Investigation of Shank Tension in Mine Roof Bolts.
NTIS: PB/80-210016 :29 pages
Samples of 5/8- by 60-inch mine roof bolts were measured under test loads by stress measurement instruments, one a magnetic system and the other an ultrasonic birefringence system. Both were designed to detect shank tensile stress by measurement of the induced compressive stress in the head of loaded, generally higher quality bridge bolts. Results of measurements made on the heads of roof bolts indicate that variations in dimensions and other head variables preclude accurate load determination on a random population of installed bolts by either method. However, the ultrasonic system offers a good prospect for recording a reference value from a specific bolt at the time of installation to be used as a basis for subsequent inspection through the life of the structure. The stress washer would be no more than a reasonably accurate steel collar within which a uniform stress would be developed from the loaded bolt.
CP; Final Contract Report;
NTIS Accession No.
Southwest Research Institute