METHOD OF INTER-HOLE DELAY BLAST

Description

Field of the invention

[0001] The present invention relates to a method of blasting, and is particularly concerned with the initiation of the blastholes with the shortest inter-hole delay time. The invention further relates to the means for blasting and delaying.

Background of the Invention

[0002] In the conventional methods of the rock blasting the blastholes are drilled into the rock to be blasted. The blastholes are at least partially charged with the explosives, and one or more initiation means are associated with the each explosive charge. Initiation signals are transmitted to one or more initiation means in the blastholes at the blast site to cause the fragmentation.

[0003] Up to now various methods of the blasting has been developed, however, the venting of the explosion gas and the production of excessive sound are considered as unavoidable companion of the blasting. Such phenomena clearly imply the loss of the energy of the explosive charged in each of the blastholes, applying much horror and shocks to the surroundings.

[0004] The efficiency of blasting can be measured by the degree of the rock fragmentation.

[0005] The delay blasting method which is delayed at a certain intervals in blasting at the open bench pit have the several advantages of enhancing the fragmentation quality of the rock, producing less vibration destruction to the structures and improving the efficiency of the blasting.

[0006] The inter-row delay blasting method is widely used in the art, and the inter-hole delay blasting is still under study stage and many experiments and studies are being made to obtain reasonable inter-hole delay time.

[0007] The most important factor is the decision of the reasonable inter-hole delay along a row in the open bench blasts, which will effect the combination of stressfields propagating from each of the blastholes.

[0008] It is important to define the inter-row and inter-hole detonation delay time that ensures the maximum quality of the fragmentation and to provide the delaying device as well as the blasting means that ensure the precise delay time.

[0009] Numerous blasting methods are known in the art that describe the arrangement of the explosive charges and the control of the detonation delay time which attempts to optimize the rock fragmentation without the need for excessive amount of the explosive material.

[0010] In one example, United States Patent US 3,903,79 issued Sep. 5, 1975, discloses a method of the blasting, wherein the fissure production occurs within 0 to 10 milliseconds of the blast initiation, the crack propagation proceeds from approximately 10 to 60 milliseconds after the detonation, and the venting and subsequent rock removal starts after approximately 100 milliseconds following the detonation.

[0011] A plurality of the charges are arranged in spaced apart rows with the detonations within a row being detonated with the time delays of 10 milliseconds or more and with the detonations between the successive rows being detonated with time delays of from 25 to 150 milliseconds.

[0012] The Document WO 2005/124272 of the ORICA group published on Dec. 29, 2005 provided a blasting method, wherein the detonations between adjacent blastholes within a group of 2-7 holes were actuated with the time delay of below 5ms to cause the collision of the stressfields, as a result of which the fragmentation quality of the rock was improved with the attenuation of the blast vibration.

[0013] Blasting engineering hand book, kyorits-pub.co.jp, 2001.8.1.printed in Japan also suggests that the detonation time delay along the row that assures the efficient quality of the fragmentation can be decided by the following formula (1).

k : Experiment Factor. ms / m, W: Minimum Burden

k= 3∼5(Langefors, 1967), 5∼8(Gustafsson, 1981), 3.3∼10(Stagg, 1987)

[0014] U. Langefors presented that the time delay is preferably 3∼5ms per metre of the minimum burden, and when the time delay is calculated by the formula (1), if W is within the range of 3∼12m, the delay time is within the range of 9ms∼60ms.

[0015] The suitable detonation time delay is presented by R. Gustafsson as 5∼8ms/m in which if minimum burden is 3∼12m, the delay time is 15ms∼96ms.

[0016] M. S. Stagg and S. A. Rholl described that the suitable time delay is defined as 3.3∼10ms per metre of the minimum burden wherein if the minimum burden is 3-12m, the delay time is 9.9ms∼120ms.
As the time delay along the rows is 9ms∼120ms and the time delay between the rows is 25ms ∼120ms, the ranges of the above time delays are similar with each other.

[0017] A surface connector disclosed in "Non-Electric Initiation System User's Guide"(Austin, January 2014) provides the time delays of 9ms, 17ms, 25ms, 33ms, 42ms, 67ms, 100ms and 200ms.

[0018] Orica published on its online about their non-electric surface connector with the time delays of 9ms, 17ms, 25ms, 42ms, 65ms, 100ms, 150ms and 200ms and presented the open pit blasting method using the electronic detonator and digital blasting system that emits a large amount of the explosion gas.

[0019] Dyno Nobel introduced surface connector providing time delays of 9 ms, 17 ms, 25 ms, 42 ms, 67ms in 2014.

[0020] The surface connectors for the blasting at the open pits and underground mines which provide the delay time of 9ms, 17ms, 25ms, 33ms,42ms, 50ms, 67ms, 72ms, 100ms, 150ms, 200ms and 250ms have been developed in US and many other countries. However, as these connectors which belong to the NONEL non-electric initiating system offer unidirectional initiation, the reliability of the initiation is low. In order to enhance the reliability of the connectors for the blast circuits, documents such as WO 2008/039484, Dyno Nobel, April 3, 2008 and WO 2010/046596, Davey Bikford, April 29, 2010, and so on, has been published for over 40 years. Yet, the inventors of the present invention clearly stated in their document WO 20008/146954, December 4, 2008, that the reliability of those unidirectional systems could never reach that of bidirectional system.

[0021] The US patent application US 7406918, Aug. 5, 2008 published a blasting method including the arrangement of the blastholes and the precise control of the time delay of the electronic detonators, wherein rockpile displacement in a desired direction is increased by the use of inter-hole detonation delays along rows of blastholes, the rows being generally perpendicular to the desired direction of displacement, of up to 4 ms per meter of hole separation in such rows.

[0022] Specific blast geometries to enhance the rockpile displacement in a particular direction include the use of an optimized blasthole pattern which is preferably staggered the pattern such that the ratio of the inter-hole spacing (a) along the rows of the blastholes (where the rows are taken to be perpendicular to the direction of the required displacement) to the perpendicular distance (w) between the rows is in the range 1:2 to 3:2 and preferably in the range of 7:10 to 6:5. Most preferably the ratio is in the range7:10 to 1:1.

[0023] Increase and decrease of the required rockpile displacement is achieved by the manipulation of the blast geometry and the delay between the blastholes.

[0024] Document WO 2011/127540 , ORICA, Nov. 20, 2011, disclosed a high energy blast, wherein the nominal inter-row delay times of the bastholes are 150 milliseconds, with an inter-hole delay along the rows of 10 ms in Row 1, 5 ms in Rows 2∼6, 15 ms in Row 7 and 25 ms in Row 8.

[0025] It demonstrates objectively that at the open bench pits the energy expended to the rock can be possibly controlled by the arrangement of the blastholes and especially by the regulation of the initiation time delay between the blastholes along the row.

[0026] Although the significant advances have been made in the blasting methods over recent years, there still remains the continued need to develop the improved methods of the blasting that provide the efficient rock fragmentation without the need for excessive quantities of the explosive materials.

[0027] Moreover, there remains the demand for the methods of blasting where the rock fragmentation quality can be improved without the excessive impact upon the surrounding environment, for example, through a large quantity of the gushed gas, the loud explosion and the excessive ground vibrations.

Object of the Invention

[0028] The inventors of the present invention paid great attention to the prevention of the enormous economic loss due to the use of the millisecond delay detonators for providing the inter-hole delay times of the detonation and the environmental impact by the venting of the explosion gas and the production of excessive sound, and disclosed the present invention.

[0029] It is an object of the present invention to provide a method of blasting the rock that prevents the explosive energy released to the venting of explosion gas and the production of excessive sound.

[0030] It is another object of the present invention to provide a method of blasting the rock that results in the improved rock fragmentation by firing the explosive charges with the inter-hole delay time with which the maximum energy is exerted on the rock and the fatigue breakdown is formed.

[0031] It is also another object of the present invention to provide a blasting and delaying mean which ensures the precise inter-hole delay time at a lowest cost.

Description of the Invention

1) A method of the shortest inter-hole delay blast at the open bench pits

[0032] The present invention relates to a method of blasting the rock offering considerably improved rock fragmentation with little explosion gas and sound, which is based on the practical experiences of more than 50 years and already manifested its efficiency for over 20 years at the open bench pits, the method being defined in independent claim 1.

[0033] Many attempts have been made to prevent the explosive energy released to the venting of explosion gas and the production of excessive sound, which only delayed the venting of explosion gas, but failed to prevent it completely.

[0034] Inventors, while performing the various blast trials, came to a conclusion that even the high resistant stemming materials (such as fast-setting concrete), stemming closed charges and deck loadings could not prevent explosion gas, and through the long terms of research, found out that the appropriate inter-hole delay time could solve this problem.

[0035] For this reason, the inventors believed that the venting of explosion gas is concerned with the collision of stress waves propagating from each of the blastholes. For example, if the stress waves propagating from two neighbouring blastholes collide with each other at a line where two blastholes join and thereby causing stress concentration, then fissure is produced within the said line prior to the production of fissures in the other parts. High pressure gas within the blastholes enlarges the fissures and finally escapes into the atmosphere prior to the displacement of the rock to be blasted.

[0036] Inventors took and analyzed the photographs of the open bench pit blasting using the detonating fuse as a blast mean, and confirmed that the venting of explosion gas occurred immediately following the detonation.

[0037] Considering characteristics of the detonating fuse and the rock, and factors of the blasting at open pits, successive creation of the stress waves from each of the blastholes results in successive combination (colliding).

[0038] At the open pit blast where the ratio of inter-hole spacing along the rows of the blastholes to the perpendicular distance between the rows at first and second rows are 1:2 and 1:1(m=a/w=0.5 and 1) respectively and the inter-hole spacings(a) are 5∼7m (the diameter of the blastholes is 265mm), stress waves propagated from the blastholes are intensive and the blasting takes place with the successive combination (colliding) of the stress waves.

[0039] The arrangement of the blastholes increases the combination (collision) of the stress waves, e.g., 2 stressfields propagating from the first and the second blastholes combine (collide) around the spot 0.5m near the wall of the second blasthole, and 3 stressfields propagating from the second and the third blastholes around the spot 0.5m, 1m, respectively, near the wall of the third blasthole.

[0040] Supposing that a row consists of the number of n holes, the successive combination (collision) of the incident stresses numbering n - 1 and the reflected stresses numbering n - 5 will result in the localized stress concentration, and at the same time the fatigue breakdown will be accompanied.

[0041] Usually, the application of the fatigue breakdown to a material decreases the strength of the material by 1/2 ∼ 1/5. The concentration of the fatigue breakdown and the production of the fissures near the walls of the blastholes are more severe than any part, by which the explosion gas starts escaping from the blastholes immediately following the initiation of the detonating fuse, where the explosion gas is vented to the height of as high as 25m∼35m.

[0042] For this reason, the collision of the stress waves should be prevented to avoid the venting of explosion gas.

[0043] Since the collision of the stress waves occurs while the stress waves from 2 blastholes meet with each other, the collision could be prevented by detonating a blasthole after the stress wave pre-propagated from the adjacent blasthole passes through.

[0044] In order to completely prevent the explosive energy released to the explosion gas and the excessive sound in blasts geometries where the ratio of inter-hole spacing along the rows of the blastholes to the perpendicular distance between the rows is in the range of 1:2 ∼ 6:5 (m=a/w=0.5∼1.2,) the shortest inter-hole delay should be applied to provide the optimized fragmentation.

[0045] The shortest inter-hole delay time chosen may depend upon the factors such as the rock type and the condition, and the blast geometry.

[0046] In a preferred embodiment, for most rock types, the shortest inter-hole delay time per metre of the inter-hole spacing ranges from 0.182ms to 0.334ms, within which range it is possible to exert maximum energy to the fragmentation of the rock and avoid explosive energy released to the production of excessive explosion gas and sound.

[0047] If the inter-hole spacing ranges from 0.5m to 7m, the shortest inter-hole delay times range from 0.1ms to 2.5ms.

[0048] The inter-hole delay time from 0ms to 0.181ms ∼ 0.333 ms per metre of the inter-hole spacing causes the environmental impact such as the venting of explosion gas and production of excessive sound, wherein even the use of the plugged-in, the deck loading and the stemming closed charges only provides the delays of a few or a few decades of milliseconds.

[0049] Use of a highly precise delay system, such as the non-electric PULKKOT firing system or an electronic initiation system, allows these delays to be controlled to within a tolerance of less than 0.1 millisecond.

[0050] A further aspect of the invention for the regions where the fragmentation of the rock is to be enhanced is to use 1~3 or above high precision detonators within each blasthole with a delay of 1.5ms or less, preferably zero, between them.

[0051] According to the invention, upper part of a column of the explosive charges may have the booster or the detonators, which, too, allows little explosive energy released to the venting of explosion gas and sound.

[0052] Preferably one of these initiators is located close to the bottom or upper column of the blasthole and the others are located further up the explosive column at the regular intervals.

[0053] Additionally, it has been found that the fragmentation and the rockpile displacement is enhanced by the use of the selected ratio of the inter-row delay to the inter-hole delay. Typically, the ratio will be in excess of 6:1 and preferably, in excess of 30:1.

[0054] Depending on the rock type and the blasthole geometry, the inter-row delay time t_row is;
t_row =25ms∼65ms, when considering the maximum improvement of the fragmentation of the rock and the displacement of the rockpile, but
t_row =65ms∼300ms, when considering the minimum displacement of the rockpile.

[0055] The inter-hole delay is usually constant along each row, however, it may be varied.

[0056] The inter -row delay per metre of the rockpile burden may be kept constant or varied from row to row depending on the quality of the fragmentation.

[0057] The position of the initiation detonators within the blastholes and the delay between the in-hole boosters within the blastholes may also vary throughout the blast, according to the fragmentation required.

[0058] If the inter-hole delay time is (0.182∼0.334)ms/m × a m, it is possible to avoid the. collision of stressfields propagating from each blastholes and provide the propagation of new stressfield within pre-propagated stressfield. For example, the stressfield propagated after the detonation of the first blasthole passes through the second blasthole, after which the second blasthole is initiated, thereby propagating the stressfield from the second blasthole within the stressfield from the first blasthole.

[0059] The stressfield propagated from the second blasthole passes through the third blasthole, after which the third blasthole is initiated, thereby propagating the incident stressfield from the third blasthole within the stressfields from the first and the second blastholes.

[0060] Likewise, the incident stressfield from the n-th blasthole will be propagated within the number of n-1 incident and reflected stressfields.

[0061] By avoiding the collision of the stressfields as described above, the venting of the explosion gas and the production of the excessive sound and also the concentration of the stress could be prevented, through which the explosive energy could be distributed more evenly on the rock to improve the fragmentation.

[0062] In addition, the production of new stressfield within a pre-propagated stressfield has influence upon the hardness of the rock.

[0063] Mechanically, if a material carries the load or the repeated load which changes with the time, the strength of the material decreases rapidly (about 2∼5 times lower) to be destroyed severely.

[0064] The successive propagation of the stressfield within the pre-propagated stressfields of various dimensions results in the rapid decrease of the hardness of the rock, thereby improving the fragmentation with the application of the same explosive energy.

[0065] The propagation of a stressfield within the pre-propagated stressfields provides the advantages of:

• preventing the collision of the stress waves, thereby avoiding the venting of the explosion gas and the production of excessive sound
• preventing the concentration of the stresses, thereby providing even distribution of explosive energy throughout the rock to be blasted,
• decreasing hardness of the rock by successively exerting the variable dynamic loads, thereby improving the fragmentation,
• maximizing the effect of tensile stress, the breaking force of which is more powerful than that of the pressure stress, thereby improving the fragmentation.

[0066] Inventors confirmed through the blasting practice of over 20 years at the open bench pits that the shortest delay time 0.182∼0.334ms/m described above provides the blasting with little venting of explosion gas and sound.

[0067] As described above the inter-hole delay blast provides the improved fragmentation of the rock.

[0068] A point 0 within the minimum burden of the open pit is influenced by the successively overlapping stresses propagating from the neighbouring blastholes.

[0069] Subject to the constancy of the blast condition (such as the charge weight, the height of the column of the explosive, the blasthole pattern, the blasthole geometry, the burden, the inter-hole spacing, the height of the stemming), better fragmentation of the rock could be provided as the number of the stressfields which influence on the point 0 increases.

[0070] The intensity of the relative stress

of the second blasthole along a row is 67% and that of the 9th blasthole along the row is 3.1%. Above percentages show that the remoter the blasthole is positioned from the point 0, the weaker the intensity of stress which influences the point 0 becomes.

[0071] Moreover, the shorter the inter-hole delay times along the row are, the more the number of the stressfields which influence on the point 0 are, thereby increasing the intensity of the combined stressfields. For example, 1.5 ms of the inter-hole delay will have 7 stressfields stressing the point 0, 5 ms delay 3 stressfields, and 17 ms delay 1 stressfield, hence the efficiency of the explosive energy of 5 ms delay is over 1.5 times greater than that of 17 ms delay and the efficiency of the explosive energy of 1.5 ms delay is over 2 times greater than that of 17 ms delay.

[0072] It is important to provide even distribution of the explosive energy throughout the rock to achieve better fragmentation using the same amount of the explosive charge.

[0073] Generally it is easier to crack the rock with the tensile stress although the intensity of which is 1/10∼1/15 of that of the pressure stress. Therefore, when the ratio of the inter-hole spacing along the rows of the blastholes to the perpendicular distance between the rows is 1:1 (m= a/w= 1), the range of the inter-hole delay per meter of the burden or the hole spacing is 0.43ms∼0.8ms in most rock types.

[0074] The reflected stressfield formed by the reflection at a free face propagates to and reaches the second blasthole within (0.43∼0.8) ms/m × a m, within which 100% of the fragmentation areas corresponding to the first and the second blastholes lie inside the incident and reflected stressfields propagating from the first blasthole.

[0075] Therefore, the intensity of the reflected stressfield, although it is weaker than that of the incident stressfield, exercises greater influence.

[0076] Efficiency of the reflected stressfield on the improvement of the fragmentation could also be proved through the wide hole-spacing blasts.

[0077] Inventors examined the propagating procedure of the stress waves in the wide hole-spacing blasts, and concluded that when the ratio of the inter-hole spacing along the rows of the blastholes to the perpendicular distance between the rows increases from 1:1 to 4:1, the propagating area of the incident and reflected stresses increases only within the fragmentation area per the blasthole, thereby improving the fragmentation.

[0078] Trials carried out by U. Langefors proved better fragmentation in the wide hole-spacing blasts. This shows that the reflected stressfield allows the enhanced fragmentation of the rock.

[0079] The maximum inter-hole delay may be limited to the time before the displacement of the rocks after the production of fissures.

[0080] If the size of the fissures within the cracked rock is more than 10mm, then these fissures can be considered as a free face, in which case, it is in fact impossible to propagate the stress waves within the rock.

[0081] Referring to the result of the high-speed shooting (quarry mangement 1992.3 25∼27p) and other information which disclosed that at the open pits each of 17ms, 33ms, 50ms after the detonation of the first blasthole resulted in the displacement of 45%, 70%, 90% of the rock, respectively, inventors limited the maximum delay time to 17ms.

[0082] Hence, the inter-hole delay time which allows the best fragmentation for most rock types and provides little venting of explosion gas and sound is;

2) The Blasting and Delaying Means

[0083] Many inventors proposed their opinions that the inter-hole delay blast may enhance the fragmentation of the rock, but such blasting method has not been widely used mainly due to the absence of the practical and cost-effective blasting and delaying means that can provide the precise delay time and the highly reliable blast circuit.

[0084] Since the unidirectional non-electric initiation systems such as NONEL, EXEL, SHOCK★STAR and SINB systems using the delay detonators with the inter-hole delay of 9ms, 17ms, 25ms, 42ms and 67ms provide the lower reliability than the bidirectional Detonating Fuse initiation system, the former is not widely used as the latter at the open pit blasts.

[0085] The inter-hole delay may be provided by the electronic initiation system, wherein the system is programmable so as to control the precise delay times. However, the production cost of such electronic system is more than 5 times expensive, and, besides, the system is liable to be effected by external interferences such as the electric or electro-magnetic field.

[0086] Inventors, on the basis of their practical experiences of over 50 years, conceived a simple idea that the above problems may be solved with the length of the shock tubes in the bidirectional initiation systems, more preferably in non-electric Pulkkot parallel initiation system, by which system the shock tubes are allowed to offer the bidirectional transmission of the initiation signals as the detonating fuses do.

[0087] The detonating fuses have the detonating velocity of 6000 ∼ 6500m/s which is 1.2 ∼ 2 times faster than the propagating velocity of the longitudinal stress waves (3000 ∼ 5500m/s) inside the rock, therefore, it is impossible to avoid the venting of the explosion gas produced by the collision of the stress waves propagating from the blastholes without the help of the delay detonators, and besides, the production cost is over 2 times expensive.

[0088] The shock tube, since its detonating velocity is 1600∼2000m/s and the deviation rate is 1.09%, could be used as a means for both blast and delay that can allow the propagation of a stressfield within another stressfield in most rock types.

[0089] Depending on the detonating velocity (D) of the shock tubes, delay times ((t_delay) per meter of the shock tube are;

[0090] In blasts at the tunnels and mines, the preferred range of the delay time per 0.5m of the inter-hole spacing is from 0.1ms to 0.4ms.

[0091] The delay time provided by 0.5 meter of the shock tube is 0.25∼0.30ms.

[0092] Since the length of the shock tube ranges from 2m ∼ 7.5m when the inter-hole spacing in blasts at the open pits ranges from 2m to 7.5m, the inter-hole delay time ranges from 1.0ms to 4.5ms.

[0093] As seen above, the shock tube, which transmits the initiation signals from hole to hole provides the most precise delay time with its length, the deviation of which is not exceeding ±0.0063ms.

[0094] The deviation of the delay time of the electronic detonator is below ±0.1ms.

[0095] In order to enhance the reliability of the blast circuit, 7 to 20 blastholes along a row may have a bidirectional inter-row delay connector (as illustrated in figures below). The said bidirectional inter-row delay connectors provide contra-directional and instantaneous operations, thereby allowing the initiation signals be transmitted from the back row to the front row if, at the open pit blast, the front circuit is cut off, wherein the inter-row delay connectors are arranged in such a manner that the last initiation signal reaches the last blasthole of the front row within or not exceeding 100ms.

[0096] The Inventors, availing above principles, disclosed in their document WO 2008/146954 (Dec. 4, 2008) new initiating system (non-electric Pulkkot parallel initiating system) with the multi-ringed circuit comprising the parallel(bidirectional) connector without a detonator and the shock tube, the system having been utilized at the open pits for the mass mining since 1995. The production cost of the system is only 75% of that of the unidirectional NONEL or EXEL systems and the reliability of the open blast circuit is advantageous over that of the electronic system. The shortest inter-hole delay blast method which used the non-electric Pulkkot parallel initiating system has already been introduced to large-scale open blasts in many mines, and produced over 1.5 billion tons of ore and rock.

[0097] The present invention offers the effective use of the length of the shock tube which was given less importance in the conventional non-electric initiating systems (such as NONEL, EXEL, SHOCK*STAR, SINB) controlling the inter-hole delay with the delay detonators. 0.1 ms∼ 4.5ms, the shortest inter-hole delay time provided with the length of the shock tube produces little explosion gas and sound, thereby exerting 1.5 times greater energy when compared with the method using the delay detonators with the inter-hole delays of 9ms, 17ms, 25ms, 42ms and 67ms to remarkably improve the fragmentation.

Description of the drawings

[0098] 

Fig.1 shows the shortest inter-hole delay blast circuit at the open pits with the inter-hole delay time 2.5ms and inter-row delay time 45ms.

Figs.2 shows the fragmenting procedure of the rock at the open-bench pit that is blasted with the shortest inter-hole delay time.

Fig. 3 shows the shortest inter-hole delay blast circuit underneath the tunnels with the inter-hole delay time 0.1ms and inter-row delay time 25ms.

Fig. 4 shows the shortest inter-hole delay blast circuit at the open and underground mines with the inter-hole delay time 1ms and inter-row delay time 30ms.

Fig. 5 shows the shortest inter-hole delay blast circuit at the open pits with the inter-hole delay time 2ms and inter-row delay time 45ms.

Fig. 6 shows the shortest inter-hole delay blast circuit at the open pits with the inter-hole delay time 3ms and inter-row delay time 45ms.

Fig. 7 shows the shortest inter-hole delay blast circuit at the open pits with the inter-hole delay time 3.5ms and inter-row delay time 45ms.

List of the reference numerals:

[0099] 

1

the bidirectional shock tube

2

the bidirectional inter-row delay connector

3

the parallel connector

4

the delay time in milliseconds

Claims

1. A method of blasting the rock, wherein the blastholes are fired with an inter-hole delay so as to produces little explosion gas and sound, the method comprising the steps of:

- drilling 2 or more rows of the blastholes in the rock, wherein a row consists of from 2 to 25 or more blastholes, each blasthole along and between the rows is adjacent to another blasthole;

- loading each of the blasthole with an explosive charge;

- connecting blast initiation means with each explosive charge; and

- firing the explosive charges via connected blasting and delaying means in such a way that each explosive charge detonates with the inter-hole delay, thereby detonating the blasthole within the stressfield pre-propagated from the preceding adjacent blasthole;

the method being characterised in that
the inter-hole delay time within which a new stressfield propagates within
the pre-propagated stressfield ranges from 0.182 ms to 0.334 ms or from 0.43 ms to 0.80 ms per metre of the burden or the inter-hole spacing.

2. A blasting method according to claim 1, wherein if the ratio of the inter-hole spacing along the rows of the blastholes to the perpendicular distance between the rows is 1:1 (m=a/w=1), the inter-hole delay time is 0.43ms∼ 0.80ms per metre of the burden or the inter-hole spacing.

3. A blasting method according to claim 1, wherein the detonation of the upper part of the columns of the explosive charges produces little explosion gas and excessive sound, thus preventing the loss of explosive energy.

4. A blasting method according to claim 1, wherein 7∼20 blastholes along a row are connected by a bidirectional inter-row delay connector, thereby enhancing the reliability of the blast circuit.

5. A blasting method according to claim 1, wherein in an open blast circuit where a row is cut off and thus the initiation signal is transmitted from a back row to the row being cut off, inter-row delay connectors are arranged in such a manner that an initiation signal reaches the last blasthole of the row being cut off within or not exceeding 100ms since the said row is cut off, wherein the inter-row delay connectors provide contra-directional and instantaneous operations.

6. A blasting method according to claim 1, wherein the ratio of the inter-row delay time to the inter-hole delay time is more than 6:1 or more than 30:1.

7. A blasting method according to claim 1, wherein the blasting and delaying means for providing the inter-hole delay time is a non-electric bidirectional firing system and provides the precise inter-hole delay time with the length of a shock tube which is requisite for transmitting the initiation signals to the blastholes.

8. A blasting method according to claim 1, wherein the blasting and delaying means for providing the inter-hole delay times is an electronic initiation system.

Ansprüche

1. Die Methode fuer Gesteinsprengung, durch Explosionen der Sprenghöhlungen von der Innenrissverzögerung die Sprenggase und -laute fast zu beseitigen, besteht aus folgenden Stufen.

- Bohren ins Gestein mit ueber zwei Risse, die Risse setzen aus den 2-25 oder mehr Sprenghöhlungen zusammen und jede Sprenghöhlung liegt an dem Riss und zwischen den Risse in der Nähe vom anderen Sprenghöhlungen.

- Das Laden des Explosivstoffes in jede Sprenghöhlung

- Die Verbindung des Sprengdetonationsmittels mit jedem Explosivstoff

- Die Detonation des Explosivstoffes durch das Sprengverzögerungsmittel, das mit der Explosion des Sprengstoffes von der Innenrissverzögerung verbunden ist. Damit wird die Sprenghöhlung in dem aus vorne liegender Sprenghöhlung schon verbreiteten Beanspruchungsfeld explodiert.

Dieses Verfahren wird wie folgt charakterisiert.
Die Verzögerungszeit der Innenrisse, im schon verbreiteten Beanspruchungsfeld ein neues Beanspruchungsfeld zu verbreiten, ist im Bereich der Abstände zwischen Widerstandsdrähte oder Höhlungen von 0.182-0.334ms oder 0.43-0.80ms pro Meter.

2. Die Sprengungsmethode nach der Forderung 1, die Verzögerungszeit der Innenriss hat die Abstände zwischen Widerstandsdrähte oder Höhlungen von 0.43-0.80ms pro Meter, wenn der vertikalen Abstandverhältnis zwischen Höhlungen und Risse in den Innenrisse der Sprenghöhlungen 1:1 ist.

3. Die Sprengungsmethode nach der Forderung 1, die Oberteilsexplosion des Schießpulverpfeilers beseitigt den Sprenggasausbruch und das Übergeräuch fast und somit werden die Verluste der Explosivstoffenergie weg.

4. Die Sprengungsmethode nach der Forderung 1, Zuverlässigkeit des Sprengstromkreises durch die Verbindung mit der Kupplung der beiderrichtenden Rissabstandverzögerung an den 7-20 Sprenghöhlungen der Innenrisse zu erhöhen.

5. Die Sprengungsmethoe nach der Forderung 1, die Kupplungen der Rissabstandverzögerung wird so eingesetzt, daß die Explosion innerhalb von 100ms seit Bruch der ganannten Risse der letzten Sprenghöhlung der gebrochenen Risse durch Signal anzeigen kann, wenn ein Riss im Freisprengstromkreis gebrochen und das Explosioinssignal von dem Hinterriss zu dem gebrochenen Riss übermittelt wird, wobei die Kupplungen der Rissabstandverzögerung gleichzeitig entgegengesetzt wirken.

6. Die Sprengungsmethode nach der Forderung 1, das Zeitverhältnis der Rissabstandverzögerung und der Höhlungabstandverzögerung ist über 6:1 oder 30:1.

7. Die Sprengungsmethode nach der Forderung 1, das Sprengverzögerungsmittel fuer die Zeit der Rissabstandverzögerung ist ein unelektrisches beiderrichtendes Explosionssystem und gibt die Verzögerungszeit des feinen Höhlungabstandes mit der Länge der plastikverkleideten Drähte für die Vermittlung des Explosionssignals den Sprenghöhlungen.

8. Die Sprengungsmethode nach der Forderung 1, das Sprengverzögerungsmittel für die Verzögerungszeit des Höhlungabstandes ist ein elektronisches Explosionssystem.

Revendications

1. Comme une méthode du dynamitage de rocher que les rainures du dynamitage font détoner avec un retard de l'inter-fente pour produire les moindres as et bruits de l'explosion, la méthode incluse lesétapesce qui suivent:

- Perforage des rochers de 2 ou plus de fentes, ce qu'un rocher consiste de 2 à 25 et plus de rainures du dynamitage, ainsi que chaque rainure du dynamitage, par fentes et entre fentes, les rainure sa voisinent l'autre rainure du dynamitage.

- Installation de charge des explosifs sur chaquerainure du dynamitage,

- Action qui connecte un dispositif d'explosion avec chaque charge des explosifs

- Action qui détone, par les moyens de retard de la détonation de dynamite, la charge des explosifs qui connecte pour que chaque charge des explosifs détone en délai de l'inter-fente. Par conséquent, les rainures du dynamitage détonent dans les aires de pression interne pré-propagés depuis les précédents rainures du dynamitage.

La méthode comprend une caractéristique ce qui suit
Le temps du retard de l'inter-fente que les nouvelle aires de pression interne dans les aires de pression interne pré-propagés se range de 0.182 ms à 0.334 ms ou de 0.43 ms à 0.80 ms par chaque mètre de ligne de résistance ou de la distance de l'inter-rainure.

2. Comme une méthode du dynamitage concernant la première revendication, ici, dans l'inter-fente des rainures du dynamitage, quant la proportion de la distance de l'espace de rainure et de la perpendicularité de l'inter-fente est de 1 à 1(m=a/w=1), le temps du retard de l'inter-fenteest0.43ms∼0.80ms par mètre de la ligne de résistance ou de la distance de l'inter-rainure.

3. Comme une méthode du dynamitage concernant la première revendication, ici, la détonation au-dessus de la partie de la pile de la charge des explosifs diminue presque tellement les jaillissements de gaz et l'excès de bruits d'explosion qu'élimine la perte de l' nergie des explosifs

4. Comme une méthode du dynamitage concernant la première revendication, ici, dans les 7∼20 rainures du dynamitage de l'inter-fente, la machine remorquée de retard connecte par les inter-fentes de deux directions et ainsi augmente la crédibilité du circuit de la détonation de dynamite.

5. Comme une méthode du dynamitage concernant la première revendication, ici, dans le circuit du dynamitage du plein air, si une fente est rompue et ainsi le signal détonation de dynamite est transmis à la fente rompue depuis la dernière fente, les machines remorquées du retard des inter-fentes doivent être disposées en tant que le signal de celle-ci est arrivée à la dernière rainure du dynamitage de la fente rompue dans le temps de 100 ms de puis que cette fente est rompue. Alors, cette machines fonctionnent simultanément en sens contraire.

6. Comme une méthode du dynamitage concernant la première revendication, ici, la proportion de temps du retard d'inter-fente au temps du retard d'inter-rainure est plus de 6 à 1 or est de 30 à 1.

7. Comme une méthode du dynamitage concernant la première revendication, ici, le moyen du retard du dynamitage assurant le temps du retard d'inter-fente est le système de détonation de non-électricité de deux directions et le temps du retard d'inter-rainure de haute précision assure par la longueur de la ligne enveloppée avec les tuyaux plastiques nécessaires que le signal de détonation transmis aux rainures du dynamitage.

8. Comme une méthode du dynamitage concernant la première revendication, ici, le moyen du retard du dynamitage assurant le temps du retard d'inter-rainure est le système électronique de détonation.

Drawing