Rock blasting and explosives engineering pdf
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- Drilling And Blasting Of Rocks Pdf
- Rock Blasting And Explosives Engineering.pdf
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Drilling And Blasting Of Rocks Pdf
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Jump to Page. Search inside document. For many people, explosives are associated with destruction, fear, and sudden death. It is not surprising that there is such widespread fear of explosives.
Military high explosives have been used, and are still being used as this is written, to spread death and devastation among people of different beliefs.
In the less violent field of rock blasting, there is to most of us something awe-inspiring about the sight of a large expanse of hard, immobile, solid rock that has been in place for millions of years, suddenly coming to life and disintegrating into thousands of tons of rubble while the ground shivers, clouds of smoke emerge, and the rumble of thunder fills the air.
It is quite right, too, that detonators, booster charges, and explosives should be treated with due respect, in the same way that one has to be careful with a mousetrap set ready with a piece of cheese, or a loaded gun. One needs to know where the trigger is, safeguard it against inadvertent triggering, and keep out of the way when the trigger is squeezed. There are regulations, rules, and laws for the use of explosives which are meant to be such a safeguard against accidents.
Remember that they exist, and go looking for them before you start handling explosives. But remember also that it is your personal responsibility to make sure you run a safe operation. The rules and regulations are a help, but nothing can replace your personal knowledge and understanding of the safety characteristics of explosives. Rock blasting is used in applications ranging in size from small boulder blasting in the back garden, using perhaps 10 or 20 g of explosive, to large-scale open pit mining operations where perhaps tons of explosive are consumed in a single round.
Rock blasting is big business. In , the total consumption of commercial explosives in the USA was 2. In prices in the USA, we may assume that the average cost. Toward the end of the s, the rock blasting explosives consumption in the former Soviet Union was about 2. Already in , we estimated the total volume of rock and ore blasted in the world to be about 3. The Scandinavian countries have a long tradition of large-scale rock blasting operations; in the hard bedrock prevalent there, blasting is the normal first step in the construction of underground hydroelectric power plants, harbors, roads, airfields, and in metal and mineral mining.
At the present time in the USA, coal mining consumes the greatest volumes of commercial explosives. Most of the coal mining in the USA is carried out as strip mining. In recent years, the explosives consumption, which closely reflects the general health of the economy, has stagnated or decreased. In a longer perspective, there is little doubt that the increasing population in the USA and worldwide, with its increasing demand for more roads, airfields, harbors, building materials, metals, mineral resources, and energy, will lead to further growth in the volume of rock blasting.
It is a very exciting science — rock materials come in a wide variety of mechanical properties and they have a rich structure of bedding planes, cracks, fissures, or joints Figure 1. The weak planes are oriented in all kinds of directions.
This science demands more of fantasy and ability to think in a three-dimensional space than the simple science of strength of homogeneous materials such as metals or ceramics. The chemical reactions in detonating high explosives run at rates that are unusually high, and the detonation-wave travels through a stick of dynamite at a rate of several thousand meters per second. The pressures generated run into the range of a , atm. In view of the complexity of the science of rock blasting, we have to simplify in order to solve its problems, and we have to simplify intelligently.
Some problems we can solve by regarding rock as a homogeneous brittle solid. Often, when we are looking at what happens in the near regions of a borehole when the charge detonates, this is sufficient. With present-day personal computers, computational solutions to several problems of this kind can be obtained with ease.
Other problems of practical blasting can be attacked by the empirical method. Many years of industrial and experimental experience have been condensed into graphs or equations that tell us how much explosive is needed to obtain this or that size fragment distribution using this or that borehole diameter.
Much of what we know about blasting pattern design falls into this category — experimental results summarized into an engineering technique of calculating charge sizes and borehole patterns to obtain the required fragmentation or the required strength of the remaining rock. Such blasting engineering calculations are increasingly being performed with the help of computers. Introduction 3 Figure 1.
The rock mass structures and rock materials encountered along a typical road tunnel are often of very varied character. The tunneling methods must be able to deal with these varying conditions with a minimum of delay, and they therefore have to be generally applicable to a variety of rock mass and rock conditions. Finally, just emerging at this time are the first efforts to combine a simplified description of the joint strength of the real rock structure with the dynamic stress or strain produced by the blast to find the rock damage or fragmentation.
All students of the science of rock blasting will meet the blast foreman or site engineer who declares that blasting is an art and not ascience and that drilling patterns and charge weights cannot, be predicted by engineers in an office, but need to be adjusted according to the feel of the material as the blasting job proceeds.
It is good to know that there is no real conflict between the blasting engineering approach and the approach of the experienced blasting foreman, just as there is no real conflict between the mechanical engineering graduate and the mechanic who has spent many years turning pieces of brass in a lathe.
The mechanic at the lathe can feel differences between different kinds of brass — all fitting into one class according to the ISO standard — that the engineering graduate has no way of distinguishing among. In his special area of experience, the foreman can add a great deal of insight and advice on the input data for the still rather crude blasting engineering calculations that we are now able to make.
The engineering calculations, on the other hand, can be a great deal of help to the blasting foreman when some radical change occurs, such as a transfer to a new blasting site or the introduction of a new kind of explosive or a new borehole size.
The blasting foreman is then out in deep water until he has performed a series of trial blasts. The drilling patterns that can be calculated in advance will be a good starting point for trial blasts that will lead quickly to an optimized blasting operation Particularly useful, of course, are the engineering calculations when we are faced with the task of predicting blasting costs, such as in planning or estimating or bidding for a new construction job or a future mining operation, in a site where no prior blasting experience is available.
Chapter 1 Rock Strength and Fracture Properties Which properties of rock are important in the context of blasting, and how do we measure them? The two questions are not easily answered, because the physical and mechanical processes involved in the blasting process are not entirely clarified and understood.
However, it is obvious that the structural characteristics of the rock mass and the strength and fracture properties of its ingredient rocks are important to know as a basis for understanding the blasting process. The following brief introduction to some selected areas of rock mechanics and geological engineering is intended to give a person not previously acquainted with these subjects a feeling for the way the rock materials and rock masses may react to the forces released by the detonation of explosive charges in drillholes.
Paradoxically, rock is both a weak and strong material. In tension, granite has only a small percentage of the strength of steel. The unconfined compressive strength is higher; for granite, about 5 or 10 times higher than the tensile strength.
With increasing confinement, however, rock becomes very strong. For example, the strength of granite under conditions of uniaxial strain is very much above that of hard steel. Because there is an element of creep involved in the mechanism of failure of rock materials, there is also an influence of the time of loading, so that for a short time, rock can stand up to a higher stress than that equivalent to its normal static strength, measured with times of loading of the order of minutes.
When we talk of shock wave loading, the typical times under stress are in the microsecond to millisecond range, and this results in about a factor of 2 increase in strength over the static value. Thus, for a plane shock wave, where the material cannot expand laterally, granite will stand a compressive stress of MPa elastically before failing. This is 6 to 8 times the strength of steel. The degree of brittleness of rock and the ability of the rock to release elastically stored deformation energy by crack propagation constitute another set of rock proper- ties that we need to know and understand in order to understand the mechanism of rock blasting.
The material property of fundamental importance in this context is the fracture toughness, and the tool for the mathematical treatment of crack propagation problems is called fracture mechanics.
An even more important property of rock in the context of blasting is the rich structure of fissures, bedding planes, cracks, flaws, or faults, generally called weak planes or joints, that are practically always present in a natural rock mass. This is particularly true when we seek to explain the degree of fragmentation of the rock mass broken loose or the extent of damage caused to the remaining rock.
Rock Strength and Fracture Properties 1. This test is made using a necked specimen to avoid fracturing at the jaws of the testing machine. The test result is dependent on the uniformity of the load, and care must be taken to use a wafer material such as cardboard or leather between the contacting surfaces to accommodate the different moduli of the press platens and the rock. The scatter of the strength values from a series of test specimens of the same rock material is considerable.
This is a result of the randomly distributed weak planes, microcracks, or flaws in the rock which greatly influence the rock strength. The flaws are often so small and the microcracks so fine that they are difficult to detect by the naked eye. There is also an element of creep in the strength and deformation characteristics of rock, as evidenced by the ability of rock to flow and deform plastically under tectonic stress over long periods of time hundreds of thousands to millions of years.
Experiments have shown that the strength of rock is time dependent, so that the compressive strength when the load is applied in 1 msec is a factor of 2 or 2. Figure 1. With confinement, that is when lateral expansion is restricted, rock in compression becomes stronger. This is because deformation to failure takes place as a shearing of weak planes.
The action of confinement is to resist shearing, partly by creating lateral forces that resist the shear motion, and partly by increasing the friction on potential shearing surfaces by increasing the normal load thereby also increasing the rock strength. In the confined shear tests, the cylindrical test specimen, which is often necked to avoid the influence of end-effects, is sheathed by a thin rubber or copper cover to prevent penetration of hydraulic fluid into the pores of the rock.
Axial load is applied by pistons inside a pressure vessel where the lateral confining load is by the hydrostatic pressure of oil surrounding the sheathed specimen. From tests of this kind, the compressive strength which is equal to the major principal stress can be mapped out as a function of lateral pressure.
In these tests, the two minor principal stresses are equal and also equal to the lateral pressure. Even more complicated tests have been devised to study rock strength behavior when all three principal stresses are different. The most interesting region from a prac- tical engineering point of view, and also when we want to understand the fracture modes of rock in the complicated dynamic stress situation around a detonating charge ina drillhole in rock, is that in which the minor principal stress is small and the interme- diate principal stress varies.
Rock Blasting And Explosives Engineering.pdf
Drilling and blasting is the controlled use of explosives and other methods such as gas pressure blasting pyrotechnics, to break rock for excavation. It is practiced most often in mining , quarrying and civil engineering such as dam , tunnel or road construction. The result of rock blasting is often known as a rock cut. Drilling and blasting currently utilizes many different varieties of explosives with different compositions and performance properties. Higher velocity explosives are used for relatively hard rock in order to shatter and break the rock, while low velocity explosives are used in soft rocks to generate more gas pressure and a greater heaving effect. For instance, an early 20th-century blasting manual compared the effects of black powder to that of a wedge, and dynamite to that of a hammer. Before the advent of tunnel boring machines TBMs , drilling and blasting was the only economical way of excavating long tunnels through hard rock, where digging is not possible.
Rock Blasting and Explosives Engineering covers the practical engineering aspects of many different kinds of rock blasting. It includes a thorough analysis of t.
Download Rock Blasting And Explosives Engineering.pdf
The Geomining Technological Institute of Spain ITCE , aware of this progress and of the importance which the breakage process has acquired in mining and civil engineering projects, has ordered the publication of Drilling and Blasting of Rocks. Rock mass reinforcement by fully grouted rock bolts in a pattern adjacent to the planned piercing hole. Blasting Plan developed by a licensed blasting company.
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Drilling and blasting
Fragmentation energy ratio is an important index to evaluate whether an explosive is used efficiently. This paper discusses the effect of water-decked blasting on fragmentation energy based on theory and numerical simulation, and three blasting tests were performed to measure the actual fragmentation energy at a granite-based field. Results show that at the same charge amount, the maximum borehole pressure of water-decked blasting is much greater than that of normal blasting in theory, which facilitates rock breaking. In numerical simulation, water-decked blasting is more beneficial to the transmission of explosive energy; therefore, the damage distribution is more uniform and the damage level is higher. In addition, water-decked blasting can reduce fly rocks and ensure the safety of rock blasting. Blasting is the most popular method in rock breaking, which is widely used in mining, foundation excavation, tunnel excavation, and so on [ 1 ]. However, as explosion is a violent chemical reaction, the explosive energy is difficult to control and utilize.
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It is an effort to transfer advances in explosives, mining, rock mechanics and computers to blasting operations. The book has been organised into three parts.
- Бринкерхофф посмотрел на нее осуждающе. - Дай парню передохнуть. Ни для кого не было секретом, что Мидж Милкен недолюбливала Тревора Стратмора. Стратмор придумал хитроумный ход, чтобы приспособить Попрыгунчика к нуждам агентства, но его схватили за руку. Несмотря ни на что, АН Б это стоило больших денег. Фонд электронных границ усилил свое влияние, доверие к Фонтейну в конгрессе резко упало, и, что еще хуже, агентство перестало быть анонимным.