The development pattern of fractured water-conducting zones (FWCZs) is closely related to mining safety and water conservation in mining areas. However, neither the development pattern nor the empirical formula in the prediction of the height of FWCZs are clear for fully mechanized caving mining conditions in wet collapsible loess areas. We took Lu’an Coal Mine as a case study, employing field measurements and numerical simulation to investigate surface subsidence and FWCZs. Under the conditions of fully mechanized top coal caving in thick coal seams, surface movement is more intense, and surface cracking is more frequent. Field measurements using boreholes indicated the ratio of fracture height to coal seam thickness was 19.1–23.4, and the ratio stays stable both by sliced fully mechanized mining and fully mechanized mining. The height of the FWCZ with fully mechanized mining is 1.37 times and 2.31 times larger than the height with sliced fully mechanized mining and ordinary mining, respectively. The numerical simulation by RFPA illustrated that the height of the FWCZ remained stable when it reached a certain rock level with the working face moving forward. Furthermore, we developed an empirical formula for predicating the maximum height of an FWCZ under fully mechanized mining conditions in wet collapsible loess areas. Finally, the research findings were applied in several coal mines to achieve safe production and water conservation. This work provides guidance for effectively mining safely and water conservation in similar geographic conditions.

Rapid urbanization in China has driven the continuous expansion of urban land over many years. While most studies have examined the scale, speed, and spatial distribution of urban expansion, few have explored its temporal evolution and convergence patterns. To address this gap, the present study employs kernel density estimation (KDE) and the log t regression test to analyze urban expansion across 315 Chinese cities from 2000 to 2022. Our results reveal that the per capita urban area increased by a factor of 1.58 amid a fluctuating process on a national scale. Moreover, the log t regression test rejects convergence at national and regional levels while identifying six distinct convergence clubs. The evolutionary trajectories of these clubs have diverged over time, with inter-club gaps stabilizing and their spatial distribution exhibiting significant agglomeration. These findings indicate that urban expansion in China remains characterized by multiple equilibria, with imbalanced growth having stabilized. Consequently, effective urban planning, along with the diffusion of capital and technology, may promote a shift towards global convergence in urban expansion dynamics.