Strata Control in in-seam roadways

strata2M (formerly MMLM) was commissioned by the German publishing company Verlag Glueckauf to translate the highly technical German mining book “Gebirgsbeherrschung von Flözstrecken”. 2 years in the making with a range of translators, linguists, mining experts and editors working very hard the translation “Strata Control in in-seam roadways” has now been finally published by Glueckauf Publishing.

“Strata Control in in-seam roadways” includes elementary mining practice and geomechanical and mine-support research for practitioners, mine planners, engineers and students.

This book traces the life story of a coal mine in-seam roadway and is arranged accordingly. The sequence of chapters closely follows the actual progress of mine roadway planning and utilization.

The book is structured so that it can be used in two different ways. It is recommended that it should be read in its entirety in order to fully understand the overall planning and design method for in-seam coal roads. The individual chapters are also self-contained and include a reference index provided for the benefit of those working on particular projects or wishing to expand their knowledge in a specific area. Subject overlapping is deliberately used to help readers simplify their search.

The chapter “RAG-Standard planning“ describes the structured approach to roadway planning and design which considers all interconnected aspects and indicates the key milestones in the life of a coal road.

Descriptions of positive and negative operational experiences from research projects, along with results obtained from testing new devices or procedures, should help support engineers avoid similar problems in the future. Direct recommendations and guidelines can be obtained from several of these projects. The new guidelines for roofbolting, issued in the late 1990s, are an excellent example of the result of intensive research work. Drawn up in close cooperation with the mining authorities, these new calculation and measurement methods have facilitated a much wider application of roofbolting.

The book is divided into the following chapters:

Geology of German hard coal deposits.
Geotechnical principles of strata control.
Rock pressure and rock stress.
Mine Layout.
Rock and roadway deformation.
Planning tools and support design.
RAG-Standard planning.
Roadway support systems.
Roadway developent methods.
Roadway monitoring.
Improving rock conditions and roadway repair.
Roof support at the T-junction zone.
The book describes the current state of knowledge relating to geological deposits and explains how in seam mine roadways are utilised as part of the longwall mining process. The stages of the roadway planning process – development, utilization, monitoring and repair – are represented in their chronological order.

Fundamental scientific knowledge with direct practical application is described in the chapters “Geology of German hard coal deposits” and “Geotechnical principles of strata control”. The succeeding chapters on rock pressure, stress and mine layout describe the geomechanical effects of multi-seam mining (areas of increased pressure caused by pillars and zones of weaker strata) in the context of the high stress conditions prevailing in the German coal fields. The effect of depth-related stress and additional load generated from mining activities is explained. Coal road development options to control additional loading are discussed in the layout planning. In particular, current geotechnical developments will allow the planning engineer to refine roadway designs to improve the outcomes. The geotechnical life-time analysis of every existing coal road is undertaken as the basis for a continuously improving comparison database. This leads to improved planning reliability, as explained in the chapter “Planning tools and support design.”

The information contained in the above chapters forms the technical basis for the different in-seam mine roadway calculation and prediction procedures.

The chapter “RAG-Standard planning” is the core of this book. Compliance with standardized planning procedures is essential when collecting reproducible data, because all planning predictions are based on empirical calculation models.

Various support systems and their support elements are explained in the chapter “Roadway support systems.” The description of cases of loss or severe damage to roadways due to operational circumstances highlights important findings and recommendations for future cases. Support design mistakes can be avoided by the use of permanent quality control – as explained in the chapter “Roadway support systems.” Expert knowledge about the correct use of secondary support systems, grouting techniques and materials such as packing and backfill materials, is of essential importance for roadway repair. New developments in support systems, support components and their operational applications are presented. These applications range from steel lagging sheets to yielding rockbolt systems.

Various techniques for underground development are emphasized in the chapter “Roadway development methods”. Examples in this chapter include: application of dry drilling techniques in water-sensitive rock or the use of detonating fuses in drill and blast development in order to create a precisely profiled excavated cross-section.

Support system related technical information from the planning process is enhanced using in situ measurements during development and use of in-seam roadways. Descriptions of successful measurement methods can be found in the chapter “Roadway monitoring.” The functions of various measuring instruments are described using detailed drawings and photographs. Measurement data needs to be transferred from handwritten records to IT supported computer storage using a logical traceable process in order to allow proper comparison of actual results with design values.

The chapter “Improving rock conditions and roadway repair” includes the process of grout injection and describes the effects of these techniques using operational cases. Subsequent repair methods for support systems that are no longer functional are also illustrated using case studies. Repair or reconstruction measures are explained and supplemented with recommendations for relevant support designs.

In conclusion, the chapter “Roof support at the T-junction zone” gives a description of support practice in these crucial longwall operational areas. The use of additional hydraulic props to support arches at the headgate and tailgate, as the arch legs are removed to allow various face conveyor drive configurations to move up, will be illustrated. The alternative application of anchor bolts to support the arch segments, depending on the gate road convergence behaviour and including associated calculations, is also described in detail.

Scores of publications and research reports from the past 20 years have been utilized as the basis for this book. Corresponding references have been given in relation to joint work by RAG and DMT, as well as the authors involved with this book. Appropriate reference has been made to third parties involved in or solely responsible for technical developments and findings. It is therefore possible to obtain further information on the range of topics covered.

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