Dehydration and deformation of intact cylinders of serpentinite

Experimental deformation of intact lizardite serpentinite samples was carried out to study the effect of the dehydration reaction to olivine + talc + water under controlled pore water pressure. The dehydration reaction dramatically increases the porosity of the sample, causing weakening, but progressive pore collapse during deformation leads to strain-hardening. The concepts of critical state soil mechanics can be used to describe the overall behaviour of the porous material. At low strain rates, a transition to linear-viscous flow was observed and inferred to be due to the formation of fine-grained olivine in the dehydration reaction. The resultant inability of the rock to support high loads during dehydration at low strain rates means that the production of high pressure water by dehydration and its subsequent expulsion will favour seismogenic failure in the surrounding rocks not directly involved in the dehydration reaction, rather than the serpentinite itself.