To meet the need for improved field test instruments, hardware and procedures were developed for rapidly determining the in-place shear strength of coal and rock. The hydraulically operated device is permissible, portable, and can be used in 3-inch boreholes at depths up to 100 feet. Field tests in a number of mines, coal, nonmetallic, and hard rock, show that the tester is practical for mine use, especially where recovery of unbroken core for laboratory tests would be difficult. In addition to eliminating the "good rock only" bias inherent in laboratory testing, the tester offers the advantages that many tests can be quickly performed in a single borehole and the results are available immediately. A technical paper presented to an international meeting in 1979 shows that the test data obtained for four different coals and four rock types are equivalent to those for conventional triaxial tests, the best laboratory strength test. The shear strength of coal and rock is important in determining pillar crushing, floor heaving, overburden collapse, roof bolt anchorage, and cutability and drillability of the materials.
Proc. 4th Cong., Int'l. Soc. for Rock Mech., Montreux, Switzerland, Sep. 3-7, 1979, PP. 509-515