波力电站岩坎爆破的技术与工艺

本文根据波力电站岩坎爆破的特点,提出了用多段毫秒雷管一次起爆进行周边预裂爆破、深孔削坡爆破和主坎斜孔抛掷爆破的程序,建立了药量计算的公式,分析了爆破震动对波力电站气室和机房的影响,论述了波力电站岩坎爆破的技术理论与工艺方法。     

Blasting Technique and Process for Rock Ridge in a Wave Power Station

A technique of peripheral presplitting blast with multi-ignitions of millisecond detonaters is put forward in this paper based on the characteristics of ridge blast for wave power station, the main ridge blasting with deep hole smooth blasting and casting blast of inclined holes. The formula to calculate explosive charge is established. Finally, the theory and process of this technique for ridge blasting are discussed.     

损伤条件下深部岩体巷道光面爆破参数研究

岩体条件复杂多变,为了提高光面爆破的适应性、改善光面爆破效果,对损伤条件下深部岩体巷道光面爆破参数进行研究。通过对深部岩体巷道光爆层原岩应力场、光面爆破机制和振动损伤特征进行分析,基于爆炸应力波和爆生气体综合作用理论,考虑高原岩应力和岩石损伤影响,提出了损伤条件下深部岩体巷道光面爆破参数确定的计算方法。研究表明, （1）高原岩应力相当于提高了岩石的抗拉强度,不利于炮孔初始裂纹的形成及贯通,宜减小周边眼间距;（2）岩石损伤后,其他条件不变,光面爆破的炮孔间距和抵抗线值可适当加大;（3）高原岩应力和损伤条件下,光面爆破的炮孔间距较小时,容易造成爆后围岩损伤,降低围岩的稳定性能,因此,提高爆破效果的同时应及时加强支护,以确保施工安全和围岩稳定;（4）本文提出的光面爆破参数计算公式,经现场爆破验证效果良好,适用于复杂多变的岩体环境。     

坚硬顶煤弱化爆破的宏观损伤破坏程度研究

根据综放开采坚硬顶煤预先弱化爆破作用的目的和特点,认为在爆炸载荷作用下坚硬煤体的动态断裂破坏也是一个连续损伤演化积累过程。通过大煤样爆破超动态应变测试,提出坚硬顶煤预先弱化爆破的爆破中区应变波峰值体积应变符合幂函数衰减规律,并在此基础上,结合Tarlor、Drady等岩石爆破损伤演化模型,建立了坚硬顶煤预先弱化爆破宏观损伤破坏程度的分布函数,给出了相应的计算参数和系数,为分析和确定顶煤弱化爆破合理参数提供了基础。     

Mechanism of tracer blasting

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.     

Numerical Analyses of the Influence of Blast-Induced Damaged Rock Around Shallow Tunnels in Brittle Rock

Most of the railway tunnels in Sweden are shallow-seated (<20 m of rock cover) and are located in hard brittle rock masses. The majority of these tunnels are excavated by drilling and blasting, which, consequently, result in the development of a blast-induced damaged zone around the tunnel boundary. Theoretically, the presence of this zone, with its reduced strength and stiffness, will affect the overall performance of the tunnel, as well as its construction and maintenance. The Swedish Railroad Administration, therefore, uses a set of guidelines based on peak particle velocity models and perimeter blasting to regulate the extent of damage due to blasting. However, the real effects of the damage caused by blasting around a shallow tunnel and their criticality to the overall performance of the tunnel are yet to be quantified and, therefore, remain the subject of research and investigation. This paper presents a numerical parametric study of blast-induced damage in rock. By varying the strength and stiffness of the blast-induced damaged zone and other relevant parameters, the near-field rock mass response was evaluated in terms of the effects on induced boundary stresses and ground deformation. The continuum method of numerical analysis was used. The input parameters, particularly those relating to strength and stiffness, were estimated using a systematic approach related to the fact that, at shallow depths, the stress and geologic conditions may be highly anisotropic. Due to the lack of data on the post-failure characteristics of the rock mass, the traditional Mohr–Coulomb yield criterion was assumed and used. The results clearly indicate that, as expected, the presence of the blast-induced damage zone does affect the behaviour of the boundary stresses and ground deformation. Potential failure types occurring around the tunnel boundary and their mechanisms have also been identified.     

Asymmetric Blasting: A Rock Mass Dependent Blast Design Method

Blasting has been the most frequently used method for rock breakage since black powder was first used to fragment rocks, more than two hundred years ago. This paper is an attempt to reassess standard design techniques used in blasting by providing an alternative approach to blast design. The new approach has been termed asymmetric blasting. Based on providing real time rock recognition through the capacity of measurement while drilling (MWD) techniques, asymmetric blasting is an approach to deal with rock properties as they occur in nature, i.e., randomly and asymmetrically spatially distributed. It is well accepted that performance of basic mining operations, such as excavation and crushing rely on a broken rock mass which has been pre conditioned by the blast. By pre-conditioned we mean well fragmented, sufficiently loose and with adequate muckpile profile. These muckpile characteristics affect loading and hauling [1]. The influence of blasting does not end there. Under the Mine to Mill paradigm, blasting has a significant leverage on downstream operations such as crushing and milling. There is a body of evidence that blasting affects mineral liberation [2]. Thus, the importance of blasting has increased from simply fragmenting and loosing the rock mass, to a broader role that encompasses many aspects of mining, which affects the cost of the end product. A new approach is proposed in this paper which facilitates this trend 'to treat non-homogeneous media (rock mass) in a non-homogeneous manner (an asymmetrical pattern) in order to achieve an optimal result (in terms of muckpile size distribution).' It is postulated there are no logical reasons (besides the current lack of means to infer rock mass properties in the blind zones of the bench and onsite precedents) for drilling a regular blast pattern over a rock mass that is inherently heterogeneous. Real and theoretical examples of such a method are presented.     

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.     

Multivariate statistical analysis approach for prediction of blast-induced ground vibration

Excavation of coal, overburden, and mineral deposits by blasting is dominant over the globe to date, although there are certain undesirable effects of blasting which need to be controlled. Blast-induced vibration is one of the major concerns for blast designers as it may lead to structural damage. The empirical method for prediction of blast-induced vibration has been adopted by many researchers in the form of predictor equations. Predictor equations are site specific and indirectly related to physicomechanical and geological properties of rock mass as blast-induced ground vibration is a function of various controllable and uncontrollable parameters. Rock parameters for blasting face and propagation media for blast vibration waves are uncontrollable parameters, whereas blast design parameters like hole diameter, hole depth, column length of explosive charge, total number of blast holes, burden, spacing, explosive charge per delay, total explosive charge in a blasting round, and initiation system are controllable parameters. Optimization of blast design parameters is based on site condition and availability of equipment. Most of the smaller mines have predesigned blasting parameters except explosive charge per delay, total explosive charge, and distance of blast face from surface structures. However, larger opencast mines have variations in blast design parameters for different benches based on strata condition: Multivariate predictor equation is necessary in such case. This paper deals with a case study to establish multivariate predictor equation for Moher and Moher Amlohri Extension opencast mine of India. The multivariate statistical regression approach to establish linear and logarithmic scale relation between variables to predict peak particle velocity (PPV) has been used for this purpose. Blast design has been proposed based on established multivariate regression equation to optimize blast design parameters keeping PPV within legislative limits.     

Wall Control Blasting Practices at BHP Billiton Iron Ore Mt Whaleback

A programme of blast improvement was initiated at the Mt Whaleback iron ore mine by BHPIO management in early-1998. One component of that work was the need to improve wall control blasting practices to better achieve the designed pit slope elements. This paper describes the geological conditions in which pit walls are developed, the mine operating equipment, the blast design concepts applied to minimise blast damage, the techniques applied in an assessment of the blast performance and the operational procedures developed to ensure that the blast concepts are effectively implemented in the production environment. Substantial changes have been implemented in both technical and operational aspects of the mining operation in order to achieve the improvements in pit wall condition, in particular recognising the need for a more flexible approach to limits blasting in response to highly variable and complex geology. The benefits to the mine are not only an improved wall condition, but increased confidence on the part of mine management that mine plans may be implemented on design and on schedule.     

Prediction and controlling of flyrock in blasting operation using artificial neural network

Flyrock is one of the most hazardous events in blasting operation of surface mines. There are several empirical methods to predict flyrock. Low performance of such models is due to complexity of flyrock analysis. Existence of various effective parameters and their unknown relationships are the main reasons for inaccuracy of the empirical models. Presently, application of new approaches such as artificial intelligence is highly recommended. In this paper, an attempt has been made to predict and control flyrock in blasting operation of Sangan iron mine, Iran incorporating rock properties and blast design parameters using artificial neural network (ANN) method. A three-layer feedforward back-propagation neural network having 13 hidden neurons with nine input parameters and one output parameter were trained using 192 experimental blast datasets. It was also observed that in ascending order, blastability index, charge per delay, hole diameter, stemming length, powder factor are the most effective parameters on the flyrock. Reducing charge per delay caused significant reduction in the flyrock from 165 to 25 m in the Sangan iron mine.     

Studies on the Effect of Burden on Blast Damage and the Implementation of New Blasting Practices to Improve Productivity at KCGMs Fimiston Mine

Wall control blasting practices arc necessary to reduce the impact of blasting on mine faces but can also have a significant negative impact on mine productivity and operating costs. The conventional practice in deep open pit mines is to use so-called trim blasts adjacent to pit walls. To provide burden relief these trim blasts have fewer rows than full production blasts and are fired to a cleared free-face: hence they are termed 'unchoked.' This practice leads to scheduling constraints on the pit operations and can cause ore dilution due to excessive muckpile movement. The use of such trim blasts stems from the perception that increased wall damage results from 'choked' blasts. These concerns are based on the unproven assumptions that blast vibration levels and explosive gas penetration increase with increased blast burden and face confinement. This paper describes work undertaken as part of a major investigation into wall control blasting at the KCGM Fimiston Mine, Kalgoorlie, Western Australia. It details a study to assess damage effects due to blast burden. Borehole air pressure measurements and borehole video camera inspections owere done behind a series of single blastholes drilled owith varying burden distances, as owell as behind a dedicated trim blast and a full production blast. It was found that the measured damage effects, including visible rock cracking, dilation, and the limited extent of gas penetration behind the blastholes, did not vary significantly with burden or blast type for the cases tested. This result was in complete agreement with detailed vibration measurements conducted by Blair and Armstrong [1] during the study, which found that vibration was independent of blast burden. As a result of these investigations, changes to the blasting practices at the mine were implemented. Dedicated trim blasts and free-face blasting have been replaced by modified production blasts and the practice of 'choking' blasts has been introduced. This has resulted in a significant improvement in productivity and cost savings without compromising pit wall integrity.     

工程爆破中径向水不耦合系数效应数值仿真

在实际工程爆破中,水不耦合炮孔是较常见的,其中水不耦合装药系数是影响爆破效果的关键因素之一。该系数取不同的值,将产生不同的应力波传播机理以及介质的损伤破坏程度。以往的研究主要集中于理论解析法和模型试验法。基于大型非线性动力分析软件LS-DYNA,采用著名的混凝土损伤Johnson-Holmquist-Concrete模型,针对无限混凝土介质水不耦合装药爆破中不同径向耦合系数Kd,展开了对比数值计算,综合分析了损伤破坏区分布和孔壁压力、加速度以及速度等与径向不耦合系数间的关系,得出的结论具有一定的参考价值。     

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.     

Modelling rock fracturing and blast-induced rock mass failure via advanced discretisation within the discontinuous deformation analysis framework

Rock mass failure is a particularly complex process that involves the opening and sliding of existing discontinuities and the fracturing of the intact rock. This paper adopts an advanced discretisation approach to simulate rock failure problems within the discontinuous deformation analysis (DDA) framework. The accuracy of this approach in continuum analysis is verified first. Then, the advanced discretisation approach for fracturing modelling is presented, and the discretisation strategy is discussed. Sample rock static failures are simulated and the results are compared with experimental results. Thereafter, with a generalised definition of the artificial joints, this approach is further extended and applied in the simulation of blast-induced rock mass failures in which the instant explosion gas pressure obtained by the detonation pressure equation of state is loaded on the main blast chamber walls and the induced surrounding connected fracture surfaces. In the simulation instance of rock mass cast blasting, the whole process, including the blast chamber expansion, explosion gas penetration, rock mass failure and cast, and the formation of the final blasting pile, is wholly reproduced.     

含预制裂纹的水泥砂浆试块在爆炸载荷作用下损伤特征的数值模拟

把能够体现岩体在冲击载荷作用下的响应特点及损伤演化的各向异性特征的损伤模型嵌入到有限元软件中，模拟了含有预制裂纹的水泥砂浆试块在爆炸载荷作用下的损伤特征。模拟结果表明，在爆炸近区产生一个损伤“重灾区”，并可根据模拟结果确定“重灾区”及爆炸损伤的范围，模拟结果与试验结果基本一致。模拟方法可以为岩土工程中经历过爆炸损伤岩体的稳定性研究提供理论依据。     

Rock mass damage from underground blasting, a literature review, and lab- and full scale tests to estimate crack depth by ultrasonic method

Rock mass damage due to blasting (BID) is important for the personnel working underground and also for rock reinforcement costs. Therefore, about 20 methods for damage assessment have been developed. The methods are shortly presented. Often several methods have to be used in combination to achieve good quantitative estimate of the damage. Some blast damage indices have been developed and one of them, the D_ib (Yu & Vongpaisal 1996) after a modification of the Index was tested in field with good result. The ultrasonic method used both in lab and field tests has limited value and can only used with good accuracy to a depth of ~0.5 m. This method is not therefore recommended for blast damage measurements where damage depth could be up to 2.5 m.     

Theoretical Derivation of a Peak Particle Velocity–Distance Law for the Prediction of Vibrations from Blasting

I would like to suggest a theoretical justification for the mathematical structure of some laws for predicting the maximum particle velocity vibration from blasting operations in the light of some basic notions of elastic and anelastic wave theory. Within this point of view, in dimensionally correct expressions, the terms pertaining to the rock, to the blast and to the seismic wave become evident and recognisable. A law is presented that can be used to forecast the maximum particle velocity on the basis of some blast design and rock parameters. Four tests of the proposed law performed with real data sets seem to confirm fairly well its reliability.     

The driving of metro tunnels at helsinki with the aid of ground freezing

Twin 6.5 m diameter tunnels were driven through saturated soil at a depth of 25 m under a street intersection with the aid of horizontal freezing. The frozen soil section was about 30 m long. Because of groundwater pressure the horizontal freeze holes were drilled with sealed casings. A new drill bit was introduced to form a tight plug at the end of the casing. The soil around the perimeter of the tunnel bores was frozen by vaporizing freon in the freeze tubes. A 2.5 m thick ice wall in sand and moraine was developed during the freezing period of 55 days. The tunnel bores were excavated under protection of the frozen arch by cautious drilling and blasting. The advance was 1.2–1.8 m per round. Permanent tunnel linings were constructed by bolting together cast iron segments.     

Blast damage control in jointed rock mass

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.