Method of blasting

Abstract

A method of blasting in which rock pile profile associated with a blast field is controlled by precise control of the detonation delay times between and/or within individual blastholes in the blast field, in combination with the control of one or more other blast parameters.

The claims defining the invention are as follows:  
     
         1 . A method of blasting in which rockpile profile of a blast field is tailored by control of rockpile displacement over the blast field as a result of blasting, this control being achieved by precise control of detonation delay times between and/or within individual blastholes in the blast field in combination with the control of one or more other blast parameters.  
     
     
         2 . A method according to  claim 1 , wherein the one or more blast parameters are blasthole geometry, explosive charge and blast initiation location.  
     
     
         3 . A method according to  claim 1 , wherein detonation delay times are controlled within a tolerance of less than one millisecond of the required and intended delay time.  
     
     
         4 . A method according to  claim 1 , wherein the detonation delay times are controlled using an electronic initiation system.  
     
     
         5 . A method according to  claim 4 , wherein the electronic initiation system is programmable.  
     
     
         6 . A method according to  claim 1 , wherein rockpile displacement in a desired direction is controlled by manipulating the inter-hole detonation delay between blastholes and/or the inter-row detonation delay between rows of blastholes.  
     
     
         7 . A method according to  claim 1 , wherein rockpile displacement in a particular direction is increased by use of a blasthole pattern in which the blastholes are staggered such that the ratio of inter-hole spacing along rows of blastholes (where the rows are taken to be perpendicular to the desired direction of displacement) to perpendicular distance between rows is in the range 1:2 to 3:2.  
     
     
         8 . A method according to  claim 7 , wherein rows of blastholes are drilled parallel to any pre-existing or newly-created free faces in the blast field which are perpendicular to the desired direction of rockpile displacement.  
     
     
         9 . A method according to  claim 1 , wherein the blastholes are generally inclined with the hole toe upwards in the same direction as the desired rockpile displacement and at an acute angle to the vertical.  
     
     
         10 . A method according to  claim 7 , wherein the displacement in a desired direction is increased by the use of inter-hole detonation delays along rows of blastholes (where the rows are generally perpendicular to the desired direction of displacement) of from 0 to 4 ms per metre of inter-hole spacing (where the spacing is defined as the hole separation in such rows).  
     
     
         11 . A method according to  claim 5 , wherein rockpile displacement is increased by use of two or more electronic initiators within each blasthole with a delay between each system of two milliseconds or less.  
     
     
         12 . A method according to  claim 11 , wherein one of the initiators is located close to the toe of the blasthole and other initiators are located further up the blasthole at regular intervals.  
     
     
         13 . A method according to  claim 1 , wherein rockpile displacement in a direction perpendicular to a row of blastholes is increased by use of selected ratios of detonation delay time between rows of holes (the inter-row delay) to the detonation delay time between holes along a row (the inter-hole delay), this ratio being in excess of 5:1.  
     
     
         14 . A method according to  claim 1 , wherein rockpile displacement is decreased by using a ratio of detonation delay time between rows of holes (the inter-row delay) to the detonation delay time between holes along a row (the inter-hole or intra-row delay) which is lower than the corresponding ratio for areas in which increased displacement is required.  
     
     
         15 . A method according to  claim 14 , wherein the ratio is in the range of 5:1 or less.  
     
     
         16 . A method according to  claim 1 , in which rockpile displacement in a blast field comprising at least three rows of blastholes is maximised without causing environmental problems by use of inter-hole detonation delay times of greater than 4 ms per metre of blasthole spacing in all or part of the front one or two rows and by use of inter-hole detonation delay times in the range 0 to 4 ms per metre of inter-hole spacing in a latter part of the row or subsequent rows of blastholes.  
     
     
         17 . A method according to  claim 1 , wherein a combination of detonation delay time and one or more blast parameters selected from blast geometry, explosive charge and blast initiation location are applied differentially over different parts of the blast field.  
     
     
         18 . A method according to  claim 1 , wherein rockpile displacement in a particular direction is increased by use of a blasthole pattern in which the blastholes are staggered such that the ratio of inter-hole spacing along rows of blastholes (where the rows are taken to be perpendicular to the desired direction of displacement) to perpendicular distance between rows is in the range 1:2 to 3:2, by use of inter-hole detonation delays along rows of blastholes of from 0 to 4 ms per metre of inter-hole spacing (where the spacing is defined as the hole separation in such rows), and by use of selected ratios of detonation delay time between rows of holes (the inter-row delay) to the detonation delay time between holes along a row (the inter-hole delay), this ratio being in excess of 5:1.  
     
     
         19 . A method according to  claim 18 , wherein rockpile displacement in a particular direction is increased by use also of two or more electronic initiators within each blasthole with a delay between each initiator of two milliseconds or less.  
     
     
         20 . A method according to  claim 1 , wherein rockpile displacement in a particular direction is decreased by use of a blasthole pattern in which the blastholes are staggered such that the ratio of inter-hole spacing along rows of blastholes (where the rows are taken to be perpendicular to the desired direction of displacement) to perpendicular distance between rows is in the range 1:2 to 3:2, by use of inter-hole detonation delays along rows of blastholes of from 4 to 40 ms per metre of inter-hole spacing (where the spacing is defined as the hole separation in such rows), and by use of selected ratios of detonation delay time between rows of holes (the inter-row delay) to the detonation delay time between holes along a row (the inter-hole delay), this ratio being 5:1 or less.  
     
     
         21 . A method according to  claim 1 , wherein rockpile displacement is controlled by precise control of detonation delay times between and/or within individual blastholes in a blast field in combination with control of at least one blast parameter selected from blasthole diameter, blasthole orientation, explosive mass, explosive energy and inter-hole detonation delay.  
     
     
         22 . A method according to  claim 21 , wherein the blasthole diameter is reduced to produce decreased rockpile displacement.  
     
     
         23 . A method according to  claim 21 , wherein the blasthole is inclined at a reduced angle to the vertical to produce decreased rockpile displacement.  
     
     
         24 . A method according to  claim 23 , wherein the blasthole is angled away from a free face in the blast field.  
     
     
         25 . A method according to  claim 21 , wherein the explosive mass is reduced to produce decreased rockpile displacement.  
     
     
         26 . A method according to  claim 21 , wherein the explosive energy is reduced to produce decreased rockpile displacement.  
     
     
         27 . A method according to  claim 21 , wherein the rockpile displacement in a particular direction is decreased by use of inter-hole detonation delays along rows of blastholes greater than the inter-hole detonation delays along rows where increased displacement is required.  
     
     
         28 . A method according to  claim 27 , wherein the inter-hole detonation delay is in the range 4 to 40 ms per metre of inter-hole spacing to produce decreased rockpile displacement.  
     
     
         29 . A method according to  claim 21 , wherein rockpile displacement is controlled by blast initiation location, reduced rockpile displacement being achieved by blast initiation distant from any pre-existing fee faces in the blast field.  
     
     
         30 . A method according to  claim 29 , wherein reduced rockpile displacement is achieved by blast initiation from the back towards the front of the blast field.  
     
     
         31 . A method according to  claim 21 , wherein the blasthole diameter is increased to produce increased rockpile displacement.  
     
     
         32 . A method according to  claim 21 , wherein the blasthole is inclined at an increased angle to the vertical to produce increased rockpile displacement.  
     
     
         33 . A method according to  claim 21 , wherein the explosive mass is increased to produce increased rockpile displacement.  
     
     
         34 . A method according to  claim 21 , wherein the explosive energy is increased to produce increased rockpile displacement.