Jinmao Ju

Land subsidence induced by underground coal mining consistently leads to persistent ponding in coal-grain overlapping areas (COAs), substantially impairing agricultural productivity. However, amid stringent farmland protection policies, mining operations face significant sustainability challenges. In this study, Guqiao Coal Mine in Anhui of China, is taken as a case, and four mining-reclamation schemes were conducted to compare patterns, and applicable conditions for each scheme are proposed based on concurrent mining and reclamation (CMR). Results show that: (1) Historically, traditional mining-reclamation (TMR) dominated due to low immediate reclamation costs despite extensive farmland loss; (2) Currently, earthwork-conserving CMR (ECMR) offers practical advantages by balancing economic investment and farmland reclamation. ECMR enhances land reclamation and reduces indirect costs, but leads to premature farmland degradation and prolonged compensation burdens; (3) Henceforth, reducing-degradation CMR (RCMR) can eliminate farmland degradation but is constrained by low coal-extraction rates, making it less feasible under current coal economic constraints; (4) In the prospective future, coupling CMR (CCMR) delays land degradation while improving reclamation efficiency, shortening the restoration cycle by 42% for ECMR, and raising coal-extraction rate to over 92% for RCMR. It restores 70% of degraded farmland and reduces seedling compensation costs by over 63 million yuan for ECMR in 30 years. CCMR also has strong performance in reducing surface ponding, maintaining grain security, and minimizing social displacement. Our findings underscore CCMR's superiority in aligning economic, ecological, and social objectives. It offers a replicable model for sustainable resource management in C1OAs globally, particularly under tightening environmental and agricultural policies.

The carbon storage in forest ecosystems is closely linked to biomass, and its dynamic changes are of significant importance for assessing forest structure and function, as well as their response to global climate change. Recently, the research on the influencing mechanism of forest carbon storage has been a hotpot in the field of forest ecology. However, it remains unclear on the relationships among stand structure, stand stability, and carbon storage. The issues needed to be answered are as follows: How are tree density, tree species diversity, stand structural characteristics, stand stability, and carbon storage correlated? Is there a direct or indirect effect between tree density, tree species diversity, stand structural characteristics, stand stability, and carbon storage? Do these factors have an impact on stand stability, and, subsequently, carbon storage? What is the crucial factor in the mechanism that influences carbon storage? Here, the natural Quercus mongolica forests in the Xiaolong Mountains were taken as the research object. Several methods, including Pearson’s correlation, the best-fitting SEM, and multiple regression, were used to examine the relationships among tree density, tree species diversity, stand structural characteristics, stand stability, and carbon storage. Our results show that there were correlations between tree density, tree species diversity, stand structural characteristics, stand stability, and carbon storage. Tree density not only directly affects stand stability but also indirectly influences it through the mediation of tree species diversity and stand structural characteristics. Meanwhile, tree density also indirectly influences carbon storage through the mediation of tree species diversity, stand structural characteristics, and stand stability. Crown volume exerts the greatest influence on stand stability, while carbon storage is mostly impacted by stand stability. Overall, the combination of tree density, tree species diversity, stand structural characteristics, and stand stability influences carbon storage (66.4%). Therefore, it is important to consider stand stability when assessing carbon sequestration potentials; furthermore, the importance of tree density, tree species composition, and stand structural characteristics should be emphasized. Our research provides a scientific basis for conservation and management decision-making in natural forests and offers novel insights as well as a scientific reference for future large-scale carbon storage investigations.

The Baishitou Tunnel of the Dali–Lincang railway project is a weakly cemented surrounding rock tunnel with geological bedding bias. The deformation of the surrounding rock on the side with the greatest stress is nearly 1 m, which seriously affects construction progress and significantly increases construction cost. In order to achieve the goal of safe, efficient, economic, and socially sustainable development in tunnel construction, it is necessary to study the large deformation of weakly cemented surrounding rock in the geological bedding bias tunnel. Engineering technicians first used field measurement methods to monitor the pressure and deformation of surrounding rock and studied the deformation law of surrounding rock pressure and deformation over time. Secondly, numerical simulation methods were used to study the stress distribution law, plastic failure depth, and initial support stress of tunnel-surrounding rock under different support schemes, and they independently designed a yielding anchor bolt with enhanced anchoring, which plays a key role in controlling the deformation of the surrounding rock. The main conclusions are as follows: (1) Through the analysis of the measured pressure data of the initial branch of the section and the displacement monitoring data of the measuring point, it is found that the deformation of the surrounding rock of the weakly cemented tunnel is large and fast. At the same time, the pressure and deformation of the surrounding rock of the tunnel are greatly affected by geological bedding bias. After the excavation of the inverted arch, the pressure and deformation of the surrounding rock at the right arch shoulder of the tunnel are the highest, reaching 0.832 MPa and 0.53 m, which are significantly greater than those on the left arch shoulder. (2) Using the numerical simulation software FLAC3D 5.0 and ANSYS 16.0, a three-dimensional numerical model of the roadway was established to simulate the stress distribution, plastic failure depth, and initial support stress of the tunnel’s surrounding rock under the influence of geological bedding bias. By comparing the support effects of different support schemes, it was concluded that under the support scheme of “I25 arch + yielding anchor bolt”, the surrounding rock failure depth was small, the stress concentration was weak, and the initial support deformation was controllable as a whole. (3) The self-designed yielding anchor bolt has good economic and applicable value, and it has received the expected support effect after field verification. (4) Various special support measures such as advanced grouting anchor rods, casing arches, or temporary cross supports are used to assist in controlling the large deformation of weakly cemented surrounding rock tunnels to a certain extent.