Tension-Torque Relationship For Mechanical Anchored Roof Bolts

Maleki, H. N.
Organization: International Conference on Ground Control in Mining
Pages: 8
Publication Date: Jan 1, 1984
Tension-torque relationships were investigated *n a coal mine for bath standard 5/8 in. (16 mm) bolts and a vibrating wire instrumented bolt, using conventional and controlled installation techniques. The instrumented bolts differed from the standard bolts by their head size and hole preparation procedures. The controlled installation technique developed by the U. S. Bureau of Nines (USBN) involved using hardened washers and lubrication in the bolt assembly, and maintaining a minimum thrust level during bolt installations. The object of this study was to determine the tension to torque ratio (lb/ft-lbs; for standard bolts and instrumented bolts for both conventional and controlled installation techniques, and to modify the bolt assembly so that the ratios would be equal for the instrumented and standard bolts for both installation techniques. It was shown that the instrumented bolts installed in faced holes had a similar tension torque ratio td that of standard 5/8 in. (16 mm) bolts installed in unfaced holes for each installation technique, and thus they were representative of other uninstrumentea bolts. This was achieved by evaluating the influence of several factors oh the relationship, including: facing the hale surface, introducing washers and lubrication in the bolt assembly, and applying different levels of thrust at installation due to bolter operator practice. The tension to torque ratio fur conventional bolts was only 21 (lb/ft-lb) for the coal mine, resulting in an installation tension of 4000 lbs (17.8 kg) with the typical installation torque of 150 to 400 ft-lb. This tension level was approximately 50 percent of the required bolt tension, and thus, it was concluded that torque standards are not sufficient to assure adequate bolt tension. .he low tension levels were due to the particular wait hardware in use, operator practice, and bolt fencing.
Full Article Download:
(1237 kb)

Additional chapters/articles from the SME-ICGCM book Proceeding of the Fourth Conference on Ground Control in Mining (ICGCM)

Truss Bolting On-Cycle in Jane Mine Lower Freeport Seam
Design Of A Roof Truss Bolting Plan For Bear Mine
Tension-Torque Relationship For Mechanical Anchored Roof Bol
A Novel System For Automatic Installation Of Cement Grouted
Load Transfer Mechanics In Fully-Grouted Roof Bolts
An Investigation Of Longwall Pillar Stress History
Impact Of Horizontal Load On Shield Supports
Interaction Between Roof And Support On Longwall Faces With
Roof Control With Polyurethane For Recovery Of Kitt Energy?s
First Caving And Its Effects--A Case Study
Staubbekampfung An Schildausbau In Bruchbaustreben (Combatin
Yield Pillar Applications--Impact On Strata Control And Coal
Constraint Is The Prime Variable In Pillar Strength
Massive Pillar Failure--Two Case Studies
Investigations Of Underground Coal Mine Bursts
Destressing Practice In Rockburst-Prone Ground
Statistical Characterization Of Coal-Mine Roof Failure: Sugg
Pillar Design - Continuous Miner Butt Section And Longwall D
Design Factors In Near-Seam Interaction
Remote Sensing For Roof Control And Mine Planning: An Overvi
Design, Construction And Performance Of A Single Pass Lining
Computer Modelling And In Situ Instrumentation Techniques: A
A Sonic Wave Attenuation Technique For Monitoring Of Stress
The Radio Imaging Method (RIM) -- A Means Of Detecting And I
Clay Veins: Their Physical Characteristics. Prediction, and
Evaluation of the Point Load Strength for Soft Rock Classifi
Ground Control Experiences in a High Horizontal Stress Field
Horizontal Stresses and Their Impact on Roof Stability at th
Ground Control Problem Associated with Longwall Mining of De
Geotechnical Aspects of Subsidence over Room and Pillar Mine
Proposed Criteria for Assessing Subsidence Damage to Surface
Surface Subsidence. in Longwall Mining--A Case Stud
An Integrated Approach to the Monitoring and Modeling of Gro