Plug improves stability of shaly roofs
- Univ. of Kentucky, Lexington (United States)
Although geologic conditions and over-stressing play major roles in roof falls, an especially common cause of falls of shaly roof is the gradual deterioration of the shale itself. The culprit in such deteriorations is the hydrophilic nature of the shale's clay mineral components, a trait causing some of the clay minerals to swell due to absorption of water from the atmosphere. Moisture enters the annular space between the bolt rod and the walls of the borehole, and then condenses on the cooler surfaces. It can then be absorbed by the shale through capillary attraction into micro cracks and bedding planes. When the condensation forms at the anchorage level, it can cause weakening of the rock, especially where the shale is under high stress with the anchor shell. To prevent migration of moisture into the roof through bolt holes, a patented plastic plug has been designed to seal the annular space between the rock and the bolt rod at the entrance of the hole. The plug consists of two halves that snap in and lock together. It can be assembled on a bolt rod in just three seconds by squeezing the two halves together just before the bolt is inserted into the bolt hole. The external and internal flanges of the plug create tight contact between the perimeter of the hole and the bolt rod, thereby sealing the annular space between the rock and the roof bolt at the entrance of the hole.
- OSTI ID:
- 5294445
- Journal Information:
- Coal (Chicago); (United States), Journal Name: Coal (Chicago); (United States) Vol. 96:4; ISSN 1040-7820; ISSN COALE
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
012031* -- Coal
Lignite
& Peat-- Underground Mining-- Strata Mechanics & Control-- (1987-)
ABSORPTION
CLAYS
COAL MINING
DESIGN
EQUIPMENT
INSTALLATION
MATERIALS
MINING
MINING EQUIPMENT
MOISTURE
OPERATION
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
ROCK FALLS
ROCKS
ROOF BOLTS
SEALS
SEDIMENTARY ROCKS
SHALES
STRATA CONTROL
SWELLING
SYNTHETIC MATERIALS
UNDERGROUND MINING
VAPOR CONDENSATION
WEATHERING