Publications Context Sensitive Rock Slope Design Solutions« » 3. Rock Excavation Methods.Blasting DesignBlasting projects must be designed with several factors in mind, including the type of explosives used, boreholediameter, and loading levels. Each type of blasting-presplit, smooth, and cushion blasting-has its own formula. Presplit BlastingAs discussed above, presplit blasting (or presplitting) is most often done before production blasting to create asecondary fracture plane that will protect the final slope face from damage in the main production blast. Table4 lists recommended borehole diameters, burden, spacing, and explosive charges for presplit blasting.Table 4. Parameters for drilling in a presplit blasting operation (modified from U.S.
Department of the Interior2001). HOLE DIAMETERSPACINGEXPLOSIVE CHARGE(mm)(in)(m)(ft)(kg/m)(lb/ft)38-441.50-1.750.3-0.461.00-1.500.03-0.10.08-0.2550-642.00-2.500.46-0.61.50-2.000.03-0.10.08-0.2575-903.00-3.500.6-1.01.50-3.000.05-0.230.13-0.501004.000.6-1.22.00-4.000.23-0.340.25-0.75In order to reduce fracturing, presplit blasting holes are drilled with smaller diameters than production holes.Presplit-hole diameter will also be influenced by many other factors, as well. For example, large-diameter holescan hold more explosives and can be spaced further apart than small-diameter holes, but can cause more backbreakif the burden-to-spacing ratios are not properly designed.
Large-diameter holes yield lower drilling and blastingcosts because they are less expensive per unit volume to drill. Large-diameter holes are better suited for relativelyhomogeneous, easily fractured rock with few planes of weakness (discontinuities) and for deep rock cuts.
Small-diameterholes use less explosives and require smaller spacing between holes, which allow for better distribution of explosives,more uniform rock breakage, less backbreak, and reduced ground vibrations. Although more holes must be drilled,small-diameter holes can be drilled quickly, resulting in a relatively low unit cost. However, this may be offsetby higher explosives costs, as more explosives are required to fill the extra holes. In addition, drilling depthson small-diameter holes are limited because the small-diameter drill bits are more likely to wander at depth thanlarger bits.Theoretically, the burden for presplit blasting is unlimited. But in reality, variations in geology that are notvisible on the outer face of the slope can limit that burden. Thus, the engineer must core the interior of theslope to identify the condition of the rock before determining the blasting design.
In any case, a minimum of 10m (30 ft) of burden is recommended for any presplit blasting procedure.Hole spacing in presplit blasting is typically 10 to 12 times the borehole diameter. In very favorable geologic conditions,spacing can be increased to 14 times the borehole diameter. Wider spacing is used for hard, competent materialwith relatively few discontinuities; in very soft and/or weathered materials, spacing is decreased. In weak andsoft formations or where corners are blasted, unloaded guide holes are recommended to direct the cracking. Theseguide holes are drilled between the normally spaced presplit holes (thus, using guide holes prevents the contractorfrom spacing the presplit holes any further apart).Holes used for presplit blasting are lightly loaded and range from 22.5 to 25 mm (7/8 to 1 in) in diameter. A heaviercharge (2 to 3 times the normal load) is used at the bottom of the borehole to ensure shearing at the floor. Acommon charge density is approximately 0.45 kg per square meter (0.1 lbs per square foot) of face area in the mainsection of the hole and 0.9 to 1.3 kg per square meter (0.2 to 0.3 lbs per square foot) at the bottom.
The loadsmay have an air annulus (ring) surrounding them to cushion the explosive blast and reduce the radial cracking aroundthe borehole. Figure 20 indicates three configurations.The authors of the DuPont Blaster's Handbook (1978) show that slurry or water gel (in the form of 'Tovex T-1') can provide excellentpresplitting results while permitting increased loading rates and reduced labor costs.
Konya and Walter (2003)recommend ammonium nitrate for all controlled blasting. For small-scale blasting (such as sliver cuts) in presplittingoperations, 50- grain detonation cord has proven effective. Three options using lightly loaded, distributed charges in presplit blasting (modified fromU.S.
Department of the Interior 2001). Smooth BlastingSmooth blasting is a type of controlled blasting that's done either before production blasting, as an alternativeto presplitting, or afterwards, either as an entirely different event or as the last delay of the production blast.Table 5 shows recommended borehole diameters, burden, spacing, and explosive charges for smooth blasting.Table 5. Parameters for drilling in a smooth blasting operation (modified from U.S.
Department of the Interior 2001). HOLE DIAMETERSPACINGBURDENEXPLOSIVE CHARGE(mm)(in)(m)(ft)(m)(ft)(kg/m)(lb/ft)38-441.50-1.7.000.05-0.550.12-0.25502.00.752.501.063.500.05-0.550.12-0.25As with presplit holes, smooth blasting holes are smaller than production holes in order to limit fracturing aroundthe drill hole. The diameter of the hole is a function of geology, as discussed above.The burden-to-spacing ratio for smooth blasting is approximately 1.5 to 1.
Hole spacing for smooth blasting is slightlygreater than presplit blasting, about 14 to 20 times the hole diameter, which means that holes are approximately0.7 to 1.5 m (2.3 to 5 ft) apart. Wider spacing is used for hard rock and closer spacing is used for weak rock.Unloaded guide holes (drilled between the normally spaced blastholes) are recommended for weak and soft formationsor for blasting corners.The charge density, diameter, distribution, and explosive type used in smooth blasting are essentially the same aswith presplit blasting. In smooth blasting, the borehole should be sealed with a tamping plug, clay plug, or othertype of stemming to prevent the charge from being extruded from the hole by charges on earlier delays. Stemmingalso prevents excessive rifting (splitting) of the rock and permits the use of lighter charges because blast energyis better contained and therefore better distributed.
Cushion BlastingCushion blasting, another type of controlled blasting that's typically done after production blasting, uses a rowof lightly loaded 'buffer' holes filled with crushed stone (stemming), which reduces the impact on the surroundingrock as well as the finished slope face. Cushion blasting can be used with both vertical and angled holes, andgood alignment is essential in both cases. The cushion holes are drilled along the final slope line and loadedwith light, well-distributed charges and fired after the main production blast.The required burden is established either by the last row of production boreholes or by a separate set of buffer holes (these buffer holes determine the burden so that the cushion blast holesproduce enough backbreak to avoid borehole traces).Table 6 shows the recommended borehole diameters, burden, spacing, and explosive charges for cushion blasting.Table 6. Parameters for drilling in a cushion blasting operation (modified from U.S. Department of the Interior 2001). Hole DiameterSpacingBurdenExplosive Charge(mm)(in)(m)(ft)(m)(ft)(kg/m)(lb/ft)50-642.00-2.501.03.001.24.000.03-0.10.08-0.2575-903.00-3.501.24.001.55.000.05-0.20.13-0.5100-1154.00-4.501.55.001.86.000.1-0.30.25-0.00-5.501.86.002.17.000.3-0.450.75-1.00-6.502.17.002.79.000.45-0.71.00-1.50Diameters of buffer and cushion boreholes are smaller than those of production holes, and buffer boreholes have aslightly larger diameter than cushion boreholes. The diameter of a cushion hole depends on many factors, as discussedabove.The burden for cushion holes varies according to the rock characteristics.
For example, the burden of hard, competentrock will be smaller than the burden of soft, easily fractured rock. It is important to conduct one or more testblasts and continually analyze and back-calculate results from production blasting to determine the proper burden,spacing, and charge density.The spacing on cushion and buffer blastholes varies depending on the bedrock type and structural characteristics,but generally ranges from 15 to 24 times the borehole diameter. The burden-to-spacing relationship varies, butspacing on cushion holes should always be less than the width of the burden being removed (U.S.
Department of theInterior 2005). When removing weak, heavily fractured material or when blasting corners, uncharged guide holescan be drilled between the normally spaced cushion holes to guide the blast-induced fracture.Charge loading in cushion blasting is similar to that in smooth blasting in that lightly loaded, well-distributedcharges are fired after the main production blast.
Charges are typically 25 mm (1 in) in diameter and charge densitiesare 0.45 to 0.7 kg per square meter (0.1 to 0.15 lb per square foot) of face area for the main borehole and twoto three times that for the bottom of the borehole. Historically, cushion holes are surrounded by some type ofstemming (crushed rock or other loose inert material that helps cushion the blast) for the entire length of theborehole. According to the DuPont Blaster's Handbook (1978), an air annulus surrounding the charge produces similar results and reducesloading time. Removing Drill Hole Traces and Blasting ScarsIn weak rock, drill hole traces can be removed by chipping away at the corners of the traces or removing the outerlayer of rock using a hoe ram, excavator bucket, or pneumatic hammer. For strong rock, it is nearly impossibleto completely remove these traces.In some cases, blasting is followed by other methods of excavation, which are used to get rid of remaining rock andsoil to create a more aesthetically appealing final face.
In cases where there is less rock to remove in the firstplace, these methods can be used on their own.« ».
As a frequent reader of SurvivalBlog I saw your recent request for articles on the farm and ranch use of explosives.My story may resonate with many of your readers in that I used dynamite for the projects mentioned here although I had no previous experience with explosives. These episodes occurred many years ago and though the legality issues (permitting, purchasing, etc.) may have changed the techniques of actually using dynamite are still applicable.Before getting into the heart of the matter I offer the following summary points:1. I am not offering advice on the use of explosives.
I am relating my experiences in the use of dynamite as an inexperienced user.2. Dynamite is a useful tool.3. Dynamite can be used by inexperienced persons who make the effort to learn how to safely do so.I had no experience using dynamite when I chose a ditching project.
There seemed to be no practical way to put the 100 yard ditch where I wanted it. In discussions with others about my problem someone suggested dynamite. The suggestion was partially in jest but on reflection I took it seriously. I bought a copy of the. I studied it and the more I did the more I became convinced that I could use dynamite for my ditching project.After carefully studying the handbook I decided that I could blast the ditch through the low swamp where I needed it.
Having made that decision the next step was to procure the dynamite. By looking up “Explosives” in the Yellow Pages” of a nearby large city (This was before an Internet), I found a vendor. This vendor was most helpful. Most importantly he told me that I would have to secure a permit for the purchase and use of the dynamite and furthermore he told me where to go to get the permit from the proper government agency. We discussed my inexperience and he took time to discuss the proper use and equipment I would need to complete my project. When I went to his facility to purchase the dynamite he also provided information on the accessories (blasting caps, fuse, crimping tool, etc.) I would need.Once I had all the material accumulated I began practicing how to use it. First I practiced lighting the fuse.
This is not nearly as simple as it appears in movies and TV. I must have lit a dozen or so pieces of short fuse before I developed a good technique as described in the handbook. I also burned and timed several various lengths of fuse to be sure that it’s burning rate was as specified.
Next I learned how to crimp the fuse in the blasting cap. Again I followed the handbook instructions. The only way to know whether it has been done properly is to try it—light the fuse and see if the cap goes off. Some Practice CappingAfter I was satisfied that I could consistently fire blasting caps I began practicing inserting the cap into a stick of dynamite to make a primer charge. I used the non sparking alloy crimping tool and prepared the charge according to the handbook instructions. Up to this point I had not had a cap in close proximity of a stick of dynamite.The next step was a big one, inserting a fused cap into a stick of dynamite and setting it off.
I took a friend with me as a helper and we went to the area I intended to blast the ditch. I crimped a fuse in a cap, inserted it in the dynamite. With a pole I punched a hole about 12” deep in the soft ground. I placed the primed dynamite it the hole, covered it with dirt, tamping it lightly.
I lit the fuse–I used a 90 second fuse–and ran.I waited, 90 seconds is a long time when waiting for an explosion to go off, and—nothing. Three minutes—nothing. I had a misfire.I reviewed what I should do from the handbook. I primed another stick and carefully carried it and placed it on top of the misfire. I lit the fuse and ran.
90 seconds later—BOOM! I had made my first dynamite explosion. The size and depth of the resulting hole indicated that both sticks had gone off. Now I could blast my ditch.Regular dynamite is 40% nitroglycerin and 60% filler. It is stable and very safe. Ditching dynamite is 50% nitroglycerin.
It is slightly less stable but is sensitive enough so that the explosion is propagated from one hole to another in the ditch by hydraulic shock. Therefore only one hole in the ditch needs to be primed.From information in the handbook I had calculated that I would need two sticks of dynamite, one on top of the other, spaced every 18” apart. Since ditching dynamite in reasonable proximity will sympathetically propagate the explosion from one hole to the next by hydraulic shock I only needed to prime one hole in the string. This time I used a 120 second fuse. I lit it and ran for the high ground. Two minutes later there was an earth shaking BOOM and water, mud, debris sent flying 100’+ in the air.
Before the smoke had cleared I ran back to see that I had blasted a beautiful ditch through a cypress swamp. In my excitement I violated a handbook rule. One hour later I had an excruciating headache from breathing the dynamite fumes.I had otherwise followed the book.
I had blasted a ditch just as I wanted in difficult terrain. I had done it safely except for the headache caused by not following the rules. Lifting StumpsSome years later I was faced with the chore of removing a dozen or so stumps from a field. Again I determined that dynamite was the best tool for the job.For the stumps I bought regular dynamite which is more stable and somewhat safer.
I also bought electric blasting caps. These are less complicated and easier to use than fused caps.Again on consulting the, I determined that the pine stumps would require two sticks of dynamite, one on opposite sides of the stump, buried at about the 2’ level below ground. I used an iron rod to probe around the stumps and find where I could push it down between roots. I would rod out a hole to the desired depth and then insert the primed stick in it. I would fill the hole with dirt, tamping it in.
I repeated this on the other side of the stump. With the dynamite in place I wired the electric cap leads to a long extension wire which would safely reach my tractor battery.
I would set off the charge by touching the wire to the battery terminals. The resulting explosion would usually cut the large pine tap root at the depth of the charge and lift the remaining upper portion of the stump out of the ground. Sometimes the stump would be thrown 12’-15’ in the air.It was an easy job to then haul the stumps out of the field. Burning Excess DynamiteThe last dynamite challenge I faced was the disposal of some which was left over from the stumping. I had about a case and half left over.
I had overestimated how much I would need. I was not concerned thinking that I would find other use for it. Before I realized it a couple of years had gone. And then a couple more. One day I looked at the old dynamite and was surprised at how much it had degenerated. The dynamite came packed in heavy plastic bags.
The bag was inside a heavy corrugated box. I had stored the boxes in a wooden chest. On examination, the corrugated boxes were deteriorated. They looked wet as if with oil. The bottom of the chest looked the same way. I knew it was bad but I did not know what to do.Not knowing where else to go, I called the Sheriff. He was reassuring and told me that he had used demolition experts from the nearby military instillation to dispose of explosives and that he could call them and ask them to get in touch with me.
A couple of days later I got a call from an Officer. He said the Sheriff had asked him to call me. He said that although they had done so previously, their policy had changed and they could no longer dispose of explosives off base.I was out of options. In desperation I asked him, “If you were going to dispose of the dynamite for me, how would you do it?” He knew what I needed. He didn’t tell me how to do it, he told me how he would do it. I followed his method.I got the materials together. On a damp foggy morning, I put a bale of hay in the edge of the field.
I wet down the rubber mat in the bed of my truck. I used these static electricity suppression measures in addition to the Officer’s description. Using gloves I carefully picked up the boxes containing the dynamite. They were so fragile that they would not have held up if the plastic bag had not been inside them.
I put the boxes on the mat in the truck and drove them to the hay. I transferred the dynamite from the truck placing it on top of the hay. I poured almost 5 gallons of diesel fuel over the hay and dynamite and set it afire. I quickly got in my truck and drove away.I was somewhat reassured in doing this as I had read in the handbook that dynamite could be disposed of by burning but I was concerned about the deteriorated state of these boxes. I did know what to expect.From a safe distance I watched the fire. For a couple of minutes it burned as expected. Then the flames grew higher and began producing a heavy black smoke, not unlike rubber tires burning.
This lasted for ten minutes or more and then the flames died down and went out.I had burned 75 pounds of old rotten (leaking) dynamite.I used dynamite to blast a ditch and remove stumps. I was able to safely dispose of old dynamite. My knowledge for doing so came from studying the Blaster’s Handbook and maybe 30 minutes discussion with the vendor and some 5 minutes with the demolition expert. The only part I consider risky was the disposal.
I should not have let the dynamite get in that state before disposing of it. Yes, Democrats are the enemy we know. But Republicans are the enemy we sleep with.Amazon made an $11 billion profit and paid no federal taxes.
In fact it received a $100 million rebate! It’s called corporatism, a fancy name for fascism. Guess which party wrote the laws creating Big Corporate, its tax indulgences and granted its special protections.Corporations are not normal natural businesses. They are a creation of government. They are granted special protections.
Does ‘corporate personhood’ and ‘limited liability’ sound natural to free enterprise? Try taking Amazon to court. Do you honestly think Jeff Bezos would see the inside of a jail?
He is protected. He has no skin in the game. Corporate CEO’s are a government-created-protected class.
If you do not tamp the charge to contain the explosion for a micro second the power of the explosion will be much less as the expanding gasses will exit the hole instead of applying the force against the sides of the rock or stump or what ever you are trying to move or remove. A good example of the increase in gas pressure is the difference in recoil between firing a blank cartridge and firing a regular cartridge. I get a kick out of watching movies where they tie large quantities of dynamite to bridge supports etc. To rob the train. Look up info on shaped charges, they will get the job done with far less dynamite and are less dangerous as the force is directed directly where it is needed.
As always know what you are doing with the tools you use, good article about a labor saving method. I almost forgot to make mention of a way to deal with old weeping dynamite. The liquid leaking from the dynamite is actually the nitroglycerin, and is very unstable. A man named Nobel figure out how to stabilize this unstable liquid and hence the first Nobel Prizes in science were started. Basically the Nitro is mixed with fullers clay and this creates a much more stable explosive. I once found my self with about 20 cases of old weeping sticks of dynamite at a mine I was hired to run.
Upon advice from the underground mining engineer I bought a bunch of sawdust from a local saw mill and donning rubber gloves we rolled the sticks in the sawdust to absorb the nitro. We then took the sawdust and saturated cardboard cases out to a cleared area and burned the whole mess with the exception of the dynamite sticks which we used in the mine.
Dupont Blasters Handbook Pdf
Because of the lessened quantity of nitro available they charged the holes with about twice as many sticks as normal. Thus we got rid of the old dynamite and got some useful work out of it. I used a lot of C-4 during the Gulf War to destroy Iraqi weapons and Ammo.
Crimping the blasting cap is probably the most dangerous part of the process. Make sure you wear good eye protection, gloves and hold it away from your body and turn your head away when making the crimp. I Have been looking at different regulations and it appears in my state you can by so much once a year for personal use with little hassle.In the future I may be Lucky enough to attend a blaster’s class.Can’t remember for sure but I believe one of JWR’s books discuss how to procure legal explosives for survival purposes. Think it was How to Survive TEOTWAWKI. I have lived in FL most of my life, but my mother was from E. Her father worked in construction and always had a case or two of dynamite, which was a very useful tool in the mountains.
Dupont Blasters Handbook Pdf
The CCCs trained him to use explosives and as a stone cutter back during the Great Depression. After he passed, the family was cleaning out his shop up on the hill and sure enough, there were a couple of cases that hadn’t been touched in decades Which gave the local PD a chance to try out their new robot They were willing and able to safely dispose of the dynamite.
My grandfather taught me how to make dynamite and caps, and taught me how to crack boulders and stumps. Back then the cops didn’t care like they do now. Caps are touchy things to press, and at least 1 in 10 would blow while in the press.
Blasters Handbook Pdf
Got my first drink after moving a case of sweaty dynamite and the bottom dropped out of the wooden crate. Grandpa and I spent the rest of the afternoon getting hammered. We burnt the sticks the next day.The safety rules limit the death and destruction when you have your accident. And it is WHEN, and not IF you have an accident.
You never know what might sensitize the explosive and set it off. I self trained in improvised weapons and explosives when I was a helicopter crewchief/aerial observer. That job could get you down behind enemy lines in a hurry. Knowing how to fight, hide, and survive are much needed skills. If you’re still in the service, stick your nose in in those books!. (JWR) is Founder and Senior Editor of SurvivalBlog, the original prepping /survival blog for when the Schumer Hits The Fan (SHTF).
He began SurvivalBlog in 2005. It now reaches more than 320,000 unique visitors weekly.JWR is a journalist, technical writer, and novelist. His survivalist novel, is a modern classic that reached #3 on the New York Times bestsellers list. Two of his other novels have also been best New York Times bestsellers.Jim is the originator of the American Redoubt movement and a frequent talk show guest on shows such as Alex Jones. He is also a retreat consultant specializing in off-grid living, rural relocation, and survival preparedness.
(HJL) is the Managing Editor of SurvivalBlog, the original blog for prepping and survival for when SHTF, where he manages the blog’s day-to-day operations, applying his diverse technical, management, and editorial expertise.HJL earned college degrees in engineering, metallurgy, and education and has worked as Technical Editor for five international technical journals and as an engineer for Sandia National Laboratories. His deep scientific background ranges from aerospace engineering to systems administration and owning his own technology-intensive business.HJL is a firefighter/EMT, and Ham radio operator. He’s a Libertarian, an Eagle Scout, and most importantly a devoted follower of Jesus and the Bible.