Investigation of Fully Grouted Roof Bolts Installed Under In Situ Conditions

Compton, Craig
Organization: International Conference on Ground Control in Mining
Pages: 11
Publication Date: Jan 1, 2005
The The National Institute for Occupational Safety ane Health (NIOSH) Pittsburgh Research Laboratory (PRL) is continuing to investigate the behavior of fully grouted roof bolts in the weak roof rock of the Safety Research Coal Mine (SRCM). This paper describes the results of three studies: A series of 24 pull tests of bolts installed fully grouted and overcored to leave 12 inches of grouted bolt. The tests compared the pull-out performance of offset-head roof bolts with that of standard 518-inch bolts; A second series of 24 tests that compared the pull-out loads obtained by bolts installed with 1 R of resin (a Short Encapsulation Pull Test or SEPT) to that of fully grouted bolts overcored to leave only 12 inches of grouted bolt, and An investigation into the pressures generated during the installation of fully grouted resin bolts. All of the bolts installed and pulled were overcored and removed from the roof after the pull tests to allow inspection of the resin. The first study found that there was no significant difference in pullout load between the offset-head bolts and the standard bolts. The second study, comparing the SEPT bolts and the partially- overcored fully grouted bolts, indicated that SEPT can significantly underestimate bolt anchorage grip factor, suggesting that the SEPT is a conservative measure of actual bolt performance. Significant loss of resin to cracks in the roof was observed in the bolts overcored in the SRCM. The third study explored one possible explanation for the resin loss, high pressures generated during bolt installation. These tests employed bolts installed in strain gauged steel tubes. The results confirmed that significant pressures (greater than 4,000 psi) can be generated during bolt installation. The results of the pressure tests, combined with the observations of resin loss in bolts installed in the SRCM, suggest that under some circumstances resin loss and under-encapsulation could take place and lead to degraded bolt performance. Glove fingering was observed in all recovered bolts to various degrees. The limited comparative data suggested that the effect of glove fingering ranged from slight to moderate. Complete mixing of the resin was observed on all of the 40 bolts recovered (28 fully grouted and 12 SEPT). Australian and U.S. resins were compared and the Australian resins were observed to have much smaller catalyst compartment areas and lower resin viscosities. These differences are suggested as potential explanations for occasional resin mixing problems noted in Australian resin bolt installations.
Full Article Download:
(10282 kb)


Additional chapters/articles from the SME-ICGCM book 24th International Conference on Ground Control in Mining (ICGCM) 24th

Keynote Address at the 23rd International Conference on Grou
Analysis and Design of Rib Support (ADRS) a Rib Support Desi
Evaluation of the Impact of Standing Support on Ground Behav
Half a Career Trying to Understand Why the Roof Along the Lo
Forecasting Roof Falls with Monitoring Technologies - A Look
Analysis of Seismic Source Parameters of Roof Falls in Time
A System to Provide Early Warning on Impending Goaf
Outcomes of the Landmark Longwall Automation Project with Re
Application of Phenolic Foam in Longwall Mining
Multiple Seam Mining Interactions: Case Histories from the H
Analysis of Entry Stability Associated with Multi-seam Minin
Failure Mechanics of Multiple Seam Mining Interactions
Engineering Classification of Ultra-close Multiple Seam Roof
Definition of Ultra-close Multiple-seams and its Ground Pres
Depillaring and Roof Bolting Practices at Quinsam Coal Mine
Seam Structure - An Important Criterion for Coal Pillar Desi
Mitigating Longwall Subsidence Effects on a Large Industrial
Impacts of Longwall Mining on Hydrology, Soil Moisture, and
Basics on the Dimensioning and the Extraction of Shaft Safet
Modeling the Arc-effect of a Coal Mine Roof
Recent Advances in Numerical Simulation of Cutter Roof Failu
Test Method for Assessing Water Degradation Potential of Coa
Geotechnical Strata Characterisation Using Geophysical Boreh
A Method for Quantitative Void/Fracture Detection and Estima
Implication of Highly Anisotropic Horizontal Stresses on Ent
Ground Control of a Mine Stope in Weak Rocks Subjected to Hi
Analysis of Highwall Mining Stability - The Effect of Multip
Highwall Mining in a Multiple-seam, Western United States Se
The Slope Stability Assessment in the Wall Overlooking the S
Numerical Modeling as a Tool to Predict Pillar Condition and
Development and Testing of a New Roof Prop
Stability Mapping System
Using Foaming Grout to Stabilize a Ventilation Raise in Very
Roof Control and Roadway Support Design in the #9 Coal Seam,
Non-confirmation Mathematics for Wall Rock Classification fo
The Influence of the First Layer Thickness of Immediate Roof
Studies on Distribution Pattern of and Methane Migration Mec
Development of a New Roof Bolt Technology to Improve Gate- R
Improved Pull out Strength of Fully Grouted Roof Bolts throu
Experimental and Numerical Methodology Assessment of Load Tr
An Investigation into the Support Systems in South African C
Investigation of Fully Grouted Roof Bolts Installed Under In
Development of the Laboratory Short Encapsulation Pull Test
A Resin Quality Testing Procedure for Collieries
Determination of Load Transfer Characteristics of Gloved Res
Fully Grouted Torque Tension Bolts Successfully Support Pitt
Shear Bond Characteristics in Grouted Cable Bolts
Overcoring Techniques to Assess in Situ Corrosion of Galvani
Development of a Laboratory Facility for Testing Shear Perfo
Mechanical Response of Split-Set Rock Bolts in Squeezing Gro
Mechanisms of Rib Sloughing and Methods of Controlling Thick
Supporting Method of the Bolted Strata in Large Deformation
Assessment of Ground Conditions Near a Mine Portal Using Gro
Detection of Abandoned Mines and Air Passages/Burning Center
Detecting Abandoned Coal Mine Entries by High Resolution Ear