Influence of Water on the Fracture Process of Marble with Acoustic Emission Monitoring

Abstract

Water has a great influence on rock fracture process, and it is necessary to explore the activity of cracks for saturated rocks at key stress points. By uniaxial compression test and acoustic emission (AE) tests, four key points of stress-strain curve for dry and saturated marble specimens are determined. Those four key stress points include: crack closure stress (point A), crack initiation stress (point B), crack damage stress (point C) and peak stress (point D). By analyzing dominant frequencies and amplitude of AE waveforms of the whole loading process and in the vicinity of key points, the fracture process of samples was studied. The results show that there are two concentrations of dominant frequency bands in both dry and saturated marble, and the ranges of dominant frequency bands of the saturated seem wider. Due to the existence of water, the number and energy of AE waveforms decrease relatively during the whole test. This phenomenon indicates that water enhances the ductility and creep characteristics of rock. The appearance of lots of AE waveform signals with low dominant frequency is the precursor information of intense crack propagation and failure for dry rock, and the effects of water increased the number of micro-tensile failures for saturated rock in the vicinity of each key point. From point A, point B, point C to point D, the proportions of H-type bands in the vicinity of each key point for dry rock show a trend of increasing — decreasing — sharply decreasing, while those for saturated rock follow the law of increasing — decreasing — increasing.