Investigation of fracture properties and microbially induced calcite precipitation (MICP) restoration in coal mining areas within the diverse Terrain of Northern Shaanxi, China

Abstract

Abstract The complex and diverse nature of coal mining sites, including different landforms and working conditions, presents challenges for rehabilitation efforts. To address this, we conducted a comprehensive experimental study focusing on microbially induced calcium carbonate precipitation (MICP) remediation, considering the fracture characteristics of coal mining sites. The MICP-restored samples were subjected to confined/unconfined compressive strength, uniaxial/triaxial permeability, and souring tests to assess their restoration efficacy. The results showed that under similar mining conditions, the average depth of parallel fractures was 0.185 m for loess ridges, 0.16 m for the valley, and 0.146 m for the blown-sand region, while the average depth for boundary fractures was 0.411 m for loess ridges, 0.178 m for the valley, and 0.268 m for the blown-sand region. Notably, parallel fractures showed negligible filling in all landforms, whereas boundary fractures in the blown-sand region were completely filled with wind-deposited sand. The valley landform was filled with alluvium and wind-deposited sand, whereas the loess landform was filled with wind-deposited sand and loess. MICP-restored soil samples in all landforms achieved a strength comparable to remolded fracture-free soil samples. Across all landforms, the maximum permeability coefficient of MICP-restored soil samples closely matched that of remolded fracture-free soil samples. Under similar topographic and rainfall conditions MICP restorations scoured 31.3 g on blown-sand region, 19.3 g on loess ridges, and 17.6 g on valleys. These research findings provide an experimental foundation for MICP repair of coal mining ground fractures.

Keywords

• Coal mining
• Ground fractures
• MICP
• Wind-deposited sand
• Loess ridges
• Valley