Water-richness evaluation method and application of clastic rock aquifer in mining seam roof

Clastic rock aquifer of the coal seam roof often constitutes the direct water-filling aquifer of the coal seam and its water-richness is closely related to the risk of roof water inrush. Therefore, the evaluation of the water-richness of clastic rock aquifer is the basic work of coal seam roof water disaster prevention. This article took the 4th coal seam in Huafeng mine field as an example. It combined the empirical formula method and generalized regression neural network (GRNN) to calculate the development height of water-conducting fracture zone, determined the vertical spatial range of water-richness evaluation. Depth of the sandstone floor, brittle rock ratio, lithological structure index, fault strength index, and fault intersections and endpoints density were selected as the main controlling factors. A combination weighting method based on the analytic hierarchy process (AHP), rough set theory (RS), and minimum deviation method (MD) was proposed to determine the weight of the main controlling factors. Introduced the theory of unascertained measures and confidence recognition criteria to construct an evaluation model for the water-richness of clastic rock aquifers, the study area was divided into three zones: relatively weak water-richness zones, medium water-richness zones, and relatively strong water-richness zones. By comparing with the water inrush points and the water inflow of workfaces, the evaluation model's water yield zoning was consistent with the actual situation, and the prediction effect was good. This provided a new idea for the evaluation of the water-richness of the clastic rock aquifer on the roof of the mining coal seam.

Comprehensive evaluation on water resource carrying capacity in karst areas using cloud model with combination weighting method: a case study of Guiyang, southwest China

It is important to maintain the sustainable development of water resources. Objective assessment on water resource carrying capacity (WRCC) is beneficial to the formulation of scientific and reasonable water management practices. In view of the problem that evaluation indicators of WRCC cannot describe the fuzziness and randomness, a cloud model was introduced into regional WRCC assessment. This study selected a typical karst area (Guiyang) as the research object to study WRCC by using cloud model with combination weighting method. WRCC was assessed from the following five dimensions: water environment subsystem, social subsystem, economic subsystem, ecological subsystem, and humanities (water resource management and policy regulation) subsystem. In addition, evaluation results after normalizing all of indicators data were also calculated. And these two kinds of evaluation results were compared with that of technique of order preference similarity to the ideal solution (TOPSIS), finding that evaluation results of cloud model were consistent with that of TOPSIS method. The cloud model realizes the transformation from qualitative evaluation to quantitative evaluation, which overcome insufficiencies of traditional evaluation methods in considering fuzziness and randomness. Results showed that during the period of 2008-2017, the state of WRCC in Guiyang was improving year by year, increasing from the serious overload carrying capacity level in 2008 to the strong carrying capacity level in 2017 (serious overload-overload-critical-weak carrying capacity-strong carrying capacity). However, some certain evaluation indicators are still in danger situation, such as population natural growth rate and use of the fertilizer per unit cultivated area, which needs to be further enhanced and improved. Moreover, the contradiction among economic development, population growth, and water resources is becoming increasingly apparent. To ensure the effective utilization of water resources in Guiyang, reasonable policies and measures should be formulated and put into effect. Research results could provide certain reference for the sustainable development of regional water resources.

Identification of groundwater redox process induced by landfill leachate based on sensitive factor method

Landfill site is a significant source of groundwater pollution. To ensure that the groundwater contamination of landfills can be controlled and repaired scientifically, the identification of groundwater pollution process is needed. On the basis of biogeochemical process of leachate pollutants in the groundwater environment, a sensitive factor method for the identification of groundwater redox process from landfills was established in this research. The method encompasses four phases, including sensitive factors selection, redox zone characterization, weight calculation, and redox zone identification. In the sensitive factor index system employed here, five indicators involving dissolved oxygen (DO), nitrite, Fe²⁺, sulfide, and CO₂ were selected. The boundary of each redox zones was determined by the quantitative method, and the weight of each indicator was calculated by combined weight method. This method was applied to a landfill site in the northeast of China. The result showed that there were five redox zones that appeared in pollution plume, including methanogenic zone (MGZ), sulfate reduction zone (SRZ), iron reduction zone (IRZ), nitrate reduction zone (NRZ), and oxygen reduction zone (ORZ). The results were consistent with the actual situation of the site. The sensitive factor method was scientific and effective to identify the groundwater redox process in landfill and can provide reference data related to investigation and remediation of groundwater pollution in landfill sites.