The mechanical behaviour and failure modes of volcanic rocks: a review

Abstract The microstructure and mineralogy of volcanic rocks is varied complex, their mechanical behaviour similarly complex. This review summarises recent developments in our understanding the failure modes rocks. Compiled data show that, although porosity exerts a first-order influence on uniaxial compressive strength rocks, parameters such as partitioning void space (pores microcracks), pore crystal size shape, alteration also play role. presence water, strain rate, temperature can strength. We discuss merits micromechanical models (which includes available fracture toughness data). that effective pressure required for onset hydrostatic inelastic compaction decreases function increasing porosity, represents cataclastic collapse. Differences between brittle ductile (stress-strain curves evolution acoustic emission activity) from triaxial deformation experiments are outlined. Brittle typically characterised by shear formation, an increase permeability. Ductile either be distributed (cataclastic collapse) or localised (compaction bands) decrease tuffs deform delocalised cataclasis extrusive develop bands (planes collapsed pores connected microcracks). envelopes compactive yield caps compared, highlighting control stresses brittle-ductile transition shear-enhanced compaction. However, these cannot explained alone other microstructural parameters, size, must Compactive elliptical, similar to sedimentary but linear Linear considered result high pre-existing microcrack density and/or heterogeneous distribution porosity. it still unclear, with data, why some not others, which attributes compaction, linear. Young’s modulus, tensile strength, frictional properties Finally, we how laboratory have used improve systems highlight directions future research. A deep rock help refine tools routinely monitor hazards posed active volcanoes.