Document Type : Original Research Paper

Authors

• Inobat Agzamova ¹
• Mukhiddin Juliev ²
• Bаtir Abdurakhmanov ³
• Nasiba Dadakhodjaeva ⁴
• Alimjan Akhunjanov ³
• Elboy Kurbanov ³
• Nodira Ibragimova ³
• Zulfizar Esanova ⁵

¹ Tashkent State Technical University, Universitet 2, Tashkent, 100095, Uzbekistan

² Institute of Fundamental and Applied Research, “TIIAME” National Research University, Kary-Niyaziy Str. 39, Tashkent 100000, Uzbekistan

³ Institute of Hydrogeology and Engineering Geology, University of Geological Sciences, Mirzo Ulugbek district, Olimlar ko'chasi, 64, Tashkent, Uzbekistan

⁴ University of Geological Sciences, Mirzo Ulugbek district, Olimlar ko'chasi, 64, Tashkent, Uzbekistan

⁵ Karshi State Technical University, 225 Mustaqillik Avenue, Qarshi, Qashqadaryo, Uzbekistan

Abstract

Underground extraction in fractured polymetallic rock masses may trigger progressive deformation and surface collapse where faults, weak cover, groundwater pathways, and mining-induced disturbance interact. This study presents an evidence-constrained engineering-geological reconstruction of five collapse sinkholes that developed near the Khandiza polymetallic mine, southern Uzbekistan, during 2016–2018. The analysis integrates underground and surface mapping records, fault-distance classes, laboratory strength data, deformation observations, hydrogeological evidence, mine-development information, and repeated field measurements. The archival fracture-voidness coefficient, used as a comparative engineering index distinct from matrix porosity, increases from 1.5–3.0% at 15–20 m from major faults to 4.5–8.0% within fault zones and their influence belts, while uniaxial compressive strength decreases from 5–10 MPa to below 1–3 MPa. Across 28 laboratory shear-strength records, cohesion averages 16.83 ± 4.81 MPa and internal friction angle 42.05 ± 2.63°, with ranges of 7.1–27.0 MPa and 36–47°, respectively. The five sinkholes reached dimensions of approximately 12 × 13 to 60 × 80 m and visible depths of 6–40 m. Archived observations indicate a deformed area of about 0.8 km² and local crack widening or settlement rates up to 1–2 mm/day. Mining control is supported by the non-backfilled caving environment, progressive roof collapse, the reported connection of Sinkhole 2 to the 1340 m horizon, and the spatial-temporal association between extraction and surface deformation. Groundwater and seismic shaking are interpreted as contributory rather than independently demonstrated causes. The proposed model is therefore mechanistic and semi-quantitative rather than a calibrated predictive simulation.

Keywords

• rock mass stability
• fracture networks
• mining-induced sinkholes
• underground mining
• hydro-mechanical coupling

Main Subjects

• Subsidence