Study of the Dynamic Fracturing Process and Stress Shadowing Effect in Granite Sample with Two Holes Based on SCDA Fracturing Method

In this paper, an experimental study on the dynamic propagation of fractures in granite samples under various injection schemes and initial stress conditions is carried out using a soundless cracking demolition agent (SCDA). Through the combination of acoustic emission (AE) monitoring, stress measurement and fracture morphology observation, the dynamic fracturing process is systematically analyzed. The stress shadowing effect between the two fractures is studied based on the results of stress monitoring and growth of fractures. The experimental results show that SCDA has a strong fracturing capacity and the stress shadowing effect between the boreholes makes the fractures tend to extend toward the direction connecting the two boreholes in the early stage of fracturing, leading to a more complicated fracture propagation mode. The change of stress within the sample can be divided into three stages, which correspond to the initiation of fractures, the initial formation of surface fractures and the stable propagation towards both sides and the lower part of the existing fractures. The fractal dimension of fractures and the roughness of fracture surfaces are quantitatively evaluated. The results show that the initial stress conditions and injection schemes are the key factors affecting the fracturing results. The smaller the side stress coefficient, the stronger the ability to form complex fractures. The optimal injection time interval varies with the selection of evaluation parameters and the fractal dimension of the sample is the highest when the injection time interval is 9 h.

Automated summary

In this study, the dynamic propagation of fractures in granite samples under various injection schemes and initial stress conditions using SCDA was experimentally investigated. The experimental results showed that SCDA had a strong fracturing capacity, and the stress shadowing effect between the boreholes led to a more complicated fracture propagation mode in the early stage.