The 58 papers in the technical program will be presented by a range of international speakers from the United States, Australia, Poland, Germany, South Africa, the United Kingdom and Canada. The program includes sections on longwall (six papers), roof bolting (10 papers), roof bolting in Trona (two papers), roof bolt load measurement (three papers), ground control (seven papers), pillar design and extraction (five papers), mine design (two papers), roof failure and management (five papers), roof rating and monitoring (three papers), chemical injection (two papers), roof support systems (two papers), seismic (three papers), surface subsidence (four papers) and surface mining (four papers).
Australian speakers on issues related to Longwall mining include Mick Kelly, CSIRO, who will describe Status of longwall research in CSIRO.
The author outlines major projects including 3D aspects of longwall geomechanics; mine gas control; rapid roadway development; top coal caving; and longwall automation.
Ross Seedsman (Seedsman Geotechnics) will present a paper on The stress path followed by coal mine roofs and pillars during longwall extraction.
Seedsman’s model implies support design in tailgates should be based on the assumption of zero horizontal stresses, which has major implications for the design of cable and bolt anchorages.
Bruce Hebblewhite’s paper (University of New South Wales) is entitled Risk assessment of geotechnical factors associated with underground thick seam mining methods.
Hebblewhite describes current thick seam (defined as more than 4.5m thick) mining research, particularly an ACARP-funded project which assessed geotechnical risks associated with single pass lonwall, multi-slice descending longwall, soutirage and related caving methods (including Chinese longwall top coal caving methods) and hydraulic mining.
Other Longwall subjects are:
Hydraulic fracturing of sandstone and longwall roof control – implementation and evaluation, D Su, J McCaffrey, and L Barletta, Consolidation Coal Company, and E Thomas and R Toothman, Consol Energy.
Describes sandstone fraccing above two panels at a mine and operational adjustments to reduce stresses from a thick massive sandstone channel.
Longwall moves at Twentymile, Michael Berdine, RAG and Ray Brandon, Dywidag.
This paper describes Twentymile’s dramatic departure from traditional recovery methods in 1997 away from chain link fencing material. The mine has incorporated a Dywidag high tenacity polyester geogrid longwall recovery mesh system.
Load and deflection response of ventilation stoppings to longwall abutment loading – a case study. D Oyler, NIOSH, G Hasenfus, Consolidation Coal Company T Barczak and G Molinda, NIOSH.
This paper presents the investigations of both large-scale lab simulations and underground measurements conducted to determine the loading response of stoppings constructed from both normal and lightweight aggregate concrete blocks.
Other papers include:
Development of a method for designing roof bolt systems, Chris Mark, Gregory Molinda and Dennis Dolinar, NIOSH.
The authors describe NIOSH work to develop guidelines for designing roof bolting systems. NIOSH evaluated the performance of roof bolt systems at 37 mines. Five roof bolt variables were evaluated: length, tension, grout length, capacity, and pattern. The competence of the roof rock was the single best predictor or the roof fall rate.
Simulation of the effectiveness of tensioned bolt on layered roof, Y Zhang and Syd Peng, West Virginia University.
The authors describe simulation studies using 3D finite element modeling with elastic-plastic materials to arrive at a rational tensioned bolt support design for some typical roof conditions.
Development of a Remote Reading Dual Height Telltale System for Monitoring Mine Roof Deformation, Dave Bigby, Rock Mechanics Technology, UK and Matt DeMarco, NSW Engineering. The authors describe a system which provides mine management with early warning of impending roof failure.
According to the authors: “Up to 100 dual height telltales can be connected, in a simple daisy chain configuration, to each of 4 underground interrogation units. These are connected … to a surface computer which displays the readings, updates the database, generates warnings and provides the user interface.”
A new rockbolt axial load measuring device, Hani Mitri and Joseph Marwan. This paper describes a new monitoring device, the SAFEBOLT (Stress and Force Evaluator in Bolts), developed at McGill University in Canada. According to authors the SAFEBOLT replaces the load cell and permits the monitoring of bolt axial load from the time of installation.
Roof instability rating (RIR) and its application in mine ground control, John Stankus, Yajie Wang, Keystone Mining Services, James McCaffery, Enlow Fork mine.
The authors describe the development of a RIR system to predict potential roof problems. The RIR systems includes five parts: quantifying each individual factor; weighting each factor; combining each individual factor together, finalizing the RIR; and setting the criteria for areas where support is needed.
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