METHOD AND APPARATUS FOR MEASURING CHARACTERISTICS OF ROCKS

摘要

An expansible shear head device within a pulling cradle is lowered into a bore hole; and the device is expanded hydraulically to exert a predetermined normal pressure on the side walls of the bore hole. The pressure plates of the device are ribbed for permitting interlocking with the rock. Vertical shear stress is exerted on the rock by pulling on the device. The shear head includes a body having a plurality of hinge points, and is laterally expansible. A laterally extendible plunger with a movable shear plate is mounted opposite to a similar shear plate which is secured to permit some deflection of the body about its hinge points from its normal parallel configuration as the shear force moves the body through the bore. The body is locked in its normal parallel configuration until the shear force is applied.