عنوان مقاله [English]
One of the methods for investigating the mechanical properties of rocks is direct shear test. It is considered as the simplest and the most commonly used methods for the shear testing of rock specimens containing a weakness plane or a discontinuity. This kind of test is normally carried out in the laboratory, but it may also be performed in the field, using a portable shear box to test discontinuities contained in a piece of drill core. As the normal and shear stresses are applied by hand pumps in the portable shear tests, there are some doubts on the accuracy of results. These ambiguities may be eliminated when using electrical hydraulic pumps instead of mechanically controlled hand pump for applying shear stress on the specimen. The shear stress increasing rate would be regular and may be controlled and changed by means of electrical pumps. As the power supplier will be a 12 volts battery, the developed shear apparatus will also be portable. A series of shear tests have been conducted using both conventional and developed direct shear test apparatus. To be able to have a close comparison, artificially made specimens containing a discontinuity have been tested. The results obtained from these apparatus show some discrepancies which makes one think about the results of the conventional portable shear box.