How to Design an Efficient Roof Bolting Plan Based on Simple In-Mine Measurements

Brest van Kempen, C. J. H.
Organization: International Conference on Ground Control in Mining
Pages: 14
Publication Date: Jan 1, 1986
The techniques developed should provide a useful tool, not only during the initial formulation of a suitable bolting plan for a new section, but also for periodic check¬ing on the utilization factor of hardware installed in the roof. Indications are that with present practice, utilization seldom exceeds 507.. Retro-fittable bolter equipment now available (FCBS?) allows doubling of the utilization factor in many cases. We are also introducing a computer pro¬gram based on the material outlined in this paper. This program can save a great deal of time in examining the real effect of implementing alternate bolting plans or using different installation techniques. It allows fine-tuning of bolt lengths, spacing and installation tension to mini¬mize roof support cost, while maximizing safe life of the mine opening. We have developed a procedure which allows easy, site-specific quantification of the need for reinforcement of a mine roof. The concept is based on the forma¬tion of a direct link between theory and empirical data to custom-fit each mine section. In its simplest form, the proce¬dure requires only recording of roof bolt torques in a sample working place (16 to 25 bolts) several times during the first week or so after initial bolting. The way in which the torque pattern changes during this time can reveal whether or not the bolts carry enough tension to maintain stability in that specific roof. From the same data, the nature of the anchorage horizon is derived. Specifically, shale or limestone can be distinguished from sandstone. If the procedure is repeated a few times (within the same mine section) with different bolt installation tensions, we can numerically characterize the roof in terms of one single value: an "effective angle of internal friction". This number can then serve to calculate trade-offs in bolting plan design, such as bolt length, bolt spacing and optimum bolt tension. Additional refinement is possible if a sagmeter is installed in the sample work¬ing place being monitored and if bolt anchorage capacity is determined. The lat¬ter can be done automatically on each bolt as it is being installed, using a system we developed and patented. Alternately, a number of pull tests could be performed. Using the sagmeter, bolt torque and anchor¬age data, it is possible to project the safe life of the supported opening. The details of the procedures described apply specifically to tensioned roof bolting, but a brief discussion paints the way for a similar analysis of full-column resin bolting also.
Full Article Download:
(4139 kb)

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

Expanded Cement: New Solutions for Age-Old Problems
Determination of Effective Column Lengths for Resin-Grouted
How to Design an Efficient Roof Bolting Plan Based on Simple
Donut Cribbing--A Hew Heavy-Duty Roof Support Concept
Development of A Yielding Steel Post
Design Procedure for Arch Canopies for Rehabilitation of Hig
Investigation of Some Alternatives to Timber Posts and Cribs
Design and Field Testing of a Mobile Roof Support for Retrea
Change in Primary Roof Support System at Quarto Mining Compa
Remote Mining Using Water for Ground Support
New Type of Load Cell for Monitoring of Roof Bolt Tension
Field Measurements of Chain Pillar Response to Longwall Abut
Integrated Instrumentation Method of Stress State, Material
A Study of Roof Caving in the Eastern U.S. Coalfields
A Simple Tool to Measure Stress in Mine Backfill
Optimization of the Stress Control Method to Improve Product
Effect of High Horizontal Stress on Coal Mine Entry Intersec
Analysis of Small-Scale Thrust Faults and Their Effect on Co
A Case History of Computer-Aided Lineament Analysis for Grou
Designing for Upper Seam Stability in Multiple Seam Mining
Behavioral Aspects of Roof/Rib Injuries--Implications for Tr
Engineering Classification of Shales
Empirical Approach to Calculate Rock Loads in Coal Mine Road
Assessment of the Rockburst Proneness in Hard Rock Coal Mine
Outburst Control in Underground Coal Mines,
The Effect of Immediate Strata on Pillar Behavior in Retreat
Roof Control Problems on Development and Longwall Gateroads
A Case Study of Longwall Roof-Supports Interaction
Tailgate Support Evaluation at Plateau Mining Company
Methods of Controlling Hard Roof in a Longwall Face