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Compressive and tensile strength tests are run on a wide range of core samples from EX to 6.00 inch diameter. Samples are cut and trimmed with a diamond saw. The ends are then ground flat to within 0.001 inch, parallel to within 0.005 inch using a surface grinder. The tests can be run in either load, strain, or stroke (displacement) control. Strain measurements accurate to 0.000001 inch are made using SR-4 strain gages. Displacement of the lower platen is measured to 0.001 inch using a LVDT. Specimen load, calculated specimen stress, specimen strain (longitudinal and transverse strain), platen position, and total test time are continually monitored by the data acquisition system. At the conclusion of a test, the data is saved to a file used to generate stress versus strain curves. All data is saved to the hard drive with a tape backup run twice per week. The test data are reported in tabular format for easy access and comparison. For elastic modulus and Poisson's ratio tests, stress versus strain graphs are appended to the report. Tests on the immediate and main mine roof strata are conducted to determine the stable unsupported span dimensions and supplementary support requirements. Coal strength tests are used for pillar strength and safety factor calculations. Direct shear strength and triaxial compressive strength provide the input necessary to calculate the bearing capacity of the immediate floor strata. The testing capabilities are listed below:
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