Extensive soft-rock floor heave in gob-side entry retaining considerably restricts the efficient and sustainable production of the mine. The mechanical capacities of roadway roof and floor strata are discussed through laboratory tests by taking the N2301 fully caving surface auxiliary transport gate road of the Ancient City Coal Mine in the Lu’an Mining Area of Shanxi Province as an engineering background. The stress distribution law of gob-side entry in mining the working surface was explored based on numerical simulation. After that, the mechanical mechanism of floor heave was studied through theoretical analysis. High lead abutment pressure and horizontal stress were superimposed in front of the working surface to cause soft-rock floor heave. The bulk weight of the high overburden was unevenly transmitted to the two sides because of the roof cantilever structure of entry retaining in the rear of the working face. The roadway floor produced an asymmetric sliding force, which caused the occurrence of floor heave. The control technology of floor heave combining the pressure relief of floor blasting and roof cutting was proposed taking account of the mechanism of floor heave. Then, the stress environment of the surrounding rock was improved by the deep hole blasting of the floor. Gob-side roof cutting was used to reduce impact of the bulk weight of the overburden on the surrounding rock deformation of the roadway. A test was conducted after verifying the control effect of blasting pressure relief on roadway floor heave through a similar simulation. Field tests indicated that the maximum floor heave was 168 mm at 250 m in the rear of the working surface, and floor heave was controlled. This study offers a more scientifically sound theoretical reference for controlling floor heave in gob-side entry retaining, which can significantly advance the sustainable development of gob-side entry retaining technology in coal mining.

Paste backfill strength exhibits obvious time-dependent growth, which directly determines the supporting effect and parameter design in longwall backfilling mining. To optimize key parameters for roof stability and surface protection, this study carried out laboratory tests, numerical simulations, and field validation on the E1302-B working face in Gaohe Coal Mine. Results show that the strength of paste backfill increases logarithmically with curing age. The optimal backfilling step distance is 2.4 m, the recommended final cured strength is 4.01 MPa with significant marginal effects, and the backfilling ratio should be no less than 92% to meet Grade-I surface protection requirements. Field applications demonstrate that under these parameters, roof deformation is controllable without fracture, and all surface deformation indexes are within 50% of the standard limits. This work provides a reliable method and practical guidance for parameter optimization in longwall paste backfilling mining.

Longwall paste backfilling mining is a core sustainable green mining technology for coal resources under buildings, railways and water bodies (BRW), yet its large-scale application is severely restricted by the sequential mining–isolation–backfilling–curing operation mode that causes low production efficiency and poor economic feasibility, which hinders the sustainable exploitation of BRW coal reserves and the ecological protection of mining areas. Taking the E1302-B paste backfilling face of Gaohe Coal Mine as the engineering background, this study systematically identified the key efficiency-restricting factors considering the face’s complex geological conditions (maximum roof–floor undulation 300 mm, 72.6% of roof–floor dip angle >1° and irregular cross-section), including low isolation efficiency, cumbersome backfilling process, prolonged paste curing time and insufficient system operation controllability. Technological innovations were carried out from four core dimensions: high-efficiency isolation, high-efficiency backfilling, accelerated curing and intelligent safety control, and a high-efficiency integrated technology system for longwall paste backfilling mining was thus formed, which realizes the synergistic improvement of mining efficiency, economic benefits and sustainability performance. Industrial test validation demonstrated that the technical system significantly boosts the efficiency of isolation, backfilling and solidification in the backfill mining cycle, cutting the time of a single backfill mining operation cycle by 57%. The annual production capacity of the E1302-B face was increased to 0.81 Mt, with a comprehensive backfilling mining cost of 466.63 CNY/t, an annual economic benefit of 108.03 million CNY and a static investment return rate of 48.96%. The E1306 face achieved an even higher annual production capacity of 1.12 Mt with a static investment return rate of 74.94%. This technology system effectively breaks the efficiency and economic bottlenecks of traditional longwall paste backfilling mining, realizes the dual improvement of backfilling mining efficiency and economic benefits, and further releases the ecological, resource and economic sustainability value of paste backfilling mining. It provides technical support and practical approaches for the large-scale application of longwall paste backfilling mining, and lays a solid foundation for the sustainable development of the coal industry under the dual-carbon goal, especially for the balanced development of coal resource exploitation and mining area ecological protection.

To address the difficulty of roof control in longwall paste backfill mining and to better capture the backfill’s ‘sequential bearing’ effect, this study proposes an elastic foundation beam model. Based on the Gaohe Coal Mine, the “coal-support-backfill” model incorporates the time-varying characteristics of paste materials. Analytical solutions for roof deflection and bending moment were derived to reveal the spatiotemporal evolutionary laws of key parameters on roof stability. Results show the filling rate is the most sensitive factor controlling ultimate roof subsidence, directly determining the roof’s actual suspended span and breaking risk. The final-set strength limits long-term deformation but exhibits a marginal diminishing effect. Conversely, early strength dominates the initial subsidence rate, preventing excessive early deformation. Additionally, increasing the filling step distance significantly increases overall subsidence, whereas support resistance improves the initial bending moment distribution. Ultimately, surrounding rock control in paste backfill stopes is a dynamic coupling of “spatial support synergy” and “temporal strength matching” providing a theoretical basis for optimizing mining safety, economy, and efficiency, which ultimately fosters sustainable green mining practices.