Underground coal mining induces significant surface deformation and environmental damage, particularly in deeply buried mining areas with thin bedrock and thick alluvial layers. Based on the case study of the Zhaogu No.2 coal mine in Xinxiang City, Henan Province, China, this study employs a comprehensive research methodology, integrating field investigations, numerical simulations, and theoretical analyses, to explore the surface subsidence features at deeply buried mining areas with thin bedrock and thick alluvial layers, to reveal the effect of alluvial thickness on the surface subsidence characteristics. The findings indicate that the surface subsidence areas span 4.2 km2 with an advanced influence distance of 540 m. The rate of surface subsidence primarily depends on the panel's position and its advancing rate. Moreover, the thickness of the alluvial layer amplifies both the extent and magnitude of surface deformation. The displacement of overlying rock primarily exhibits a two-stage progression: the thin bedrock control stage and the alluvial control stage. In the thin bedrock control stage, surface subsidence initiates with relatively low subsidence values and amplitudes. Subsequently, in the alluvial control stage, surface subsidence accelerates, leading to a rapid increase in both subsidence values and amplitudes. These characteristics of rock formation displacement result in distinct phases of surface subsidence. Furthermore, the paper addresses the utilization of surface subsidence areas and proposes a method for calculating reservoir storage capacity in these areas. According to calculations, the storage capacity amounts to 1.05e7 m3. The research findings provide valuable insights into the surface subsidence laws in regions with similar geological conditions and practical implications for the management and utilization of subsided areas.

Large deformations of strata caused by shallow tunnel excavation in urban reclamation areas pose a serious threat to geological safety. In this paper, geo-mechanical model tests and numerical simulations were conducted to investigate the large deformation characteristics based on the Haicang tunnel in Xiamen, China. First, the tunnel excavation process using the double side drift method was simulated to reveal the large deformation characteristics and influencing factors. Then, geo-mechanical model tests were conducted to further investigate the deformation characteristics, stress release patterns and pore water pressure evolution. The results show that groundwater and the thickness of the backfill soil are the primary factors affecting the deformation behavior. Meanwhile, the stress release and pore water pressure dissipation resulting from the core construction procedure are direct causes of large deformation. The research results can serve as a reference for the prevention and control of large deformation in shallow buried tunnel construction.

Coal occupies a dominant position in China's energy structure. However, overburden failure is the root cause of several safety and environmental issues. With the successive proposals of green mining and the dual-carbon strategy, the green development of coal-based energy has become the priority development direction. Overburden grout injection has become the preferred choice in the green mining technology system. The potential ecological health risk of heavy metal contamination in fly ash matrix soil was analyzed and evaluated in Xinyi coalmine. It is pointed out that only using fly ash as grouting material may cause irreversible harm to groundwater system. Based on the solid waste utilization and sustainable development, the close packing theory was adopted to determine that poorly graded gangue can be used as filling aggregate. Meanwhile, the passivation characteristics of loess to reduce the heavy metal in fly ash by increasing the water-stable aggregate content were elucidated. The properties and parameters of grouting materials composed of gangue, loess, and fly ash were analyzed, and a reasonable upper limit of slurry concentration was determined to be 72%. The field application indicates that the maximum surface subsidence is 473 mm, and the damage degree of buildings is within grade I, liberating 163 Mt of coal resources under the buildings. The harmless treatment of solid waste has been achieved, effectively reducing the negative external impact of coal mining. It is equivalent to saving 95.95 million yuan while promoting the green, safe, and sustainable development of coal enterprises.

Permafrost landscape dynamics were investigated between 1998 and 2012 at Neleger, near Yakutsk, in central Yakutia, to determine the effects on permafrost of clear cutting of larch forest. Changes in ground temperature, soil moisture, seasonal thaw depth and surface subsidence at a control (forest) site and a site cleared of forest were associated with vegetation recovery and climate change. Before clear cutting (1998-2000), permafrost temperatures were similar to the 1998-2012 average. After cutting (2001-04), permafrost temperatures decreased in the undisturbed forest site, but increased in the cleared site. The thermal disturbance of clear cutting caused increases in thaw depth and led to 4.8cm of ground surface subsidence. Significant warming of permafrost in 2005-08, coincident with maximum snow depth and precipitation, caused up to 14.6cm of additional ground subsidence, which represented the maximum changes observed in the landscape. Between 2009 and 2012, permafrost began to stabilise and subsidence was restricted to 1.8cm. The reduced thaw depth and the growth of young birch shoots during this period indicated stabilisation of permafrost conditions and the beginning of landscape restoration. Copyright (c) 2016 John Wiley & Sons, Ltd.

Thawing of ice-rich permafrost followed by surface subsidence results in irregular, depressed landforms known as thermokarst. Many remote sensing studies have identified thermokarst landforms and mapped their changes. However, the intrinsic dynamic thermokarst process of surface subsidence remains a challenge to quantify and is seldom examined using remote sensing methods. In this study we used spaceborne interferometric synthetic aperture radar (InSAR) data to map surface subsidence trends at a thermokarst landform located near Deadhorse on the North Slope of Alaska. A pipeline access road constructed in the 1970s triggered the thawing of the permafrost, causing subsequent expansion of the thermokarst landform. Using Phased Array type L band Synthetic Aperture Radar images acquired by the Advanced Land Observing Satellite-1, our InSAR analysis reveals localized thermokarst subsidence of 2-8cm/yr between 2006 and 2010, equivalent to an ice volume loss of about 1.2 x 10(7)m(3)/yr. Comparisons between InSAR subsidence trends and lidar microtopography suggest a characteristic time of 8years of thermokarst development. We also quantitatively explain the difficulty, uncertainties, and possible biases in separating thermokarst-induced, irreversible subsidence from cyclic seasonal deformation. Our study illustrates that InSAR is an effective tool for mapping and studying active thermokarst processes and quantifying ice loss.