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By S. R. Dismuke

Ore at the Magmont Mine in southeast Missouri is extracted by the room and pillar method on two and sometimes three horizons. In 1991, an innovative plan was formulated for recovery of high grade ore in pillars using cable bolts to accommodate spans of more than 27 m (90 ft). A test area was subsequently selected and a recovery plan developed. A cooperative rock mechanics study effort by COMINCO METALS, the U.S. Bureau of Mines and the University of Utah was later established. When initially opened in 1968, the planned production rate was about 1,000,000 tons per year. Due to declining reserves, the production rate was decreased to 630,000 tons per year in November 1992. Pillar recovery now accounts for approximately 40%-50% of the mined tonnage and plays a vital role in allowing Magmont to continue to operate.

Apr 13, 2011

By Matt Leeming

Several of the underground mines in the UK require a significant number of cable bolts to be installed, remedially, to control worsening roadway conditions. Often the access is limited and the only power source is compressed air. Machines for this duty are generally designed to perform with 100 psi but regularly only half of this is available. This paper seeks to outline the difficulties this situation causes the Rock Bolting Engineer, highlight the technical requirements for a machine of this type to succeed and detail a solution offered by our engineers.

Jan 1, 2007

By Stephen C. Tadolini, John P. McDonnell

"High-strength cable bolts have been used for ground support in underground coal mines for many years. Cable bolts are routinely used as secondary ground support in numerous longwall gateroad support applications, areas that possibly experience the most severe conditions in current underground coal mining. Additionally, when mining ground conditions deteriorate, engineers oftentimes recommend cable supports as a principal solution because of the established credibility for successful ground control. Nevertheless, there is still a reluctance to utilize non-tensioned cable supports as an effective primary roof support alternative.This paper provides historical and recently documented examples of non-tensioned cable supports utilized as an effective primary ground support method in a western U.S. underground coal mine, and it will continue the technical discussion between the differences of various degrees of tension in cable supports with respect to ground behavior and reactions.INTRODUCTIONResin-grouted cable supports are widely used to support difficult ground conditions throughout the world. Through the use of innovative applications and configurations they have proven to be a major paradigm shift in roof support and ground control technology in the U.S. (Tadolini and Koch, 1993; McDonnell et al., 1995; Tadolini and Gallagher, 1994; Tadolini and Trackemas, 1994)Today, the basic cable bolt support consists of a high-strength steel cable installed in bore holes that range in diameter from 25 to 50 mm (1 to 2 in) depending on the strand size and drilling equipment. Cables are offered in both bright and galvanized, for corrosion protection, and range in capacity from about 30 to 60 tons. An example of a resin-grouted cable bolt and the key components is shown in Figure 1. The steel cables are flexible and the support length is not limited by the height of the opening. Lengths of up to 10 m (32 ft) have been supported with high pattern densities when standing supports were not operationally feasible. The most common lengths are 3 to 5 m (10 to 16 ft). An important physical characteristic is that PC-strand has an ASTM minimum elongation requirement of 4%. For comparison purposes, the ASTM 432-08 Standard Specifications for Roof and Rock Bolts and Accessories specifies elongation requirements for traditional roof bolts are a minimum of 12% for grade 40, 9% for grade 60, and 8% for grade 75 materials, respectively. Traditional roof bolts can stretch and elongate twice the length that cable bolts can, which makes design considerations challenging."

Jan 1, 2010

"Above ground, elevated belt conveyors that span more than 200 m (656 ft) between support points can cross valleys, rivers, forests and buildings with a minimal footprint. The cable bridge conveyor (CBC) is a new type of suspension bridge based belt conveyor system that has long spans between support points. It combines a typical belt conveyor and an improved simple suspension bridge to form a conveyor bridge. The improved simple suspension bridge places a widened bridge deck directly on suspended cables, without the need for high truss towers. The benefits include reduced cost and increase aerodynamic stability compared to conventional suspension bridges. The CBC’s compatibility with current belt conveyors allows versatility in application.A belt conveyor is a ubiquitous material handling system. Conveyors can be placed directly on ground or elevated above ground by support structures. Considerations of cost, design, environment, civil work, safety and process requirements are all factors in choosing the ground-based or elevated conveyors (Zhang, 2014). The ground-based conveyor has the lowest structural cost when the conveyor is placed on an existing road. Maintenance access is easy and straightforward. Compared to the groundbased conveyor, the elevated conveyor can cross existing buildings and structures, give passage to traffic beneath the conveyor, has a smaller footprint and requires less civil work to pass mountainous areas. The drawback of the elevated conveyor is higher structural cost, which can be compared with savings in civil work and other benefits. Conventional elevated conveyors are supported by rigid truss-type structures, with a typical span of 15 to 25 m (50 to 82 ft) between concrete support bents or steel trestles. Triangular truss, using steel pipes instead of hot rolled steel sections, is more efficient. The typical span of a triangular truss-supported conveyor is around 30 to 40 m (100 to 130 ft), while the weight is about 10 percent less than conventional box truss with a shorter span (Jennings, 2013).Long-span elevated structures based on suspension bridge is another step forward in increasing the distance between support bents, reaching 100 to 400 m (330 to 1,312 ft) and beyond. The wide distance between the support points of an elevated conveyor offers unique benefits. The conveyor can cross rivers, valleys, highways, forests and other obstacles with minimal footprint and reduced civil work. The versatility from long-span conveyors makes bulk material transportation over previously impossible terrains now a feasible option."

Jan 1, 2014

"Above ground, elevated belt conveyors with span >200m between support points can cross valleys, rivers, forests and buildings with minimal footprint. The Cable Bridge Conveyor is a new type of suspension bridge based belt conveyor system that has long span between support points. It combines typical belt conveyor and the improved simple suspension bridge to form a conveyor bridge. The improved simple suspension bridge places a widened bridge deck directly on suspended cables, without the need for high truss towers. The benefits include reduced cost and increase aerodynamic stability compared to conventional suspension bridges. The Cable Bridge Conveyor’s compatibility with current belt conveyors allows the versatility in application. INTRODUCTION Belt conveyor is a ubiquitous material handling system. Conveyors can be placed directly on ground or elevated above ground by support structures. Considerations of cost, design, environment, civil work, safety and process requirements are all factors in choosing the ground based or elevated conveyors (1). The ground based conveyor has the lowest structural cost, where the conveyor is laying on an existing road. Maintenance access is easy and straight forward. Compared to the ground based conveyor, the elevated conveyor can cross existing buildings and structures, give passage to traffic beneath the conveyor, has smaller footprint, and requires less civil work to pass mountainous areas. The drawback of the elevated conveyor is higher structural cost, which can be compared with savings in civil work and other benefits. Conventional elevated conveyors are supported by rigid truss type structures, with typical span of 15m to 25m between concrete support bents or steel trestles. Triangular truss, using steel pipes instead of hot rolled steel sections, is more efficient. The typical span of triangular truss supported conveyor is around 30m to 40m, while the weight is about 10% less than conventional box truss with shorter span (2). Long span elevated structure based on suspension bridge is another step forward in increasing the distance between support bents, reaching 100m~400m and beyond. The very wide distance between support points of an elevated conveyor offers unique benefits. The conveyor can cross rivers, valleys, highways, forests and other obstacles with minimal footprint and reduced civil work. The versatility from long span conveyors makes bulk material transportation over previously impossible terrains now a feasible option."

Jan 1, 2015

By C. Webb, M. A. Tuck

This paper describes the application of a cable disc elevator to continuous lift ore vertically from underground mines. Application of this system requires the tensions developed within the cable must remain within the carrying capacity of the cable including applicable safety margins. A critical element occurs at starting the system when it is fully loaded which requires the force developed by the system to exceed the static friction forces. This paper describes the laboratory rig developed to investigate the static friction forces. Details of the results of tests on three different ores for both dry and wet conditions are given. These results are discussed.

Nov 19, 2020

By George J. Conroy

Types and causes of short-circuit and open-circuit faults in mine portable trailing cables are discussed, and techniques for locating these faults are described. Time domain reflectometers (TDR) , tone generator, infrared sensing, and high voltage methods are covered. The paper summarizes Bureau of Mines research, including development of a ~DR/tone generator sender with auxiliary probe.

Jan 1, 1975

To find solutions for common safety problems encountered in the handling of trailing cables, based on observations at many different surface mining operations. Approach Practices in handling trailing cables were Investigated through personal visits to over 40 mines, supplemented by visits to cable manufacturers and cable repair service companies. The most effective solutions to the safety problems en-countered were noted and are described In the project final report. Examples are given in this Technology News. Accident Experience Most cable-related injuries occur as a result of workers lifting, pulling, tripping, or being struck by the cable. The Table gives the frequency of occurrence for injuries reported during a recent 3 1/2 year period.

Jan 1, 1982

This paper presents a virtual prototype for the stress analysis of cable shovel components based on combination of flexible and rigid body approach. The general mechanical system of the cable shovel is modeled as a multi-body system with rigid and flexible bodies. The relevant theories applied for the dynamic model are described in terms of Lagrangian multi-body dynamics and finite element method. A virtual prototype of the cable shovel is built in the Automatic Dynamic Analysis Mechanical System (ADAMS) environment, which allows visualizing the motion of general mechanical system and analyzing the dynamic stress of structural components of the cable shovel. An example is given to perform dynamic stress of durability analysis for the boom and handle. Attention of this study is devoted to the mechanisms of damage of the cable shovel and also the critical high stress areas. Keywords: Cable shovel, Von Mises stress, Virtual prototype simulation, Stress virtualization.

Jan 1, 2009

By S. Frimpong

Cable shovels are used for primary excavation in in-situ and/or pre-fragmented formations in surface mining operations. Poorly fragmented hard rock formations and random occurrence of hard boulders in soft formations cause extreme variability of material diggability, resulting in varying shovel stress loading. The stress loading of a shovel’s front-end assembly could result in fatigue failure. Conventional design process, which uses physical shovel simulation studies, is very costly and time consuming for achieving statistically significant results. In this paper, rigid and flexible multi-body dynamic theories are used to develop component stress loading and deformation models of the cable shovel, and solved in the ADAMS/NASTRAN/FLEX environments. Detailed simulation experiments are carried out to examine the performance, reliability, durability and efficiency of the P&H 4100A under varying in-situ formation conditions. The results show areas of high stress fields with a maximum stress of 313.31 MPa at node 441 within the hoist rope. The reliability of the results is confirmed by comparing existing test data. The study is significant because it provides a solid foundation for further study of failure life analysis of the cable shovel components.

Jan 1, 2007

By Ning Shi

This paper suggests an alternative design approach for an innovative shovel dipper, for use in ground conditions where cutting of virgin ground rather than scooping of blasted material is required. Not only does the new design have an optimized dimension ratio (width:height:depth) and attachment arrangement (angle, position), but also a non-linear pro¯le in 2D and 3D. The approach is based on the simulation of a shovel's duty cycle to verify a pilot dipper model. In order to achieve a realistic simulation that could be used to evaluate a dipper design, the model is e®ectively a descriptor of actual shovel activity under soft ground conditions. The shovel geometry, motion and operation, with an emphasis on digging and dumping kinematics and dynamics are the principal elements of the simulation. The simulation considers a fresh face location, repeating tucking, digging and dumping swing motions within the geometric range of the machine, ending when no more face material remaining within reach without re- positioning. The simulation yields digging force, friction force, trajectory, ¯ll time, ¯ll factor, etc, which may be integrated into two basic considerations: power draw (output) and volume delivered (production), as indicators of dipper performance. The simulation has been used as a tool to modify an existing dipper design, prior to looping further simulation cycles. Ultimately, an optimized or totally-new-concept shape is realized. A prototype dipper as a fractional scale model will be built to verity the performance under actual mining conditions.

May 1, 2004

By Brian R. Castle, James J. Scott

INTRODUCTION Referring to a ground support system as a 'band-aid' borders on getting cute, but the application of cable slings in U.S. mining is somewhat analogous. Where problems in the roof or rib require additional support, the versatile cable sling is the answer in a variety of conditions. To fully understand how and why cable slings are used today we must briefly review their development history. Much of the thrust over the last five to seven years in ground support fixtures has been the development of hybrid systems. Taking the best of two or more existing roof bolt fixtures and marrying them into a new fixture which exhibits the good characteristics without the bad of the parent systems. Resin point anchored mechanical bolts, continuous threaded rebar bolts, and others have all be- come important fixtures in rock mass stabilization. HYBRID GROUND SUPPORT SYSTEM The cable sling system is also a hybrid, both in its parentage and in its ground support characteristics. See figure 1. Cable slings combine the techniques of cement. grouting high-strength cables, Friction Rock Stabilizers, and truss-like suspension into a versatile and high- strength ground support system. 1/2" high-strength cable is cement grouted in place in a manner similar to pre-

Jan 1, 1983

By Dennis R. Dolinar, Lewis A. Martin

Cable bolt technology used by the U.S. coal industry was developed to a large extent in the 1990s. Today, these cable systems include both cable bolts and cable trusses to provide supplemental and secondary support in gate roads. This cable technology is significantly different than the cable systems in use in either U.S. hard-rock mines or Australian coal mines. Development of this technology was initiated and spurred by research efforts of the U.S. Bureau of Mines, and has continued under the health and safety programs of the National Institute for Occupational Safety and Health (NIOSH). It was also followed up by work of roof support manufacturers to create an essentially new support system. In this paper, the important support characteristics of both cable bolts and cable trusses are discussed. The design of cable systems and the basis for that design for tailgate and headgate situations are reviewed and explained. Case histories are presented on the application of these support systems based on experience gained at a number of in situ test sites.

Jan 10, 2000

By Stephen C. Tadolini

The U.S. Bureau of Mines, in cooperation with the Cyprus- Plateau Mining Company, has conducted research to provide an alternative to traditional secondary support systems in a two-entry, yield pillar gate road. As recent as two years ago, it was impossible to imagine a gate road supported solely with internal high-strength resin-grouted cable supports that would virtually eliminate the necessity for crib or concrete external supports. The support system evaluated consisted of 1.6-m (5-ft) full-column resin-grouted bolts and 4.8-m (164) long cable supports installed in conjunction with wire mesh and "monster-mats." Cable loading and roof deformations were monitored to evaluate the behavior of the immediate and main roofs during first and second panel extractions. The stress and loading histories for the panels and yield pillar were monitored to evaluate the stress transfer and pillar performance in conjunction with the roof and floor behavior. The test results indicated that the designed support system successfully maintained the roof during the extraction of two longwall panels and dramatically reduced the cost of secondary support. This paper will describe the theory of a cribless support system, the advantages of cable supports, and present the pillar, roof, and floor measurements made to assess the support performance during longwall retreat mining.

Jan 1, 1995

By Stephen C. Tadolini

Cable supports offer several advantages over traditional secondary support methods. Cable supports enhance stress redistribution to pillars and gob areas, minimize or eliminate timbers and cribs which reduce ventilation capabilities, eradicate material handling injuries related to the placement of crib supports, and provide a cost-effective alternative to secondary support. The U.S. Bureau of Mines has designed and installed cable supports to improve the stability of tailgate entries in an underground western coal mine. Two entries closest to the Iongwall panel were solely supported with high-strength cables installed with cement grout. Basically, with modifications in the intersections, 360 ft of roadway nearest the longwall panel was supported with two rows of 22-ft-long cables installed on a 7-ft spacing. Approximately 250 ft of a second bleeder entry was supported with two rows of 16-ft¬long cables installed on a 7-ft spacing. Individual cable loads were monitored with hydraulic U-cells and pressure pads. The roof behavior was simultaneously monitored with differential magnetic sag stations and closure meters on 25-ft spacing during longwall panel retreat to evaluate the response of the immediate and main roofs. Cable supported gateroads appear to be a viable alternative in secondary support when compared to wood timbers and cribs. This paper describes the theory, application, and advantages of cable supports and presents the results of the mine measurements made to assess the cable performance during the retreat process of longwall mining.

Jan 1, 1993

By P Ridley

EnergyAustralia’s Sydney Central Business District (CBD) cable tunnel network will form a loop 6.2 km in length. The 3.2 km long, 3.5 m, diameter city east cable tunnel (CECT) currently in design, will complete the loop in 2014. This paper discusses the ventilation design of the CECT, considering operation for four functions:1. normal (unmanned),2. access (manned),3. purge, and4. emergency fire modes.The dominant design criterion which determines the required ventilation capacity for CECT is the specification of an upper air temperature limits of 35°C (dry bulb) and 24°C (wet bulb) for manned access, during all ambient weather conditions and cable heating loads. Simplistic static heat transfer analyses do not yield a sufficiently accurate calculation of tunnel air temperature and humidity to provide a safe and yet economical design. The primary refinement in the analysis discussed in this paper is associated with modelling of the system’s dynamic behaviour.Our means of analysis is through a thermo-fluid-dynamic simulation of the interactions between the diurnally and seasonally varying loads (cable heat generation, ambient air conditions and groundwater inflow), tunnel airflow and the resulting tunnel air temperature and humidity. These simulations are validated using experimental data from the existing city south and city west cable tunnels.Fire life safety scenarios are also analysed and discussed in association with the ventilation design. Ventilation strategies are developed for dealing with such emergency fire situations.The understanding and insight provided by the work offers the ability to optimise ventilation plant provisions in future cable tunnels, particularly long and high energy density tunnels.

Mar 8, 2011

By G. J. Conroy

Cable whip occurring during normal movement of a shuttle car can result in a personnel hazard and excessive tensions in the cable. This Bureau of Mines report discusses preferred payout and reel-in torque settings to reduce cable whip. A simplified adjustment procedure is described.

Jan 1, 1974

Hang ventilating air curtains so that they can be installed, moved, opened and closed more easily than curtains that are spadded or nailed in place. Approach Low-leakage plastic curtains fitted with grommets along the top were threaded onto a steel cable which is suspended from roof bolt plates. The system was tested in two mines. How It Works The curtains are threaded onto a steel cable which is suspended from roof bolt plates by S-shaped hooks. See Figure 1. The outby end of the cable is reeled off a hand operated winch; the inby end of the cable is anchored to a roof bolt plate by means of a cable grip and an S-shaped hook. To install the curtains the following procedure is used. First, the winch is located at least 5 feet outby the last open cross-cut. The base of the winch can be secured to the mine roof with short roof bolts, only about a foot long.

Jan 1, 1978

By Matthew J. Hrebar

SINCE the first installation in 1936, the use of rubber-tired equipment for secondary mine haulage has increased rapidly. From August 1936 to January 1944, approximately 750 rubber-tired units were placed in operation. Of these, 650 units were installed after January 1940. During the year 1941, it per cent of the mobile loaded bituminous tonnage was hauled by rubber-tired equipment. This percentage increased to about 20 per cent during 1943. The first rubber-tired units were battery-powered tractor-trailer types. In the year 1938 the battery-powered self-contained car was introduced. In 1939, the cable-powered self-contained car made its appearance. These self-contained units are our modern "shuttle cars." By the end of 1941, approximately 15 per cent of the shuttle cars in operation were cable-powered. Installations made during 1942 and 1943 increased the proportion of cable-powered cars to about 40 per cent of the total number of shuttle cars in use. There is a marked trend toward cable-powered cars, although one need not make many trips to mines where both types are used to discover that opinions are highly controversial as to the relative advantages and field of use of each type. It is natural for mining engineers in the coal-mining industry to have diversified opinions regarding the use and application of coal-mining machinery. Coal mining is not a standardized industry; natural conditions vary from mine to mine. However, it is surprising how many operations in scattered fields arrive at the same conclusions and adopt similar methods. This happens not so much through cooperation and exchange of ideas as through hard, costly experimentation, involving months of low production and relatively high costs. What then, are the reasons for increased use of cable cars? Could it be that present scarcity of materials is forcing their use? True, battery cars require considerably more auxiliary equipment, but during 1942 it was no more difficult to obtain than shuttle-car cable. Furthermore, the trend toward cable cars started before curtailments on mining equipment took effect. Undoubtedly, cable-reel shuttle cars were introduced to produce coal at a lower cost by simplifying trackless mining through the elimination of auxiliary equipment, and by reducing the first cost on equipment. The theory of cable-powered shuttle cars is well based, as can be proved by successful operations. Many operators have weighed the advantages and disadvantages of each type carefully before choosing the type most suitable to their operation. Others have taken much for granted and accepted one or the other without much thought. At many small operations, low first cost is apt to be the deciding factor. One large company, with considerable experience in the use of battery locomotives, preferred to use cable cars even though it was neces¬sary to reduce the section voltage from

Jan 1, 1944

By M. A. Raza

Cable shovels are capital-expensive and primary production equipment in many surface mines. The forces acting on the shovel dipper vary as the dipper moves through the muck-pile. The variations in the forces cause stress loading of the components of shovel and dipper resulting in unplanned downtimes, reduced shovel efficiency, and high mining costs. A potential solution to the above problems is the deployment of an intelligent shovel excavation (ISE) technology, with real-time formation identification, recording, and knowledge transmission capabilities. This research advances the ISE technology by developing dynamic model of cable shovel dipper using Newton-Euler techniques. The model includes the dynamic cutting and dynamic weight forces acting on the dipper as it moves through the muck-pile.

Jan 1, 2011