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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。 相似文献
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This paper addresses the effects of randomness of initial damage in a rock mass and the critical tensile strain of the rock material on its dynamic responses and damage under explosive loads. A fuzzy definition is proposed to describe the fuzzy nature of failure phenomenon in a rock mass. The initial damage of the rock mass is estimated using the longitudinal and transverse elastic wave velocities. By using statistical analysis, the initial damage of the rock mass is found having the Beta distribution. The statistical estimation of a damage state and properties of randomly damaged rock mass are evaluated by the Rosenbluth's point estimate method. In numerical calculation, an isotropic continuum damage model with the initial damage and the cumulative damage dependent on an equivalent tensile strain is suggested to model the rock mass behavior under blast loads. A Beta distribution is proposed to represent the probabilistic distribution of the damage variable of the rock mass under explosive loads. Several types of membership functions are suggested to represent the fuzziness of material failure. Based on the fuzzy–random probabilistic theory, a model including both the effects of randomness and fuzziness is proposed for the failure analysis of rock mass under explosive loads. The suggested models are coded and linked with an available computer program AUTODYN2D through its user's subroutine capacity. The fuzzy failure probability and dynamic responses of the rock mass are calculated. Numerical results are compared with those obtained from independent field tests. 相似文献
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The strike direction of open intragranular microcracks in quartz and feldspar host grains was determined using optical transmission and reflection microscopy on eight oriented samples taken in two study areas in Precambrian basement rocks of southern and south-central Sweden.For an area of about 160 km2 (SW of Västervik) and two sample locations (W of Uppsala), the vast majority of open microcracks displays a strong preferred NW–SE strike direction. According to the common assumptions that natural cracks in crystalline rocks are predominantly extensional (mode I), and that open cracks belong to the latest microcrack generation, these strike directions should reflect the (sub-) recent main horizontal stress direction (σH) of the recent tectonic stress field.This conclusion is supported by corresponding directions known from in situ stress measurements and focal plane solutions in the vicinity of the study areas. It is remarkable that even in samples taken close (i.e. a few hundred metres) to recently active large scale faults the orientation of microcracks does not deviate from this common direction. This may point to slip on already softened faults, very local stress reorientations (e.g. m-scale) or that local stress relief was accomplished by other processes at micro-scale, e.g. mechanical twinning in favourably oriented feldspar crystals, or slip on grain boundaries. 相似文献
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A Practical Procedure for the Measurement of Fragmentation by Blasting by Image Analysis 总被引:1,自引:0,他引:1
Summary. The operation of a digital image analysis system in a limestone quarry is described. The calibration of the system, required
in order to obtain moderately reliable fragmentation values, is done from muckpile sieving data by tuning the image analysis
software settings so that the fragmentation curve obtained matches as close as possible the sieving. The sieving data have
also been used to extend the fragment size distribution curves measured to sizes below the system’s optical resolution and
to process the results in terms of fragmented rock, discounting the material coming from a loose overburden (natural fines)
that is cast together with the fragmented rock. Automatic and manual operation modes of the image analysis are compared. The
total fragmentation of a blast is obtained from the analysis of twenty photographs; a criterion for the elimination of outlier
photographs has been adopted using a robust statistic. The limitations of the measurement system due to sampling, image processing
and fines corrections are discussed and the errors estimated whenever possible. An analysis of consistency of the results
based on the known amount of natural fines is made. Blasts with large differences in the amount of fines require a differentiated
treatment, as the fine sizes tend to be the more underestimated in the image analysis as they become more abundant; this has
been accomplished by means of a variable fines adjustment factor. Despite of the unavoidable errors and the large dispersion
always associated with large-scale rock blasting data, the system is sensitive to relative changes in fragmentation. 相似文献
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钻孔内小自由面条件下对岩矿石局部进行准确地爆破破碎并非易事,这一问题的解决将有助于便捷地通过钻孔获取大量的矿物岩石,提高水溶法采盐、地浸采铀的作业效率,同时使得通过钻孔开采某些具有重大潜在价值的难采矿产成为可能,这无论对钻孔取样还是钻孔采矿都具有重要的意义。论述了钻孔内岩石爆破破碎涉及的技术问题,并对钻孔内岩石爆破破碎若干影响因素进行了分析。在充分考虑各种岩矿赋存条件的基础上,采取合理的加载形式获得钻孔局部岩层较好的爆破破碎效果是可行的。 相似文献
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Rock fracturing by explosive energy: review of state-of-the-art 总被引:1,自引:0,他引:1
M. R. Saharan H. S. Mitri J. L. Jethwa 《Fragblast: International Journal for Blasting and Fragmentation》2006,10(1):61-81
A study of the dynamic rock fracture initiation and propagation due to explosive energy is presented through a detailed state-of-the-art review. Explosive energy dissipation in crushing and fracturing is examined and the various means to enhance the explosive energy utilization for dynamic rock fracturing are reviewed. The study highlights the need for a better understanding of the dynamic fracturing process particularly in the presence of in situ stresses in the rock mass. 相似文献
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M. Monjezi H. Amiri A. Farrokhi K. Goshtasbi 《Geotechnical and Geological Engineering》2010,28(4):423-430
The main objective in production blasting is to achieve a proper fragmentation. In this paper, rock fragmentation the Sarcheshmeh
copper mine has been predicted by developing a model using artificial neural network. To construct the model, parameters such
as burden to spacing ratio, hole-diameter, stemming, total charge-per-delay and point load index have been considered as input
parameters. A model with architecture 9-8-5-1 trained by back propagation method was found to be optimum. To compare performance
of the neural network, statistical method was also applied. Determination coefficient (R
2) and root mean square error were calculated for both the models, which show absolute superiority of neural network over traditional
statistical method. 相似文献
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A. M. Ferrero G. Forlani R. Roncella H. I. Voyat 《Rock Mechanics and Rock Engineering》2009,42(4):631-665
The location and orientation of rock discontinuities, which are traditionally obtained from geological surveys with obvious
drawbacks (safety, rock face accessibility, etc.), may also be derived from a detailed and accurate photogrammetric or laser
scanning survey. Selecting from the point cloud determined on the rock face a set of points distributed on a particular discontinuity,
location, dip, and dip direction can be computed from the least-squares estimate of the plane interpolating the set of points.
Likewise, the normal vector to the surface may be computed from an interpolation or approximation of the surface by appropriate
functions. To become a real alternative (both in terms of productivity as well as accuracy) to a traditional survey, interactive
or automated software tools are necessary, to allow the efficient selection of the point sets on the discontinuities or the
interpretation of the normal vector pattern. After introducing the two best technologies available today for data acquisition
and their performance, the paper presents an approach, based on the random sample consensus (RANSAC) procedure, to the segmentation
of the point cloud into subsets, each made of points measured on a discontinuity plane of the rock face. For each subset,
the plane’s equations coefficients are first determined by robust estimation and then refined by least-squares estimation
after outlier removal. The segmentation algorithm has been implemented in RockScan, a software tool developed to facilitate
the interaction with the point cloud in the identification of the discontinuities; rather than using the three-dimensional
(3D) data, selection of regions of interest is performed on oriented images of the rock face. Finally, application of RockScan
to four different test sites is discussed and results presented. The sites differ in size (from tens to hundreds of meters),
rock surface characteristics, and the technology used to produce the point cloud (in three cases photogrammetry, in the fourth
laser scanning), giving the opportunity to test the methodology in different contexts. In the first and in the fourth site
an extensive traditional survey has been performed, providing reference data to validate the RockScan results. 相似文献
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A series of detailed small-scale tests have been made to investigate the use of short delays to promote better fragmentation caused by shock wave interactions. The block design had a size of 650/660 × 205 × 300 mm (L × W × H) and two rows with five Ø 10-mm blastholes in each row. The spacing (S) and burden (B) were 110 and 70 mm, respectively, giving an S/B ratio of 1.6. The results showed no distinct differences or high improvements of the fragmentation when the delays were in the time range of interactions compared with no shock wave interactions. The decrease of x 50 (mean size) was around 20 % at a delay time ~1.1 ms/m burden compared with longer delays like 2 ms/m. A statistical analysis of the results has been made to evaluate the minimum at short delays and it is not significant. 相似文献
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介绍了刃具斜切入破岩的试验装置及试验结果,推导出了跃进载荷的计算公式,并对试验结果进行了理论分析,探讨了影响刃具侵入岩石难易的因素和影响破岩比功大小的因素。 相似文献
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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
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Stability is a key issue in any mining or tunnelling activity. Joint frequency constitutes an important input into stability
analyses. Three techniques are used herein to quantify the local and spatial joint frequency uncertainty, or possible joint
frequencies given joint frequency data, at unsampled locations. Rock quality designation is estimated from the predicted joint
frequencies. The first method is based on kriging with subsequent Poisson sampling. The second method transforms the data
to near-Gaussian variables and uses the turning band method to generate a range of possible joint frequencies. The third method
assumes that the data are Poisson distributed and models the log-intensity of these data with a spatially smooth Gaussian
prior distribution. Intensities are obtained and Poisson variables are generated to examine the expected joint frequency and
associated variability. The joint frequency data is from an iron ore in the northern part of Norway. The methods are tested
at unsampled locations and validated at sampled locations. All three methods perform quite well when predicting sampled points.
The probability that the joint frequency exceeds 5 joints per metre is also estimated to illustrate a more realistic utilisation.
The obtained probability map highlights zones in the ore where stability problems have occurred. It is therefore concluded
that the methods work and that more emphasis should have been placed on these kinds of analyses when the mine was planned.
By using simulation instead of estimation, it is possible to obtain a clear picture of possible joint frequency values or
ranges, i.e. the uncertainty. 相似文献
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Changshou Sun Douglas W. Later Gang Chen 《Fragblast: International Journal for Blasting and Fragmentation》2001,5(4):235-246
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. 相似文献
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Numerical Analyses of the Influence of Blast-Induced Damaged Rock Around Shallow Tunnels in Brittle Rock 总被引:1,自引:1,他引:1
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. 相似文献
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A discrete element code has been used to simulate impact-induced rock fragmentation in rock fall analysis using a simplified
impact model inspired by the theory of vibrations for foundations on elastic media. The impact velocity, the angle of incidence,
pre-existing fractures, and the ground stiffness all play important roles in impact fragmentation. Based on the simulation
results, impact fragmentation occurs locally at the impact zone without generating large fragments for a homogeneous rock
block. Large fragments are generated only when there are open pre-existing fractures in the rock block or when there are fully
persistent closed fractures. Softer ground tends to reduce the potential for impact fragmentation. Energy transformation and
failure occur only during impact including approach and restitution stages. Friction energy loss accounts for most of the
energy loss during the fragmentation process, while tensile cracking energy loss is not significant. 相似文献