Influence of Structural Stress Concentration and Structural Irregularity on Longwall Gateroad Roof Control

Su, Daniel
Organization: International Conference on Ground Control in Mining
Pages: 9
Publication Date: Jan 1, 2002
Following several roof falls in the E3 longwall development of a Consol Pennsylvania Coal Company underground coal mine, an underground roof geology reconnaissance program consisting of twenty-nine 20-foot deep roof holes had identified the presence of thick sandstone layers with abundant shale and micaceous streaks. The base of the sandstone was 4 to 8 feet above the roof line within the fall areas. The presence of micaceous streaks created extremely pronounced planes of weakness in the sandstone. A structural irregularity, which extends into the E4 and E5 developments, exists between crosscuts I 1 and 30,where all roof falls occurred. Immediately to the east of this structural irregularity lies a huge syncline. The presence of thick sandstone units within the typically all shale environment and within such a structural irregularity helps to maximize stress concentration and creates closely spaced joints in the sandstone, which explains why many cracks are present in the macroscopically massive sandstone upon development. The approaching E2 longwall gob to the south and on the down-dip side, on the other hand, provided horizontal stress relief in the sandstone, which helps to explain the many roof falls in the E3 development that occurred during or immediately after the formation of the E2 gob. Finite element modeling confirmed the presence of such horizontal stress relief. Since the E3 longwall was a right-handed face, stress concentration was expected at the longwall headgate T -junctions, and further delamination of the sandstone was expected upon arrival of the E3 longwall face. Based on the results of the roof geology reconnaissance program and a roof stability analysis that took into account up to eleven parameters, supplemental headgate and track roof support consisting of 16-foot and 20-foot long cable bolts was successfully implemented within the zone of thick sandstone with micaceous streaks and structural irregularity and at other potential roof instability areas along the E3 development. The cable bolts were designed to be anchored at least 4 feet above the sandstone unit into the mostly competent sandy shale layers. No headgate roof control problem was reported within the sandstone and structural irregularity zone during E3 and the subsequent E4 longwall extractions.
Full Article Download:
(1914 kb)

Additional chapters/articles from the SME-ICGCM book Proceedings 21st International Conference on Ground Control in Mining

Pre-Driven Experimental Longwall Recovery Room Under Weak Ro
Longwall Mining-Induced Abutment Loads and Their Impacts on
Influence of Structural Stress Concentration and Structural
The NIOSH Shield Hydraulics Inspection and Evaluation of Leg
Study on Top-Coal Loss and the Optimum Drawing Interval of L
Stress Measurements for Safety Decisions in Longwall Coal
Re-Use of Rectangular Bolted Roadways in a Cover Depth > 100
Numerical Modeling of the Gob Loading Mechanism in Longwall
Deep Cover Pillar Extraction in the U.S. Coalfields
Evaluation of Pillar Recovery in Southern West Virginia
A Case History Investigation of Two Coal Bumps in the Southe
A Linear Coal Pillar Strength Formula for South African Coal
Anchorage Pull Testing for Fully Grouted Roof Bolts
Comparison of Some Aspects of Bolting Mechanisms Between Ful
Eclipse System Improves Resin Anchored Rebar Bolting
Design Considerations for Tensioned Bolts
Field Testing of the Fully Grouted Thrust Tensioned Bolts
Improvement in Pre-Tensioning of Strand Bolts in Australian
The Introduction of Roof Bolting to U.S. Underground Coal Mi
Support of Coal Mines in the United Kingdom
The Use of NDT Methods to Determine the Condition of Rockbol
Rockbolted Support of Retreat Longwall Gateroads at 1000m De
Roof Screening: Best Practices and Roof Bolting Machines
Numerical and Physical Modeling as Planning Tools for Rockbo
Stone Mine Design in Highly Fractured Rock
The Importance of Underground Stone Mine Roof Geology
Utilization of Ground-Penetrating Radar to Determine Roof Co
An Examination of the Loyalhanna Limestone's Structural
Highwall Stability in an Open Pit Stone Operation
Overview of Safety Considerations with Highwall Mining Opera
Highwall Monitoring to Combat Rockfall Accidents at Opencast
Seepage and Reinforcement Behavior of Grouting Into Slaking-
Floor Heave in Shallow Room-and-Pillar Mining
Analysis of a Stability Problem in an Underground Coal Mine
Comparison of Acoustic Emission and Stress Measurement Resul
Acoustic Scanner Analysis of Borehole Breakout to Define the
Estimating Rock Strengths Using Drilling Parameters During R
New developments with the coal mine roof rating
Application of geotechnical and geophysical parameters to im
Development of a Risk Rating System for Use in Underground C
Empirical and analytical design of large openings at a propo
Shear Mechanism for Mining-Induced Fractures Applied to Rock
Evaluating Techniques for Monitoring Rock Falls and Slope St
Developments in Sealant Support Systems for Ground Control
Stability Control of Clusters of Deep Openings Around Shaft
The Use of Pneumatic Stowing in Germany Considering Subsiden
A 3-D Semi-Analytical Method for Subsidence Prediction and S
Theory and Technology of Mining Subsidence Control by Grouti
Surface Subsidence Due to the Combined Effects of Undergroun