Document YZRVgw0b845va52OXr0Br6ey

Il Ii I ROC-LOCTM 540 MINING KIT I : INSTRUCTIONS FOR HANDLING AND USE 1 TM AMERICAN CYANAMID COMPANY / AM-9"' Chemical Grout ROC-LOC1" Mining Kits A EROS PR AYS 52 Binder USHO 002655 ROC-LOCTM 540 MINING KIT INSTRUCTIONS FOR HANDLING AND USE 3C0CT-v*t.I0OC FIG. 1 MIX THOROUGHLY FIG. 2 j POT LIFE AND CURE TIME | | j j ' TEMP. MAX. WORK- ING POT TIME MIN. LIFE MIN. POT CURE TIME MIN. CURE TIME IN PLACE HRS. 43" F. oO 75 30 7"C. 16 24 32 45 58 35 44 25 30 1 5 21 FIG. 3 130 24 90 18 75 8 36 1 NOTE: THE ROC-LOC CURE TIME IN MASSIVE STATE (POT CURE TIME) IS FAST. WHILE IN PLACE IT IS CONSIDERABLY SLOWER. READ HANDLING INSTRUCTIONS CAREFULLY. NOTE: Bolt holes should be drilled to exact depths so that mixed ROC-LOC will not be wasted at hole bottom. Over drilled holes should be filled to proper bolt depth with tamping clay. Clean holes thoroughly with blow pipe or water, especially down holes. 1. Cyanamid ROC-LOC 540 Mining Kit consists of a shipping container (which also serves as the mixing vessel) and three plastic bags; the largest contains ROC-LOC paste, the medium size ROC-LOC hardener, and the smallest, the ROC-LOC activator and a measuring spoon. The volume of mixed ROC-LOC is 540 cubic inches (8, 850 cc. ). A one-inch I. D. polyethylene transfer tube and piston are also supplied. The transfer tube should be at least one foot longer than the drill hole and the piston handle at least two feet longer. 2. First, cut off one corner of the bottom of the large plastic bag containing ROC-LOC paste and squeeze out into the steel shipping pail. Add ROC-LOC hardener to the ROC-LOC paste and mix until color is uniform. If a screwtype power mixer is used, an extension collar can be made for the can which will help prevent splash. The mixture will gel in time indicated in Pot Life Chart (Fig. 3). Mixed ROC-LOC cannot be used after it has gelled, and bolts or re-bars should be in place before elapsed working times shown in Fig. 3. If all of the mixture cannot be used in time shown, smaller amounts can be mixed in other containers. Exact proportions of ROC-LOC paste and hardener are not critical (about 4-to-l by weight or volume is good). If the application will not use all the paste, this bag should be resealed. For low temperature use, the third ingredient, ROC-LOC activator, should be added to ROC-LOC paste before mixing with ROC-LOC hardener. See Fig. 8 for dosages. USHO 002657 Safety Precautions and Handling Suggestions for ROC-LOC Mining Kits 1. ROC-LOC paste mixed or unmixed, is combustible and burns like crude oil (flash point 150F. ). 2. Vapors are nonexplosjve and nontoxic, but can cause eye and skin irritation. Use of rubberized gloves when handling kits is suggested. 3. ROC-LOC hardener is combustible; ignition temperature is 700?F. (370C. ). 4. ROC-LOC hardener may cause skin irritation on prolonged contact. 5. Uncured ROC-LOC is soluble in standard paint solvents and emulsifies readily with full strength liquid detergents. Cured ROC-LOC is insoluble in everything and can only be removed from tools and equipment by chipping or burning. Cured ROC-LOC does not melt at high temperatures, but burns like oil-soaked wood. Ignition temperature and flash point are 700 F. (370C. ). 6. For longest shelf life, store kits at 60F. (16C. ) or lower. Freezing temperatures will not harm ROC-LOC Mining Kits but will greatly increase viscosity. Do not in stall ROC-LOC kits at temperatures below 45F. (7C. ). Warm ROC-LOC kit con tainer to this temperature in hot water. ROC-LOC kits have a guaranteed shelf life of at least six (6) months. 7. Uncured ROC-LOC on hands can be removed easily with standard hand soaps and hot water. CAUTION: Both kit components may cause skin and eye irritation. Avoid contact with eyes and prolonged contact with skin. If either kit component gets in eyes, wash eyes with fresh water from running hose for 10 minutes. Gelation and Curing of ROC-LOC The mixed ROC-LOC hardens in two stages: 1. Gel Stage: A thick, nontransferable plastic mass forms first. The time of formation is- the gel time or pot life. ROC-LOC cannot be placed in this state and the maximum working times given in Figure 3 are the safe time periods during which gelation will not occur. 2. Cure Stage: ROC-LOC gradually cures to a hard, resilient mass. Again, the time required depends on the rock temperature. In large masses as in the original container, it will become very hot and cure quite fast. These pot cure times are shown in Figure 3. Temperatures in this case may read 300F. (150C.) with some fuming, but there is no danger or fire hazard. In a hole ROC-LOC cures much slower due to the lower temperature and in-place cure times are shown in Figure 3. In moist mine air, ROC-LOC surface exposed to air may remain tacky after the inner mass has fully cured. ' 3. Activators: At temperatures below 65 F. (18C. ) it may be necessary to speed up both of the above stages by adding ROC-LOC activator. The dosages of ROC-LOC activator to be used for different gel times at various temperatures are shown in Figure 8. A measuring spoon is added in the kit. 3- - USHO 002659 MIXED VOLUME REQUIRED FOR VARIOUS RE-BAR HOLE SIZE COMBINATIONS RE-BAR NO. RE- BAR SIZE AREA-Sq. IN. 5 5/8" 6 3/4" 0.3068 0.4418 7 7/8" 0.6013 89 1" 1V8" 0.7854 0.9940 It l'/4" 1.2272 II |3/8" 1.4849 12 i>/2" 1.7671 DRILL HOLE DIAMETER AREA Sq. In. ROC-LOC VOLUME (CUBIC INCHES PER FOOT OF HOLE) 7/8" 0.6013 4.7 2.5 l" 0.7854 7.6 5.5 2.9 |l/8" 0.9940 10.9 8.8 6.2 3.3 11/4" 1.2272 14.7 12.5 10.0 7.0 3.7 P/8" 1.4849 18.8 16.6 " 14.1 11.2 7.8 4.1 11/2" 1.7671 23.3 21.2 18.6 15.6 12.3 8.6 4.5 IV 2.0739 28.2 26.0 23.5 20.5 17.2 13.5 9.4 4.9 |3/4" 2.4053 33.5 31 .3 28.8 25.8 22.5 18.8 14.6 10.2 2 " 3.1416 45.2 43.1 40.5 37.6 34.2 30.5 26.4 21.9 21/2" 4.9087 73.4 71 .9 68.7 65.8 62.4 58.7 54.6 50.1 (I)notes: FIGURE 9* ir HAS BEEN FOUND FROM EXPERIENCE THAT THE ANNULAR SPACE IN ACTUAL ROUGH BORE DRILL HOLES IS ABOUT 33% GREATER THAN THE THEORETICAL VOLUME. THE VOLUMES LISTED IN THE TABLE INCLUDE THIS 33% EXCESS. (2) TRANSFER TUBE (I" I. D. ) HOLDS 9.42 CUBIC INCHES OF MIXED ROC-LOC PER LINEAR FOOT. . . -O - USHO 002661 l APPL.1CA FIONS OF LOOPED RE-BAR I. Wedge Type - Bonded Full Length, Permanently Stressed This installation is best suited for permanent anchor age of foundation bolts, especially for holes with diameters larger or smaller than those of commonly available expansion shells. Re-bar actually has slight bend put into it during placement to wedge it temporarily. 2. Re-bar Threaded at Both Ends with Expansion Shell, Bonded Full Length, Permanently Stressed This type is used where immediate roof support is required for safe working conditions, or where a prestressed bolt is needed. Typical applications are broken roof or pillars, or at intersections in coal mines. 3. Re-bar Threaded at One End with Collar Plate, Bonded Full Length This type is useful in raises and shafts where pro tection of workmen is required during subsequent operations. Wire mesh can be hung on end of bolt, and the nut tightened to full torque when ROC-LOC has cured. This system provides the best form of roof support. Re-bar shown is straight, but actually it should have a slight bend put into it during insertion to hold it in place while the ROC-LOC is setting. Bending is also suggested in horizontal holes to prevent bar from lying flat on bottom of hole. 4. Dowel Pin, Bonded Full Length This type of support is most useful in ore passes and chutes where continuously falling rock loosens ' a regular bolt almost immediately. The re-bar can be replaced with wire rope in some cases. Re-bar can be wedged into hole by bending slightly. The dowel pin technique is also excellent for anchor ing crushers, slushers, etc., to concrete foundations. -7- USHO 002663 Item CHEMICAL AND PHYSICAL PROPERTIES OF CURED ROC-LOC After 48 Hrs. at 70 F. Fully Cured ROC-LOC Plain Concrete Color Specific Gravity Compressive Strength, psi Tensile Strength,- psi at 77 F. " at -40 F. Gray 1.32 10, 000 2, 000 - Gray 1.32 20,000 8,100 8, 500 2.4 2000-8000 250-700 Tensile Elongation, % 1.0 2. 6 Flexural.Strength, psi77F. Flame Ignition Temperature, F. 3, 200 - 12,300 700 400-1200 Self-Ignition Temperature, F, - 700 Volumetric Resistivity, ohms/cm . Surface Resistivity, ohms 2.0 x1016 1.1 x 1012 Dielectric Constant 3.5 Coefficient of Thermal Expansion in/in/ F. 8. 7 x 10_i> c 4x10 -oL 4-7 x 10 Thermal Conductivity Btu/hr. /ft. Z/F. /in. 1.3 14.4 - 24.0 Corrosion Resistance Not attacked by dilute acids or alkalies. Slowly decomposed by strong caustic or cone, sul furic acid. Not affected by salt. Resistant to almost all solvents. Disintegrates in dilute sulfuric acid and sulfate-b earing waters. SoLubiLity Insoluble in water, oils, solvents, acids and alkalies. Deflection Temperature under load, F. 176 122 USHO 0 0 2 6 6 5 NOTE: The maximum strength values reported above are approximate values for the fully cured state. When properly installed, and after sufficient time for curing has elapsed, the ROC-LOC anchorage has these characteristics. The information contained in this bulletin, to the best of our knowledge, Is true and accurate. Any recommendations or suggestions are made without warranty or guarantee, since the conditions of use are beyond our control. Nothing contained herein shall be construed to imply the non-existence of any relevant patents nor to constitute a permission, inducement, or recommendation to practice any Invention covered by any patent owned by AMERICAN CYANAMID COMPANY or by others, without authority from the owner of the patent. 4-2119-1500 - 9/64 9- - Printed in U. S. A. USE OF RESINS ( IN MINE ROOF SUPPORT I I PART II "APPLICATIONS" i i D. C. McLean and Sam A. MacKay / AM-9'" Chemical Grout ROC-LOC,v Mining Kits AEROSPRAY 52 Binder July 1964 USHO 00 -2Fig. 1. - VARIATIONS OF FULLY BONDED REINFORCING BARS USHO 002668 has largely been pioneered in the construction field, wi especially good work being reported from the Snowy Mountains Hydroelectric Authorit in Australia.Techniques developed there using cement grouted bolt are now being adapted in many large government construction projects in this country with excellent results. The applications described in this paper are those in which Cyanamid's ROC-IDC Mining Kits were used exclusively. Slus'ner Drifts and Finger Raises (Box Hole Brows, Dashes) A common problem with metal mines employing block caving methods is that of maintaining the roof in slusher drifts, especially at the intersections of these drifts with the feed raises thru which the large fragments of broken ore fall. Typical sections are shown in RLgures 3 and 4. In ILgure 3 the drift is normally cut 7 ft. wide by 8 ft. high initially. The rock involved is a hard norite (diabase) which is usually competent but has block cleavage. This roof has a tendency to fall out in large blocks when subjected tooperating stresses. Depending upon the initial condition of the roof, the drift is either lined with 2 to 3 ft. of concrete or is left as is temporarily It is bolted first in either case. Upon use, normal wear and blasting against the brow (to break up large "hangers") gradually wears or breaks away the brow to the final position indicated so that the ore can then flood the drift, making operation of the slusher impossible. Conventional bolts do little to support the roof, since they are rendered useless almost immediately due to sloughing around the collar plate and subsequent loss of tensions. During the.life of a drift, it may be necessary to re- conerete a orow ; ;r ; times to restore its original countour, at a cost of S20CC to 5-TOC er restoration. USHO 002670 6- - Fig-re 4 shows how the problem was attacked with grouted bolts. Steel reinforcing rods (7/8" dia. x 6 ft.) were installed fully grouted on 24" to 30" centers, across the drift and up into the brow, \bout 25 brows were supported in this manner, 30 60 ^ bolts being used per brow. Sixty cubic inches of resin were placed in each bolt hole. Bolts of all three types were used in an attempt to determine what degree of difference in bolt performance would occur. Ambient temperature was 45 F. Resins gelled in about 30 minutes, and were well cured in 2k hours. Post-tensioned bolts had 200 to 300 ft. lbs. torque applied after 48 hours. Installations were made in October and November, 1962. Although a full evaluation of the performance of these installations will not be possible for about another 6 months to a year, the condition of the roof has been maintained in a satisfactory condition to the degree that the mine management is convinced the resin installations have resulted in appreciable savings in maintainance costs. The economic objective in this case is to prevent one or more concretings of the worn brow during its life span. The comparative total costs are as follows: Cost of Reconcreting Brow Cost of Resin Bolting 35 bolts at $2.00 each 2100 cu. in. resin at 4^/in3 Resin transfer equipment Labor (including drilling) (3 men - 1 day at $25/day) Total Resin-Bolt Installation Cost $ To 34 5 75 $2500 $ 234 Savings in Maintenance Costs $2266 USH0 002672 It is quite apparent that where grouted bolts can be shown to be effective, the savings in preventive maintenance can be appreciable even when factors such as loss of production during rsconcreting are neglected. Rock Passes at loading Points These structures are common but very critical since large tonnages of ore from many production areas must be kpet moving continuously thru them. Figure 5 shows an unusual rock pass structure in the Garson Mine. It was unfortunate that this pass had to be driven thru a highly altered, brecciated zone, with the result that the wall rock in the pass tended to crumble when subjected to the impact of moving rock. The life span of this 6 ft. x 6 ft. x 50 ft. pass was required to be 10 years during which time 200,000 to 300,000 tons of ore and development rock would be transferred thru it. It was feared that with the broken ground condition existing, this., pass might enlarge within a relatively short portion of its life span (18 months) to a point where the level station and main haulage way would be endangered. Standard bolts were known to be completely ineffective. Before such a condition of en largement would be reached ( a point where the pass had attained dimensions of about 10 ft. x 12 ft.), it would be necessary to shut the section down and install a backed steel lining to restore its original dimensions. The steel lining (3/3" thick) would be expected to handle about 40,000 tons before new steel wculd be required. USHO 002674 -10- The operators decided to try resined bolts to consolidate the broken ground, using the general pattern shown in Figure 6. At this point the rock pass had enlarged to a size of about 3 ft. x 3 ft. Thirty- eight stressed and thirty-seven unstressed bolts were used in an attempt to get a relative evaluation. All bolts were 7/3" rebar - 6 ft. long installed in 1 1/4" dia. drill holes. Seven bolts were used in each row with rows on 4 ft. spacings. Ambient rock temperature was 80F. Sixty cubic inches of R0G- LOC raining resin used in each bolt hole. This gelled in about 20 minutes and attained a high degree of cure within 2 hours. Both "sausage" kits and bulk kits were used in this test. Tensioned bolts were tightened to a torque value of 200 to 300 ft. lbs. The grouted bolt installation was made in October, 1962. As of January, 1964, this pass has shown very little sign of wear although 25,000 tons of development rock has been put thru it. There is every indication that this pass will not require repairs for at least another 2 to 3 years. Of special interest is the fact that there is no apparent difference in the condition of the tensioned wall rock and the untensioned. The comparative economics involved in this case are most interesting: ' Cost of 3acked Steel liner (6 ft. dia. x 3/3" boiler plate cylinder backed with cemented tailings) -370/linear ft. x 50 = 33500 USHO 002676 Cost of Resin Bolting 38 Stressed Bolts at $2.00 each 37 Plain rebars at $1.00 each Drilling labor (2 men x k shifts x $25/day) Resin Installation Labor (3 men - 1 shift) 4500 cu. in. resin at k/in^ Resin transfer equipment $ 76.00 37-00 200.00 75-00 180.00 15-00 Total cost of resin-bolt Installation $583 It is quite apparent from this cost comparison that the use of grouted bolts has resulted in a maintenance saving of at least $2900. Large Ore Passes One of the major problems confronting metal mines operating on multiple levels is that of maintaining main ore passes from enlarging to the point where operating levels are threatened with being undermined. A typical system of ore passes is shown in Pigure 7. The areas in the passes that are subject to greatest wear are those occurring at inter sections and turns. Obviously, a conventional roof bolt is useless in maintaining an intact wall in a pass, since the first rock thru the pass batters the bolt heads and collar plates, loosening them almost immediately It is usually necessary however, to go to the expense of installing these bolts while the pass is being driver, in order to protect the miners from rock falls during excavation. If the ore pass happens to go thru badly broken ground, a very serious maintenance problem exists, for which the grouted bolt is really the only possibility for salvation. ` USH0 002678 Such a condition was encountered at Creighton No. 6 Mine in November, 1962. A sketch of the actual ore pass involved is shown in Figure 3. This was a new pass which was required to have a life span of many years and handle a large volume of rock. The ground thru which it was driven was badly, fractured along its entire length, and it was feared from past experience in similar ground that trouble would be encountered within a very short time. It was decided at first to resinbolt the top and bottom 30 ft. of the hanging wall of this ore pass, again using both tensioned and untensioned bolts. Ultimately, however, it was decided to do the whole hanging wall. ' The resin-bolt program used in this case utilized 350 bolts made of 6 ft. lengths of 7/8" rebar installed in 1 l/k" drill holes. The bolt pattern adopted is shown schematically in figure 9. The bolts were placed on about 2 ft. centers, using rows of 6 bolts. The two types were alternated from side to side about every thirty feet. Untensioned bolts were installed using "sausage" type kits (R0C-L0C 20 Mining Kits). Tensioned bolts were installed with resin utilizing transfer tubes and kits similar to R0C-L0C 60 Mining Kits. Sixty cubic inches of resin were used per hole. All holes were essentially horizontal. Ambient temperature was o0F. Tensioned bolts were tightened to 200 to 300 ft. lbs. of torque immediately. Resin-Bolting Costs This project was a major undertaking that involved the setting up of staging at about 7 ft. intervals throughout the length of the pass so that new bolt holes could be drilled and the resin placed. Figures are not available for the cost of installing the staging and USH0 002680 -16- for the drilling preparation. However, it is possible to get a realistic estimate of the cost of the resin-bolt phase of this project by assuming that the resin bolts could have been installed initially while the pass was being driven. Thus, the staging and drilling would only be done in the usual manner. The extra costs involved in using the resin bolts are about -as follows: 175 Rebar tensioned 175 Rebar "spears" 21,000 cu. in. R0C-L0C boltsat #2.00 at $1.00 , resinat $ ,04-/in Resin transfer equipment Labor to install resin (3 men - 6 shifts - at 25.00/shift/man) Total Resin-Bolt Installment Cost 350.00 175.00 840.00 } 50.00 450.00 $1865.00 On February 1, 1964, after handling 10,000 tons, this ore pass was examined and found to be in excellent condition with very little degradation of the walls. Of interest again is the fact that there appeared to be no difference in the condition of the walls supported by the two types of bolts. Total ore handled by this pass will be 36,000 tons. On the basis of the performance observed in this ore pass, this mine has currently adopted the practice of using resined bolts initially for wall support in all new ore passes. Also, because wear has been so slight and because no apparent difference exists between the tensioned and untensioned bolts, the mine staff has concluded that the ore pass walls can be adequately reinforced against wear with 3 ft. lengths of 7/3" rebar "spears" (untensioned). This permits savings in bolt and resin costs and greatly simplifies installation, since no equipment other than a transfer tube and a double-jack are required. USHO 002682 DIAGRAMMATIC ONLY -18- z o oz ui z ou a. oz cri 1Dm- LLi Z o Nl gO _ UJ UZ < UJ Q- E zi ze> IO- UOJ' z (- UJ </i --1 tu tip 2o 3* o QC a. UJ u_ o o H u UxJ t- UuJ. LL z o UJ UJ H rX; q<; ao CD Coo'] o X Ui ZD Z O < < _j u o xuj v- Z u< O O' zQ S! z< uI- uo < O' I DO u_ -20- In a study of the stress distribution in a post-tensioned (p) reinforcing bar in concrete, Mains'1 ' determined that a load applied after the reinforcing bar had been set is distributed along the bar in the manner illustrated in Figure 13. Note that with the deformed bar, the load is taken up by the bond between concrete and bar in the section nearest the face. In the case of a 12,000-lb. load, this is taken up in a segment approximately 12" long. This suggests immediately that a properly designed pattern of post-stressed grouted bolts should permit the development of a compression band very close to the roof line where it would do the greatest good in combating sag and the devastating tensile stresses accompanying it. Another interesting point which Mains1 data make apparent is that the bond stresses developed by deformed bar (Curve B) are much greater than those of the plain round bar (Curve A). This permits the transfer of forces to the concrete (or rock, in the case of a bonded bolt) within a very short length of bolt. These data confirm the postulate of Pender et al., that a grouted bolt will take over a load thru bond stress over a short bonded length. USHO 002686 -22- Miscellaneous Applications for Grouted Bolts All of the applications that have been tested with grouted bolts cannot be described fully here, but we hope to present more examples in a subsequent paper. We can say briefly that resin-grouted bolts have also proved effective as: slusher drift pins, slusher and crusher foundation bolts, and chain anchor pins (for ore control at feed points). Another interesting concept that has been explored which shows promise is that of prebolting. Importance of Blasting It is of utmost importance in any ground control program (in new tunnels or entries) that the blasting practice employed be very carefully developed for each type of ground so that overbreaking and severe blast damage within the roof are held to a minimum. Despite the higher first costs, it makes sense to use smooth blasting techniques (as described by Langefors^) in attempting to maintain the roof in prime condition. Once the best blasting technique is developed, it is still more important to see that the blasting is closely supervised to insure there is no reversion to the so-called "standard practices" which again are usually the worst possible for most "bad" ground. It could probably be shown that half of the "bad ground" conditions en countered are generated by the mining practices employed. Evidence is now available from many sources in the underground construction field to indicate that change-over to smooth blasting techniques has made a tremendous improvement in the condition of wall and roof rock. USHO 002688 -24- References 1. D. C. McLean, "Use of Resins in Mine Roof Support," Mining Engineering, Vol. 16, No. 1, pp. 36-40, January, 1964. 2. R. M. Mains, "Measurement of the Distribution of Tensile and Bond Stresses Along Reinforcing Bars," Journal of the American Concrete Institute, Title No. 48-17, PP* 225-252, November, 1951* 3. E. 3. Pender, A. D. Hosking and R. PI. Mattner, "Grouted Rock Bolts for Permanent Support of Major Underground Works," J. Inst. Engineers (Australia), Vol. 35 Nos. 7 & 8, July-August, 1963* L. Ulf Langefors, "Smooth Blasting," Water Power, May, 1959> PP* 2-8. 5. T. A. Lang, "Theory and Practice of Rock Bolting," A.I.M.E. Transactions Mining, Vol. 220, pp. 333-348 (1961). 6. P. Schuermann, "Reduction of Rock Movements in Roadways by Various Methods of Reinforcing Rock/" Proceedings of Fourth International Conference on Strata Control'and Rock Mechanics, May, 1964 (to be published). USHO 002690 L/ C' I'.l .V A M JT Jt> AMERICAN CVANAMID COMPANY INDUSTRIAL CHEMICALS DIVISION BERDAN AVENUE WAYNE. NEW JERSEY 07470 TELEPHONE. (AREA CODE 201) 831-1234 March 4, 1965 Mr. L. E. Clark, Jr. Chief Engineer U. S. Steel Corporation Fairfield Works P. 0. Box 599 Fairfield, Alabama 35;-;6;- Dear Mr. Clark: ` Thank you for your letter requesting information on our ROC-LOC^^ Mining Kits. We are enclosing our data sheet on the ROC-LOC 540 package as well as two reprints titled Use of Resins in Mine Roof Support. Part I gives background data on our development work. Part II cites specific applica tions carried out at International Nickel Company, Sudbury, Ontario. ROC-LOC kits are available through this office priced at $20.00 per kit F.O.B. Linden, New Jersey. The transfer tube assemblies, as shown on Figure 5 of the ROC-LOC 5^0 data sheet, are priced at $2.75 each at seven foot tube lengths. The enclosures cover information on your other questions, such as instal lation technique, pull test data, etc. If you have any questions after reviewing these, please do not hesitate to let us know. Thank you again for your inquiry and interest. Very truly yours, MCB/jc Enclosure M. C. Behre Supervisor, Special Projects Explosives & Mining Chemicals Department USHO 002653 USHO 002654