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By Denise Mueller, Axel Preusse

"In 2010, the fracking discussion in Germany caused a number of changes in German law, which came into force in 2016. Especially the production of gas had to be regulated. With the legislation amendment, the “Subsidence-Area Mining Regulation” (in German: Einwirkungsbereichs-Bergverordnung) has been revised, too. The changes expand the compensation of mining damages, especially to the extraction with drilling from the surface and underground storage. Although the “Subsidence-Area Mining Regulation” has been revised, the area of main influence (subsidence of 10 cm) remains to determine a relevant boundary for mining damages. The determination and prediction of this boundary above caverns are presented in this paper. In addition, further elements of ground movements and their relevance to mine damages are analyzed. The usage of the area of main influence to fix a relevant boundary for mining damages does not correspond to the relevant elements of ground movements. A limit for differences in subsidence (tilt) or horizontal changes in length should be preferred to describe the relevance of mining damages on buildings. Furthermore, this paper outlines the the meaning of using the area of main influence to fix a relevant boundary for mining damages. INTRODUCTION The “Federal Mining Act” (in German: Bundesberggesetz, short: BBergG) forms the central legal standard to cover subsidence in Germany. The mining authority refers to the following regulations (Preuße et al., 2015): the “Subsidence-Area Mining Regulation” (in German: Einwirkungsbergverordnung, short: EinwirkungsBergV; since 1982) the “Mine-Surveyor Mining Regulation” (in German: Markscheider-Bergverordnung; short: MarkschBergV) the “Deep-Drilling Regulation”"

Jan 1, 2017

By Arthur Miller, Andrew Weakley, Heather E. Lawson

"IntroductionDynamic failure events in an underground coal mine, or “bumps,” are defined as “the sudden, violent bursts of coal from a pillar or pillars or a block of coal, resulting in a section, the whole pillars, or the solid block of coal being thrown into an open entry” (Peng, 2008). Reports of disastrous and often fatal dynamic failure events date back over one hundred years in the United States. Mining practices and technologies have significantly evolved over the course of the last century, yet these events continue to occur. The events at Crandall Canyon, Utah (Gates et al., 2007) and Brody No. 1 Mine in West Virginia (Barker and McNeely, 2014) are two recent failure events that resulted in a total of eleven fatalities. These events testify to the fact that dynamic failure remains an imperative safety concern. Furthermore, their continued occurrences indicate that engineering controls have proven inadequate at wholly mitigating the problem.Multiple conditions have been associated with the occurrence of dynamic failure phenomena, including• thick, competent strata that can create a bridging effect, resulting in high abutment stresses (Rice, 1935; Holland and Thomas, 1954; Iannacchione and Zelanko, 1995; Agapito and Goodrich, 2000; Peng, 2008; Whyatt, 2008; Whyatt and Varley, 2010)• overburden thicknesses greater than 500–700 ft. (Rice, 1935; Peng, 2008)• a strong coal that is resistant to crushing (Rice, 1935; Peng,2008) or that is “uncleated or poorly cleated, strong…sustains high stress and tends to fail suddenly” (Agapito and Goodrich, 2000)• the presence of sandstone channels or rolls that can serve to concentrate stresses (Iannachione and Zelanko, 1995; Agapito and Goodrich, 2000)• fracturing of strong units above or below the coal seam (Whyatt and Varley, 2010)• slip along pre-existing discontinuities (Peperakis, 1958; Whyatt and Varley, 2010)• multiple seam mining interactions (Campoli, Kertis, and Goode, 1987; Iannachione and Zelanko, 1995; Newman, 2002; Peng, 2008)• mining sequences that can cause anomalously high stress concentrations (Campoli, Kertis, and Goode, 1987; Iannachione and Zelanko, 1995)"

Jan 1, 2015

By Keith D. Koper, Kris L. Pankow, Derrick J. A. Chambers, Michael K. McCarter

"In a mining environment, high quality seismic event catalogs are often useful in interpreting local stress states and identifying areas with elevated ground control risk. Installation, operation, and maintenance of local/in-mine seismic networks, however, may be prohibitively expensive, and mine operators may not anticipate the need for seismic data until unusual mining conditions arise. If regional, generally public, seismic instrumentation could be used to reproduce the results generated by local/in-mine instrumentation to an acceptable degree of fidelity, it would be a valuable and inexpensive tool for mine planners and ground control engineers.In this study we apply subspace detection—a non-traditional seismic event detection technique—to data from a sparse, regional network. The process is employed to identify mining induced seismicity (MIS) from an underground coal district. The results are compared to a seismic event catalog produced by a local seismic array operating within the permit boundaries. Additionally, we analyze the performance of two different stations of the same sparse, regional network in identifying blasts at a surface coal mine for which we have a detailed blasting log. In both cases data from stations between 10 and 60 km away from mining activity are used. We also explore the trade-offs between the number of detections and the number of false positives, which is influenced heavily by detection thresholds and the number of stations used in the process.For the surface mine we are able to identify more than 90% of the production blasts documented in the blasting log. We also find that the detected blasts from each of the four active pits produce waveforms similar to one another. The results are not dependent on source-receiver distance, and by requiring detections to occur on both stations the number of sure false positives is reduced to zero. In the underground mining district we identify between 30% and 75% of the events detected by the local array, depending on the acceptable number of false positives and the source-receiver distance. We also find many events that were missed by the local array, showing that regional subspace detection can usefully augment traditional local catalogs. Moreover, subspace detection can provide an estimate on event location and classification using data from as little as one seismic station."

Jan 1, 2015

By Benjamin Mirabile

"Current and emerging practices to ventilate longwall gobs are prompting increased design and analysis of standing support requirements related to longwall mining. Specifically, additional design methodologies are being employed to evaluate standing supports in the #2 entry of a 3-entry longwall system.Numerical modeling will be used to evaluate the performance of standing support in the #2 entry between gobs of longwalls in the Herrin No. 6 seam. The performance of standing support in the #2 entry will be evaluated based on the following: (1) The effectiveness of standing support in maintaining an open airway in the #2 entry; (2) The interaction of standing support in the #2 entry with standing support in the longwall tailgate; and (3) Loading conditions of longwall pillars. Initial numerical modeling activities are focused on evaluating the roof to floor convergence in the #2 Entry and using the ground reaction curve concept for support design.Numerical modeling indicates that, like standing support in tailgates, supports in the #2 entry require some type of yield mechanism to withstand initial uncontrolled convergence. Numerical modeling also suggests that support density can be lower than that used in a tailgate support application. The numerical models used for initial investigation of support performance in the #2 entry are limited in their ability to evaluate support performance. The magnitude of uncontrollable convergence can be estimated with LaModel software. Near-seam conditions have not been investigated in this research since the LaModel software does not have the ability to evaluate inelastic rock behavior.IntroductionDuring the past three decades, many researchers have investigated standing support performance in longwall tailgate entries. Very little attention was paid to the middle entry of a threeentry longwall gateroad. As longwalls retreated, no personnel would travel the #2 entry, and the entry was considered part of the longwall gob. In response to recent mine disasters, regulatory agencies and operators have devoted more attention to these entries. Prior to the Upper Big Branch mine disaster, little or no secondary support was applied in these entries. Unlike secondary support in longwall tailgates, there is little empirical knowledge or quantified research specifically applied to secondary support in the #2 entry. This paper outlines initial steps used to develop a design methodology for secondary support in the #2 entry."

Jan 1, 2015

By Baisheng Zhang

The definition of Ultra-close multiple seams as defined by the floor disturbance depth, h, due to mining in the upper seam is proposed: it refers to those coal seams that are spaced very closely, i.e. h,, the distance between seams, is small or equal to h, , and mining of any one of the seams will significantly affect the others. Those seams are called the ultra-close multiple seam group. Theoretical formula for defining it and practical examples are given in this paper. Underground measurements and numerical analysis show that in ultra-close multiple seam mining, the characteristics of ground pressure due to lower seam mining is different from that of single seam mining. The major differences is that the roof, as a result of damaged caused by the upper seam mining, is full of factures; the roof broke up in the belt entry and fell down easily; support loading at the face was small without clear periodic weighting phenomenon. Based on these results the roof structure model and roof control theory for ultra-close multiple-seam are established.

Jan 1, 2005

By Terry Medhurst

Geophysical logging is routinely undertaken as part of most Australian coal mining exploration programs. Typically, the main application is the determination of coal seam depth and the qualitative estimation of coal quality, lithology and rock strength. For rock strength estimation, sonic transit times relate to the elastic properties of the rock and provide a general correlation with uniaxial compressive strength. However, experience has shown that site-specific relationships are necessary to account for different geological environments. In this paper we describe results from a series of recent studies that have provided a more comprehensive method of geotechnical strata characterisation using detailed lithological interpretation and rock property estimation from borehole logs. This has resulted in an improved method of estimating rock strength via the determination of the proportions of quartz and clay plus the porosity. We also propose a rock classification scheme based on geophysical log analysis. This builds on the existing acceptance of the sonic log as an indicator of rock strength and adds scores according to the moisture, cohesion, porosity and quartz content inferred from the geophysical logs. The new scheme can be related to existing mapping based schemes such as CMRR and the Q-system.

Jan 1, 2005

By Kot F. v. Unrug

In spite of the extensive research and accumulated experience from mining operations, an appropriate pillar design remains an open issue. Due to the shrinking reserve base, present mining operations move to more challenging conditions. There are usually thinner seams and geologic conditions are often unfavorable. For instance, mine roof and floor are weak or deteriorate rapidly when exposed to moisture fluctuations in mine atmosphere. It is common that pillars of current operations are more- squat than several decades ago when the bulk of pillar research have been carried out in thicker seams. The methods of pillars calculations were developed regionally (in particular countries) to suit design needs for the most important seams, from which the majority of coal production was coming (e.g. Pittsburg or Pond Creek seams in the eastern of US). Most of the pillar formulae use similar approach by assigning weights (using constants) to the influence of coal (seam) strength and pillar widthheight ratio on its final strength. That mechanistic approach has sound theoretical base and good data supporting its validity. However, what seems to be missing is a qualification system of the mine conditions, which are outside of the data base or do not comply with the theoretical model applied in pillar strength formulae. This paper attempts to address that issue in two major categories, first when only a drill core data are available, and second during the mine development observations can be made directly on a coal seam. The composition of a coal seam is also addressed, (which often changes rapidly across the reserve), and discussed its influence on pillar's structural performance. In summary a set of practical design rules is presented.

Jan 1, 2005

By Luis Giraldo

Rock bolt installation characteristics near roof falls have been identified as contributing to failure. One documented and regularly occurring failure mechanism is loss of anchorage between the grout and the rock wall of the bolt hole. Key contributors to the integrity of the grout interlocking with the rock mass are the diameter of the hole relative to the diameter of the bolt, resin versus cement type grouts, rock type, and condition of the hole. Smooth bolt holes consistently exhibit less rock bolt load bearing capacity than rough walled holes. The goal of this study was to quantify the benefits of borehole conditioning and develop a systematic approach that would allow improvement of roof bolt performance. A new rock drilling technology, the Helical Drag Bit (HDB), was used in the early stages of this project to condition the borehole. The HDB cuts a prescribed helical groove in the borehole wall. When a bolt is grouted into a hole that has been conditioned using the HDB, the grout fills the helical groove and provides a stronger, more reliable mechanical lock between the rock and the grout. This paper presents results of a series of tests conducted in the laboratory and in the field. Short encapsulation pull out tests have demonstrated considerable increase in pull out strength and more consistent bolt performance when hole geometry is modified using the HDB. The results have also shown that greater load bearing capacity improvements are obtained in mines with weak roof rock, where it is most needed. Additionally, bolts recovered for examination suggest that hole conditioning during roof bolting reduces the effects of finger gloving. Therefore, mines with stronger roof rock could also benefit from hole conditioning. A new roof bolt that uses the HDB principle has been designed and tested. The new system works with existing bolting equipment requiring minimal modifications to the traditional procedure used for installation of fully grouted rebar bolts. The use of these higher anchorage capacity bolts will allow mines to reduce severe injuries and fatalities resulting from ground failures while maintaining or increasing productivity.

Jan 1, 2005

By Dr. Daniel W. H. Su

t is both an honor and privilege for me to nominate Dr. Daniel W. H. Su for the inaugural Syd S. Peng Ground Control in Mining Award. I can think of no better candidate than Daniel that is deserving of this award ? an award to recognize technical excellence in advancing ground control technologies [and] approaches. Daniel?s education and career spans over three decades. Having graduated from National Cheng Kung University in Taiwan in 1972 with a B.S. degree in Mining and Petroleum Engineering, he spent the next four years in the Taiwanese military and mining industry, before moving to the United States, where he enrolled in West Virginia University?s Mining Engineering Department. He received his M.S degree in Mining Engineering from WVU in 1978; then in 1982 became the first person to ever receive a Ph.D. in Mining from WVU. His thesis was titled, ?Development of Ultrasonic Techniques for the Measurement of In Situ Stresses?.

Jan 1, 2006

By Behdeen Oraee-Mirzamani

Tunnel stability has an important role in the production process of an underground coal mine. There are various methods for analysing tunnel stability, such as numerical methods and analytical methods. In this paper, numerical methods (Phase2 software) have been used to determine tunnel wall displacement in a mining tunnel of the Parvade underground coal mine. The Ground Reaction Curve has also been drawn using analytical methods to determine tunnel wall displacement. The comparison of results from the numerical method and the analytical method show a noteworthy difference in the tunnel wall displacement. The displacement calculated by the numerical method shows a lower value than that of the analytical method because the numerical method is more suited to modeling the various coal and rock layers, as well as the shape of the excavations found in coal mines. The methodology used in this paper together with the results obtained from both methods can serve as useful tools for the coal mine design engineer when determining the ground support requirements.

Jan 1, 2013

By Bruce W. King, David A. Newman

"Underground mines have always been an integral part of the limestone industry. However, beginning in the 1990s, the number of underground limestone mines has increased for many reasons including• Stripping ratios at surface quarries have become uneconomic.• Existing surface quarries have reached the mineral boundaries, and the remaining stone reserves are underground.• Surface access to the entirety of the limestone reserve is limited by development or infrastructure.• The once-rural setting of the surface quarry is now surrounded by subdivisions and development. An underground mine is less intrusive and takes the mining operation out of the public eye.• For larger markets, an underground mine enables year-round production without the sequence of overburden stripping in the winter to expose mineable stone for summer production. This is common at many surface quarries.Multiple-level operations are a natural extension of the decision to mine underground. Most limestone reserves, for example, the Tyrone-Oregon-Camp Nelson, Hermitage-CartersLebanon- Ridley, and Salem Limestones, are sufficiently thick to accommodate multiple levels. Multiple-level mines should be planned by considering each level separately and then integrating the individual levels into a larger mine plan. Failure to plan all the levels of a multiple-level mine in concert can result in ground control (back, pillar, floor, and inter-level sill pillar) problems attributable to stress transfer and interaction between the levels or the necessity to leave a thicker sill pillar between adjacent levels.Multiple-level mine planning begins with geology. Once the upper level back horizon is identified, the geology, rock strength, and physical properties in each level are used to• identify the optimal back horizon• quantify whether back support is required and, if so, the type, spacing, and length of the back support• determine the pillar centers• determine the total mining height, including floor shots"

Jan 1, 2016

By Bruce K. Hebblewhite

This paper provides an overview of the international ?state of the art? with respect to underground coal mining methods used in seams of thickness greater than 4.5 m, through a review of a selection of high performing thick seam mining operations around the world?both Single Pass Longwall (SPL) and Longwall Top Coal Caving (LTCC). The paper discusses the recent operational experiences from these selected faces, together with the ground control issues faced, and identifies some of the major, inherent geotechnical factors that can influence the mining method selection, design criteria, and ultimate performance, from both an operational and safety perspective. It is clear that both of these methods are developing quickly? not only from an operational and equipment perspective, but also from the understanding of critical geotechnical criteria. There is an increasing role for both methods in thick seam environments, although the higher SPL faces will only be successful in the near to mid-term under benign geotechnical environments. Regardless of the method, a thorough understanding of the critical geotechnical factors is a key to successful implementation of either method.

Jan 1, 2013

By Jingyi Cheng

Many longwall panels in China are laid out along the dip direction such that the direction of longwall retreat mining is along the strike direction of coal seams. Downward mining longwall panels in steeply inclined seams refers to those that are laid out in a non-uniformly developed fold structure where the seam is not only steeply dipping, but also highly undulated along the strike direction, causing longwall mining extremely difficult because it has to deal with large dip angles that vary both in the mining and faceline directions. Obviously, the characteristics of mine pressure and overlying strata movement in downward mining longwall panels in steeply dipping seams have unique patterns that are very much different from those cases of mining the flat or gently inclined coal seams. The effects of those unique patterns presented a big challenge to production and safety. Almost all previous and current researches on ground control have been concentrated on issues related to the flat and gently inclined coal seams. Conversely, research on steeply inclined coal seams, especially those with large angle variation both along the seam dip and strike directions is almost none. Therefore, it is very important to initiate a study to better understand the characteristics of mine pressure and overburden strata movement for this special type of geological condition. The objective of this paper is to monitor and analyze the characteristics of mine pressure and overlying strata movement in downward mining longwall panels in steeply inclined seams, the angle of which varies greatly along both the seam dip and strike directions. The measured data has conclusively demonstrated that the characteristics of mine pressure and overlying strata movement in downward mining longwall panels in steeply inclined seams are different from those for the flat and gently inclined coal seams. The large downward angles of coal seam undulation along the strike (mining) direction can obviously affect the roof movement and reduce strata pressure. Study in this research showed that appropriately increasing the rate of mining (or face advance) is positive to roof control.

Jan 1, 2013

By Robert P. Kudlawiec

The use of Mobile Roof Supports (MRS) in pillar retreat mining has been a fairly recent occurrence in coal mining operations in the United States (1988). Determining the pillar block configuration, the crosscut and entry centers, the number of entries developed, the method of ventilation, and the type and mixture of equipment used arc all factors in establishing a successful pillar retreat operation. This paper will evaluate and report on the history of one coal company's relationship with MRS usage for pillar retreat mining and focus on the company's use of horizontal pillars (inverted-blocks) for the panel configuration.

Jan 1, 2000

By Ry Stone

"There have been many design practices utilised within the coal mining industry to arrive at the minimum densities of primary ground support required during roadway development. This paper demonstrates the practical use of empirical databases, and focuses on the main drivers for ground support as demonstrated in conceptual models.Golder Associates’ empirical databases used for ground support include a Primary Roof Support Database and a Primary Rib Support Database. Both are based on successful ground support designs installed in mines in Australia, the US, the UK, South Africa, New Zealand, and Europe. The term “successful” refers to those designs that were used on a repeated basis for the purpose of roadway development.The Primary Roof Support Database indicates that the major factors influencing successful roof support designs are roof competency, expressed as the Coal Mine Roof Rating (CMRR), and in situ stress. As roof displacement is essentially a function of horizontal stress and roof competency, in order to provide some form of measure as to the likely magnitude of roof deformation during roadway development, the depth of cover is divided by the CMRR to arrive at a “Stress Strength Ratio” (SSR). The database indicates that the higher the SSR, the greater the likelihood that the roof will require higher densities of support.In regard to the Primary Rib Support Database, it is evident from the current database that the primary factors affecting the capacity of rib support required for a successful design are roadway height and depth of cover. In order to provide some form of measure as to the likely magnitude of rib deformation during roadway development, the depth of cover is multiplied by the height of the roadway to determine a “Rib Deformation Rating” (RDR). Similar to the roof, the database indicates that the higher the RDR, the greater the likelihood that the rib will require higher densities of support.These databases have been used to help determine the minimum primary ground support designs required at many mine sites in Australasia, Europe, and the US. This paper will demonstrate the effectiveness and practicality of these databases at two selected mines in Australia and the US.In order to improve the Primary Rib Support Database, this paper will also propose a new rib deformation rating based on the addition of site specific coal strength data for the Australian mines. The proposed rating attempts to capture the main variables that define the behaviour of a buckling column."

Jan 1, 2015

By Anthony Spearing

There are approximately 68 million rockbolts installed annually in underground coal mines in the USA (Tadolini and Mazzoni, 2006). The most utilized is the passive fully grouted resin rebar bolt, which constitutes almost 90% of the primary support in US underground coal mines. Resin-grouted rockbolts are a very effective and safe support, but their performance still needs to be further optimized and improved. This paper investigates their performance and suggests operating conditions to optimize the performance of resin-grouted rockbolts. In addition, this paper discusses a small-scale test that can also be used to evaluate the performance of rockbolts that is quicker, easier, and less costly than short encapsulation tests.

Jan 1, 2014

By Victor V. Nazimko

Longwall mining technology without interpanel pillars is feasible from a geomechanical point of view. A set of pillarless longwall layouts are proposed including tailentry pillar recovery, headentry pillar recovery and drivage of a new tailentry, partial headentry pillar recovery and combination mining in which advancing panel entries are used for retreating panels. The following mitigative measures are proposed in order to enhance the stability of entries near the panel: driving crosscuts obliquely to the longwall face line, advance support of entries and crosscuts, localized destressing of the chain pillars by horizontal slotting, and partial stowing of the gobs behind the pillars being recovered. A new technology of recovering barrier pillars on the setup entry side is also proposed. This technology uses the same regular longwall face for interpanel pillars extraction.

Jan 1, 1994

By André Vervoort

To learn more about the fundamental roof behaviour in South African coal mines, accurate underground measurements of roof deflection were conducted in bord and pillar panels during development and pillar extraction. To conduct these measurements a survey levelling technique was adapted. The overall system reading accuracy was established as being within 0,4 mm on a 15 m sighting distance. The underground sites were modelled and, for a roadway development, similar symmetrical curvatures were calculated by a linear elastic model, as were measured underground. In a pillar extraction panel, a significant amount of bed separation was measured and the roof underwent an a-symmetric movement due to the close presence of the mined out area at one side of the roadway.

Jan 1, 1992

By Houquan Zhang, Yu Wu, Yanlong Chen, Zhenfu Luo, Aihong Lu

"A non-destructive detection scheme for bolt installation quality was designed by adopting the method of non-destructive detection on bolt installation quality. Based on the field measurements, a random non-destructive detection method for determining the characteristic length including anchoring length, free segment length and initial axial load of bolt was discussed, and the characteristics of increasing bolt axial load in the initial stable stage was obtained. The results show that the bolt axial load and deformation of surrounding rocks correlate each other. Compared with the traditional detection technique for bolt installation quality, the non-destructive detection method has obvious advantages such as random, accuracy, and economic. The method provides a reliable basis for bolt support optimization and stability control of surrounding rocks.INTRODUCTIONBolt support in roadway can make the surrounding rocks and bolt form a structure in the early stage of roadway development through the bolt pre-tension, which can maximize the self-bearing capacity of surrounding rocks. Thus it is a form of active support (Kang, 2007). In order to make the bolt play an active supporting role, it needs to ensure the installation quality of bolting. Thus the bolts can supply a high initial anchoring force and control the deformation of surrounding rocks (Shan, 2009; Wei, 2012). Moreover, bolt supporting is a concealed work. Once installation quality problems appear; it will be difficult for effective detection and screening (Xie, 2008).THE PROBLEMS OF BOLT INSTALLATION QUALITY IN COAL MINE AND ITS DETECTIONThe Problems of the In Situ Bolt InstallationDue to the problems in installation environment, machine, and technique, and workers proficiency (Li, 2003), there are many problems exist in bolt installation. If the borehole depth is too long, the anchoring agent will accumulate at the bottom of the bore, which reduces the anchoring length. Furthermore, if the borehole depth is short due to the poor geological condition, the exposed part of the bolt will be too Jong and the pallet cannot cling to the rock face, which prevent the pre-tension from being applied. The pre-tension is very important for bolt installation. If pre-tension is insufficient the rock bolt cannot control the deformation of surrounding rock efficiently and the bolt anchoring force will decrease considerably. The bolt length is another important parameter for anchoring quality, which will affect the control area of bolt supporting. In addition, the cleanness of drill hole has a great influence on the effective anchorage length of bolt. If the drill hole cleaning is not enough, it will directly affect the anchoring agent and the contact area of surrounding rocks, which will decrease the effective anchorage length and initial anchor-force."

Jan 1, 2016

By Bruce K. Hebblewhite

BHP Billiton Illawarra Coal operates Dendrobium Mine in an area 10-20km west-northwest of Wollongong in the Southern Coalfield of New South Wales, Australia. The mine recently completed longwall mining in Area 3A adjacent to an overhanging rock feature known as Sandy Creek Waterfall, which had been identified as a significant, and potentially sensitive natural surface feature of the environment. This waterfall lies within the Sydney drinking water catchment area, in a surface terrain of variable topography where non-conventional subsidence behaviour such as valley closure, and far-field horizontal movements are known to occur, over and above conventional subsidence responses to mining. As a part of the conditions of approval to mine, Illawarra Coal undertook to protect the waterfall and the section of Sandy Creek immediately upstream of the waterfall from the effects of longwall mining using an innovative management process and an array of very high resolution monitoring systems. This paper outlines the type of non-conventional subsidence effects that can occur; the range of different monitoring regimes adopted in response to such effects in order to develop an understanding of the valley closure phenomenon in proximity to the waterfall and provide suitable early warning data. The paper also describes the management processes that were adopted, incorporating the use of these monitoring regimes in order to successfully protect the waterfall from the valley closure effects of mining four adjacent longwall panels in close proximity to the waterfall while continuing to maximise recovery of the coal resource in the area. The management structure adopted involved a technical committee, a steering committee, and an external independent reviewer. The technical committee was responsible for design of the monitoring systems, interpretation of the results, and making timely recommendations to the company steering committee who were then able to make informed decisions on when to cease mining each adjacent panel. The steering committee comprised Illawarra Coal management and technical personnel. Although the steering committee took advice from the technical committee, all decisions relating to mining were made by the steering committee. An external reviewer was engaged by the steering committee at the end of each longwall panel to review the results, interpretation and management decisions. This management structure was effective in successfully protecting the very sensitive structure of Sandy Creek Waterfall from potential impacts of nearby mining in the midst of active ongoing natural erosion processes.

Jan 1, 2014