A Shear Model for Rock Microfracture Size Estimation Based on AE Measurement

Moment tensor analyses suggest that shear microfractures dominate the compressive characteristics of most rock materials. However, the microfracture sizes estimated by the traditional shear model are unrealistically large. This paper presents a novel shear model for microfracture size estimation in sandstone specimens based on AE measurements. The sizes of 342 microfractures were estimated via the proposed model; most are found to range from 0.0022 to 1.80 mm with an average microfracture size slightly smaller than the average grain size. The microfracture size distribution characteristics observed here are similar to those observed by microscope for stressed sandstone, suggesting that more realistic microfracture sizes can be obtained with the proposed model than the traditional shear model.