REDUCING ROCK FALL HAZARD DURING MINE RESCUE OPERATIONS

INTRODUCTION:
To many people, rescue from elevated, sometimes vertical, locations brings about thoughts of heroism mixed with brawn and self-sacrifice. Most of us can certainly conjure up images of harrowing cliff rescues where the entire technical effort is hanging from a few seemingly small nylon ropes hundreds of feet above the ground. Such is the vertical realm of technical rope rescue—a vast technical field of which I am an instructor of—both professionally, and as Battalion Chief of (rope) Operations for a northern Arizona Fire District.

The area in which I live and practice my climbing and rescue skills is a veritable vertical-to-steep angle landscape—one which sometimes lures the unfortunate backcountry traveler into situations requiring rope rescue. While I could tell the reader of a myriad hazardous technical rope rescues we have performed over the years, this is not an article about that. However, in light of these, what I call “perceived” dangers, we should try and identify the real hazards relating to the rope rescue team—whether in the mine setting or in any other vertical environment.

There can be no doubt: Hazards abound in any system constructed by the rescue team for the purpose of overcoming the forces of gravity—whether in the vertical or steep angle realm. Briefly consider anchors pulling out, ropes being accidentally severed, equipment failure, or, worse yet, team member incompetence leading to catastrophic failure as things that the team must be on guard against. Yet, through continual practice and regimented team and personal training, these things mentioned can be minimized, to say nothing of controlled. It is through the repetition of training that the team gains understanding and attains the sound judgment to avoid, say, dubious anchors, situations which would cut the rope, or member incompetence, etcetera.

Rope rescue can often be surrounded by profound misconception, both by the general public, and, sometimes unknowingly, by the rescue professional as well. For instance, when many rescuers think of a particularly “hazardous” or “dangerous” technical rope rescue operation, thoughts turn immediately to the high rock cliff rescue like the Yosemite “big wall” rescue. However, while these may be technically and logistically demanding rescues in themselves, they are not in my experience, the real killers. The real hazard lurks elsewhere.

In all the years I have been in this field and in all of the various rescue courses to industry and mining that I have taught, I have never seen the potential for injury to a rescue team or member more extreme than that of the hard rock open pit mine site. The single most volatile ingredient which gives me reason to state this is rock fall onto the rescue team attempting the rescue of a fellow mine worker.

HAZARD: ROCK FALL!
This article pertains to the litter stretcher extrication of a worker or workers in a piece of equipment which has accidentally breached a earthen berm in the following two locations within most hard rock open pit mines:
Mine pit access road— Roads constructed from the bottom of the pit to the top. This road may transect many horizontal benches as it descends. Heavy hauling equipment travel this road carrying ore bearing materials. High berms are built along the embankment side of the road to help deflect operated equipment.
Dump site— An area where mined material is dumped into a depression or previously mined area. Hauling equipment backs up to the edge and deposits material sometimes in conjunction with a dozer to push it over. A small berm is usually left at the edge.

It is a well known fact that the rock strata into which these pits are excavated has usually been disturbed by both mechanical means and explosives. Why else would benching be mandated for the safety of workers in this environment? Rock continually falls due to the unstable nature of the geology within the mine. (At least in Yosemite, you have walls which have not been recently disturbed.)

Most mines employ a system of excavation and, subsequent to ore removal, deposition in huge land fills in areas already mined out. These dumps are terrific in magnitude; many of the slopes I have taught on are in excess of 300 feet in length. The material dumped at the upper edge continually pours down over the face continually reaching an angle where the friction is equalized with the gravity acting on the downward movement of the material (called the ‘angle of repose’). Rescue party-induced rock fall is an ever present danger. Not only that, but the ropes from the rescue party to the top can also induce rock fall onto the team below.

COMPARISON IN RISK: ROCK SCALING
For comparison, consider a rock scaling operation where the hard rock scaler suspended on rope over the edge is involved in prying rocks—both large and small— off excavated cut rock faces (sometimes along mountainous highways). A rule imperative for the survival of the scaler from rock falls is not to pass anything on the way down which can fall of them later. Seems easy enough, and by strict adherence to this simple rule, the scaler is pretty much guaranteed safe passage through a most hazardous and life threatening rock fall situation. Looking closer then at the average scaling operation, we can see that, other than from falling, it is considered a relatively safe roped procedure as long as the scaler adheres to this rule.

As it turns out, this fundamental scaler’s rule cannot be applied to the dump or benched open pit mine rescue operation. Since the rescue party descending into these situations cannot “scale as they go” because the loose materials depth is seemingly endless. Any manual dislodging of material would certainly cause chain reaction sliding of material above. Consequently, the potential for subsequent rock fall caused by rescue team movement is a distinct possibility. It is also considered not only possible, but more probable since rescue ropes above them to the top are constantly contacting the unstable surface.

MINIMIZING ROCK FALL HAZARDS
There are some techniques which can minimize the potential for rescue party-induced rock fall.

• Rescue set up location
• Steep angle rescue technique
• Use of high directionals

1. Rescue set up location:
To alleviate the potential for rock fall onto the victim(s) of such an accident, the rescue team should set up the top-most station a safe distance to either side of where the accident occurred. (See Figure 1.) This distance will be determined by factors like:
How far down the victim is.
Type of material (could the material injure, if dislodged).
Benching (falling material will be stopped).

It should be noted that rolling material of irregular size and shape will not always travel down the fall line like water would run down a sloped sheet of glass. The material often takes a “fanning” pattern relative, as I have said, to the length of the slope. Usually a transverse distance of roughly 20% of the height of the slope should be adhered to for safe rescue operations. For instance, on a slope of about 200’, displace the rescue top station about 40’ to the left or right of the accident. Once on the bottom, the rescue team can travel laterally to the victim(s).

2. Steep angle rescue technique:
The steep angle litter evacuation of a patient is always performed in an “in-line” position, meaning that the litter is traveling up the embankment head-to-foot parallel to the direction of movement—up or down the fall line. Usually three (called a “delta carry”), or rarely four (“quad carry”) rescuers, called “bearers”, are attending the litter with patient to the top station where the ambulance is waiting. Because of all of the people hanging off of this litter, the rescue party on the whole is extremely heavy. Anchors, systems and connecting hardware should be planned for a sufficient safety factor of at least 10:1.

Correct steep angle in-line upward or downward movement requires appropriate braking systems for lowering and pulley systems or winches for raising. In addition, a second rope safety, referred to as a “belay”, should always be managed in the event that the main lowering or lifting rope fails. It should be noted that, in the event of main line failure, a significant impact (shock) force will be attributed to the second rope belay system. Only a belay technique able to withstand tremendous forces should be implemented in these cases. Proper application of these systems is not a focus of this article and should be mastered by the rescue team before heading for the slope.

During mine steep angle evacuations, bearer body position is paramount to keeping loose rock in position. (See photo #6.) Since the bearer is literally supported by the litter and the rope system above, they should be aggressively leaning back at a position perpendicular to the slope angle. Many inexperienced rescuers I have trained resist this and try and stand up (vertical). Two things happen which can lead to rock fall if this is done: The first is that the force on the top station system drops off and the supporting ropes drop to the slope above because of the lack of tension, furthering rock fall hazard.

The second thing standing up does is produce a “kick out” effect of loose material. The bearer can stumble, drop the litter to one side and aggravate injuries to the patient.

3. Use of High Directionals:
In the earlier years of teaching mine rescue courses, I was surprised by the amount of rock which was dislodged by the ropes above the litter party during these steep angle evacuations. After one nearly clobbered one of the litter bearers, I felt it was time to look for a solution. Thinking about this problem later, I settled upon another technique I already used in other forms of high angle rescue and highline work. There was one difference though; I would need to also elevate the belay line as well—something rarely done in cliff or industrial rescue.

Elevating both of these ropes by the use of high directionals (HD’s) keeps them away from the surface above the rescue party. No contact—no rock fall. (See Figure 2.) The HD itself is merely a pulley. Also, tension through at least the main rope must be maximized and maintained at a rough constant (by the bearers leaning back) to keep the ropes above the slopes surface. As the rescue party gets farther away from the HD (hence, lower), even this tensioned rope will begin to droop slightly, forming a detectable crescent which may begin to contact the slope well above. To eliminate this potential, continued elevation of the ropes at the top station HD will keep the ropes well above the surface.

A technique called “marrying” involves taping1 the slack belay rope at 20’—25’ intervals to the tensioned main rope and will keep this rope from dragging on the ground. Otherwise, maintaining tension on the belay line by using a small amount of friction in series with the belay function will also serve the same purpose. If using tape, it will need to be installed and removed beyond the HD by a rescuer standing on the berm assigned only to that task.

Two various methods of establishing high directionals have been found to be acceptable:
1. Use of summoned mine equipment
2. Use of artificial high directionals

Obviously, the summoning and subsequent use of mine equipment, hopefully with a movable arm like a crane, is the easiest method of elevating lines. Also, it is easy for the crane operator to continue elevating the ropes as the rescue party gets farther out. This should be done very, very gently, as any sudden jerks up or down will be compounded to the rescue party. In any event, the HD attached to the crane should be directly over the berm and never more than 8’ off the ground (less if using the tape method of marrying the ropes). Use separate pulleys on separate slings on the end of the crane for the main and belay ropes to eliminate the critical point.

The building of a HD in the field by the rescue team is more dependent on practice—the type of practice which will lead to eventual proficiency. These HD’s are referred to as artificial high directionals, or AHD’s to use the rescue acronym. It relies on at least two wooden or metal poles 10’ in length and at least two rope guys for stability (4” dia. poles or 4x4’s with rounded edges work well). Working together, these two very different components made up of compression and tension elements will serve to elevate the lines. While there are many different types of AHD’s which can be built, all fall short of practicality due to insufficiency of anchors in the loose mine environment.

Due to this limitation, I have found that the sideways “A” frame, or S-A frame, is the best option for use over loose earthen berms. Similar to a regular “A” frame transverse to the rescue ropes, the S-A frame is turned 90 degrees to where the two poles are in-line with the rescue ropes. Again, this orientation makes the S-A frame very stable from front to back, but less stable from left to right. This instability is corrected by the use of two tensioned guys off to each side of the two pole frame. Since this is the top of the berm, a picket system is driven easily into the soft material on each side, secured with a second if needed. Very little force should be directed into the guys at all if proper orientation is carefully engineered. This means that the two ropes passing through the HD should be pulling directly down and not to either side.

S-A frame poles may be bolted or whipped & frapped together. Care must be exercised in engineering the system so that the resultant force created by the two component forces in the tensioned rope falls within the “throat” of the leg’s spread. If this is not anticipated correctly, the S-A frame can either tip violently forward or backwards. Consequently, the spread between the two 10’ poles should be as wide as is allowable by the terrain, but never less than 60 degrees. Wider is better at first. Later, through an understanding of physics gained through practice, a team can narrow this spread. A hole for each leg should be provided, and a rope connecting each at the bottom should be tied to resist the spreading action when the rescue force is applied.

Anchorage of the rescue ropes (belay and main) should be made on a piece of mine equipment summoned for the purpose. Anchoring low to the ground and within 20’ of the S-A frame on the high berm will serve to make the angle of the tensioned rope equal on each side of the HD; this allowing the S-A frame to be placed nearly straight up.

A small 4:1 pulley system with a self-minding ratchet is employed from the apex of the S-A frame to hoist the HD into position as the rescue party gets farther down the slope.

CONCLUSION:
Rescue or recovery of fellow mine personnel is a practice nobody wants to see enacted. We all hope it is never needed. However, the fact is that it is not a matter of if, but more a matter of when an accident will occur. As professionals, our charge is to be prepared for, what some may say, is inevitable. The ultimate respect and concern we as rescuers can express for anyone injured within the mine environment is to be fully prepared to professionally extricate and treat resulting injuries with compassion and expertise. Even more important than all of this is the ultimate goal of not getting injured or killed in the process of helping our fellow miner.