Thermal Recovery of Backfilled Pit in the Gulianhe Strip Coalmine in the Hola Basin in Northern Da Xing’Anling Mountains, NE China

Ruixia He,Xinyu Li,Xiaoying Jin,Yadong Huang,Yan Li,Futing Ma,Hongwei Wang,Huijun Jin,Doudou Jin,Meiquan Zhu

doi:10.3389/feart.2022.806022

Abstract

In the northern Da Xing’anling Mountains in Northeast China on the southern margin of the Eastern Asia permafrost body, the ground thermal state and boreal ecological environment are sensitive to climate change and human activities. Since the 1980s, the Hola Basin here has been continuously and extensively developed. In particular, open pits and later backfilling in strip coal mining alters land–atmospheric hydrothermal exchanges in permafrost regions, leading to serious damages to the permafrost environment and boreal forest. After mining, pits need to be backfilled timely and properly for hydrothermal recovery of Xing’an permafrost and the boreal ecological environment. In this study, based on the comparative analysis of monitored ground temperatures in backfilled and undisturbed areas, influencing factors of thermal recovery after backfilling were analyzed through numerical simulations. Results show that the thermal recovery of permafrost in the backfilled area is closely related to temperature, depth, material, and soil moisture content of backfill. The warmer, finer, and thicker the backfill soils, the longer the permafrost recovery. Thermal recovery of permafrost also depends on the moisture content of backfill; the shortest recovery occurs at 15–25% in the backfilled soil moisture content. Based on numerical simulations and combined with enlightenments from features of the ecosystem-protected Xing’an permafrost in Northeast China, a composite configuration of organic soil, crush-rock layer, and proper re-vegetation measures is advised. Based on prudent regulation of heat transfer modes, this composite backfilling method can effectively cool the backfilled ground and can even possibly offset the climate warming.

Highlights

Coal is one of the important pillar industries in most northern countries
Validation and parameterization of numerical model are based on field monitoring data of ground temperature in Borehole T1
Numerical simulation results of ground temperatures in the permafrost zone are in good agreement with field monitoring data, as indicated in the similar changing trends of simulated and monitored ground temperatures (Figure 5)

Summary

Introduction

Coal is one of the important pillar industries in most northern countries. With the exploitation and transportation of coal resources, some problems of environmental pollution and ecological damage have become increasingly prominent and widely concerned, with serious impacts on the sustainable development of coalmine enterprises and the ecological environment (e.g., Bell et al, 2001; Pandey et al, 2014; Qian et al, 2017). It is important to protect the natural environment in the processes of coal resource exploitation and to propose reasonable, economical, and effective measures for solving engineering problems in the mining area. Pit backfilling is the most effective and economical method for land reclamation after coal mining It reduces geohazard risks and protects the environment and helps recover surface vegetation after land reclamation (e.g., Moreno-de Las Heras et al, 2009; Erener, 2011; Zhang L. et al, 2015; Wang et al, 2016, 2021a, 2021b). Because of paucity of field monitoring data, the influencing mechanisms for and factors on ground temperature recovery in backfill areas have not yet been studied systematically (e.g., Li et al, 2014; Cao et al, 2016; Gao et al, 2017). Key influencing factors for the thermal recovery of backfilled soils, such as backfill materials and their properties, are seldom mentioned

Methods

Results

Discussion

Conclusion