Static mechanical properties and shock loading response of granite

Abstract

In granitic rocks the quasi-static uniaxial strain loading paths are often observed to diverge from their failure envelopes (uniaxial stress). Similar behavior is observed in Westerly granite and Climax stock granodiorite when they are tested in uniaxial strain to 10 kbar and in uniaxial stress to 22 kbar at strain rates of 10−4 s−1. Failure in the latter tests occurs only by brittle fracture. Plane shock loading occurs under conditions of uniaxial strain, and upon loading to slightly above the Hugoniot elastic limit, yielding is consistent only with brittle fracture. The shock data cannot be reconciled with the low results if loading occurs along the uniaxial strain path at low . A plausible explanation may be made, however, if the low uniaxial strain path and the failure envelope are adjusted to strain rates consistent with those of shock deformation. Thus in response to a shock wave, granite loads to peak stresses near 30 kbar; beyond this a slight relaxation occurs. As peak stress is further increased, relaxation is followed by a sudden loss of rigidity in the 50- to 60-kbar range, which is interpreted as intersection with the failure envelope.