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<p>Carbon dioxide phase&#xa0;transition fracturing (CDPTF) represents an environmentally sustainable method for rock fragmentation, with applications in coal seam permeability enhancement, tunnel excavation, and open-pit mining operations. However, current CDPTF research primarily focuses on rock specimens without inherent flaws, leaving uncertainties regarding internal flaw pressure and damage characteristics in flawed rocks. To investigate these aspects, this study conducted CDPTF experiments on specimens containing pre-cracks and pre-holes, monitoring flaw pressure and lateral strain measurements. The research methodology incorporated scanning electron microscopy to examine fracture characteristics in the erosion zone and rock fracture surfaces, while mercury injection tests assessed rock damage at various positions. The results demonstrate that under CDPTF conditions, pre-crack specimens fracture along the crack orientation; the breakdown pressure of pre-crack specimens increases when the crack width is increased or the crack length is reduced. Conversely, larger pre-hole diameters correlate with decreased breakdown pressure in pre-hole specimens. As release pressure intensifies, the microscopic characteristics of the pre-crack sandstone’s erosion zone and fracture surface transition from intergranular to transgranular fracture patterns. The high-pressure gas impact generates an erosion zone at the sandstone specimen’s top. Additionally, stress waves induce damage to the sandstone, reducing its pore structure complexity, with damage severity increasing in proximity to the nozzle.</p>

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Breakdown Pressure and Damage Characteristics of Flawed Rocks Subjected to Carbon Dioxide Phase Transition Fracturing

  • 期刊论文

  • 发表日期：

    2025年3月10日

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  • Shuaishuai Niu,
  • Shengtao Zhou,
  • Xuedong Luo,
  • Zong-Xian Zhang,
  • Nan Jiang,
  • Xianzhong Meng,
  • Yu Lei

摘要

Carbon dioxide phase transition fracturing (CDPTF) represents an environmentally sustainable method for rock fragmentation, with applications in coal seam permeability enhancement, tunnel excavation, and open-pit mining operations. However, current CDPTF research primarily focuses on rock specimens without inherent flaws, leaving uncertainties regarding internal flaw pressure and damage characteristics in flawed rocks. To investigate these aspects, this study conducted CDPTF experiments on specimens containing pre-cracks and pre-holes, monitoring flaw pressure and lateral strain measurements. The research methodology incorporated scanning electron microscopy to examine fracture characteristics in the erosion zone and rock fracture surfaces, while mercury injection tests assessed rock damage at various positions. The results demonstrate that under CDPTF conditions, pre-crack specimens fracture along the crack orientation; the breakdown pressure of pre-crack specimens increases when the crack width is increased or the crack length is reduced. Conversely, larger pre-hole diameters correlate with decreased breakdown pressure in pre-hole specimens. As release pressure intensifies, the microscopic characteristics of the pre-crack sandstone’s erosion zone and fracture surface transition from intergranular to transgranular fracture patterns. The high-pressure gas impact generates an erosion zone at the sandstone specimen’s top. Additionally, stress waves induce damage to the sandstone, reducing its pore structure complexity, with damage severity increasing in proximity to the nozzle.