The friction-transfer method, which is described in this paper, can be used for in situ determination of intact rock strength. With this method it is possible to estimate the equivalent uniaxial compressive strengths (UCS), using appropriate calibration graphs. In this method a specially devised apparatus fits over the top the partial core and is clamped to it. To measure the rock strength, torque is applied using an ordinary torque meter and the maximum torque at failure is recorded. Comparative studies of UCS values and friction-transfer test results showed that a strong correlation exists between UCS and the friction-transfer readings. The measured values for uniaxial compressive tests ranged from 26 to 207 MPa. The average coefficients of variation of laboratory and site tests were found to be less than 14% for uniaxial compressive tests and less than 12.5% for the friction-transfer method. Fully saturated rock samples showed between about 18%–56% reduction in their torsional and core compressive strengths compared with their respective values obtained under dry laboratory conditions.
Experimental Study of Rock Strength by Using Friction Transfer Method
