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1.
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
2.
J. Kemeny E. Mofya R. Kaunda P. Lever 《Fragblast: International Journal for Blasting and Fragmentation》2002,6(3):311-320
One of the fundamental requirements for being able to optimise blasting is the ability to predict fragmentation. An accurate blast fragmentation model allows a mine to adjust the fragmentation size for different downstream processes (mill processing versus leach, for instance), and to make real time adjustments in blasting parameters to account for changes in rock mass characteristics (hardness, fracture density, fracture orientation, etc). A number of blast fragmentation models have been developed in the past 40 years such as the Kuz-Ram model [1]. Fragmentation models have a limited usefulness at the present time because: 1. The input parameters are not the most useful for the engineer to determine and data for these parameters are not available throughout the rock mass. 2. Even if the input parameters are known, the models still do not consistently predict the correct fragmentation. This is because the models capture some but not all of the important rock and blast phenomena. 3. The models do not allow for 'tuning' at a specific mine site. This paper describes studies that are being conducted to improve blast fragmentation models. The Split image processing software is used for these studies [2, 3]. 相似文献
3.
A. S. Tawadrou P. D. Katsabani 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(4):233-242
This paper is an application of artificial neural networks (ANNs) in the prediction of the geometry of surface blast patterns in limestone quarries. The built model uses 11 input parameters which affect the design of the pattern. These parameters are: formation dip, blasthole diameter, blasthole inclination, bench height, initiation system, specific gravity of the rock, compressive and tensile strength, Young's modulus, specific energy of the explosive and the average resulting fragmentation size. Detailed data from a previous investigation were used to train and verify the network and predict burden and spacing of a blast. The built model was used to conduct parametric studies to show the effect of blasthole diameter and bench height on pattern geometry. 相似文献
4.
In this paper, an experimental methodology is presented using digital image techniques to assess the internal microcracks and to quantify the rock damage within rock cores. The second part of the work is devoted to the numerical estimation of the tensile blast induced damage evolution law. The set up methodology is then applied to a set of limestone cores which were sampled before and after a real field blast round. The image analysis algorithm which was developed during the present work is based on a segmentation technique that uses a particular thresholding. Petrographic parameters, such as crack number, orientation, extension, centroid position were computed as a first step aiming at a fine characterization of the cracked medium. The most important estimated parameter is the specific crack area which is defined as the ratio between the crack area and the total image area. This parameter was taken as the rock internal damage. A dynamic tensile damage ordinary partial differential equation is numerically solved and calibrated with the obtained data in order to derive a general blast induced damage evaluation law within the muckpile blocks. The application of the numerical algorithm to cores coming from sampled blocks before and after real field blasts allowed the estimation of damage parameter and dynamic stress evolution histories as well as an estimation of the microfracturing activation and growth energies used during the blast. 相似文献
5.
This paper presents the results of ground vibration analysis induced by blasting during the construction of the Istanbul Kadıköy–Kartal metro tunnel. Different rock formations in this tunnel route were encountered during the excavation with blasting. As a first stage, the test site is divided into 6 main regions with respect to lithology changes in the rock units and Hoek's Geological Strength Index value of these rock units. During the excavation, a total of 659 events were recorded in 260 shots by vibration monitors. Scaled distance and peak particle velocity data pairs belonging to these shots were carefully recorded and analyzed statistically. As a result of this analysis, empirical relationships between scaled distance and peak particle velocity were established with higher correlation coefficients specific to each region. Finally, the particle velocities and frequency values of all blast events were evaluated according to Turkish Environmental Regulation, the United States Bureau of Mines (USBM) and the German DIN 4150 Norms in order to predict the influence level to the neighboring buildings and structures. 相似文献
6.
Summary The Delivery Tunnel North starts in Lesotho and continues into South Africa. It is divided into two sections by the Caledon and Little Caledon rivers. It runs through the mudrocks and sandstones of the Tarkastad Subgroup, and the Elliot and Molteno Formations. The tunnel was excavated by a double-shield tunnel boring machine, except for the sections beneath the two rivers, which were constructed by drill and blast methods. The tunnel boring machine was selected to bore through the anticipated changing ground conditions and also was capable of installing the segmental lining of the tunnel. Boreability tests showed that the sandstones and siltstones had good boreability, but that it was very low in the dolerite dykes. At depth, the weaker mudstones presented the worst tunnelling conditions, giving rise to squeezing ground and to shear failure with accompanying overbreak. Initially a small amount of cracking occurred in the tunnel lining but this was reduced significantly as experience was gained. Cracking was observed predominantly in the weaker rock types, and this was probably associated with overbreak. 相似文献
7.
For construction in rock a thorough pre-investigation is important in order to avoid unforeseen conditions which may delay the work. It is crucial to remember the results from this investigation in the further work, and use the experience from the construction to update the geological prognosis and reduce the uncertainties. Different geophysical methods have proved valuable tools in such investigations. In this work the electrical imaging is evaluated with regards to the method's applicability. The evaluation is done qualitatively by comparing the electrical imaging with tunnel documentation from a tunnel in Southern Sweden. By evaluating the result continuously when making the tunnel a more detailed geological prognosis can be compiled and used in the continued work with the tunnel. The parameters used for the comparison are lithology, Q, RQD, weathering and water leakage. The result was that virtually every change in electrical resistivity image coincides with a change in rock conditions. The general trend was that high resistivity corresponded with good quality gneiss whereas low resistivity corresponds to poor quality rock e.g., high weathering, low RQD, low Q and/or several lithological contacts. The intermediate resistivity is often amphibolites or rock with water bearing fractures. The results were supported by in-situ resistivity measurements inside the tunnel and resistivity logging in a core drilling. Geoelectrical imaging proved to give valuable information for a detailed geological model, which could be compiled for a section where the tunnel had not yet been drilled as a help for planning of the continued tunnel work. As is the case other geophysical methods it is clear that for the interpretation of data a priori information about the geological setting is necessary. 相似文献
8.
9.
P. H. S. W. Kulatilake T. Hudaverdi Qiong Wu 《Geotechnical and Geological Engineering》2012,30(3):665-684
The paper refers the reader to a blast data base developed in a previous study. The data base consists of blast design parameters, explosive parameters, modulus of elasticity and in situ block size. A hierarchical cluster analysis was used to separate the blast data into two different groups of similarity based on the intact rock stiffness. The group memberships were confirmed by the discriminant analysis. A part of this blast data was used to train a single-hidden layer back propagation neural network model to predict mean particle size resulting from blast fragmentation for each of the obtained similarity groups. The mean particle size was considered to be a function of seven independent parameters. An extensive analysis was performed to estimate the optimum value for the number of units for the hidden layer for each of the obtained similarity groups. The blast data that were not used for training were used to validate the trained neural network models. For the same two similarity groups, multivariate regression models were also developed to predict mean particle size. Capability of the developed neural network models as well as multivariate regression models was determined by comparing predictions with measured mean particle size values and predictions based on one of the most applied fragmentation prediction models appearing in the blasting literature. Prediction capability of the trained neural network models as well as multivariate regression models was found to be strong and better than the existing most applied fragmentation prediction model. Diversity of the blasts data used is one of the most important aspects of the developed models. 相似文献
10.
It is a well known fact that rock mass properties influence the process of fragmentation considerably. Model blasts and field investigations were carried out to find the effects of rock mass quality and joint orientation on tunnel blasting. Propagation of shock waves are partially restricted by joint planes. It was observed that the blast results (i.e., average fragment size and depth and cross-sectional area of the broken zone) were considerably influenced by joint orientation. Accordingly, it has been concluded that loading equipment with a larger capacity and deeper blast holes are required in formations with joint planes perpendicular to the tunnel axis. The number of blast holes, however, should be greater when joints are parallel to the tunnel axis. Furthermore, the powder factor (kg/m3) has been found to be directly related to rock mass quality (Q). Optimisation of pull, powder factor and overbreak is required in the case of weak formations with joints perpendicular to the tunnel axis. The use of contour blasting technique seems to be essential in poor and fair rock masses to minimise the overbreak, reduce the support cost and improve the stability of the opening. 相似文献
11.
T. Mark Harrison Marty Grove Oscar M. Lovera E. J. Catlos Jessica D&#x;Andrea 《Journal of Asian Earth Sciences》1999,17(5-6)
The key to comprehending the tectonic evolution of the Himalaya is to understand the relationships between large-scale faulting, anatexis, and inverted metamorphism. The great number and variety of mechanisms that have been proposed to explain some or all of these features reflects the fact that fundamental constraints on such models have been slow in coming. Recent developments, most notably in geophysical imaging and geochronology, have been key to coalescing the results of varied Himalayan investigations into constraints with which to test proposed evolutionary models. These models fall into four general types: (1) the inverted metamorphic sequences within the footwall of the Himalayan thrust and adjacent hanging wall anatexis are spatially and temporally related by thrusting; (2) thrusting results from anatexis; (3) anatexis results from normal faulting; and (4) apparent inverted metamorphism in the footwall of the Himalayan thrust is produced by underplating of right-way-up metamorphic sequences. We review a number of models and find that many are inconsistent with available constraints, most notably the recognition that the exposed crustal melts and inverted metamorphic sequences not temporally related. The generalization that appears to best explain the observed distribution of crustal melts and inverted metamorphic sequences is that, due to specific petrological and tectonic controls, episodic magmatism and out-of-sequence thrusting developed during continuous convergence juxtaposing allochthonous igneous and metamorphic rocks. This coincidental juxtaposition has proven to be something of a red herring, unduly influencing attention toward finding a causal relationship between anatexis and inverted metamorphism. 相似文献
12.
Fractures developed around high pressurized gas or air storage tunnels can progressively extend to the ground surface, eventually leading to an uplift failure. A tool reasonably reproducing the failure patterns is necessary for stability assessment. In this study, a numerical method based on the element-free Galerkin (EFG) method with a cohesive crack model is developed to simulate fracture propagation patterns in the rock mass around a tunnel under high internal pressure. A series of physical model tests was also conducted to validate the reliability of the developed method. A qualitative agreement between physical model tests and numerical results can be obtained. The in situ stress ratio, k, has a strong influence on both the position of crack initiation and the propagation direction. The numerical analyses were extended to full-scale problems. Numerical tests were performed to investigate the prime influencing factors on the failure patterns of a high pressurized gas circular tunnel with varying parameters. The results suggest that initial in situ stress conditions with a high k (larger than 1) is favorable for construction of pressurized gas or air storage tunnels. 相似文献
13.
Surface movements were measured in the Gotthard massif as the Gotthard Base Tunnel was excavated. These movements might damage concrete dams constructed on the surface valleys. The leading assumption of this work is that deformation is induced by the dissipation of pore pressures in the massif caused by tunnel drainage. Deformations induce both horizontal and vertical surface displacements. Horizontal displacements, may lead to valley closures if they are in opposite direction, which would induce negative effects on arch dams. An analytical solution is derived using the method of images and an approximated integration of deformations to calculate the movements and the flow rate collected in the tunnel. Numerical calculations were carried out in 2D (vertical cross section) and 3D to investigate the problem under different conditions and to study the effect of parameters. The 3D models permit to incorporate the presence of a vertical fracture perpendicular to the tunnel that increases the drainage and pressure drop as it is hit by the tunnel. It was also possible to simulate the impermeabilization works in the tunnel to reduce drainage and consequently, movements. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
Groundwater level and chemistry changes resulting from tunnel construction near Matsumoto City, Japan 总被引：3，自引：0，他引：3
Before tunnel construction began, the groundwater chemical compositions and levels around the tunnel were studied to determine
if water compositions could predict whether surface water will be influenced by tunnel construction. When the chemical composition
of the well and springwater was similar to that of the tunnel seepage water, and the altitude of the well and spring was above
the tunnel level, the groundwater level in the well and spring was influenced by draining tunnel seepage water. Therefore,
comparing the chemical compositions of surface water and groundwater may be used for predictive purposes. However, the results
of this study showed there was no noticeable chemical composition change in springwater prior to changes in groundwater level
at a particular site. The changes in the hydrology of the plateau caused by tunnel construction were also studied, using measurements
of the changes in groundwater chemistry as well as changes in groundwater levels. Prior to tunnel construction, river discharge
was greater. Following tunnel construction, some river discharge decreased because springwater was drained as tunnel seepage
water and the spring in the catchment dried up. Tritium concentration indicated that 3 years after tunnel construction, surface
water did not reach tunnel levels in spite of groundwater level lowering and remaining unconfined groundwater being drained.
Received: 17 January 1996 · Accepted: 10 July 1996 相似文献
15.
Luigi Sambuelli 《Rock Mechanics and Rock Engineering》2009,42(3):547-556
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. 相似文献
16.
北京地铁国贸站隧道周围土体的蠕变试验研究 总被引：1，自引：0，他引：1
北京地铁10号线国贸站需穿过现有的国贸立交桥梁群桩基础,为研究该区域土体的流变性质对隧道-土层-桥梁基础及上部结构长期变形的影响,在室内进行了隧道周围土体的三轴排水蠕变试验,并给出了适合描述该土体蠕变性质的Mesri模型的参数。研究表明,隧道周围土体存在一定的蠕变特征,但稳定蠕变速率不大,偏应力较小时,Mesri模型的计算结果与试验结果吻合较好,而偏应力较大时与试验结果稍有差别,但该模型总体上能够较好地描述这一地区土体的蠕变变形特征。 相似文献
17.
Rapid vibration estimation usually relies on charge weight scaling laws. These empirical curves that fit field data are sometimes involved in linear superposition models. A scaled charge weight superposition model combines the traditional charge weight scaling law within a linear superposition framework so that the influence of timing and blast design parameters may be assessed. The model involves an extra parameter of time overlap and poses a partial explanation for the over-estimation of blast vibration levels sometimes predicted by linear superposition models. It is suggested that the time overlap parameter be determined from measured vibration data. The new model recovers the Holmberg-Persson equation for near-field vibration from a single blast hole. Three examples compare the predictions of the new model with those from a linear superposition model. The results indicate a consistent, but not compelling demonstration of the predictive power of the scaled charge weight superposition model. Further verification studies are recommended using a wide range of blast types and scaled distances to points of interest. The new model lies between a traditional charge weight scaling law and a linear superposition model. It ignores waveform superposition explicitly but assumes non-linear interaction between adjacent charges in a blast within a user-defined time window. In that sense, the scaled charge weight superposition model offers an alternative method for rapid vibration estimation. 相似文献
18.
Displacement analysis of tunnel support in soft rock around a shallow highway tunnel at Golovec 总被引：3，自引：0，他引：3
Within the last 10 years Slovenia has been constructing its highway network. The Golovec tunnel, as a part of Slovenia's capital ring is thus one of the most important connections of Ljubljana to the east and to the north. It is a double tube three-lane tunnel in soft rock with small to medium overburden. Its construction, following NATM, caused huge problems to all parties involved. The tunnel support was well monitored during its construction, which gave the authors a good opportunity to analyse the results.The Golovec tunnel is constructed through one of few hills surrounding Ljubljana, of Carboniferous age, consisting of clastic rock: siltstone, claystone and sandstone. Golovec hill belongs to the first of two overthrusting zones from this area, so the rock is strongly faulted.Tunnel monitoring consisted of daily 3-D tunnel tube displacement measurements in 97 measuring sections, and of two measuring sections within the tunnel with more complex measuring equipment, to monitor stress changes and rock deformations around both tunnel tubes. Monitoring of the surface 3-D movements gave us the opportunity to study the influence of the tunnel construction on the surface above it. The tunnel, its geology, construction procedure and monitoring results are described in the first part of the paper.The second part consists of the interpretation of monitored results, with an emphasis on results concerning development and evolution of the excavation-damaged zone in the rock around the tunnel. Back-calculations, performed as a basis for the interpretation procedure, are also presented in this part. Calculations of the propagation of the tunnel destressed zone and stress-field around the tunnel, up to the surface, were performed by means of numerical model with the finite difference method. The evolution of tunnel displacements and their prediction was based on the use of Back Propagation Neural Networks, whose principles are presented in one chapter of this paper. Results showed that the most important, for the final settlement at the surface above the tunnel, was the time of installation and rigidity of the primary support. On the basis of the calculated final displacements, this support could easily be strengthened in a short time, when necessary. 相似文献
19.
Analysis of support requirements for a shallow diversion tunnel at Guledar dam site, Turkey 总被引：2，自引：0，他引：2
Engineering geological properties and support design of a planned diversion tunnel at Guledar dam site, which was located at the North of Ankara, Turkey were studied in this article. The main purpose of the construction of the planned tunnel is to regulate, drainage and to provide water for irrigation purposes. The diversion tunnel runs mainly through formations of limestone, sandstone and diabase. Rock masses at the site were characterized using Rock Mass Rating (RMR), Rock Mass Quality (Q), Rock Mass Index (RMi) and Geological Strength Index (GSI). RMR, Q, RMi and GSI were determined by using field data and mechanical properties of intact rock samples, measured in the laboratory. Support requirements for the planned diversion tunnel were determined accordingly in terms of the rock mass classification systems. Recommended support systems by empirical methods were also analyzed using 2D Finite Element method. Calculated parameters based on empirical methods were used as input parameters in the finite element models. The results from both methods were compared with each other. This comparison suggests that more reliable support design could be achieved by using the finite element method together with the empirical methods. 相似文献
20.
K. Thuro 《International Journal of Earth Sciences》1997,86(2):426-438
Usually the main subject in preliminary site investigations prior to tunnelling projects is the prediction of tunnel stability.
During the past years in conventional drill and blast tunnelling, problems have occurred also connected to the accurate prediction
of drillability in hard rock. The drillability is not only decisive for the wear of tools and equipment but is – along with
the drilling velocity – a standard factor for the progress of excavation works. The estimation of drillability in predicted
rock conditions might bear an extensive risk of costs. Therefore, an improved prediction of drilling velocity and bit wear
would be desireable. The drillability of a rock mass is determined by various geological and mechanical parameters. In this
report some major correlations of specific rock properties and especially geological factors with measured bit wear and drilling
velocity are shown.
Drilling velocity is dependent on a lot of geological parameters: Those principal parameters include jointing of rock mass,
orientation of schistosity (rock anisotropy), degree of interlocking of microstructures, porosity and quality of cementation
of clastic rock, degree of hydrothermal decomposition and weathering of a rock mass. Drilling bit wear increases with the
equivalent quartz content. The equivalent quartz content builds the main property for the content of wear-relevant minerals.
For various groups of rock types different connections with the equivalent quartz content could be detected. In sandstone
bit wear is also dependent on porosity or the quality of the cementation. Finally, an investigation program is submitted,
which helps to improve the estimation of rock drillability in planning future tunnel projects.
Received: 14 June 1996/Accepted: 10 January 1997 相似文献