Refinement and mechanized construction of dual flexible-formwork sealing walls in connecting roadways

To address the engineering drawbacks of sealing walls in connecting roadways, including low construction efficiency, high risk of structural instability and poor long-term airtightness, this paper proposes a novel dual-wall sealing structure. Based on site investigation, numerical simulation and field engineering practice, systematic refinement analyses were carried out on the geometric dimensions and material properties of the sealing wall. Combined with a self‑developed vehicle‑mounted pumping system, a safe and efficient construction technique for sealing walls was established. The results show that the control of wall thickness on roof subsidence presents a clear diminishing marginal effect, and 1.0 m is determined as the recommended thickness. The concrete strength grade shows a non-linear negative correlation with both the maximum principal strain and maximum shear strain inside the sealing walls; both strains follow a quadratic‑polynomial decay relationship, and C25 is selected as the recommended strength grade. Using these parameters, a complete rapid construction technology for flexible formwork sealing walls based on the vehicle-mounted pumping system was developed and preliminarily trailed. Relying on synergy of underground mobile slurry pumping trucks, spatial framework constraint systems, and high-strength fabric flexible bags, the trial realized reliable roof‑contact performance and high‑pressure one‑shot forming. Field tests demonstrate the feasibility of the proposed technology. Compared with conventional rigid‑formwork construction, it reduces the required workforce from 13 to 9 workers, shortens the construction duration from 4 shifts to 3 shifts, and cuts the comprehensive cost by about 52% (approx. 626 RMB/m³). The research outcomes can provide practical references for sealing wall construction under similar shallow-buried mining conditions.