Underground

3D Stress Effects of Longwall Caving as Revealed by Microseismic Monitoring

The use of microseismic monitoring to resolve caving issues and to provide warning of weightings, windblasts and other caving related problems has been demonstrated by a number of ACARP and industry funded projects. In this, the latest project, the direct association between microseismic ....  read more

ACARP Scholarship - A Method for the Design of Longwall Gateroad Roof Support

A longwall gateroad roof support design method for roadway development and panel extraction is demonstrated. It is a hybrid numerical and empirical method called Gateroad Roof Support Model (GRSM), where specification of roof support comes from charts or equations. GRSM defines suggested roof ....  read more

Anchorage and Failure Mechanisms of Fully Encapsulated Rockbolts: Stage 2

The results of this second stage project have contributed to the state of knowledge and further understanding of the mechanics of fully encapsulated or full column rockbolts (FERB). The project included several investigations intended to improve current rockbolting practices in the field ....  read more

Applicability of Measurement While Drilling Concept on Characterising Coal Mine Roof

Underground roadways in coal mines are critical to maintain continuous production of coal. Roadways need to be stable, reliable and functional. One cause of roof instability in underground coal mines is inadequate roof support due to insufficient geological and geotechnical information. ....  read more

Application of 50 to 60 Tonne Cable Pre-Loads to Roof Control in Difficult Ground Conditions

This project has successfully met all aspects of the following original objective: "to establish a package of existing technology items that allows the installation and pre-loading of cable tendons in the range of 50 to 60 tonnes and to conduct installation trials and basic field evaluations in ....  read more

Assessment of Convergence Based Roof Support Design For Longwall Abutment Loads

The aim of Stage two of project C24015 was to develop a roof support design approach that takes account of differing roof conditions, effect of support type and stiffness that can be used for mine design and in the strata management process. An analytical framework was developed for roadway ....  read more

Assessment of Longwall Mining Induced Connective Fracturing

In underground mines the mining induced permeability change in the overburden is the single most important factor that impacts water and gas flow. Empirical estimates of mining induced permeability change are inaccurate. This project aimed to quantify the permeability change resulting from ....  read more

Assessment of Longwall Mining Induced Connective Fracturing of Overburden Strata

As the Australian mining industry operates under strict environmental accountability, the ability to reliably predict and manage mining-induced water inflows and aquifer interference is critically important. Estimating the height of longwall mining-induced fracturing and the height of complete ....  read more

Assessment of Mine Roof Integrity

A prototype tool has been developed to allow testing for instability and zones of weakness in a mine roof. The tool measures the velocity of a seismic wave passing through the rock mass. In general  ....  read more

Automatic Real Time Assessment of Windblast Risk

The main objective of this project was to automatically assess the risk of experiencing a windblast in a longwall operation. The logical extension of the risk assessment was the automatic generation of an alarm should the risk exceed pre-determined levels.

Certain conditions need to ....  read more

Carbolt Self Monitored, Yieldable Carbon Fibre Cable Bolt for Ground Control

In general, there is a variety of rockbolts and roof support systems available on the market for mines to choose from. The most common type is the rock bolt, which consists of a metal rod with an anchoring component and a face plate. Some bolts are manufactured out of glass fibre reinforced ....  read more

Coal Destressing - Implications and Opportunities for Moderate to Deep Mines

The phenomena of coal shrinkage due to gas desorption is well-known in the field of coal gas testing.  The impact of this on roadway stability has not been widely recognised, as in the past most gassy seams were relatively thin (<3m) and the roof and floor were typically ....  read more

Coal Geomechanics Review - Scoping Study

On the recommendation of the Underground Research Sub-Committee, ACARP commissioned Golder Associates Pty Ltd to carry out a review of ACARP's underground geomechanics-related research with Professor E T Brown AC as the nominated reviewer. The objective was "to ....  read more

Consolidation Grouting of Fault Zones in Longwall Mines

Structurally related falls on the southern longwalls at North Goonyella Coal Mine are a continuing problem. Geotechnical monitoring, primary/secondary support design systems, in combination with standard Face Management Systems have helped reduce the number of fall events. NGCM's current ....  read more

Cost Effective Use of PUR and Optimising Large-Scale Injected Strata Reinforcement

The project arose from a recognition that both small-scale and large-scale injected strata reinforcement techniques have the potential to play significant roles within the coal mining industry where the preferred support methods such as tendons, standing support and face powered supports ....  read more

Definition of Coal Mine Roadway Roof Failure Mechanisms

The aim of this report is to discuss the roof failure mechanisms in development roadways within coal mines. This is achieved by a discussion of failure modes within the rock mass and how they interact to cause the commonly observed gross deformation of the roof.

The commonly observed ....  read more

Detection of Incompetent Mine Roof Stage 2

This document reports on the work undertaken during 1996 as the second part of a project aimed at developing new technology to aid the reliable and objective evaluation of roof conditions in underground coal mines. Of particular concern are mines with conglomerate roofs, as found in the Great ....  read more

Determination of Stress Relaxation in Drill Core Using Laser Micrometry

This project brings together two techniques as a relatively cheap and rapid means of assessing underground horizontal stress conditions. These techniques are measurement of drill core relaxation using a laser micrometer and core orientation using palaeomagnetism. Drill core able to be ....  read more

Developing Prevention Techniques for Stress Corrosion Cracking Failures of Rock and Cable Bolts

In the past two decades, there has been a notable increase in reports on Stress Corrosion Cracking (SCC) failures of rockbolts and cable bolts in Australian underground coal mines. This trend is not limited to Australia, as similar failures have been reported in underground coal mines where ....  read more

Development of a Numerical Modelling Approach to Better Understand the Effect of Cable Bolt Performance on Roof Failure Mechanisms in Varying Rock Mass Conditions

This project provides an improved numerical modelling approach to enhance mine safety, increase productivity and reduce costs via fit-for-purpose designs and more effective applications of cable bolts in different geotechnical environments. The project objective was to better understand the ....  read more

Development of an Intrinsically Safe, Integrated Wireless Communications Network with a Distributed Array of Geotechnical Sensors

For over 20 years, SCT Operations (SCT) have provided a range of industry standard geotechnical instrumentation, including Tell-Tales (Rock-IT/Clock-IT), instrumented bolts, three dimensional stress monitoring cells and shear strips. This project outlines the development of a wireless enabled ....  read more

Development of Borehole Shear Monitoring Device for Routine Application in Coal Mine Roadways

This project outlines the development of a cost effective, routine shear monitoring instrument for deployment in ungrouted boreholes. The system will be based on an existing MEMS (Micro Electrical Mechanical Systems) sensor from Holville that is certified (IECEx 12.0034X) intrinsically safe ....  read more

Development of Hydraulic Fracturing to Control Windblast

This project was conceived following the first successful application of hydraulic fracturing to control caving at Moonee Colliery. The routine use of hydraulic fracturing at Moonee has provided a unique opportunity for development and refinement of hydraulic fracturing technique in a mining ....  read more

Development Of New Testing Procedure For The Assessment Of Resin Performance For Improved Encapsulated Roof Bolt Installation In Coal Mines

In underground coal mining, the resin bond between the rock bolt and the strata is one of the critical elements of a roof bolting system, yet the Australian coal industry does not have an agreed standard for bolting system evaluation. A program of field and laboratory studies was undertaken to ....  read more

Dynamic Response Of Longwall Systems And Their Relationship To Caving Behaviour

Massive strata overburden units are known to influence support loading on longwall faces. Past studies of the conglomerates in NSW and sandstones in Qld have identified factors such as unit thickness, proximity to coal seam, immediate roof strength and panel width that may all play a role in ....  read more

Dynamics of Wind Blasts in Underground Coal Mines

In some underground coal mines where the roof comprises strong and massive rock, the roof strata do not cave regularly as extraction progresses but 'hang up', leading to extensive areas of unsupported roof. These areas can collapse, suddenly and often without warning, compressing the  ....  read more

Effectiveness of Shotcrete in Underground Coal Mines

The primary objective of this project is to quantify the effectiveness, applications, and benefits of shotcrete in underground coal mines. Shotcrete refers to a ground-support system that is pneumatically sprayed, typically onto the exposed surface of an excavation face, to produce a compacted ....  read more

Electromagnetic Emissions Monitoring to Warn of Wind Blasts and Gas Outs

Electromagnetic signals are emitted by rocks as they fracture, in much the same way as acoustic signals, but by different processes and with different characteristics. The object of this project was to evaluate the potential usefulness of the emissions (EME) as warning signals, to complement ....  read more

Engineered Mine Design in Soft Strata Environments - Geomechanical Behaviour of Soft Floor Strata in Underground Coal Mines

The work described in this thesis has been concerned with investigating the geomechanical behaviour of soft floor strata in underground coal mines, especially in the context of bord and pillar layouts. Many cases of significant  ....  read more

Establishing Anchorage and Failure Mechanisms of Fully Encapsulated Roof Support Systems

The Australian underground coal mining industry consumes 5 to 6 million rock bolts per annum. It has been independently concluded that between 30%-35% do not perform to specification. This represents an annual expenditure of $35-$40 million. There are no standardised methods for assessing rock ....  read more

Establishing the Strength of Irregular and Rectangular Pillars

The publication in 1995 of the UNSW Pillar Design Methodology provided the Australian coal industry with a tool for designing square shaped coal pillars to a high degree of ....  read more

Evaluation of the Chinese Outburst Assessment Methodology and Its Applicability to Australian Low Permeability Coal Seams

Australian coal mines use gas content as the primary index for assessing outburst propensity and risks, with gas composition, coal types and the presence of structures taken into consideration. This approach has been effective in preventing fatal outbursts over the years. However, as mining ....  read more

Floor Stability – A comprehensive investigation into failure mechanisms and controlling factors

Several underground coal mines in Australia have been experiencing excessive floor deformation in roadways, better known as floor heave. Although the phenomenon does not generally have safety implications, unexpected floor heave can cause financial losses due to production delays. The modes of ....  read more

Geophysical Assessment of Fracture Grouting

There are very high safety and production risks associated with mining through any weak zone associated with a fault or fractures. The mining industry seeks to reduce this by using fine, high pressure grouting techniques to stabilise such geomechnically weak zones. However considerable ....  read more

Geotechnical Design of Roof Support and Reinforcement

The aim of this project was to develop an engineering design methodology for roof support so that alternative bolting strategies can be compared qualitatively in terms of productivity, cost, safety, and risk. Such a design methodology will provide a framework to assess development rate ....  read more

Ground Engineering - Principles and Practices for Underground Coal Mining

This text is not published via the ACARP website.  It is available from Springer: http://www.springer.com/gp/book/9783319250038

ACARP was pleased to support Emeritus Professor ....  read more

High Tensile Strength Support and Ventilation Membrane

During a 1997 ACARP-funded mission to South Africa, an acrylic-based polymer membrane called Evermine (formerly known as Everbond) was identified as having considerable potential for Australian coal mining environments. Evermine was developed in South Africa for the CSIR Mining Technology ....  read more

Hydraulic Fracturing in Coal Mining

This project was conceived as a follow up to ACARP Project C9024 “Development of Hydraulic Fracturing to Control Windblast” which focussed on the experience of successfully introducing hydraulic fracturing to control windblast at Moonee Colliery. A range of potential ....  read more

Improving Cavity Prediction on Longwall Faces Through a Combination of Reliable Convergence, Canopy Attitude and Leg Pressure Monitoring

Most Australian coal mines have shield leg pressure monitoring in real time to aid the identification and remediation of roof control problems and to assist in the identification of faulty legs and yield valves. Newer longwalls are now equipped with tilt sensors that allow convergence ....  read more

Improving Safety & Performance of Timber Chock Constructions

Timber chocks are used on a systematic basis to support longwall tailgate roadways by 13 Australian longwall operators. At least five other operators use timber chocks on an as-needed basis. Typically, it requires about 80 acres of Australian hardwood forest to supply enough timber to chock one ....  read more

Improving the Up-time Efficiency of Roadway Development Units by the Use of Reduced Primary Bolting Densities and Routine Secondary Support

This ACARP project sought to demonstrate that significant improvements could be obtained in the up-time efficiency of longwall gate road development units by optimising roof support practices and utilising improved support technology. The project built on the results of earlier ACARP-sponsored ....  read more

Integrating In-Situ Stress Patterns with Basin to Local Scale Structures in the Nebo Synclinorium, Bowen Basin

Understanding the regional to local variability of stress field should be the starting point for mine design and practices because the stresses control the geotechnical behaviour and ground conditions of mine sites. The state of stress in most of the Australian basins is well understood. ....  read more

Investigation Into Roadway Roof Support Design Using the Geophysics Strata Rating

This project was aimed to investigate methods of using roof monitoring data in combination with geophysics based models of strata conditions for roadway roof support design. The project has enabled development of an analytical model/graphical technique that provides a measure of both support ....  read more

Longwall Rock Mechanics In Massive Strata

This report provides a description of the problems associated with mining in geotechnically massive strata. This is backed up with some cases drawn from the literature. The emphasis is then given to outlining the processes to determine what makes strata behave in a massive manner. This ....  read more

Mapping of Tensile Failures in Longwall Mining through New Microseismic Procedures

The objectives of the project were to develop new microseismic methods to map tensile microseismic events round operating longwalls, and apply the new methods to the data set collected from microseismic monitoring projects already undertaken by CSIRO.

Methods of noise filtering in the ....  read more

Maximising In-Situ Stress Measurement Data from Borehole Breakout using Acoustic Scanner & Wireline Tools

The role of horizontal stress in affecting strata behaviour in underground coal mines has been well documented. In Australia, the nature and depth of the underground coal resources has resulted in high levels of horizontal stress, typically 2-3 times the vertical stress, and up ....  read more

Measuring the Height of Fracturing above Extracted Longwall Panels to Improve Reliability of Groundwater Impact Predictions

Longwall mining is a mining method widely used in the Australian underground coal industry. The disturbance to the strata overlying the mining horizon caused by longwall mining is recognised to impact the groundwater system and, in some cases, surface water systems as well. This project aimed ....  read more

Mechanical Behaviour of Reinforcement Elements Subjected to Shear

Strata control is one of the core risk areas in underground coal mining. The use of appropriate technology for ground support whether it be roof or ribs, primary or secondary and the effective management of this technology can be pivotal to achieving a safe and economical viable mining ....  read more

Modelling the onset of fracture-induced instabilities for underground mining operations

The propagation of fractures in coal seams and the surrounding rock mass can lead to instability at the face of longwalls or roof and ribs of underground roadways, resulting in injuries or delays to mining operations. In practice, bolt and cable systems are widely used to prevent roof failures ....  read more

Monitoring System for Improved Roof Management

This project concerns the development of a new instrument that is cheap, reliable and capable of routinely determining accurately strata shear deformation. Data from this shear monitor can be used to help assess support performance under changing geological and loading conditions.

The ....  read more

Multi Seam Layout Guidelines and Feasibility of Partial Chain Pillar Removal

Australian coal deposits commonly have coal seams in close proximity, however over recent times, underground mining has typically concentrated on the single seam mining of the most economic seam. The proximity of seams within the Hunter Valley in particular, lends ....  read more

Optimisation of Roof Bolt Length Based on Improved Resin Performance

This study compared the performance of two types of resin capsules used for full encapsulation of roof bolts in underground coal mines. The first, a 15:1 mastic to catalyst capsule which is the predominant system used in Australian mines, despite some well-documented problems. The second, a ....  read more

Optimising the Selection of Fully Grouted Cable Bolts in Varying Geotechnical Environments

The primary objective of this research project was to develop a laboratory-scale test facility in Australia that can be used to determine the behaviour and assess the load transfer performance of fully grouted cable bolts under axial loading conditions. The facility had to be capable of testing ....  read more

Performance and Cost Effectiveness of Timber Chock Construction

Eleven Australian longwall operators systematically support longwall tailgates with timber chocks. Average annual expenditure is approximately $180,000 with one operator expending over $500,000/annum on  ....  read more

Performance Evaluation of Flexibolt Flexible Roof Bolts

The FLEXIBOLT flexible roof bolt was initially developed under NERDDC Project 1334. A number of collieries expressed interest in further development of the FLEXIBOLT so it could be applied as either long (>3m) or short tendons in the production environment.  To this end the project ....  read more

Performance of Cable Bolts Under Axial Loading Subjected to Varying Geotechnical Conditions

This project contributes to an improvement in mining geomechanics through better understanding by geotechnical engineers of the behaviour of different types of cable bolts leading to more informed decision-making in the design of ground control systems leading to a safer working environment. ....  read more

Premature Rock Bolt Failure

This project was initiated in 1999 to address the observed phenomenon of premature failure of rock bolts in a number of Australian collieries, and with a particular focus on the problem of Stress Corrosion Cracking (SCC) in rock bolts. SCC occurs by the slow progressive growth of stress ....  read more

Premature Rock Bolt Failure: Stage 2

A previously funded ACARP project (C8008), conducted by the same collaborative research team, investigated the problem of premature failure of rock bolts due to stress corrosion cracking. That project was reported in April, 2002.

Stress corrosion cracking is defined, in ....  read more

Prestressing of Strands to Improve Cable Performance

High load capacity cable bolts and Flexibolts have the potential to be pretensioned to relatively high loads of 30 tonnes while still allowing further roof deformation and bolt loads to increase before  ....  read more

Real-time Rockmass Response from Microseismics

Microseismics is routinely used in hard-rock mines as a hazard-management tool for rockbursts. Its use in coal, however, has been limited by the challenges of seismic propagation in a coal environment. CSIRO, with support from ACARP and the industry, has been working to adapt the technique for ....  read more

Real-time Seismic Roof Condition Mapping Ahead of Longwall Mining

Poor roof conditions in a coal mine longwall panel may result in rock collapse. This can cause significant interruption to mine production. The ability to image roof conditions - stress and degree of fracturing - ahead of the face gives the mine the opportunity to proactively respond to such ....  read more

Reducing the Hazard of Windblast in Underground Coal Mines

Wind blast in coal mines and its equivalent, air blast, in metalliferous mines have been of concern to the Australian underground mining industry for many years. Although the most recent fatality due to wind blast in a coal mine took place in 1976 at Eastern Main Colliery, incidents involving ....  read more

Reducing the Subjectivity of CMRR Calculation Using Machine Learning

The Coal Mine Roof Rating (CMRR) is a key input parameter for roof support design. This work aims to reduce the subjectivity of CMRR calculation by integrating geophysical logging data and laboratory data through the application of advanced machine learning algorithms, and to apply the ....  read more

Reinforcement Techniques for Weak Rock

The objectives of this project were to define the application of alternate reinforcement and support strategies for the stabilisation of weak strata.

They were achieved ....  read more

Reliable Estimation of Horizontal Stress Magnitudes from Borehole Breakout Data

STAGE TWO

The primary objective of this stage of the project was to develop a simple and reliable method to predict in situ horizontal stress magnitudes from existing borehole breakout data. In situ stresses are always crucial parameters for engineering designs and underground ....  read more

Review of Barrier Pillar, Bleeder, Chain Pillars in Weak Strata and Thick Coal

Prior to the commencement of this project, a number of mine sites had experienced adverse conditions in roadways in the vicinity of goafs.  These adverse conditions could not be easily explained with the understanding of strata behaviour at that time.

The strata  ....  read more

Review of Rib Failure Mechanisms in Underground Coal Mines

This project consisted of field measurement of rib deformation including monitoring of rib bolt loads and rib yield characteristics using a range of measurement techniques. The project aimed to assess the effectiveness of current industry rib support patterns with regards to the nature of rib ....  read more

Rib Support Design Methodology for Australian Collieries

The aim of this project was to provide the Australian coal industry with a rib support design methodology and computer based design tool that can be utilised by colliery engineers and geologists who have sufficient experience and training in relation to underground ....  read more

Roadway Roof Stability and Its Attainment through Pre-Tensioned Bolting

This report contains details of four small scale field trials of pretensioned roof bolting, achieved by the incorporation of a thrust bearing as a fraction washer between the dome washer and nut of a roof bolt head assembly.

The ....  read more

Roadway Stability Monitoring System

This report describes the outcomes of a project that focussed on the development and trialling of a unique radar sensing technology to monitor roadway deformation in underground coal mines.

The development of technology capable of accurate and reliable monitoring of continuous regions ....  read more

Roadway Stability Monitoring System

This report describes the outcomes a project that focussed on the next phase of development of a radar sensing technology designed to monitor roadway deformation in underground coal mines. The previous project, C25062, developed and trialled a proof-of-concept system. The primary goal of this ....  read more

Roof and Goaf Monitoring for Strata Control in Longwall Mining

The application of seismic monitoring techniques in Australian coal mining has been tested by a seismic monitoring study carried out at Gordonstone Mine. The intention was to map the extent of fracturing associated with longwall mining in the  ....  read more

Roof Condition Monitoring Ahead of a Longwall Face: Phase 1 - Initial Assessment and Experimental Tr

The trend of longwall coal mining goes to longer and wider longwall panels for more production. The exhaustion of coal resources near the surface forces the panels to go deeper into higher stressed and more geologically complicated environments. Implementing tougher safety regulations requires ....  read more

Shear Testing of the Major Australian Cable Bolts Under Different Pretension Loads

This report deals with shear testing of the major Australian cable bolt types using the Megabolt Integrated Single Shear Testing Rig (MISSTR). The MISSTR apparatus was selected to determine the cable shear strength values and to evaluate the debonding characteristics of various profiled cable ....  read more

Standing Support - It's Time for an Engineered Solution

This project was commissioned to develop a better understanding of the underlying strata mechanics of high deformation tailgate environments and to determine the required engineering characteristics of artificial supports to control such environments.

The project findings ....  read more

Subsidence Control Using Coal Washery Waste

This report is the final report of the ACARP project - C16023 Subsidence Control Using Coal Washery Waste. The main objective of this project is to provide technical knowledge to support a trial of overburden grout injection technology to control mine subsidence in an Australian mine. The ....  read more

System for Early Prediction of Catastrophic Roof Failure

The project aims to develop a system to measure, on a routine basis, the horizontal pressure acting through the roof strata of underground coal mine roadways. This  ....  read more

Systems Approach to Pillar Design

The Australian coal mining industry, through AMIRA, JCB and ACARP have funded research into pillar design methods for over 10 years with several million dollars worth of industry funds expended.

As a result of the research projects, several approaches to pillar design have evolved ....  read more

Underground Thick Seam Rib Support Using Active Reinforcement Stage 3

Active rib bolting has been evaluated as a means of improving rib support effectiveness and reducing bolt densities in high gateroads. This project (Stage 3) has demonstrated that pre-loading rib bolts does  ....  read more

Understanding and quantifying the hydraulic characteristics of the overburden

Quantifying the hydraulic characteristics of the longwall overburden and surrounding surficial area that is influenced by the longwall extraction is crucial to determining the impact of mining on the local groundwater and surface water systems, understanding water flows to the mine workings ....  read more

Update of Stress Concentration Effects About Longwall panels for Improved Mine Planning

Recognition of horizontal stress concentrations about longwall panels was made during the 1980's and 90's. The nature and factors which influence the stress concentration has become more apparent with further

experience and study of the phenomenon in a wider range of geotechnical ....  read more

Use of Pro-active Resin or Grout Injection for Roadway Stabilisation by Promoting Improved Rock Mass Competence

This project addressed and evaluated a basic hypothesis, namely that the early injection of material into open bedding planes in the roof of a mine roadway that would substantially adhere to the rock, would have significant reinforcing benefits, the impetus for the project being published ....  read more

User Friendly Computer Program for Modelling Fracture Induced Instabilities in Underground Mining Environments

The propagation of fractures in coal seams and the surrounding rock mass can lead to instability at the face of longwalls or roof and ribs of underground roadways, resulting in injuries or delays to mining operations. In practice, bolt and cable systems are widely used to prevent roof failures ....  read more

Wind Blast and Methane Expulsion: Extension of Field Monitoring to Generalise the Results of Projects C7031 and C8017

Caving is a fundamental aspect of most modern underground coal mining operations. However, in some mines where the roof comprises strong and massive rock, caving does not occur readily, resulting in an extensive mass of unsupported rock spanning a large void in the goaf. Such a 'hang up' may ....  read more