Water Disaster Research Articles

Evaluation of the Water Yield of Coal Roof Aquifers Based on the FDAHP-Entropy Method: A Case Study in the Donghuantuo Coal Mine, China

The water yield of coal seam roof aquifers is the key factor for evaluating and controlling water disasters in coal seam roofs. To evaluate the water yield of the sandstone aquifer in the roof of the Carboniferous-Permian Damiaozhuang Formation no. 8 coal seam in the Donghuantuo Mine, North China, seven main controlling factors affecting the water yield of sandstone aquifers are determined, including the permeability coefficient, consumption of drilling fluid, core recovery, aquifer thickness, brittle-plastic rock thickness ratio, fault scale index, and fault point density. Further, the fuzzy Delphi analytic hierarchy process (FDAHP) and entropy weight method (EWM) are used to calculate the subjective and objective weights of each main factor, respectively, and a combination weight model (CWM) is proposed based on the least square method to compose the comprehensive weights. Then, an improved water yield property index (IWYPI) model is established, and the water yield zoning map of sandstone aquifers is acquired. Engineering practice shows that the evaluation accuracy of the water yield property index (IWYPI) model based on the CWM is as high as 93.75%, which is 18.75% and 12.5% higher than that of the water yield property index (WYPI) model based on the FDAHP and EWM, respectively. The research results propose a novel method for evaluating the water yield of coal seam roof aquifers and can provide scientific guidance for the prevention and control of water disasters in the no. 8 coal seam roof of the Donghuantuo Coal Mine.

Roadway transient electromagnetic signal analysis and its testing system improvement

Roadway transient electromagnetic method has been widely used in detecting mine water disaster ahead of roadway excavation face. Due to the strong mutual inductance between transmitting-receiving coils, the early-stage data obtained by this method are seriously distorted and the effective resolving time of transient electromagnetic (TEM) field is greatly lengthened, which leads to the shallow blind area of exploration. To improve the ability of transient electromagnetic testing system and to resolve short-range geoelectric abnormalities in front of the roadway excavation face, we provided the expression functions of the primary TEM field and the receiving system’s impulse response, restored the data recorded by instrument theoretically and compared the differences between the recorded data and the pure secondary TEM data. We found that the factors, including the increase in the current switch-off time, the decline in the receiving coils’ inherent resonant frequency, the enlargement in the mutual inductance between transmitting-receiving coils, and the mismatch in the receiving circuit’s damping resistance and so on, could significantly affect the early-stage TEM data, which results in a great delay in the effective resolving time. Based on the above findings, we improved the TEM testing system, compared the monitored data obtained using the original and improved testing system. It demonstrates that the improved testing system shortened the effective resolving time, which greatly enhanced the reliability of early-stage data and efficiently resolved the geoelectric abnormal zones closer to the roadway excavation face.

Theoretical and numerical investigations on mining-induced fault activation and groundwater outburst of coal seam floor

Mining activities carried out above an aquifer, especially in the hanging wall of normal faults, generally involve the risk of water inrush. For a better understanding of the mechanism inducing groundwater outburst through fault floor, the analytical and numerical simulation methods were applied to investigate the process of fault activation driven by mining and hydraulic loads. The influences of the advancing distance and fault dip were conducted. The results exhibit good agreement between the theoretical calculation and the numerical simulation. The fault activation by induced tangential stress change has a positive correlation with the advancing distance and a negative correlation with the fault dip angle. The stress concentration factor increases significantly when the excavation process enters the horizontal range of fault projection, following the stress peak and failure zone approaching the coal seam from deep to shallow along the fault. For the cases with a constant advancing distance, the smaller the fault dip is, the earlier the water-inrush channel will be formed. The research results in this study reveal the theoretical mechanism of fault activation and groundwater inrush of coal seam floor above a confined aquifer and thus provide valuable insights for the prevention and risk assessment of mine water disasters in underground engineering.

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.

Study on Hydrochemical Characteristics of Ordovician Limestone in Jiaozuo Mining Area

In order to understand the source of groundwater inrush and its hydrogeochemical evolution path truly, determine the evolution characteristics and development trend of water cycle, and effectively solve the problem of water disaster in mining area. In this paper, Jiaozuo mining area, a typical large water mining area of North China type, is selected as the study area. Taking the Ordovician aquifer in the study area as the research object, the Ca2+ hydrochemical equilibrium model of Ordovician limestone water system is established by analyzing the characteristics of concentration gradient field and the relationship between the hydrochemical ions (Ca2+、K++Na+、Mg2+、Cl-、SO42-、HCO3-) and TDS in the mining area, it made a systematic study on the characteristics of Ordovician limestone water circulation, and analyzed the recharge, runoff and discharge characteristics of groundwater in different areas of the mining area. The results show that the Ordovician limestone water in the Jiaozuo mining area has a weak leaching effect in the north and southwest, but a strong leaching effect in the southeast, which shows a runoff characteristic from the north and southwest to the southeast.

A novel treatment method and construction technology of the pipeline gushing water geohazards in karst region

Due to the complex geological structure and abundant groundwater system in karst areas, the gushing water disasters of mines in karst areas are characterized by large flow rate, high velocity and frequent occurrence, which have become an unavoidable social problem, further caused huge economic losses and casualties. In this paper, a novel treatment method and construction technology were summarized and put scientifically forward a set of management procedure for karst gushing water treatment to guarantee security production during mine construction in karst region. The construction procedure includes safety assessment policy, precise exploration method, collaborative grouting mode, curtain closure technology and effectiveness inspection system, furthermore the precise exploration method, grouting material, construction steps and effectiveness check for the karst gushing water treatment are introduced in detail. Finally, the engineering application was successful conducted using the karst pipeline gushing water procedure in treatment object of water inrush of mine belonged to China Resources Cement (Pingnan Country) limestone mine co., which the total quantity of gushing water reached to 117700 m3/d. The engineering trial demonstrates the applicability of this treatment process and accumulated for the similar projects so as to further perfect the treatment method and technology of water inrush in karst conduit.

Prevention and Control of Water Inrushes from Subseam Karstic Ordovician Limestone During Coal Mining Above Ultra-thin Aquitards

Horizontal directional drilling technology was used to prevent and control water inrushes from the Ordovician limestone strata at the Sangshuping coal mine in the Hancheng mining area by drilling and grouting the contact zone along the top of the aquifer. Considering the hydraulic conductivity of the floor failure zone, we used the modified water inrush coefficient method to estimate the critical thickness of Ordovician limestone that had to be grouted. We carried out directional borehole exploration from both ends of the mining face and combined the results with borehole water pressure tests to determine appropriate grouting techniques and parameters; we then analysed the effectiveness of the grouting. 3-D seismic and ground transient electromagnetics (TEM) were used to detect areas of anomalous resistivity and geologic structure in the mining area, while DC and TEM geophysics were used to detect water-bearing areas ahead of the roadway. After the roadway was developed, TEM, DC resistivity sounding, and audio-magnetotellurics were used to explore water-bearing areas under the roadway and the mine floor. Radio waves were used to detect the structure of the mining face and changes in coal thickness. Finally, based on the results of exploration, an inspection program was devised using conventional boreholes supplemented by directional boreholes to comprehensively evaluate the feasibility of mining under pressure. The study showed that the failure depth of the floor was 15 m and that the top of the Ordovician limestone was no longer water-bearing and was now a relative aquitard. The water inrush coefficient was reduced to less than 0.073 MPa/m, which will ensure safe mining and extend the lower limit of safe mining in the area. This provides a technical reference for prevention and control of Ordovician limestone water disasters in similar coal mines.

“The Population is not Guaranteed Against Major Shocks”. Organization of Protection against Water Disasters in the South of the Russian Empire in the 18th – early 20th centuries

“The Population is not Guaranteed Against Major Shocks”. Organization of Protection against Water Disasters in the South of the Russian Empire in the 18th – early 20th centuries

Theoretical Research and Numerical Simulation on Water Resistance Mechanism of Textile Bag in Water Passage

It is an important problem in the mine water disaster prevention and control to control the large passage moving water. Traditional grouting technology is to put coarse aggregate and fine aggregate downward first and then grouting treatment. But the aggregate and cement flow distance is long, consumption is large, cost is high, and easy to appear secondary water inrush. Centering on the technical difficulties in the rapid construction of the blocking body of the moving water passage, a water-blocking textile bag was invented. The purpose of blocking the tunnel water inrush was achieved by grouting inside the bag body, which fundamentally realized the rapid blocking of the large passage through water under the condition of moving water. However, the mechanism, water plugging law, and design parameters of water blocking roadway with textile bag are still unclear. In this paper, the slip law and stability of the textile bag in the moving water and the deformation characteristics caused by the dynamic water pressure are theoretically analyzed and simulated. Through theoretical analysis, the ultimate antihydraulic stress value of a textile bag of a certain specification is calculated, and the parameters of the textile bag that affect the stability of the bag body are also determined. Xflow was used for numerical simulation analysis to study the deformation characteristics of the textile bag under water and the law of water barrier. The simulation analysis focuses on the water resistance effect and flow field distribution characteristics of the textile bag in the water passage under the condition of low flow rate and low pressure, as well as the stability and self-deformation characteristics of the textile bag under the condition of high flow rate and high pressure. The accuracy of the limit resistance to water pressure of the textile bag obtained from theoretical analysis is verified. The results show that the theoretical analysis is consistent with the simulation results. The textile bag can realize the fast controllable plugging of the large water passage of moving water within the limit of the antihydraulic stress.

In situ measurement of water accumulation in overlying goaf of coal mine-a transient electromagnetic-based study

Water accumulation detection in mining areas is the primary technical means for preventing mine water disasters. To study the distribution of water accumulation in the goafs of the Xingnong coal mine in Jixi, the present paper systematically analysed the water accumulation regularities in the goafs based on the applied and theoretical studies using transient electromagnetic (TEM) methods for the detection of goaf water accumulation characteristics. Because of the high sensitivity of transient electromagnets to low resistance and water, the water body distribution in the goafs is determined by the exhibition of low resistance by the water bodies. Furthermore, the water-bearing anomalies are located depending on the conductivity difference among media. The analysis of the in situ measurements for the Xingwang coal mine revealed four water-rich goaf anomalous zones within the detection area, of which one was located in the shallower part and three were located in the deeper part. The water-retention capacity of the fault zones was analysed, with more reliable degree of control attained by analysing a fault with a large throw. A broad area of highly distinct low-resistance anomalies appeared in the vicinity of the fault. The suspicious water-containing anomalies were verified through field drilling experiment, proving the reliability of TEM in detecting the water distribution in the coal mine goafs.

Influence of Gully Land Consolidation on Phreatic Water Transformation in the Loess Hilly and Gully Region

Gully Land Consolidation (GLC) is a proven method to create farmlands and increase crop yields in the Loess Hilly and Gully Region, China. However, GLC influences phreatic water transformation and might cause the farmlands water disasters, such as salinization and swamping. For exploring the influence of GLC on phreatic water transformation and mitigating disasters, a series of indoor experiments were conducted in the artificial rainfall hall. Then, we simulated the phreatic water transformation patterns under more conditions with HYDRUS-3D. Finally, an engineering demonstration in the field was performed to validate our research. The indoor experiments indicated that GLC could increase phreatic water outflow rate 4.39 times and phreatic water coefficient (PWC) 2.86 times with a considerable delay. After calibration and validation with experimental data, the HYDRUS-3D was used to simulate phreatic water transformation under more soil thickness and rainfall intensities. Accordingly, we summarized the relationship among PWC, rainfall intensities, and soil thickness, and therefore suggested a blind ditch system to alleviate farmlands disasters. Field application showed that a blind ditch system could avoid disasters with 3.2 times the phreatic water transformation rate compared to loess. Our research provides implications for sustainable land uses and management in the region with thick soil covers.

Recognition and Prevention of Bed Separation Water: Based on Trapezoid Platform Model

In recent years, bed separation water inrush, as a new type of water disaster, has posed serious threat to mining safety in China’s many coal mines. This study focused on periodic water inrush accidents in the No. 7335 working face owned by Xuzhuang Coal Mine, Jiangsu Province, China. Based on the theory of key strata, the formation positions of the separation layer in the overlying strata were first identified; next, the trapezoid platform model of the fracture of the overlying strata was introduced for illustrating the evolutional process of the bed separation space and accurately calculating the position and the geometrical morphology of the bed separation space. On that basis, the relation between the fracture of the overlying stratum and the inrush of bed separation water was revealed with the use of the plate theory. Moreover, the prevention and control measures of the bed separation water were formulated. Research show that the arrangement of the diversion drilling holes can successfully eliminate the threat of the bed separation water to the lower working face.

Application of Magnetic Resonance Detection in Goaf Water in Wuhai

The mine water disaster in our country has always been the key factor restricting the development of coal production. Due to the unreasonable small coal mine development, mining in some mining area, the destruction of the waterproof coal pillar, lead to the formation of the mined-out area, and goaf water. Because the goaf water does great harm to coal field exploration and development, the prevention and control of goaf water disasters are very important. In this study, aiming at a large area of exploration space, the method of magnetic resonance can be used to detect groundwater, and two magnetic resonance instruments are used to work together. In order to ensure the accuracy and effectiveness of the data collected by the two instruments, improve the efficiency of exploration work and save field exploration time, the basic model of detecting groundwater with magnetic resonance sounding (MRS) method instrument is established, the influencing factors of MRS are analyzed, and the effective signal value of detecting groundwater with MRS instrument is calculated. Through numerical simulation, the optimal distance between the coils laid on the ground when the two MRS instruments are working at the same time is determined. Furthermore, the practicability of the method is verified via a field case performed in a mining area in Wuhai, China. This method can be used as a guide for large-scale field exploration in the future.

Research and Exploration of Water Storage Law in Goaf of Merger and Reorganization Coal Mine Based on Computer

With the application of modern technology represented by computer, in recent years, the probability of coal mine safety production accidents has been declining. However, the current coal mine water disasters still occur, and a considerable proportion of accidents are caused by water inrush from goaf. The destructive characteristics of coal mine goaf water make it necessary to carry out the relevant research on the occurrence law of coalmine goaf water. Based on this, this paper first analyses the characteristics of water disaster in the goaf of merger and reorganization coal mine, then studies the computer-based investigation and exploration mode of water accumulation in the goaf of merger and reorganization coal mine, and finally puts forward the prevention and control strategy of water accumulation in the goaf of merger and reorganization coal mine based on computer.

Study on Cross Main Tunnel Mining Next to Large Fault Structure

Fault structure cut continuity of coal seam, inducing rock burst accident and mine water disaster easily, which bring serious threat to coal resources mining. Working face layout is very important, when next to fault structure and cross main tunnel mining. Based on a mining technical problem in Hongqi coal mine (Jining China), which 3161 working face next to large normal fault F6-2 and cross main tunnel mining, using methods of theoretical analysis and numerical simulation to study the above technical problem. Main research works are as follows: (1) With theory of mining stress distribution, calculate the minimum safety rock pillar thickness, and contrast with the thickness of floor strata, determine feasibility of cross main tunnel mining. (2) According to elastic–plastic failure theory of coal pillar, determine the critical width of coal pillar to keep stable. (3) Using FLAC3D to establish numerical model of 3161 working face mining, analyze distribution and evolution of mining stress. Research results could give a guidance to cross main tunnel mining next to fault structure.

Discriminant analysis of mine water inrush sources with multi-aquifer based on multivariate statistical analysis

Accurate and effective identification of the source mine water inrush water is vital for warning system implementation and post-disaster rescue decision-making and is crucial for mine water disaster prevention plans. To fully excavate the hydrogeological information carried by the water samples of different water sources, and fully consider the influence of the correlation between the ions and the existence of multi-collinearity on the discrimination results, so as to improve the accuracy of the inrush water source discrimination, this study conducted multivariate statistical analysis and discriminant analysis on 37 water samples of three types of water sources in Xutuan coal mine, and established the Fisher discriminant model for mine water inrush sources based on fuzzy cluster analysis and factor analysis. The discriminant accuracy of the model was tested using re-substitution and cross-validation, and compared with the discriminant result of traditional Fisher discriminant model. The results showed that the discriminant accuracies of the re-substitution and cross-validation were 91.9% and 89.2%, respectively, while the discrimination accuracy of cross-validation of the traditional Fisher discrimination model was 86.5%. The discrimination accuracy of this model was higher than that of the traditional Fisher discrimination model. Therefore, the Fisher discriminant model for mine water inrush sources based on fuzzy cluster analysis and factor analysis established in this study can improve the accuracy of a water source discrimination model, and can provide a useful reference for mine water disaster prevention.

Typical Coal Mines in Hancheng Mining Area of China and its Management Reseach

In order to promote the work of prevention and management of coal mine water disaster in China, it took Panlong coal mine, Xiayukou coal mine and Xiangshan coal mine in Hancheng mining area as object of study. Methods of prevention and management of Ordovician limestone water inrush and water inrush from old and empty areas were put forward. Some examples were chosen to approve these methods’ practicability. At last, enhancing management of coal mine and improving stuffs’ comprehensive quality were proposed.

Optimal location of water level sensors for monitoring mine water inrush based on the set covering model

Water inrush is one of the major mining disasters that may lead to numerous casualties. The development of information techniques makes it possible to monitor the occurrence and evolution of water inrush. Then, locating monitors for water inrush becomes a primary problem. This study presents a method of optimal location of water level sensors by constructing a set covering model. The monitoring scope of the water level sensor at each location in a given time is computed first based on the numerical simulation of water spreading along mine tunnels. In this simulation, the water inrush quantity is assigned using the mine drainage capability over which an accident may occur. Then the greedy algorithm is used to optimize the number and positions of water level sensors. As results, a mine water disaster can be monitored in the given time after it happened. The proposed method is then verified in the Beiyangzhuang coal mine in the North China. The results show that at least 22, 36, 42, 64 and 106 water level sensors are needed to monitor water disasters in the whole mine within 60, 30, 20, 10 and 5 min, respectively.

Model-based Seismic Imaging and Analysis of Karst Water Hazards in Coal Mining

Accurate detection of karst water is the premise of karst water disaster control in coal mines. It is difficult to identify karst geological characteristics based on seismic data, so to solve this problem, a digital model including the coal measure strata and complete karst system was established based on the karst status of a coal mine in the Huaibei area of China. The entire process of seismic acquisition, processing, and interpretation was simulated and then the model was restored according to the seismic interpretation. Based on the results, karst identification and water inrush risk prediction were tried. The results allowed the overall karst geological framework, karst cave system, and stratum contact relationships to be restored more truly. Thus, seismic data can provide accurate geological information for large-scale hydrogeological mine exploration.

Evolution of Water Hazard Control Technology in China’s Coal Mines

We analyzed the regional nature of China’s coal mine water disasters based on three aspects: the main water source, water-conducting passages, and threat level of water hazards. The development of water hazard control technology in China’s coal mines, including exploration and assessment of hydrogeological conditions, water inrush mechanisms, and predictive technology were all reviewed. We then focused our discussion on the calculation theory and methods behind mine inflow prediction, methods of dewatering and depressurizing, and technology for mining under water pressure and water-blocking grouting. Finally, we present the evolving trend of coal mine water disaster prevention and control technology, which is characterized by accuracy, transparency, environmental considerations, informatization, and intelligent technology.