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Ultrasonic stress transfer: a direct test of rock bolt integrity.

Authors
Moulder-GR; Howard-PL; Hesler-JC; Tarpley-WB Jr.
Source
Denver, CO: U.S. Department of the Interior, Bureau of Mines, Contract J0295037, 1983 Aug; :1-84
Link
NIOSHTIC No.
10003382
Abstract
A device was developed that measures dynamic stress (ultrasonic energy) transfer through installed rock bolts, a measure that is directly proportional to the degree of grout bonding of the bolt to the mine roof structure and thus the ability of the bolt to bear static stress. The rock bolt bond tester (rbbt) is a handheld portable device that shows three ranges of bolt bond condition; i.e., one-third (bad bond), two-thirds (marginal), or fully bonded. These are shown respectively by a red, yellow, or green light that displays for 4 s. Rbbt performance was verified with 2 1/2- to 8-ft bolts installed in various types of mine roof structures (sandstone, shale, and boney coal-mud), and is now being tested by the Bureau of Mines in mines across the United States. The unit is about the size of a five-battery flashlight and contains the transducer, electronics, and battery pack. The rbbt is designed for extreme ease of operation, requiring only manual contact with the bolt and signal readout. The batteries are rechargeable and the package is designed for durability in a mine environment.
Keywords
Rock-bolts; Ultrasonic-tests; Bonding; Dynamic-tests; Anchors; Fasteners; Stress-waves; Anchoring
Publication Date
19830801
Document Type
CP; Final Contract Report
Fiscal Year
1983
NTIS Accession No.
PB84-165802
NTIS Price
A06
Identifying No.
OFR 31-84; Contract-J0295037
NIOSH Division
DRC
Source Name
Denver, CO: U.S. Department of the Interior, Bureau of Mines, Contract J0295037
State
PA; CO
Performing Organization
Energy & Minerals Research Company
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