We investigated differences of overburden failure induced by mining multiple seams in ascending and descending sequences under a large water body. A case study that involves mining in an ascending sequence was the Beizao coal mine, which is under the Bohai Sea, and one that involves mining in a descending sequence was the Cuizhuang coal mine, which is under Weishan Lake. Using numerical simulations with the same geological conditions as the in-situ measurements, the effects of different interburden thicknesses on mining were compared. The results showed that the ratios of the heights of water-conducting fractured and caving zones to the cutting height both increased as the interburden thickness was reduced. An ascending sequence is recommended where there is a thin interburden and thin bedrock, and where the mining seams obviously interact. The descending sequence is recommended where there is no apparent interaction between the seams. Both will produce a relatively small water-conducting fractured zone. In dieser Studie wird der Einfluss des Abbaus von mehreren Kohleflözen in unterschiedlicher, d. h. aufsteigender und absteigender, Reihenfolge auf ein Deckgebirgsversagen in Zusammenhang mit großen Wasservorkommen untersucht. Eine Fallstudie behandelt einen Kohleabbau mit aufsteigender Abbausequenz in der Beizao Kohlemine, welche sich unterhalb des Bohai Sees befindet. Eine weitere Studie untersucht eine absteigende Abbaureihenfolge am Fallbeispiel der Cuizhuang Kohlemine unterhalb des Weishan Sees. Durch numerische Modelle, bei denen die geologischen Bedingungen an die jeweiligen Vor-Ort Messungen angepasst worden sind, werden die Einflüsse unterschiedlicher Zwischenmittelmächtigkeiten verglichen. Die Ergebnisse zeigen, dass die Verhältnisse der Mächtigkeiten wasserführender, geklüfteter und aufgelockerten Zonen zur Abstichhöhe jeweils zunehmen, wenn die Zwischenmittelmächtigkeit reduziert wird. Eine aufsteigende Abbausequenz ist zu empfehlen, wenn geringe Überdeckungen bzw. geringe Deckgebirgsmächtigkeiten vorliegen und sich Kohleflöze offensichtlich gegenseitig beeinflussen. Eine absteigende Abbausequenz ist zu empfehlen, wenn eine gegenseitige Beeinflussung der Flöze nicht zu erkennen ist. Beide Abbausequenzen führen zu relativ schmalen, wasserführenden Auflockerungszonen. 研究了大型水体下近距离煤层上行和下行开采时覆岩破坏的差异。以渤海下上行开采的北皂煤矿和微山湖下下行开采的崔庄煤矿为例,通过相同地质条件下的现场实测结果和数值模拟结果对比,分析了开采顺序和夹矸厚度(煤层间距)对覆岩破坏发育高度的影响。结果表明:随着夹矸厚度的减小,裂采比和垮采比均有所提高。在薄夹层、薄基岩和开采导致的覆岩破坏相互作用明显时,推荐采用上行开采方式;在厚夹矸和开采导致的覆岩破坏相互作用不明显时,推荐采用下行开采方式。两种建议开采方式均有助于减小导水裂隙带发育高度。 Hemos investigado diferencias en la falla por sobrecarga inducida por la minería de múltiples veas en secuencias ascendentes y descendentes bajo un gran cuerpo de agua. Un caso de estudio que involucra minería en una secuencia ascendente se realizó en la mina de carbón Beizao que está debajo del mar Bohai mientras que uno que involucra minería en secuencia descendente fue la mina de carbón Cuizhuang que está bajo el lago Weishan. Usando simulaciones numéricas con las mismas condiciones geológicas que las medidas in situ, se compararon los efectos de diferentes espesores sobre la zona minera. Los resultados mostraron que las relaciones de las alturas de las zonas de fractura y de cuevas por las que se conduce el agua, se incrementaron cuando el espesor se redujo. Una secuencia ascendente se recomienda donde hay un delgado cuerpo de rocas y donde las vetas obviamente interactúan. La secuencia descendente es recomendada donde no hay una interacción aparente entre las vetas. Ambas producirán una zona relativamente pequeña de fracturas por la que se conduce el agua.

Concrete is a cornerstone material in the construction industry owing to its versatile performance; however, its inherent brittleness, low tensile strength, and poor permeability resistance limit its broader application. Graphene, with its exceptional thermal conductivity, stable lattice structure, and high specific surface area, presents a transformative solution to these challenges. Despite its promise, comprehensive studies on the multifunctional properties and underlying mechanisms of graphene-enhanced concrete remain scarce. In this study, we developed a novel concrete composite incorporating cement, coarse sand, crushed stone, water, and graphene, systematically investigating the effects of the graphene dosage and curing duration on its performance. Our results demonstrate that graphene incorporation markedly improves the material’s density, brittleness, thermal conductivity, and permeability resistance. Notably, a comprehensive analysis of scanning electron microscopy (SEM) images and thermogravimetric (TG) data demonstrates that graphene-modified concrete exhibits a denser microstructure and the enhanced formation of hydration products compared to conventional concrete. In addition, the graphene-reinforced concrete exhibited a 44% increase in compressive strength, a 0.7% enhancement in the photothermal absorption capacity, a 0.4% decrease in maximum heat release, a 0.8% increase in heat-storage capacity, and a 200% reduction in the maximum penetration depth. These findings underscore the significant potential of graphene-reinforced concrete for advanced construction applications, offering superior mechanical strength, thermal regulation, and durability.

Concrete is a cornerstone material in the construction industry owing to its versatile performance; however, its inherent brittleness, low tensile strength, and poor permeability resistance limit its broader application. Graphene, with its exceptional thermal conductivity, stable lattice structure, and high specific surface area, presents a transformative solution to these challenges. Despite its promise, comprehensive studies on the multifunctional properties and underlying mechanisms of graphene-enhanced concrete remain scarce. In this study, we developed a novel concrete composite incorporating cement, coarse sand, crushed stone, water, and graphene, systematically investigating the effects of graphene dosage and curing duration on its performance. Our results demonstrate that graphene incorporation markedly improves the material’s density, brittleness, thermal conductivity, and permeability resistance. Notably, the graphene-reinforced concrete exhibited a 44% increase in compressive strength, a 7.5% enhancement in photothermal absorption capacity, and a 200% reduction in water permeability compared to conventional concrete. Additionally, the composite showed a 5.5% decrease in maximum heat release and a 13% increase in heat storage capacity. These findings underscore the significant potential of graphene-reinforced concrete for advanced construction applications, offering superior mechanical strength, thermal regulation, and durability.