Effects of zeta potential on microcrack growth in rock under relatively low uniaxial compression

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Abstract
The seismic velocity, attenuation, and acoustic emission were measured to detect and monitor microcrack growth in samples of Inada granite as they were held under constant uniaxial compression. The samples were saturated with two kinds of aqueous solutions, aluminum nitrate solutions and potassium nitrate solutions, and the ζ potentials at the rock (mineral)‐water interface were varied with different concentration of the salts in the solutions. The axial stress was held constant at 94 MPa, that is, the stress at the onset of dilatancy for the present sample. At this stress level, the development of microcracks, which was indicated mainly by the decrease in velocity (>10%) of elastic waves propagating in the direction perpendicular to the axis of stress, was found to occur after certain time has elapsed and to be strongly affected by the ζ potential. An “incubation period” for the microcrack growth (i.e., brittle creep) becomes shorter, and subcritical crack growth rate becomes higher as the ζ potential approaches zero. A model of tensile cracking in a rock loaded in compression (circular hole model) was proposed to explain the observed time‐dependent microcracking, and some chemomechanical mechanisms of the ζ potential effects are discussed.