MSHA - Directorate of Technical Support

A Troubleshooting Guide for Roof Support Systems (TGRSS)

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Over the last 20 years, roof support technology has made numerous advances since the original wedge and slotted bolts of the 1950's. By comparison, the roof supports used today are more complex and specialized than the supports used in the past, providing mines with a varied selection of supports from which to choose. As a result, when problems with supports are encountered, it is more difficult to determine whether it is the result of geological changes, poor installation practices, or malfunctioning supports. The purpose of this guide is to provide a logical sequence to resolving the most common problems encountered with roof supports.

In order to simplify the troubleshooting procedures, the roof supports were classified into the following 5 categories:

Mechanical Bolts Bolts using an expansion anchor without resin.
Fully Grouted Bolts Non-tensioned, headed rebar.
Tensioned Rebar Bolts  Threaded deformed bar using a grout anchor and tension nut.
Point/Combination Anchored Bolts  Two-piece bolts using a grout anchor and a tensioning coupler without an expansion anchor.
Mechanically Anchored Resin-Assisted Bolts  Tensioned grouted bolts using expansion anchors.

Classifying the supports makes it easier to emphasize problems that are unique to a particular support type.

The problems and probable causes listed in each section are the result of data accumulated from years of laboratory and field investigations. The troubleshooting charts included in these pages are quite comprehensive, however, due to the diversity of variables affecting strata control, were not intended to solve every conceivable problem that might be encountered.

For More Information Contact:

Mine Safety and Health Administration
Technical Support Roof Control Division
Pittsburgh Safety and Health Center
P.O. Box 18233
Cochrans Mill Road, Bldg. 038
Pittsburgh, PA  15236