槽眼和崩落眼间的破碎带大小来确定。确定,崩落眼直径对爆破结果的影响     

槽井探施工点滴经验

一空隙爆破法在槽探施工中,往往有的槽子布置在村庄或其他建筑物附近,为了保护建筑物不受破坏,爆破时只要求使岩石松动,不使它飞散,因此就应少装药。但当岩石较硬时,如果药装的太少,则炸药集中于炮眼底部而爆不开。为解决这个问题,我们采用了空隙爆破法,如图,在炮眼内隔一节炸药装一节竹节或癸花楷(去心),利用炸药的诱导性而使下一节药爆炸。这样一方面延长了炮眼的装药长度,不致因药少集中于眼底而炸不开;另一方面而炸药分布于炮眼全长上,爆破后的块度较均匀,减少大块处理。     

水下炸礁工程施工技术

我局从1985年以来,在大连、丹东等地进行了水下炸礁工程(即水下的岩石爆破)的施工,共施工炸礁爆破孔533个计3470m,炸方量达74000m~3.施工     

某输水工程隧洞预裂爆破施工技术应用分析

爆破是隧洞施工的主要开挖工艺,本文以辽宁某输水工程为例,对输水工程隧洞施工过程中的爆破施工技术进行分析,采取钻爆法施工,计算了线装药密度、炮孔数目、炮孔间距、炸药单耗、装药量等参数,并对施工关键技术和质量控制方案进行对比,确定应在本隧洞预裂爆破施工中,根据实验和经验公式确定的爆破参数,发现爆破后的隧洞轮廓面较完整,效果比较理想,损失较小。说明选用的爆破参数可行,为以后的类似工程具有指导意义。     

岩体结构对岩石爆破效果的影响

分析了爆破冲击波的传播特点，指出了对岩石破坏最大的是拉伸应力波，并对岩体结构对岩石爆破效果的影响进行了探讨。     

Fragmentation Energy in Rock Blasting

The theoretical explosive energy used in blasting is a common issue in many recent research works (Spathis 1999; Sanchidrian 2003). It is currently admitted that the theoretical available energy of the explosives is split into several parts during a blast: seismic, kinetic, backbreaks, heave, heat and fragmentation energies. Concerning this last one, the energy devoted to the breakage and to the creation of blocks within the muckpile can be separated from the microcracking energy which is devoted to developing new and/or extending existing micro cracks within the blocks (Hamdi et al. 2001; López et al. 2002). In order to investigate these two types of energy, a first and important task is to precisely study the main parameters characterising the two constitutive elements of the rock mass (rock matrix and discontinuity system). This should provide useful guidelines for the choice of the blasting parameters (type of explosive, blasting pattern, etc.), in order to finally control the comminution process. Within the frame of the EU LESS FINES research project, devoted to the control of fines production, the methodology was developed in order to: (1) characterize the in situ rock mass, by evaluating the density, anisotropy, interconnectivity and fractal dimension of the discontinuity system and (2) evaluate fragmentation (both micro and macro) energy spent during the blasting operation. The methodology was applied to three production blasts performed in the Klinthagen quarry (Sweden) allowing to estimate the part of the fragmentation energy devoted to the formation of muck pile blocks on one side and to the muckpile blocks microcracking on the other side.     

Analysis of the Effect of Borehole Size on Explosive Energy Loss in Rock Blasting

In this paper, studies were conducted on the effect of borehole size on explosive energy loss in rock blasting. Since most industrial explosives are nonideal ones, the charge size and the confinement condition have significant impact on the detonation performance of these explosives. Analyses indicated that smaller boreholes will cause more loss of explosive energy than larger ones. This is especially true for most industrial explosives. The paper presents the analyses of energy loss for a number of different explosives with various borehole sizes. Based on these analyses recommendations and guidelines were given for borehole size determination in rock blasting operations.     

Theoretical Concept to Understand Plan and Design Smooth Blasting Pattern

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.     

岩石爆破能量分析的数值方法

本文通过球形装药与岩石爆炸作用的力学分析,给出确定爆炸能量利用率的数值方法。通过算例,对于以破碎为主要目的的岩石工程爆破,爆炸能量利用率约为50%,爆炸作用初期的爆炸能量传递率约为40%。对于算例涉及到的炸药和岩石,两者的波阻抗越接近,爆炸能量利用率就越高。     

松辽盆地改造残留的古火山机构与现代火山机构的类比分析

现代火山机构形态有盾状、锥状和穹状,可按喷发样式进一步划分为7种类型。据此分类,在松辽盆地周缘剖面及其北部徐家围子断陷区可识别出4类火山机构：盾状火山机构,由喷溢相熔岩组成,可夹有薄层爆发相火山碎屑岩;层火山机构,由互层的熔岩与火山碎屑岩组成,喷溢相与爆发相交替的序列明显;火山碎屑锥,几乎全部由火山碎屑（熔）岩组成,爆发相为主;熔岩穹丘由高粘度的流纹质、英安质熔岩堵塞火山口后缓慢挤出形成,喷溢相和侵出相发育,兼有火山通道相。盆地内埋藏火山机构最小坡度为3°,最大坡度为25°,底部直径为2～14 km,分布面积为4～50 km²,火山岩厚度为100～600 m;总体上呈现出数目多、个体规模小、受区域大断裂控制、具裂隙式-多中心喷发、彼此相互叠置的特征。火山岩岩性和岩相是控制松辽盆地古火山机构类型及形态的主要因素。     

Improving Collar Zone Fragmentation by Top Air-Deck Blasting Technique

Air gap in an explosive column has long been applied in open-pit blasting as a way of reducing explosive charge, vibration, fly rock and improve fragment size. In conventional blasting a greater amount of explosive energy is lost in the generation of oversize fragments. Oversize fragments reduces loading and hauling efficiencies of equipment which requires secondary blasting. Recurring oscillation of shock waves in the air gap increases the time over which it acts on the adjacent rock mass by factor of 2–5. Top air deck blasting technique trial conducted with an application of gas bags at Chimiwungo pit resulted in an improved fragmentation of about 94 % less than 950 mm. Results obtained from the analysis of muckpile images using split-desktop exhibited that the mean fragment size was 264.81 mm and F20, F80 and top-size were 41.99, 683.18 and 1454.69 mm respectively. Optimum crusher feed size was as large as 1200 mm and crushed down to the 40 mm and only a small percent of the material was above 1200 mm. Gas bag application resulted in a significant reduction in explosives load in production holes without loss in fragmentation or movement of the collar zone. This reduced total cost of charging as compared to conventional blasts with a variance of $20, powder factor was dropped to an average of 0.86 kg/bcm. The technique reduced the cost of bulk blend explosive by 15 %, reduced overall cost of charging per hole by 12 %, enhanced premature ejections. The overall blast results were satisfactory, 443,624 tonnes of blasted material from the block which represented 90 % of the total muckpile material was within 900 mm size. The overall muckpile blasted was well fragmented.     

Propagation Characteristics of Blasting Stress Waves in Layered and Jointed Rock Caverns

The existence of joint fissures makes explosive actions between rock masses more complex. Therefore, it is of great significance to carry out experiments studying blasting stress waves propagating in jointed rock masses. Based on the Froude Similarity principle, the geological mechanical models of intact rock masses and jointed rocks have been proposed. A blasting vibration experiment was carried out and demonstrated that the propagation of the blasting stress waves and changing structures have an important relationship. A numerical simulation of the blasting stress wave propagation law in a layered jointed rock mass was carried out. This study found that with an increase in the joint angle, the peak velocity of blasting stress wave, transmission coefficient and reflection coefficient all gradually increased, while the attenuation coefficient gradually decreased. With an increase in joint spacing, the attenuation rate of the blasting stress waves increased.     

Effect of Geological Structure on Flyrock Prediction in Construction Blasting

Blasting is sometimes inevitable in civil engineering work, to fragment the massive rock to enable excavation and leveling. In Minyak Beku, Batu Pahat also, blasting is implemented to fragment the rock mass, to reduce the in situ rock level to the required platform for a building construction. However, during blasting work, some rocks get an excessive amount of explosive energy and this energy may generate flyrock. An accident occurred on 15 July 2015 due to this phenomenon, in which one of the workers was killed and two other workers were seriously injured after being hit by the flyrock. The purpose of this study is to investigate the causes of the flyrock accidents through evaluation of rock mass geological structures. The discontinuities present on the rock face were analyzed, to study how they affected the projection and direction of the flyrock. Rock faces with lower mean joint spacing and larger apertures caused excessive flyrock. Based on the steoreonet analysis, it was found that slope failures also produced a significant effect on the direction, if the rock face failure lay in the critical zone area. Empirical models are often used to predict flyrock projection. In this study five empirical models are used to compare the incidents. It was found that none of the existing formulas could accurately predict flyrock distance. Analysis shows that the gap between predicted and actual flyrock can be reduced by including blast deign and geological conditions in forecasts. Analysis revealed only 69% of accuracy could be achieved if blast design is the only parameter to be considered in flyrock projection and the rest is influenced by the geological condition. Other causes of flyrock are discussed. Comparison of flyrock prediction with face bursting, cratering and rifling is carried out with recent prediction models.     

Theory and Practice of Air-Deck Blasting in Mines and Surface Excavations: A Review

The mechanism by which the explosive energy is transferred to the surrounding rock mass is changed in air-deck blasting. It allows the explosive energy to act repeatedly in pulses on the surrounding rock mass rather than instantly as in the case of concentrated charge blasting. The air-deck acts as a regulator, which first stores energy and then releases it in separate pulses. The release of explosion products in the air gap causes a decrease in the initial bore hole pressure and allows oscillations of shock waves in the air gap. The performance of an air-deck blast is basically derived from the expansion of gaseous products and subsequent multiple interactions between shock waves within an air column, shock waves and stemming base and shock waves and hole bottom. This phenomenon causes repeated loading on the surrounding rock mass by secondary shock fronts for a prolonged period. The length of air column and the rock mass structure are critical to the ultimate results. Several attempts have been made in the past to study the mechanism of air-deck blasting and to investigate its effects on blast performance but a clear understanding of the underlying mechanism and the physical processes to explain its actual effects is yet to emerge. In the absence of any theoretical basis, the air-deck blast designs are invariably carried out by the rules of thumb. The field trials of this technique in different blast environments have demonstrated its effectiveness in routine production blasting, pre-splitting and controlling over break and ground vibrations etc. The air-deck length appropriate to the different rock masses and applications need to be defined more explicitly. It generally ranges between 0.10 and 0.30 times the original charge length. Mid column air-deck is preferred over the top and bottom air-decks. Top air-deck is used especially in situations, which require adequate breakage in the stemming region. The influence of air-deck location within the hole on blast performance also requires further studies. This paper reviews the status of knowledge on the theory and practice of air-deck blasting in mines and surface excavations and brings out the areas for further investigation in this technique of blasting.     

Prediction of Flyrock Distance in Open Pit Blasting Using Surface Response Analysis

Flyrock is a rock thrown to greater distance than desired and is a dangerous and unwanted phenomenon in surface mines, particularly, when blasting is proceeding close to human occupation and dwellings. The prediction of flyrock distance is critical in defining the statutory danger zone of blasting and has evaded blasters for quite some time. Control of flyrock with its distance prediction involves identification of key variables and understanding their influence. Theoretical models though provide a good understanding of the phenomenon, the confidence that can be assigned to such models is still very less. This study presents novel method to identify, merge and consolidate independent variables into a simplified equation for flyrock distance prediction without compromising on the actual field applications. Field investigations were carried out in several mines and relevant data were generated relating to flyrock. The key parameters, namely, explosive, blast design and rock mass nature were characterized and analysed. An empirical model involving the key contributors for flyrock generation and distance prediction were assimilated and a new equation was developed based on actual data collected by employing surface response analysis. The developed model was found to be statistically significant and validated. Sensitivity analysis was conducted to ascertain the role of independent factors on flyrock distance.