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- 9 - RESCUE SUBSYSTEM The Committee is investigating drilling and res cue-team techniques to save coal miners who, because of physical injury or gases in the mine atmosphere, have not been able to egress following an explosion or fire. Drilling There have been a limited number of times in the past when miners have not been able to egress nor rescue teams able to enter mines and the only means of rescue was through holes drilled from the surface. If refuge chambers are constructed in coal mines, there will be more occasions when miners will survive subsequent explosions and rescue holes will have to be drilled. The principal interest of this Committee is in the rescue of trapped coal miners; however, the same drilling equipment can be used to rescue miners in salt mines, potash mines, or tunnels. The drilling systems described here have been optimized for rescue from rather flat-lying bituminous coal seams less than 1, 500 ft below the surface with overlying rock of relatively low strength. The highest strength rock expected to be encountered will be quartzite of approximately 25, 000-psi compressive strength, which in a very few areas may be as thick as 60 ft. Appendix C contains a detailed discussion of the drilling system and the assumptions made in arriving at the design. The recommended drilling system would consist of a highly mobile probe and search drill that could drill a 6- to 8-in. hole to depths of 1, 500 ft with capability to go to 2, 500 ft. This drill would be air-transportable by military aircraft, drill reasonably straight holes with no more than 6-in. deviation per hundred feet of depth, drill 12, 000-psi rock at a rate of 100 ft per hour or more and strong quartzite at a rate of 20 ft per hour or more. It would have maximum traveling dimensions of 8 ft wide and 10 ft high. It would have a 1/4-in. wire hoist with the capacity of 2, 500 ft and would use air circulation for removal of cuttings from the hole. The system would also include a rescue drill capable of drilling an 18- to 28-in. hole to a depth of 1, 500 ft with the capability of being extended to 2, 500 ft. This rig would also drill with air circulation for cuttings removal and would be capable of setting casing for the
- 10 - 28-in. hole to a 500-ft depth. It would drill 12, 000-psi and weaker rock at the rate of 17 ft per hour and 25, 000-psi quartzite at 6 ft per hour. It would have a hoist drum capacity of 2, 500 ft of 3/8-in. wire rope. To assure the availability of highly experienced and skilled drilling crews, the Bureau of Mines may want to contract with a drilling company to guarantee the availability of experienced drilling crews at times of emergency. It would be necessary for these crews to familiarize themselves with the Bureau of Mines equipment and maintain this familiarity by drilling a few holes each year. Rescue Teams Many coal operators maintain well-equipped and well-trained rescue teams that have participated in almost every coal mine emergency in the United States. These teams deserve high commendation for their bravery and efficiency of operation. They have been greatly handicapped, however, by lack of knowledge of the location of survivors. In a number of instances miners could have been saved if rescue teams had known their location. Either the seismic or the electromagnetic communications system described previously could provide information that would permit rescue teams to direct their efforts to recovering the areas in which the miners are trapped. Rescue efforts are also slowed by the time required to explore for fires or "hot spots" and to replace stoppings blow-out by the explosion. The Bureau of Mines is investigating the use of infrared spectrometers to detect fires or "hot spots" at distances up to 1, 000 ft. An infrared spectrometer is being used in the recovery of the Consol No. 9 mine at Farmington, West Virginia. Studies are now under way by the Committee to determine if high-expansion ratio, quick-setting, rigid foams can be used for the construction of stoppings under emergency conditions. Rigid foam is now used in mining operations but the size and speed of the foam- making equipment render it unsuitable for emergency use. If this study shows the technique to be feasible, development should proceed through selection of the optimum foaming materials, development of the best techniques, and construction and testing of a number of stoppings.
- 11 - A typical rescue operation, using the proposed equipment, might be carried out as follows: As soon as the men on the surface are aware that an explosion or fire has occurred, they would notify workers in the areas of the mine still having communications of the haz- ard and, if it could be determined, of the best escape routes. They would notify company, state, and federal mining officials and, from available evidence, determine the locations in which survivors would most likely be trapped. Thus far, this is the procedure now in use. Next, an area should be located on the surface above the places in which survivors are expected to be found. The Bureau of Mines would immediately dispatch electromagnetic or seismic location and communication equipment and drilling rigs to the site. Other drilling rigs in the area would be requisitioned if needed. Rescue teams would begin immediately to determine if danger of subsequent explosions exists and, if not, to restore ventilation and to explore the affected areas of the mine. If there is danger of additional explosions, the Bureau's drilling crews should move to the approximate location and prepare to drill. The location and communication equip- ment would begin searching in the most likely areas immediately upon arrival. Meanwhile, workers underground in the unaffected areas should proceed out of the mine, carrying with them emergency breathing devices and carbon monoxide detectors. The atmosphere should be tested frequently for carbon monoxide because prior emergencies have shown that men frequently succumb before realizing that carbon monoxide is present in dangerous concentrations.
