So a more look into the pre split design was recommended mostly to establish optimum parameters for hard rocks. Over the past decades, some significant surveys on smooth and presplit blasting have been conducted by many researchers. Comparison of presplit and smooth blasting methods for. Pre splitting is a controlled blasting technique with applications in open pit mines. If pre splitting is not appropriate, trim blasting may still provide a good final wall. Also, the design or audit of designs for specialist applications like underwater blasting. A new perimeter control blast design concept for underground. Audit of drilling and blasting practices and available blasting data to determine aspects of the site practices. Production mining is conducted by excavators in backhoe configuration working on 2m flitches after blasting on. It also partially reflects the blast generated strain waves and so reduces the strains that are experienced beyond the split.
Pre splitting in open pit mining is performed by arranging a row of blasting holes behind the main blast pattern. Special blasting technique free download as powerpoint presentation. Design the detonation sequence import updated pit surveys to the blast design create pre split holes output once data is entered, the blast pattern is displayed. Rock blasting and control overbreak fhwa us department of. Effect of a presplit plane on the frequencies of blast. Trim blasts the aim is to break rock mass to the pre split or final wall line not to break through the line. Following are the techniques of controlled blasting. In the case where a pre split is inclined, the shear force along the pre split is reduced and weaknesses b and c in the final wall remain intact.
The main objectives of pre splitting in open pit mining are. Pre split design theory various theories have been put forward over the years regarding the mechanism by which a presplit mine is formed. The pre split blast design parameters being practiced. Geovia surpac drill and blast design dassault systemes. Where the pre split blast has failed to create a continuous fracture plane over the full length of the pre split holes, with. Figure 87 analysis of efficient blast design efficient blast designs combined with the proper choice of explosive can produce better fragmentation with associated lower operating costs compared to blast designs and explosives used under adverse conditions.
Example showing drill hole locations of a successful blast design in australia that. The crack helps to screen the surroundings from ground vibrations during the firing of. Once this process is complete a full drill pattern is drilled in front of the pre split and blasted. Pre split blast design for openpit and underground mines. Thus, a blasting foreman must be allowed certain flexibility for changing a blast design within certain limits. Zare and bruland discussed the influence of smooth blasting on two tunnel blast design model. Selection of best wall control blast method design blast based on. Most of these theories involve the interaction of the ground vibrations resulting from the detonation of the explosives in the pre split blast holes. Influence of joint conditions and blast design on pre. A practical, yet technically sound design procedure for presplit blasts. The ground vibrations induced by them have been monitored with the different distances through the corresponding devices. Design of controlled blasting presplitting in golegohar iron ore. Design of controlled blasting presplitting in golegohar iron ore mine, iran.
In addition, the angle drilling option on the pit viper only allows the tower to be tilted backwards in increments of 5 degrees and the diameter of the holes they drill are too large for the small charges of explosives required in order to obtain a good result with the presplit blast. Design of controlled blasting presplitting in golegohar iron ore mine, iran s. Choose from the following options once the pattern is produced. Special blasting technique strength of materials pressure. Benches may be designed and carried forth with more. Dynamic photoelastic studies on delayed pre split blasting. This will allow double bench highwall holes pre split holes to be drilled. Clearly, a good pre split with a poor trim blast will not work a poor pre split with a good trim blast also will not work. The presplit blast design parameters being practiced. Firing of the pre split charges splits the rock along the designed. Presplitting rock in the presence of a static stress field, by harry r. Effective pre splitting is a key feature of wall control blasting. To understand differences of smooth and presplit blasting for the excavation of rock wells, two field experiments using these two techniques are implemented at the same test site, respectively.
If productivity and safety benefits are to be gained, these methods need to be improved in order to accurately predict pre split performance. If blast fume is present it will most likely be seen in an overburden or pre split blast and rarely in the parting shots due to the small amount of explosives used. Rock fragmentation control in opencast blasting sciencedirect. Predicting blastinduced damage for open pit mines using. Basically, this technique consists of creating a continuous crack or presplit at a desired finished excavation line by initially firing a line of closely spaced, lightly loaded holes drilled there. The design wall angles vary around the pit from to 85 degrees. Dec 17, 2009 following are the techniques of controlled blasting. Combined with blast dynamics, the scope of stressinduced cracks around blast holes and the maximum length of secondary cracks induced by detonation gas was calculated. Presplitting is carried out in both transitional fig 2 and fresh rock fig 4, with trim blasting employed to further reduce the damage to the walls.
Preliminary tests on presplitting rock in the presence of an in situ static stress field were undertaken to study the influence of a horizontal static stress field on the creation of a vertical presplit fracture plane. The pre split is one such technique, deployed when there is no free face and, thus, involving several interactions of rockmass properties, including strength, joint spacing and joint orientation, with respect to blastholes, blast design, explosive configuration, blasthole deviations and. Drilling and blasting is the controlled use of explosives and other methods such as gas pressure blasting pyrotechnics, to break rock for excavation. The first phase, completed in 2007, performed blast tests on 30foot span panels. Keywords blasting, blast damage, open pit mining, pre split blasting. Those limits can be described using scientific and empirical guidelines that are well established in the blasting literature. Blind application of design formulas will result in optimal results in certain rock types, but not so in others. Pdf presplitting is a controlled blasting technique with applications in open pit mines. Normal production blast consists of detonation of 68 rows involving 140200 holes in. Presplit blastholes are fired before and immediately in front of the blastholes. In general blast fume is not a common occurrence at the mine. It is practiced most often in mining, quarrying and civil engineering such as dam, tunnel or road construction. Pre split holes can be stemmed if the noise from the firing of. Although pre split designs generally share a common design feature of closespaced.
The results indicated the good excavation qualities could be both achieved by the two design models with the smooth blasting. This video gives a brief look at the drilling of the presplit for. Pre split design features see burden and spacing change borehole position. Soundwall blasting met by the technique of presplitting, developed in the united states in the late 1950s. Developing an effective presplit design that can vary by rock type and. Berms are 8m wide and are planned at 20m vertical intervals and along the ramps. Drill and blast design course is a oneday session designed for experienced users of surpac with an interest to follow a blast design from start to finish. Combined with the shallow depth seams geological conditions in shigetai mine, shendong mining area, this paper uses the theoretical analysis and the software of lsdyna3d numerical simulation to uncover the deephole pre split blasting mechanism for controlled roof caving, thence presents the roof caving design. Pf kgm3 total explosives in the blastvolume of rock. Pre split blasting is an important element in this slope creation process. La11097ms, controlled blasting and its implications for. These approaches are highly theoretical and in the authors opinion do not provide a practical method for pre split design. Singh has made notable contributions in explosives science and blasting technologies to solve practical problems in the mining industry encompassing the fields of optimal use of explosives energy in rock fragmentation, explosives energy partitioning, blast vibrations, wallcontrol, fragmentation control, blast design in mines and tunnels, pre. These tests indicated that it is easier to fracture the rock parallel to the.
The vibration results illustrate that at the same monitoring distance and. Geovia surpac drill and blast design 1 day the surpac. Automatic blast report planned vs actual field real information holes geometry. Presplit spacing will vary, depending upon rock characteristics, size of the. Blasts may have to be redesigned or rescheduled for more favorable atmospheric conditions to minimize air waves. If the pre split row is not able to be doublebenched, a reduction in the berm width is produced due to. Most mining operations use historical designs or rulesofthumb for designing pre split blasts. First international symposium on rock fragmentation by. Nioshtic2 publications search 20032990 a practical. These models include the blast design geometry, initiation, and explosive energy. Chemical industries manual, which recommends the charge loads and blast hole pattern for. A pre split comprises of a single continuous row of drill holes which are packed with explosives and blasted. Simha et al, usa the influence from specific charge, geometric scale 115 and physical properties of homogenous rock on fragmentation. Before firing the inner holes, the lightly charged perimeter holes are initiated simultaneously, creating a split between the blasting zone and the.
Johnson department of health and human services centers for d isease control and prevention national institute for occupational safety and health. Avoid pre splitting too far ahead of the production blast. This situation improves with increasing inclination of the pre split firing too e arly and thus increasing confinement in the back of the blast. To minimize damage to the rock a prerock, a pre split blast surface excavation or smoothwall blast underground may be used to create the final excavation surface. The main objectives of presplitting in open pit mining are find, read.
Nioshtic2 publications search 20032990 a practical, yet. The second phase, completed in late 2010, provided more comprehensive study, including static testing of over 50 singlespan and multispan panels, evalu. Because the design, implementation, and effects of blasts can be controlled within wide limits, mine are able to. Mining issues the design wall angles vary around the pit from to 85 degrees. Misfires misfires happen when a loaded hole, portion of a loaded hole, or several loaded holes fail to detonate during a blast.
This was one of the most rocky home sites that ive ever blasted, more than 50 individual blasts, 60 truck loads of hard granite. Chapter 8 blast design figure 82 staggered pattern figure 83 sing figure 81 square or rectangular pattern. Deephole presplit blasting mechanism and its application. The order and timing of the detonation of the individual blast holes is regulated by the initiation system. When the face was exposed, approximately 5 months after the pre split blast, the field team returned to the mine in order to take assessment photographs. In addition, the angle drilling option on the pit viper only allows the tower to be tilted backwards in. To fully appreciate the relationship between damage and blasting, it is necessary to understand how the design of blasts affects over break and ground vibrations. Design and application of blasting parameters for presplitting hard roof with the aid of emptyhole effect. To be able to safely achieve and maintain steepened final slopes, good blast design techniques must be available and applied together with close operational control. Line drilling, trim cushion blasting, smooth contour or perimeter blasting, pre splitting, selecting and employing various parameters of blast design, using modern technology, precise and accurate timing delays, muffle blasting at critical and congested areas. Because the design, implementation, and effects of blasts can be controlled within wide limits, mine are able to promote stability by controlling blast induced damage. Export drill locations to survey instruments create basic explosives analysis and cost reports for each design. Agne rustan et al, sweden regulations of the process of hard rocks fragmentation 143 by blasting. Presplit holes may be drilled on an angle if the geology and drill allow for it.
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