Water Richness Zoning and Evaluation of the Coal Seam Roof Aquifer Based on AHP and Multisource Geological Information Fusion

Roof water disaster is one of the most serious disasters in the process of coal mine safety mining in China. The thickness of modern comprehensive mechanized coal mining is large, which has a great impact on the roof aquifer, and the threat degree of water disaster is also increasing. Therefore, the evaluation of the water richness of the roof aquifer is an important work for coal mine water prevention and control. In order to systematically evaluate the water-rich property of an aquifer in a coal seam roof, this paper couples multisource geological information based on an analytic hierarchy process (AHP). The characteristics of the roof aquifer, hydrogeology, and structure are determined to be the main control factors of K2 limestone water richness evaluation. Under the main control factors, seven independent water richness evaluation indexes, including aquifer depth, aquifer thickness, borehole water level, borehole water consumption, faults, folds, and collapse columns, are divided, and a normalized water richness coupling evaluation model is constructed, which realizes the zoning and evaluation of a water-rich aquifer in a coal seam roof.

Numerical assessment of the water-flow hazard to workers in the water disaster of underground mine

Understanding the details of the water-flow hazard (WH) to workers in water disasters is extremely important in disaster-risk management. This paper aims to develop a numerical assessment model for the WH affecting worker safety. An assessment model of WH is proposed for water disasters in the underground mine, which includes two characteristics: (a) from water-disaster environment to WH of workers and (b) from multiple influencing factors to quantitative comprehensive quantification. To verify the feasibility of WH, it is applied to a water disaster in an underground coal mine. The simulation results highlight that the WH model can assess the hazard value of worker-1 (m = 72 kg, H = 1.72 m) at paragraph – 6134 and paragraph – 8840 of roadway, with different water-flow conditions, in the whole time of the disaster. Meanwhile, the differences between WH for three workers, worker-1, worker-2 (m = 95 kg, H = 1.82 m), and worker-3 (m = 60 kg, H = 1.62 m), under the same flow conditions are provided by the curve. Moreover, dynamic visualization of WH is achieved, which shows how the hazard of worker-1 changes into the time of 2, 5, 11, 19, and 27 h after a disaster in the full mine. Therefore, this numerical assessment can be used to evaluate the hazards posed by water flow to workers, which meets the urgent demands of water-disaster management for underground mines.

Analysis of Key Factors Affecting Water Disaster in Deep Mining and Establishment of a Water Disaster Evaluation Method Suitable for Different Mining Depths

Deep mining is the current and future mining focus in the coalfield of North China. Therefore, it is necessary to establish a water inrush assessment method suitable for deep mining. The conventional water inrush coefficient ( T ) method is simple to use, but its accuracy is low when the mining depth is very small or large because it neglects the role of the aquifer water yield. The main purpose of this paper is to introduce a simple water inrush risk assessment method that is more applicable in deep mining than the T method. In this study, the hydrogeological characteristics in deep mining were studied and the role of the aquifer water yield in water inrush was analyzed. Afterwards, an improved T method considering the aquifer specific yield ( q ) was established. In the new method, the critical water inrush coefficient changes with changing q following a negative correlation. The parameter thresholds were determined based on systematic data analyses of 186 mining cases. The results of the statistical analysis show that the accuracy of the new method at different mining depths is higher than that of the T method.

System for Prevention and Control of Old Goaf Water during Coal Mine Re-mining

One integrated mine was currently threatened with an old goaf water disaster, therefore, the development of an advanced detection-guarantee system for roadway excavation with no blind area was imperative. Further, multiple geophysical exploration in combination with two types of boreholes were used to explore and drain water technology, with the anomalous geophysical area as the target area, The conventional borehole with the largest water outflow was taken as the target spot, at a low elevation of the mining area, and a remote directional borehole was used to drill into the old goaf along the stable rock strata below the coal seam floor to intercept the dynamic recharge water, which increased the efficiency of roadway excavation 4–9 times. The ‘isolated island’ old goaf water in the mining face was controlled through multiple geophysical exploration combined with the full-coverage exploration technology by conventional boreholes, and the water-rich anomalous area and geological anomalous area were determined, thus ensuring the safety of the mining face in terms of old goaf water. The technology for advanced short-distance exploration, advanced estimate, roadway exploration, and dynamic old goaf water with drainage was used to comprehensively guarantee real-time, safe mining. This system for the prevention and control of old goaf water was applied to a control project for the old goaf water disaster in the 101 mining face. At present, 1.37 Mt of coal has been safely mined from this mining face. The technical system has improved The Detailed Rules for Water Disaster Prevention and Control of Coal Mine (NCMSA 2018), and improved the technology for the prevention and control of old goaf water under conditions where the upper portion in the same coal seam was destroyed by a small-scale coal mine and re-mining.

Dynamic Evaluation Method of the EW-AHP Attribute Identification Model for the Tunnel Gushing Water Disaster under Interval Conditions and Applications

The gushing water disaster in tunnels is a kind of harmful and risky engineering disaster. It has become a key problem to evaluate the risk of tunnel gushing water accurately and objectively. A case study of a typical highway tunnel is performed for theory and practice analysis. For this reason, the risk identification is carried out on the assessed objects, and 10 evaluation indexes are determined. In turn, the risk evaluation index system and classification standard are established. Furthermore, the entropy weight method and the analytic hierarchy process are combined to assign the weight to each evaluation index. Therefore, a dynamic risk assessment system, including the pre-evaluation model and the postevaluation model, is constructed with the attribute identification model. As a result, the tunnel section with a high risk of water inrush is accurately assessed, which is consistent with the construction situation on site. Moreover, it is verified that the assessment results are reliable, which can provide a reference for the similar projects.