Quantitative evaluation and planning method of shallow surface water response in multi-face mining—Case study regarding Zhuanlongwan coal mine

Abstract

Multi-area coal extraction can cause aquifer depressurisation and subsurface dewatering, in which the mechanism of overburden permeability and shallow water responding to underground gob keeping extending is the key. This paper focuses on the water resource protection in ecologically fragile mines in western China. With the equivalent permeability coefficient(EPC) and subsurface hydraulic responses as basis, the paper conducted mathematical statistics and theoretical analysis to construct a decision-making model for multi-panel longwalls and a longwall design methodology that considered subsurface water stability. Firstly, fitting the field measurement data produced an empirical equation regarding the height of water-conducting fracture zone (HWCFZ), and a model for quantifying the correlation between the damage values of effective soil units and effective bed rock units was established, by which the EPC was quantified. Secondly, the paper developed a subsurface water quantification model that considered infiltration recharge to study the subsurface piezometric evolution with varying geometry, range, and number of longwall units, further revealing the subsurface water responses to varying mining zones. Finally, a model for evaluating the subsurface water depressurisation was proposed and applied to study the subsurface water responses to multi panels in Zhuanlongwan Coal Mine. The longwall design obtained via the decision-making model agreed with the piezometric variation in the mine, suggesting that this research can provide theoretical and technical supports for green mining.