ENGIN5514: Production Drilling and Blasting
- Thrust: An axial force known as “thrust” may be defined as a force exerted in the direction of feed. This load compresses the drill. along of your axis. The cutting force is in the direction of drill rotation, whereas the pushing force is in the direction of the spindle axis (perpendicular to thrust force). The pushing force and cutting force are in opposite directions. The drill section contains it. It may be assessed indirectly via torque determination. When it comes to the machining process, drilling is one of the most significant. The ability to forecast cutting forces is vital in order to improve the design
and manufacture of items since thrust force and drilling torque measurement are indications of the resistance of the material against the entry of the cutting tool.
The measurement of thrust and torque, which provide critical information on the cutting force, aids designers in their quest to better understand the heat production and temperature fluctuations that occur during friction drilling operations on difficult-to-machine materials. Drill diameter and depth of cut both have an effect on the thrust force during experiments, which rises as the drill diameter increases. The drill tip angle and the feed rate also had an impact on the torque behavior.
- Percussion: Percussion drilling is a drilling technique which includes lifting and lowering heavy equipment to shatter rock, and requires steel casing tubes to protect the borehole from collapsing. Percussion drilling is carried out by breaking up the formation by repeated strikes of a heavy bit or a chisel within a casing pipe. Percussion drilling is performed by smashing the rock with powerful blows delivered by a massive chisel-shaped bit hung on a cable. Percussion drilling is a drilling process which includes lifting and lowering heavy tools to shatter rock and requires steel casing tubes to protect the borehole from collapsing. By dropping a heavy cutting as well as hammering bit from above, connected to the drill by a rope and otherwise cable, percussion drilling creates a reverberating impact in the hole or temporary casing (Ugolnikov et al, 2020). The term “Cable tool” is often used to describe this method. Tripods are often used to steady equipment. The cutting or hammering bit loosens soil or hardened rock in the borehole by spinning the rope or cable up and down, and this loose soil or rock is collected with a bailer. To prevent the hole from caving in, a temporary casing made of steel or plastic may be used, much as it would be while hand augering. This temporary casing will have to be taken out before the permanent well screen and casing can be set up.
- Rotation: Rotary drilling is usually used to drill enormous holes in large quarries, open-pit mining, petroleum production, and other areas. When it comes to rotary operations like drilling, cutting, and crushing, there are presently two options.
The shear force from drag bits and (1) rotational crushing by high-point loading on the rock from three cones. The rotary cutting may be used utilized to drill tiny boreholes in soft rocks (Poma, et al 2020). It is common to practise in coal mines, for instance, to employ rotary drilling to create holes no larger than 25 mm in diameter for the purpose of installing bolts. Rocks of a medium to hard consistency may be crushed using a rotary crusher, while those of a soft consistency can be cut using a rotary saw. Rock is crushed while it is spun by a rotary crusher, the most common kind of which is a three-cone drill bit with numerous teeth or buttons covering its cutting edges, similar to a planetary gear. The drill’s own mass provides the downward push, while rotation is provided via the drill pipe’s tip. Hydraulic or electric motors generate the rotation, and typical rotational rates range from 50 to 120 rpm. Compressed air is commonly utilized to discharge clippings from the bottom of the hole. One factor in how well drill cuttings are removed is the distance between the drill pipe and the hole’s wall. Drilling velocity is diminished when the spacing is either too small or too large. Rotary drilling may be used for boreholes with diameters between 203 and 445 millimeters. Rotary drilling has been the standard approach for most open-pit mines. Although slanted boreholes are preferable for rock blasting, rotary drilling machines are not suited to drill them.
- Indexing: Using an indexed crank and index plate, indexing divides the circumference of a cylinder into equal sections. To prevent the component from becoming misplaced when the operator chooses to rotate it to any arbitrary angle, indexing plates are employed. Indexing is achieved in percussion drilling by rotating a winged or button bit along a set arc in between strikes. Roller-bit drilling achieves indexing via the spacing of teeth on revolving cones a specified distance apart. Indexing does not significantly alter the drilling process or influence drill performance, such as rate of penetration while using impact (percussion and roller-bit) instruments for rock drilling. The authors suggest using drop tester observations of crater volumes to predict how easily rocks may be drilled.
- Flushing: Water or a thicker liquid (such as a combination of water and clay) is pushed into the borehole by the rod and bit as part of this drilling technique. Broken rock particles are conveyed upward by a water circulation that flows along the outer edge of the rod, between the walls of the borehole and the rod (direct flushing). Alternatively, water flows into the borehole around the rod and then out of the rod at the top of the borehole (indirect flushing). Different flushing procedures are employed to remove the cuttings (trash) from the borehole depending on the geology of the location. The air flush method employs compressed air to operate a down-hole air hammer on the end of the drill string that helps to break up the rock formation. Crushed rock pieces and any water that runs into the well during drilling are blown to the surface by the compressed air used to power the down-hole air hammer. When drilling, a mud flush is used to remove debris from the borehole and improve efficiency by using water and polymer. Drill bits consisting of hard metals like tungsten are used in the mud flush method to bore through the substratum.
- Rifle bar: A rifled steel bar used for turning drill steel in a machine drill. In rotation by a fluted rifle bar, the piston has a tubular form and surrounds the bar utilizing a rifle nut. The bar is linked to the static components of the hammer by rachets. The front end of the piston features splines that fit into those of the rotating chuck. As a result, the piston will rotate in the same direction as the drill steel on its return stroke. The rifle bars come in varying pitches so that every 30. 40 or 50 strokes a full rotation is completed.
- Pull down: The drill rig applies pull-down tension while beginning a new hole as well as at various times during the drilling process. Such pull-down pressure is delivered by a bolt or cable but rather a chain system, whether by hydraulic motors. While previous rotary rigs often used screw, cable, or chain pull-down systems, modern drill rigs frequently employ hydraulic power for these actions. The rate of penetration is determined by the driller’s pull-down pressure. Pull-down pressure matching to the formation is an important aspect of rotary drilling’s skill. Drill bits, pneumatic cylinders, and the straightness of the borehole are all susceptible to damage from too much pull-down force. In this light, increasing the pull-down strain may not be the most effective drilling strategy.
Ans.2: Diamond drilling is used for a wide variety of applications, from big duct openings to tiny pipe or cable holes to larger holes for anchoring bolts or analyzing concrete samples. It is possible to dig holes to almost infinite depths. Diamond drilling permits exact holes to be drilled through practically any material – including stone, metal, concrete, and even reinforced concrete. Diamonds, the hardest natural substance on Earth, are placed in the drill bit to give it this strength. Another distinctive characteristic of diamond drill bits is that they are hollow, enabling water to be pushed through to keep the point of drilling cool and reduce the spread of dust – excellent for restricted places. Check out our case studies to see how the diamond drilling method has been put to use in a variety of settings (Bilim et al, 2017). As an added bonus to the durability of diamond drills, this technique is also non-percussive and silent, so it won’t disturb the neighborhood too much while it’s at work. There is a wide variety of tools available, from little portable units to massive, high-performance, radio-controlled systems. Diamond drilling may be used to make a variety of holes that are uniform in size and shape. Our technology allows us to drill holes with a diameter range of 12mm to 650mm, and we can use “stitch drilling” (drilling several overlapping holes) to create even bigger apertures. As this technology is non-percussive, causing very minimum vibrations, it decreases the chance of chips and fractures – great for when the rest of the structure has to be maintained. Diamond drilling is often used to bore holes in a structure for the installation of electrical wiring, plumbing, piping, and ducting.
To retrieve the core, one may use many techniques, including:
Chrome-Plated Inner Tubes: Inner tubes that have been chrome plated have an exceptionally smooth interior. These tubes are perfect for cracked ground and other situations where extracting the core might be difficult because of the smooth, firm surface. Tubes that have been chrome-plated have the added advantage of being resistant to rust. Because of the subterranean environment’s high humidity and sulfide levels, most tubes get rusty and pitted, making it more difficult to remove a core. However, chrome-plated tubes will not rust so long as the chrome is intact. Although these tubes are somewhat pricey, they will prove to be cost-effective in the long run. Try one out for your hard extractions, and you’ll notice straight away.
Linseed soap: If you’re not ready to spend on the chrome-plated tubes just yet, no worries. One tip typically utilized by skilled drilling professionals is to put linseed soap on the inside surface of the tube before you use it. This technique has been in use for as long as drilling has, and for good reason. Simple to use and inexpensive, linseed soap is a great all-around option. It comes in tubs, and you simply take a handful and shove it into the opening of the tube. As the soap travels down the string of rods, it is pushed through the inner tube and into the groundwater below. These are just a few pointers that will improve the efficiency and quality of your drilling. If you’d like to know more about grilling tips or methods, or if you have a task you’d want to discuss, feel free to contact us. At BG Drilling, we’ve got you covered.
Choose the right core bit: Selecting the proper core bit is crucial to ensuring a successful core recovery, thus it’s important to get the knowledge necessary to do so. Factors connected to ground that you should examine include rock hardness, whether the ground is competent or fractured, variability and abrasiveness. In addition, considerations such as the kind of drill rig, amount of expertise, depth of drilling intended, and understanding of the region will all figure into your pick. Learn more about picking the proper core bit here.
Consider drilling fluid additives: Drilling fluid additives are another product that may aid in core recovery and should be considered when encountering challenging conditions. If we need to drill in sandy or gravelly ground, we may apply addition to make the ground more stable and less abrasive. Other chemicals may minimize swelling in clay or shale situations. A solution like Torqueless is crucial for cleaning and lubricating your downhole equipment and maintaining the temperature of your core bit. By mixing Torqueless into our drill water, we can keep all the metal components (inner tubes, latch heads, wireline, etc.) clean and free of debris that may clog our tools.
Perform regular maintenance: Once we’ve settled on a bit, it’s important to keep in mind that we should always be drilling using well-maintained tools. The inner tube, core casing, and spring should all be completely rinsed after each time the core is removed. Clean tubes receive core easily and descend quicker. Perform a thorough check of the latch head. Look for signs of wear and damage on the latches, landing shoulder, inner tube cap, spearhead, and other parts, and replace them if necessary. Robco EP1004 is an excellent example of extreme pressure or multi-purpose grease that should be used when pumping into the bearing assembly. The casing and spring of our central lifter should be thoroughly oiled. After cleaning, the core spring should be removed as far as it will go from the front of the case, and a thin coating of grease should be applied between the spring and the core case to ensure smooth operation. This will assist eliminate any potential barriers to the core’s entry.
Ans.3: Drilling from below requires a hammer to be attached to the end of the drill rod. When pressurized air is introduced to the drill, it drives the hammer placed on the bit into the ground, where it rotates and impacts at the same time. The drill cuttings that have become loose are picked up by a flushing stream and carried upwards. This technique is often used for piercing hard to extremely hard rock, as well as huge boulders. DTH hammer refers to a tool that may be placed into a bore after being connected to the end of a drill string. It’s a miniature jack hammer used to shatter hard rock into little particles that can be flushed away by the DTH hammer’s air exhaust.
When solid rock is in the way of a bore, a down-the-hole hammer can be lowered to break it up. The DTH hammer may be thought of as a little jackhammer. It functions similarly to a length of drill pipe and attaches to the end of a drill string through a threaded connection. It’s air-powered and has a high cycle rate, much like other jackhammers, but instead of just hammering, it rotates and drills at the same time. While it digs into the rock, its chisel-like tip spins as it does so, reducing the solid material to powder and shards. The chips, as well as dust, are blasted out of the bore by the DTH axe’s air exhaust, that is pneumatically driven. Drilling through rock is said to be just as fast with small portable rigs using a DTH hammer as it is with massive truck rigs.
Down-the-hole drilling is to push the hammer which behind the drill bit by compressed air through the drill pipe. Since the drill bit is guided in a straight and steady path by the outer cylinder of the hammer, the piston may hit the bit with more precision. This ensures the effect of energy is not lost in joints and allows for significantly deeper percussion drilling.
The impact on the rocks through its force at the bottom of the hole, makes the drilling operation more efficient and straight.
Additionally, DTH is preferable for drilling large holes in hard rock, especially rock with a hardness of 200Mpa or higher. In contrast, drilling into rock with a pressure of less than 200 MPa results in significant energy loss, poor drilling efficiency, and extensive bit wear. Drilling and slagging efficiency suffers because soft rock does not absorb the full force of the piston of the hammer during the strike.
Down-the-hole drilling, which is powered by compressed air, is more effective. This approach moves at a considerably more leisurely pace. As the depth grows, the performance declines. The top hammer drilling depends on hydraulic energy, thus its performance stays steady regardless of the depth.
The negative is the top hammer drill needs regular component replacement over time since the tension generated quickly generates wear and damage.
DTH drills are mechanically better from an efficiency aspect when compared to the top drilling cousin. The top hammer drilling strategy produces a constant performance, making it the appropriate option for profitable drilling at very low levels.
For purpose of designing drill bits, optimizing associated drilling operating parameters, and predicting rate of penetration, rock drillability is a comprehensive index that reflects the ease of drilling a hole in the rock mass. The hardness of the rock is a key factor in determining how easily it can be drilled and how quickly a drill can penetrate it.
- Density and texture of rocks
- The pattern type of Rock Fracture
- Structure of the formation or rock mass.
The Mohs scale is used to determine a mineral’s hardness. It is recommended to conduct many tests on a sample of rock to get an accurate reading of its average hardness since rocks sometimes include more than one mineral. Mohs’s hardness testing kit is not only for the lab; it can be used in the field as well.
The grain structure of the rock may be visually inspected to classify its texture and drilling condition.
How easily a rock fracture when hit with a hammer is a measure of its drillability. There are five criteria for drilling that correspond with rock type and fracture.
The term “formation” refers to a specific stage in the development of the structure of rock. The five drilling conditions are made feasible by the distinct formations. Big rocks allow for fast drilling rates, but blocky and seamy ones slow it down significantly.
Drillability is affected by several factors, including bit type, formation characteristics, drilling fluid characteristics, bit weight, rotation speed, as well as bit hydraulics.
Bits with long teeth and a large cone offset tilt have the best penetration rates. These components are best suited for usage on softer surfaces. The lowest cost per foot drilled is achieved by using the longest teeth available while yet keeping an adequate bearing life for optimum bit performance.
Characters involved in formation, The rock’s final strength of concrete is the most important factor in determining its permeability. The rate of penetration slows down as the compressive strength increases.
PROPERTIES OF DRILLING FLUID
•Penetration rate is affected by the density, rheology, filtration, and viscosity of the drilling fluid.
• solids content and size dispersion
If the density of drilling fluid were to be reduced, the water potential at the hole’s bottom , immediately below the bit, might rise, as will the pressure differential, or “overbalance,” among the borehole as well as the pore water pressure of the overlying formation.
- Mud Rheology
Pressure Variation Across the Region of Cracked Rock Underneath the Bit is Controlled by the Mud’s Granular Content. Raising the solid material decreases the filtration rate and consequently boosts the pressure difference. As was noted earlier, the penetration rate lowers as the differential pressure grows.
- Aborting Bit Run
The option to cease a bit run may not always be clear in exploratory drilling. A bit must be pulled out if the bushings are worn out and then the cutters are worn out to the level that it is no longer practical to continue cutting with bits.
Ans.5: Many factors contribute to a good core rehabilitation. We can make some approximations about two of the variables involved. Stratigraphy, geomorphic, rock mechanics, architecture, underground aquifers, metallurgy, rock mass content, and erosion are all examples of geological features. Next, there is the technical side, which involves choosing the correct rig, core barrels, coring bits, hydraulic fracturing, weight on bore (WOB), Speed, and volume of the services for better drilling fluid. Core boring in geological work is primarily used to document, categorise, and evaluate rock mass properties concerning their application for various geotechnical projects, as described above. Among the several rock mass categories, RMR system, Q-system as well as rock qualities designation are beneficial and widely utilized methods in geotechnical research. Just using stone designation, JSN, joint roughness, junction modification, water intake, plus stress reduction ratio, the Q-system classifies a rock mass (SRF). In addition to measuring the amount of jointing and block size, Deere developed the RQD, which is compatible with NX-size components. While undertaking a geotechnical research, the RQD measurement is commonly obtained as part of the recording of drill cores. This helps obtain the largest core extraction so that the presence and extent of problem spots, such as deteriorated zones, fissures, cracks, shale as well as clay layers, etc., could be recognized, and relevant activities may be done to increase it, according to rock mass categories.
Ans.6: During RC drilling, the driller will use dual wall drill rods, which consist of an outer drill rod and an inner tube, to create holes in the ground (Liu et al, 2020). These hollow inner tubes allow the drill cuttings to be brought back to the surface in a continuous, steady flow. Ranger’s Reverse Circulation configurations include the rig, a support Truck, Booster, auxiliary compressor truck and a crew vehicle.
RC Drilling working
The reciprocating pneumatic piston is driven by the onboard compressor. In turn, the piston drives a drill bit composed of tungsten steel, which is particularly developed to break through resistant rock.
Identical to air core boring, samples are brought to the surface inside rods (Liu et al, 2020). That can be ac achieved through the use of dual walled drill rods: an external drill rod with only an interior tube. Simply by pumping pressurized gas through the shaft, the samples may be brought to the top by a volumetric action of wind.
When cuttings are brought to a diverter at the top of the hole, they are routed via a hose and around a cyclone to slow them down. Over a splitter, a predetermined fraction of the cyclone’s output is sent to a collection bag. The exploratory drilling crew then gather the samples aligned to the hole depth and set them out for the customer to record, and then transport them to the lab for analysis.
RC drilling benefits over other drilling technologies.
1. Improves air core drilling for penetrating hard rock, thanks to the drill bit’s abrasive qualities and the kinetic energy it imparts to the rock.
2. Offers more precise sampling, and cuts are easy to classify. The collected samples also include information on the location and depth from which they were obtained, simplifying and improving mineral resource detection.
3. Perfect for arduous conditions. Drilling using RC equipment is preferable in inaccessible areas because it requires far less water than diamond drilling.
4. Fourth, there is less potential for contamination. Cuttings are contained inside the inner tube of the drill bit, so they don’t contaminate the samples.
5. It’s quicker and more efficient, which means it saves money and generates more money for you. More ground may be drilled in a day with RC drilling, which can reach depths of 200–300 feet. Drilling operations may be completed more quickly, allowing for more rapid delivery of data to customers. As a result of the increased productivity, fewer workers are needed to operate the drill rig. RC drilling is more cost-effective than other methods since the equipment is powerful and can withstand tough conditions. Cost savings of 25- 40% have been shown with RC drilling.
Ans.7: The Drilling Rate Indicator (DRI) is a method for determining how tough a certain rock is to drill. The brittleness test (S20) and the Sievers’J (SJ)-miniature drill test provides the basis for the DRI. When a linear connection can be constructed between the dependent and independent variables, linear regression techniques are most useful. Different types of linear regression models were utilized to characterize the correlations between DRI and rock strength, UCS, and BTS in this investigation.
The data was analyzed and interpreted using the t-test for independent samples and the one-way analysis of variance. The statistical analyses were performed in two phases. Initially, test data are simply analyzed without any sorting. First investigation suggests that UCS values are useful for data classification. The second step included evaluating the DRI values of rocks with UCS values by utilizing simple and multiple linear models of regression.
Ans.11: Stemming is a substance that is deposited inside of a blast hole to assist keep gases from escaping. Stemming may be used to bridge mud seams or weak layers, and it is most often placed at the top of a blast hole. Misplaced stemming might result in even smaller fragments.
Stemming is typically a rock or sand material that is generally put on top of the explosive in a blast hole.
Many blasters employ stemming, since it may minimize the air overpressure levels from a blast by more than 98 percent when properly confined. Additionally, correct stemming may lead to considerable cuts in fragmentation and reduction of mucking cycle durations by more than 18 percent.
This is because stemming is what guarantees the explosion is shattering the rock and not producing noise. The appropriate stemming will increase the effectiveness of the explosive.
If blast holes are tossing stemming into the air, there is a significant possibility the blast holes are under-stemmed. This causes air overpressure to rise by as much as 6 dB and may increase the P80 size by more than 10% in a typical blast.
Conversely, if the shot is over-stemmed the quantity of explosive in the blasthole is lowered and the fragmentation size is also increased. Over-stemming a blast may also lead to big stones emerging from the top of the bench.
In order to achieve effective explosive usage, stemming must be carefully considered and analyzed as a primary blast design variable.
The decision a mine makes for the material that is utilized for stemming is one of the most critical aspects of blasting. Stemming materials normally occur in four basic types: liquids, solids, sands and gravels, and crushed rock.
Ans.13: The most extreme conditions may lead to the ground being designated as hot and reactive. An organized and well-thought-out plan is required for blasting in hot and/or reactive ground. This plan should account for the requirement to measure and classify the ground, as well as the implementation of goods and methods to mitigate the risk of explosion. Blast crew employees need specialized training and oversight, and they must also be well-prepared for delay and breakdown situations.
One or more blast holes may explode prematurely and on their own, due to a runaway reaction between sulfide minerals and ammonium nitrate, anywhere from a few minutes to several days after loading. In this context, “hot earth” refers to rock that has been heated to a temperature of 55 degrees Celsius or more by chemical, geothermal, or combustion processes. It’s easier to find, but it’s just as dangerous as reactive ground if it’s not managed correctly.
Even in the most challenging hot and reactive ground blasting scenarios, with ground temperatures exceeding 100 degrees, Orica has proven technology, procedures, and employees to accomplish the job.
Current methods and potential future avenues for reactive ground risk management were analyzed. Different tools are needed to handle the reactive ground, and the literature on the topic highlights the contrasts between spontaneous combustion and reactive ground. The findings pertain to activities Leading and suggestions from mine workers, a third-party laboratory, and explosive suppliers Methods of Stemming; Liners Used in Drilled Hole; Examining the allowable degrees of explosives as well as the degrees in the pit, emphasizing the need of blowing the perforations promptly when the explosive temperature reaches 90°C, using temperature monitoring systems readily commercially available (AyalaCarcedo, 2017). At the end of the inquiry, recommendations are made that will help the mining firm develop a way to reduce the risk of working in the reactive ground.
Ans.14: Blasting activities may have undesirable noise and vibration implications if not handled appropriately very strong vibrations transmitted through the ground as a result of blasting might cause significant damage to buildings. Vibrations may be felt by humans at far less intensities than those required to inflict even cosmetic damage to the most fragile of buildings. Blasting in the context of mining, quarrying, construction, or other activities may cause discomfort and even injury to anyone in the area (Bhatawdekar et al, 2019). All blasting must be conducted properly by a qualified individual in line with best practices in environmental management to reduce the potential for damage to buildings and individuals sensitive to noise and other vibrations transmitted through the ground.
If blasting during the preferred hours is impossible, stricter airblast overpressure and ground vibration constraints should be imposed, and blasting should be limited in frequency and intensity.
If the bomb location is far away from a noise-sensitive neighborhood, then there is little chance that residents there will be disturbed by the explosions.
External ground vibration monitoring
If it cannot be shown that the explosion site and the measurement location are on the same underlying stratum, then the ground-borne vibration transducer (or array) used in the measurement will need to be linked to a mass of at least 30kg to ensure good coupling with the ground (Vijayakumar et al, 2021). The largest exposed area of the mass should be concealed at ground level.
The ground-borne vibration transducer (or array) should be located between the blasting site and any building or structure that may be impacted by noise, at a distance of at least the longest dimension of the foundations of such building or structure.
Ans.15: A variety of techniques may be used to keep an eye on explosions, including:
Preparing test specimens, predicting blast load, using high-end gear like high-speed cameras and pressure sensors, and validating experiments are all necessary steps in conducting field blast testing. The charge weight is often capped at a maximum amount due to constraints imposed by cost and the maximum feasible blast charge weight to be employed.
To study shock-wave-related issues in a controlled laboratory environment, researchers may rely on shock tubes, which have already been put to use in a broad range of domains in both basic and applied sciences. Physical as well as chemical processes that generate one-dimensional, nondissipative flows may be studied using tubes.
Blast Pendulum Systems
Pendulum devices placed in blast chambers might be used to take blast observations for laboratory investigation of minor structural elements. Typically, the force delivered into the specimen’s frontal face is measured using a four-cable psychometric pendulum system. The greatest achievable energy of the system, following its dissipation via plastic work, may be inferred from the recorded oscillation swing because of the direct relationship between pendulum amplitude as well as energy stored.
However, field studies using a blast simulator are not without their drawbacks. They may be costly and risky, and they don’t always provide the kind of clear visual evidence and quantitative data on structure reaction that would be useful in designing for an explosion. In order to generate explosion-like loadings on buildings in a controlled laboratory environment, the blast simulator was created and built.
The impacts of large explosions may be mitigated, or at least mitigated to some degree, by using blast chambers. They are manufactured for a variety of objectives, including the detonation of munition, research into various aspects of explosive loading and explosive properties, and the creation of various kinds of materials or building components. Intention drives the chamber’s design, so to speak. While the plastic reaction is taken into account when designing a chamber for a single extreme event, the liner-elastic response is taken into account while designing a chamber that can endure numerous detonations without damage.
- Paddock blasting: It is a method of reducing a solid body, like rock, to pieces by utilizing an explosion. Drilling holes, inserting charges and detonators, setting off the explosives, and then removing the debris are the standard steps in every blasting operation (Scott, 2020). Upon explosion, the chemical energy in the explosive is unleashed, and the compact explosive gets changed into a brilliant gas with immense pressure. In a tightly packed hole, this pressure may surpass 100,000 atmospheres. The tremendous pressure shatters the region next to the drill hole and exposes the rock beyond to extremely high stresses and strains that cause fractures to develop. The gas pressure causes the fissures to widen, and the yielding rock in front of the drill hole advances. If the distance of the hole to the nearest surface is not too considerable, the rock in front of the hole will break loose. Holes are thus located as to need a minimal amount of explosive per volume of rock shattered (called the powder factor) (called the power factor). Most blast-hole designs are based on the idea that fragmentation is most uniform if the exploding charge is within a specified distance from an exposed face of the rock(Scott, 2020). To break up a big body of rock, charges are put in a sequence of holes drilled such that, when the holes closest the exposed surface are fired, the explosions generate freshly exposed faces at the right distances from the next set of holes, in which firing of the charges is somewhat delayed. The holes are shot in a predefined sequence, at intervals of bare thousandths of a second.
- Cushion blasting: The effect on the surrounding rock and the final slope face may be lessened by using a controlled blasting technique called cushion blasting, which is normally performed after production blasting. Cushion blasting may be utilized with both vertical and angled holes, and proper alignment is needed in both circumstances. The cushion holes are bored along the final slope line and filled with mild, well-distributed charges, and fired after the main production explosion. A cushion blasting approach that minimizes damage to the hole bottom while yet allowing for rapid excavation is described. step 1. Drilling in rock bodies vertical blasting holes that have collinear circle centers and are in rows; step 2. laying a cushion layer on the hole bottom of the blasting holes, the cushion layer being loose sand, rock powder, or fine sand; step 3. Adopting a rope to draw an energy dissipation seat to enter the blasting holes, and enabling the bottom surface of the energy dissipation seat to be placed on the cushion layer, and step 4. Adding blasting powder inside the blasting holes and detonating the blasting powder after blocking it (Varangaonkar, 2020). The current invention is appropriate for one-time creation of excavation for dam foundation surfaces and slope path protection layers and has benefits such as a simple technique, cheap cost, and a good excavation impact.
- Decoupling: In decoupled charge blasting, the filling medium considerably decreases the peak pressure at the borehole wall. With a rising decoupling coefficient, the pressure peak at the borehole wall attenuates with a modest degree of attenuation, which is a quantitative process. The decoupling coefficient on stress development in decoupled charge blasting is examined. Different filling materials are discovered to have a considerable influence on the transfer of blasting energy. Compared with coupled charge blasting, decoupled charge blasting with air as the filling medium reduces the blasting stress peak in the specimens; while within a certain decoupling coefficient range, the decoupled charge blasting with plasticine as the filling medium increases the blasting stress peak in specimens. The blasting stress attenuation index in specimens displays the pattern of an initial rise and subsequently a reduction with an increasing decoupling coefficient, where the decoupling coefficient corresponding to the maximum stress attenuation index is defined by the filling medium. In addition, the numerical modeling findings reveal that, in decoupled charge blasting, the filling medium considerably decreases the pressure at the borehole wall. With an increasing decoupling coefficient, the pressure at the borehole wall attenuates with a modest degree of attenuation.
- Lifters: Shotholes bored along the floor of a tunnel for elevating the rock to floor level. They are fired after the cut holes, or by delay detonators in the cartridge. Drilling a series of lifter holes and line holes in a certain manner to excavate a tunnel’s rock face. The line holes eliminate the need for excessive face cleaning while maintaining an acceptable grade or slope for the excavation. Lifter holes are drilled at an acute angle into the tunnel face, with the drilled axis running perpendicular to the tunnel face. Line holes are bored at a less acute angle than the lifter holes and are placed at right angles to them. Lifter holes are bored to a greater depth than line holes and do not intersect. A charge of explosives is placed in the lifter holes. Each line hole is disposable and aids in rock breaking. In the next sections, we’ll have a look at the many drilling designs that have been devised for addressing the blasting of drifts. The patterns seen here are the result of early incisions that are subsequently blasted into using holes drilled in the surrounding material. This process, known as stopping, gives rise to many different names for the supplementary holes depending on their location: wall holes, roof holes, and floor holes (also known as lifters) for the outside holes, and stoping holes or cut spreading holes for the inner holes.
- Easers: Easer is a highly adaptable and transportable raise borer, particularly intended for making small to medium-sized openings, which eliminates the need to drill holes around the cut to widen the cut area before the trimmers can break out the ground to the appropriate proportions. With a conventional 203 mm (8 in) pipe and a 228 mm (9 in) pilot drill bit, the Easer rig can bore opening holes up to 60 m in length and 750 mm in diameter. All essential equipment, except the drill rods, is included in the carrier, and no site preparation is required beyond hooking up to power and water. Additionally, and most crucially, the Easer is wheel-bound, making it very simple to transfer to wherever it is required in the mine.
- Primer: Primers, also known as priming compositions, are substances used to ignite detonators with an instantaneous blast of flame. Primers may be detonated by mechanical stress, friction, or a short application of heat (from a burning fuse or an electrically heated wire) (like the impact of the firing pin of a gun).
The blasting cap may include either a primer or a detonator, depending on the user’s preference for setting off the explosion. Primer is a powerful yet delicate explosive used to set off the primary column in the blast hole. Even those with a very little core load are susceptible to damage from a detonating cable or cap. Filling a cartridge with high-velocity explosives such as 60% ammonia gelatin, gels, slurries, or cast primers with a blasting cap is adequate for priming blasting agents with holes up to 2 1/2 inches in diameter.
- Throw blasting: The throw blasting technique relies on explosive force to shatter and carry a rock mass straight onto a berm, reducing the need for motorized mining equipment like draglines. The expense of managing the overburden is drastically cut down by using the throw blasting method. Its significance is growing daily as a result of this economic benefit. The technical aspects of the cast blasting method are the focus of this study. The method’s economic viability has been thoroughly discussed.
Ans.17: Drilling, blasting, clearing smoke, and loosening fly-rock from above timbers, mucking, hoisting, and timbering are the conventional steps in sinking a mine shaft. Timbering can indeed be completed as the final operation of a process, during digging as well as messing as long as significant blasting protection or bulkhead is used to safeguard the men below harm by falling debris, or in segments, whereas another action is ceased; that is, if indeed the facades of the propeller stand well, a few sets can be positioned at one time showing several fracking cycles all through which no timbering is accomplished (Mohanty, 2020). For the most part, while sinking a shaft through rock, it is done in stages by drilling a series of holes in a predetermined pattern to gradually increase the depth of the shaft. After the holes have been filled with explosives, they are blasted in a certain order to ensure maximum damage is done with the available charge. For this reason, cut-holes are used, similar to how they are used while driving horizontal heads, however, the process is somewhat different and is according to the operator’s preferences and the surrounding environment. For the most part, while doing heading work, it’s best to break the rock as coarse as possible while still making it manageable for one person or the loading machine (Mohanty, 2020). In shaft operations, however, it is better to shatter the rock as tiny as cheaply feasible because of the increased ease in digging it out of the bottom of the shaft using pick and shovel, because a mucking sheet cannot be utilised to shovel from as in driving headings.
For rock blasting, the explosive is detonated with the help of an initiation mechanism, which supplies the first burst of energy needed for the explosion. It needs an initial energy source, a distribution network to get that energy to each blast hole, and an in-hole component to set off a detonator-sensitive explosive. Explosives used in mining, building, quarrying, and other industries need detonators to be set off. If the explosive doesn’t go off as planned, the rock blaster might be seriously injured. Recent years have seen the development of electronic starting devices for use in civil blasting. Compared to traditional pyrotechnic delay detonators, the delay durations in these systems are far more precise, allowing for more effective blasting. The purpose of detonators is to set off explosive charges. Definitions of several kinds of detonators are provided below.
• When a resistance wire is embedded in a pyrotechnic composition and an electric current is sent through it, a detonation is produced.
• The term “non-electric detonator” refers to a detonator that does not use electricity, such as one that uses a shock tube, gas tube, or detonating cord to set off the explosion.
• Instantaneous detonators are those that have no delay mechanism, allowing them to explode with almost no lag time.
• An electronic detonator is a detonator in which the time delay is controlled electronically, whereas an electric or non-electric detonator does not involve such a delay.
• The components of an electronic initiation system include the blasting machine, the measurement tools, the wire system, and the electronic detonators.
The advantages of an electronic blast-initiation system :
Using an electrical blast-initiation system has several benefits, including more precision, better control over the explosion itself, and heightened safety.
Pros of Using a Detonating Cord In addition to being quite precise, detonating cord is also simple to use, robust, insensitive, and unaffected by electric risks.
Disadvantages of Using Detonating Cord
Flyrock or sub-surface rock shifting may create misfires and cut-offs in the detonating cord; downward initiation in the charge column can produce low-order deflagration and make the charge more dense, even to the point of “dead press;” and the detonating cord might disrupt stemming material.
- The downsides of an electronic blastinitiation system are that: It needs additional training.
- It is more sophisticated.
- It is more costly.
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