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<p>Most existing research on layered rock anisotropy focuses on soft and hard interbedded formations, leaving the pure structural effect of bedding planes on lithologically uniform hard brittle rock largely unexplored. Layered dolomite recovered from the deep Daxiagu Tunnel is investigated in this study, where the intact matrix and bedding planes share identical dolomite lithology but vary in microstructural compaction. A comprehensive experimental program comprising Brazilian splitting, uniaxial, and triaxial compression tests integrated with acoustic emission (AE) and digital image correlation (DIC) is conducted across bedding dip angles from 0° to 90° and spacings from 10 to 25&#xa0;mm. Experimental results indicate that the mechanical parameters of the dolomite exhibit an exponential attenuation with decreasing bedding spacing, capturing a structural transition from isolated microstructural defects to an interconnected weak network. Compressive strength displays a pronounced U-shaped anisotropy dictated by the shear stress state on the bedding interfaces, while higher bedding density prolongs the fracture process and alters the macroscopic failure mode. Furthermore, a dual control mechanism governs rockburst proneness: weak bedding planes pre-dissipate strain energy via premature microcracking, whereas the high in-situ stress environment severely compacts the intact matrix, enhancing its ultimate energy storage capacity. Although currently limited to laboratory-scale static loading without considering dynamic excavation disturbances or size effects, these findings yield direct practical implications for deep tunnel stability management. Support designs must prioritize shear resistance and extended anchoring within 30° to 60° dip zones, while targeted destressing techniques must be implemented in intact matrix zones to mitigate violent strainbursts.</p>

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Fracture Evolution and Mechanical Anisotropy of Layered Dolomite

  • 期刊论文

  • 发表日期：

    2026年7月7日

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  • Ruihan Li,
  • Zhigang Yao,
  • Yong Fang,
  • Junyang He,
  • Song Pu

摘要

Most existing research on layered rock anisotropy focuses on soft and hard interbedded formations, leaving the pure structural effect of bedding planes on lithologically uniform hard brittle rock largely unexplored. Layered dolomite recovered from the deep Daxiagu Tunnel is investigated in this study, where the intact matrix and bedding planes share identical dolomite lithology but vary in microstructural compaction. A comprehensive experimental program comprising Brazilian splitting, uniaxial, and triaxial compression tests integrated with acoustic emission (AE) and digital image correlation (DIC) is conducted across bedding dip angles from 0° to 90° and spacings from 10 to 25 mm. Experimental results indicate that the mechanical parameters of the dolomite exhibit an exponential attenuation with decreasing bedding spacing, capturing a structural transition from isolated microstructural defects to an interconnected weak network. Compressive strength displays a pronounced U-shaped anisotropy dictated by the shear stress state on the bedding interfaces, while higher bedding density prolongs the fracture process and alters the macroscopic failure mode. Furthermore, a dual control mechanism governs rockburst proneness: weak bedding planes pre-dissipate strain energy via premature microcracking, whereas the high in-situ stress environment severely compacts the intact matrix, enhancing its ultimate energy storage capacity. Although currently limited to laboratory-scale static loading without considering dynamic excavation disturbances or size effects, these findings yield direct practical implications for deep tunnel stability management. Support designs must prioritize shear resistance and extended anchoring within 30° to 60° dip zones, while targeted destressing techniques must be implemented in intact matrix zones to mitigate violent strainbursts.