Field Measurements of Compaction Seepage Characteristics in Longwall Mining Goaf

Abstract

The spatiotemporal evolution of goaf caving zone compaction characteristics has important influences on surface subsidence, spontaneous combustion and gas and water migration characteristics in goaf. In this paper, the permeability of the caving zone during the advance of a longwall face is calculated based on the permeability calculation model and gas drainage data; additionally, the compaction stress and compaction time of goaf are measured by a borehole stress meter. The internal relations among compaction stress, compaction time and permeability at different positions in the caving zone are quantitatively analyzed. The results show that the farther away from the boundary of the caving zone, the lower the permeability, the greater the compaction stress and the longer the compaction time are. It is also confirmed by numerical simulation results. At the same time, the distribution characteristics of and quantitative relationships among compaction stress, compaction time and permeability are given. In addition, compaction time increases with the increase in the rate of advance of the longwall face, but the change is not large. Based on the above study, the space–time evolution of gob compaction characteristics is preliminarily grasped, which provides theoretical guidance for designing pressure relief gas drainage boreholes and the longwall face layouts.