Water Inrush Disaster Research Articles

Study on the Safety Thickness of Rock Strata for Outburst Prevention in Deep Tunnel Based on Numerical Modeling and Backpropagation Neural Network

Water inrush and mud inrush pose a serious threat to safe construction in underground engineering, but it is very difficult to determine the safe distance of outburst prevention rock mass. Based on deep-buried tunnel engineering, this paper proposes a method to determine the safe distance from water inrush disaster between the tunnel and the fault fracture zone. This method combines numerical modeling and backpropagation (BP) neural network. By means of numerical simulation, the internal influence law of the water pressure, lateral pressure coefficient, fault fracture zone width, and tunnel burial depth on the surrounding rock is analyzed. The evolution law of the minimum safe strata thickness under a single variable and the correlation degree between minimum safe strata thickness and various disaster factors are revealed. Based on the BP neural network analysis of the simulation results and the measured data of Wulaofeng Tunnel, the calculated values of safe strata thicknesses of fault fracture zone (F10) were determined. The results show that the thickness of the safe rock strata increases with increasing water pressure, lateral pressure coefficient, fault fracture zone width, and tunnel burial depth. The minimum safe thickness of F10 of the tunnel ranges from 7.1 m to 7.4 m, and 10 m is reserved in the actual project. The calculated results are consistent with the reserved thickness value in the construction. This conclusion can provide a reference for similar projects.

Prediction of tunnel water inflow based on stochastic deterministic three-dimensional fracture network

With the rapid development of national infrastructure construction, the water inrush disaster of “strong burst, high water pressure and large flow” is more and more frequent in the construction process. To achieve high-precision prediction of tunnel water inflow, based on the Yue Longmen Tunnel, according to the structural plane detection data in the study area, combined with the Monte Carlo algorithm and using “parent-daughter” and “step–structure” correction mode, this paper constructs a random deterministic three-dimensional fracture network seepage model. Based on the three-dimensional fracture network seepage model and the principle of flow balance, the water inflow of each mileage section of the Yue Longmen Tunnel is solved by numerical calculation method, and good results are obtained through comparison and verification. The research results have important theoretical significance and engineering application value for tunnel water inflow prediction.

Water Inrush Mechanism and Treatment Measures in Huali Highway Banyanzi Tunnel—A Case Study

In the process of tunnel construction, the water inrush disaster is one of the main engineering geological disasters. In karst strata, different types of water-bearing structures or karst water bodies develop and occur in the soluble rock layer, and tunnel excavation easily forms new drainage channels, resulting in water inrush in the tunnel. Based on the project of the Huali Highway Banyanzi Tunnel, this paper studies the water inrush characteristics, water inrush mechanism, and treatment measures of the karst tunnel. According to the basic data, combined with field investigation, data monitoring, geological radar detection, tracer test, and numerical simulation, the characteristics and hydrogeological conditions of the tunnel water surge were investigated and analyzed. In addition, the mechanism of tunnel water surge was further summarized. Moreover, the tunnel water-gushing management measures are optimized and verified based on the tunnel water spraying mechanism.

Discriminant Analysis of Water Inrush Sources in the Weibei Coalfield, Shaanxi Province, China

Water inrush disasters in mining areas are one of the most serious geological disasters in coal mining. The purpose of this study is to study the establishment of a water chemical database and water inrush source discrimination model in the Weibei coalfield to provide the basis for regional hydrogeological conditions for future mining under pressure in the Weibei area, as well as a basis for the rapid identification of water inrush sources in the Weibei coalfield. In this paper, a conventional hydrochemical and trace element discrimination model for mine water inrush was established, and the hydrochemical characteristic files of the entire mining area were integrated. Based on 10 indicators, three hydrochemical discrimination models of rock stratum aquifers were established. Through the Mahalanobis distance test, it was found that the six selected variables, K+ + Na+, Mg2+, NH4+, Cl−, SO42−, and pH, have significant discrimination ability and good effect and can effectively distinguish the three main water inrush aquifers in the Weibei mining area. Then, the clustering stepwise discriminant analysis method was used to select 24 water samples and 14 trace element indicators from the conventional water chemistry test results. Based on principal component analysis, a principal component analysis discriminant model of trace elements was established for the four main aquifers. The accuracy and misjudgment rate of the Bayes multi-class linear discriminant using conventional ions as explanatory variables were 64.3% and 35.7%, respectively, showing a poor discriminant effect. On this basis, seven characteristic trace elements were analyzed according to Bayes multi-class linear discriminant analysis, the mutual influence and restriction relationship regarding the migration of these seven trace elements in the groundwater system of the mining area was determined, and the modified Bayes multi-class linear discriminant analysis model of trace elements for the water inrush source was established, which was more accurate than the conventional ion Bayes multi-class linear discriminant analysis model. The accuracy rate reached 92.9%. This research is of great significance for mine water-source identification and water-inrush prevention guidance.

Analysis method of the water inrush and collapse in jointed rock mass tunnels: A case study

Water inrush disaster occurs easily when the tunnel is close to the water rich fault fracture zone. To clarify the disaster evolution process and the critical thickness of the water-resistant rock mass is the key problem of the prevention and control of water inrush disaster in jointed rock tunnel. However, the water inrush disaster in jointed rock tunnels involves solid-fluid interaction, and the conventional single-phase numerical method is difficult to realize the real simulation of the disaster. To solve this problem, we gave full play to the advantages of the discontinuous deformation analysis method (DDA) in simulating solid motion and the smoothed particle hydrodynamics method (SPH) in simulating fluid motion, and the two-dimensional DDA-SPH (2D DDA-SPH) method was used to simulation the solid-fluid interaction in the water inrush disasters. Firstly, the 2D DDA-SPH method was used to replicate the solitary wave experiment, named Scott Russell's wave generator, and the result of the simulation was almost the same with experiment, which verified the accuracy of 2D DDA-SPH method in simulating solid-fluid interaction dynamic problems. Secondly, taking the Yonglian Tunnel as the research object, we simulated the water inrush disaster in the F2 fault of Yonglian Tunnel under the condition of different thickness of water-resistant rock mass. Based on the results of the simulation, the critical thickness of water-resistant rock mass was determined, which was about 5m. Lastly, we analyzed the process of the water inrush disasters based on the movement state of the fluid near the water-resistant rock mass. And we divided the process of the water inrush disasters in the jointed rock mass into three stage, which were mutation stage, cataclysmic stage and stable stage, which provided a theoretical basis for the prevention and control of water inrush in jointed rock tunnel.

RETRACTED ARTICLE: A hybrid DEM+SPH coupling method and its application in modeling water and mud inrush disasters

RETRACTED ARTICLE: A hybrid DEM+SPH coupling method and its application in modeling water and mud inrush disasters

Geo-mechanical model test on the water inrush induced by zonal disintegration of deep tunnel under hydro-mechanical coupling

With the increase of burial depth, complex geological environments such as high in-situ stress and high seepage pressure will inevitably affect the generation of zonal disintegration and may induce water inrush disasters during the excavation of the deep tunnel. A true three-dimensional geo-mechanical model test is conducted to study the mechanism of water inrush induced by zonal disintegration under hydro-mechanical coupling. The distribution and variation of different physical information during excavation, including displacement, stress and seepage pressure, are comprehensively analyzed. Test results reveal that zonal disintegration may induce water inrush when the tunnel is excavated under the coupling action of high stress and high seepage pressure. The excavation disturbance causes the stress in the rock mass to be oscillating. As a result, rupture and non-rupture zones appear alternately around the tunnel. With the increase of seepage pressure, the rock mass in non-rupture zone, which acts as the water barrier, is damaged and connects with rupture zone to form a water inrush channel. Eventually, high-pressure water pours into the tunnel to form a water inrush disaster. The reproduction of this special phenomenon will provide an important test basis for further theoretical and numerical studies.

Evaluation Method of Water Hazard Control Effect of Coal Seam Floor in Deep Mining: Sequence Verification Evaluation

Deep, highly pressurized aquifers seriously threaten the exploitation of resources of North China coalfield. At present, there is no particular guidance system to evaluate the prevention and control effect of water inrush disaster in deep coal seam mining. Therefore, this research focuses on the evaluation of the method for confined water disaster prevention and control effect of deep coal seam mining. Based upon various methods, such as effective thickness and water resistance capacity of aquifuge, water inrush coefficient, GIS (Geographic Information System) analysis of grouting data, dense drilling verification, and professional analysis system based on integrated sequence evaluation, the evaluation of the method for confined water disaster prevention and control effect of deep coal seam mining was put forward for the first time. The proposed method was called the “sequence verification evaluation (SVE)” method. The prevention and control of the effects of Ordovician water inrush disaster in deep mining of Huanghebei coalfield was evaluated using the proposed SVE method. The results show that the SVE method can effectively reflect the prevention and control of the effects of water inrush from confined water and provide scientific basis for the safe production of deep coal seam mining.

A Comparative Study on Steady-State Water Inflow into a Circular Underwater Tunnel with an Excavation Damage Zone

Excavation damage zones that occur around tunnels usually lead to a change in rock permeability, which has an impact on the water inflow into tunnels and even induces water inrush disasters. For a better understanding of the effect of the excavation damage zone, analytical solutions that consider the excavation damage zone are developed based on the review and modification of the solutions that consider linings and grouting circles. Then, both analytical solutions and the finite element method are applied to estimate the water inflow, and the results are in good agreement. The effect of the excavation damage zone on water inflow is analyzed based on an impact factor of the excavation damage zone and evaluated in a real engineering case, and the seepage-preventing effects of grouting are discussed. The results reveal that the water inflow increases with increasing permeability and thickness of the excavation damage zone and that there is a limit for the effects of the excavation damage zone. In addition, the effect is stronger for underwater tunnels with small water inflows and stabilizes gradually as the magnitude of water inflow increases. The increase in the impermeability and thickness of the lining and grouting circle can reduce the effect.

Physical model experiment research on evolution process of water inrush hazard in a deep-buried tunnel containing the filling fault

In deep tunnel engineering, water inrush disasters caused by filling faults occur frequently, which has generated wide interest in the fields of rock mechanics and fluid mechanics. The rock mass similar material was prepared with river sand as aggregate, cement as a binder, and clay as a regulator, and the similar material of the fault was composed of river sand and gravel, which laid a good foundation for the development of physical model experiment. Then, using the self-designed visualization test system of the two-dimensional model of a deep-buried tunnel filling fault water inrush, four physical models were laid by changing the fault width, fault cross distance, and fault cross angle to study the influence of different hydraulic pressures. In addition, the evolution process of water inrush disaster and the distribution characteristics of seepage weakening failure zone, hydraulic buckling failure zone, and excavation disturbance failure zone were analyzed and discussed. Furthermore, the justification classifications of tunnel risk were established to characterize the process of water-inrush of different schemes for different loading water pressure. The research results further reveal the evolution characteristics of rock fissures, connection, and formation of water inrush channels, and provide an important basis for reducing and controlling the occurrence of such tunnel water inrush disasters.

Potential hydraulic connectivity of coal mine aquifers based on statistical analysis of hydrogeochemistry

Mining activities interfere with the natural groundwater chemical environment, which may lead to hydrogeochemical changes of aquifers and mine water inrush disasters. This study analyzed the hydrochemical compositions of 80 water samples in three aquifers and developed a water source identification model to explore the control factors and potential hydraulic connection of groundwater chemistry in a coal mine. The results showed that the hydrochemical types of the three aquifers were different. The main hydrochemical compositions of the loose-layer, coal-bearing, and limestone aquifers were HCO3·Cl–Na, SO4·HCO3–Na, and SO4–Na·Ca, respectively. The correlation, Unmix, and factor analyses showed that the hydrochemical composition of groundwater was controlled by the dissolution of soluble minerals (such as calcite, dolomite, gypsum, and halite) and the weathering of silicate minerals. The factor score plot combined with Q-mode cluster analysis demonstrated no remarkable hydraulic connection among the three aquifers in the study area. The water source identification model effectively identified the source of inrush water. Moreover, the mixing ratio model rationally quantified the contributions of the three aquifers to inrush water.

Study on Characteristic Raman Shift Screening Method Based on MPA for Raman Spectrum of Mine Water Inrush Source

In the process of mine water inrush disaster prevention, accurate and rapid identification of water inrush source type is of great significance to coal mine safety production. However, traditional hydrochemical methods have shortcomings such as time-consuming and complex detection. Therefore, a new idea of identifying mine water inrush source by Raman spectroscopy is proposed. Goaf water, roof sandstone fissure water, Ordovician limestone water, Taiyuan limestone water, and surface water as well as their mixed water samples are selected as research objects, and Raman spectral data of different water samples are collected by the Raman spectroscopy system. To eliminate the influence of laser power fluctuation and spectrometer system noise in Raman spectrum acquisition, detrend correction (DC), multiplicative scatter correction (MSC), standard normal variate transformation (SNV), first derivative (FD), and mean centering (MC) were used to preprocess the raw Raman spectra. Due to the large dimension and long analysis time of Raman spectrum data, the marine predator algorithm (MPA) is used to screen the characteristic Raman shifts of the Raman spectrum of water samples, and the characteristic Raman shift information that can best characterize the mine water samples is obtained. Finally, to verify the feasibility of MPA screening the characteristic Raman shifts of Raman spectrum of mine water inrush source, the selected characteristic Raman displacement information is used as input to construct BP neural network (BP), k-nearest neighbor algorithm (KNN), support vector machine (SVM), and decision tree (DT) classification models, respectively. Experiments show that SNV has the best preprocessing effect on the raw Raman spectrum, which can effectively eliminate part of the noise in the Raman spectrum data and improve the accuracy of Raman spectrum identification. Using MPA, 226 characteristic Raman shifts can be screened from 2048 Raman data points, reducing the number of Raman shifts to 11.04%, and the modeling accuracy of characteristic Raman shift information screened by MPA is higher than that of full Raman data. In addition, the average analysis speed of BP, KNN, SVM, and DT water source identification models is 7.61 times faster than that of all Raman data. The results show that MPA is adopted to screen the characteristic Raman displacement of mine water source Raman spectrum, which can effectively reduce the redundancy of Raman spectral data and greatly improve the speed of Raman spectral analysis, which is of great significance to ensure the real-time detection of the mine water source.

Experimental study on the mechanical properties, acoustic emission characteristics, and permeability evolution of sandstone under triaxial hydromechanical coupling

AbstractIn situ stress and groundwater have important effects on the deformation and stability of deep underground rock masses. Therefore, it is extremely important to study the mechanical properties and permeability evolutionary processes of rocks under hydromechanical (HM) coupling. The purpose of this study was to investigate the mechanical properties and permeability evolution of sandstone using triaxial compression tests under different confining and seepage pressures. The test results show that the confining pressure can increase the strength of sandstone, whereas the seepage pressure has the opposite effect. The initial and maximum permeabilities were positively correlated with seepage pressure and negatively correlated with confining pressure. The confining and seepage pressures had little effect on the change in initial permeability. As a common parameter of acoustic emission (AE), cumulative AE counts can intuitively reflect the permeability evolutionary process in the sandstone failure process. A permeability evolutionary early warning model for the sandstone failure process under HM coupling is proposed. The results are helpful for understanding the influence of in situ stress and seepage pressure on deep sandstone and the permeability evolutionary mechanism, and they can be used to provide early warning of water inrush disasters in deep underground structures.

Study on the Microscopic Mechanism of Grouting in Saturated Water-Bearing Sand Stratum Based on VOF-DEM Method

During the construction of tunnels in saturated water-bearing sand stratum, water and mud inrush disasters often occur. Grouting is the most convenient and effective method to improve the mechanical properties of the soil and prevent groundwater seepage. The reasonableness of the Discrete Element Method (DEM) contact parameters is verified by comparing the repose angle test with that obtained by simulations. The grouting model of saturated water-bearing sand stratum was established based on the Volume of Fluid-Discrete Element Method (VOF-DEM). Then, the effects of sand stratum porosity and grouting pressure on grouting were discussed. The results show that (1) in dense sands, the permeation diffusion of the slurry dominates, whereas in loose sands, the compaction zone is well developed. (2) Loose sand has a wider propagation of stress and dense sand has a larger increase in the stress state. (3) In loose sand the slurry diffusion is significantly affected by gravity, whereas in dense sand the slurry diffusion along the dominant path of the grouting pipe wall boundary is obvious. (4) The range of slurry diffusion and compaction zone is positively related to the porosity and grouting pressure. (5) In loose sand with grouting pressure below 200 kPa, no compaction diffusion occurs during the grouting process, whereas in dense sand, when the grouting pressure is below 500 kPa no compaction diffusion occurs during the grouting process.

Investigation on the evolution mechanism of water and mud inrush disaster in fractured rock mass of mountain tunnel

Water inrush is one of the major disasters during tunnel construction. Due to its characteristics of great harm and difficult prediction, it has always been the focus of research. In order to reveal the mechanism of fault water inrush, a laboratory experiment is adopted to simulate tunnel excavation. The results show, firstly, the pore water pressure and soil pressure of model are unchanged before the fault is exposed; after the fault is exposed, the pore water pressure and soil pressure of vault decrease first, followed by the arch and haunch, and the decline of arch and vault is greater than that of haunch. Secondly, excavation has the greatest impact on the displacement of rock mass directly above the tunnel axis, and the farther away from the axis, the smaller the impact. Thirdly, the seepage channel around vault begins to expand, and clear water begins to seep out after the fault exposure. As the sediment in the crack is carried out by water flow, the clear water gradually becomes turbid, seepage channel changes from pore flow to fissure flow and then to pipe flow. Finally, Comsol is used to analyze the fault water inrush mechanism from the perspective of permeability change, and the correctness of model test is verified by comparing with engineering practice.

Mechanism Analysis of Delayed Water Inrush from Karst Collapse Column during Roadway Excavation Based on Seepage Transition Theory: A Case Study in PanEr Coal Mine

Water inrush disaster is one of the major disasters affecting the production safety of coal mines following roof caving, fire, gas outburst, and dust explosion disasters. It is urgent to reveal the water inrush mechanism and take effective measures to prevent the disasters. More than 80% of water inrush accidents occur around geological structural zones such as faults and karst collapse columns (KCCs). The water inrush events from KCCs caused huge economic losses and heavy casualties, and the water inrush process often shows certain hysteresis characteristics. Taking the water inrush disaster from a KCC during roadway excavation in PanEr Coal Mine of Huainan Mining Area as the case study, the delayed inrush mechanism of KCC was analyzed from the aspects of floor failure, KCC activation, seepage transition, and water inrush development characteristics. The results show that the rock mechanical properties and the excavation depth are the main factors affecting the floor failure characteristics. The seepage transformation from pore flow to fracture flow and pipeline flow, with the change in internal composition structure, is the internal mechanism of the delayed water inrush from KCC. The research is of great significance for the prediction and prevention of water inrush disasters from KCCs.

Identification of Mine Mixed Water Inrush Source Based on Genetic Algorithm and XGBoost Algorithm: A Case Study of Huangyuchuan Mine

Mine water inrush disaster seriously threatens the production of coal mine. Rapid and accurate identification of mine water inrush sources is a key premise for mine water disaster prevention. The conventional research on the identification of water inrush source has focused on a single source, and the identification of mixed water samples from multi-source aquifers in deep coal mining environment is not yet fully explored. In this study, absorption spectrum technology was introduced into the identification of water inrush sources. The absorption spectra of the water samples with different mixing ratios were prepared using the ultraviolet and visible spectrophotometry (UV–Vis) spectrophotometer. In addition, spectral data preprocessing such as scattering correction, baseline correction, smoothing and denoising, and data enhancement were conducted to reduce the influence of experimental error, environment, radiation, molecular interaction, and other factors on the spectral data. Furthermore, a genetic algorithm (GA) was used to improve the seven parameters of the extreme gradient boosting (XGBoost) algorithm, such as learning rate, base model selection, tree parameters, regularization parameters, and iteration times. The deep-learning classifier of mine mixed water sources based on GA-XGBoost was established and used to identify 66 groups of mixed water sources in the Huangyuchuan Mine. The simulation results show that spectral preprocessing and normalization enhancement effectively improved the accuracy of the discriminant model. After 100 cross-validations, the average recognition accuracy of the GA-XGBoost model was 94%, and the results were accurate and reliable. This study provides a new direction and method for the identification of water inrush sources, particularly for mixed water inrush sources. It may also serve as a technical reference for decision-makers to formulate effective coal mine water inrush prevention and control programs and for mine water disaster prevention in similar coalfields in North China.

Calibration of Water Inrush Channel and Numerical Simulation of Water Inrush Process in Coal Mine Roof

The surrounding rock of a coal mine roof fractures with the excavation of the underground working face in coal mining. These mining-induced fractures are connected and extended upward to form water inrush channels. A water inrush accident may occur when there is a sufficiently large water source. To elucidate the formation mechanisms of the roof water inrush channel and the characteristics of water inrush in goafs, we performed a case study of No.18401 Panel of Xiqu Coal Mine in China and determined whether the roof water inrush channel is connected by theoretical calculation and microseismic monitoring. The modified mechanical parameters of rock masses were embedded into the numerical model based on microseismic data. Microseismic monitoring and numerical simulation were organically combined to analyze the connection process of the water inrush channel, after which the roof water inrush channel is calibrated on the No.18401 Panel. We established a non-Darcy flow model for water inrush in the water-conducting fractured zone of mines by coupling the Darcy, Forchheimer, and Navier–Stokes equations. Finite element language and its compiler (FELAC) was used to study the water inrush mechanism of non-Darcy seepage. The results show that the pressure, velocity, and porosity in the water-conducting fractured zone are non-uniform in water inrush occurrence and development, and the mixed fluid mainly passes through the “dominant channel.” The development of water inrush is accompanied by the release of the hydrostatic pressure in the aquifer, the sudden increase of the velocity at the water inrush position, and the increase in fluid concentration. Hence, the underground water inrush can be predicted and prevented by monitoring the aforementioned indicators. This research is of great significance for the calibration of the water inrush channel of the roof and the prediction of water inrush disasters.

Dynamic simulation of the water inrush process in tunnel construction using a three-dimensional coupled discontinuous deformation analysis and smoothed particle hydrodynamics method

Water inrush, which is a major cause of geological disasters during tunnel excavation, can worsen construction conditions and result in casualties. It is thus important to study the water inrush process for mitigating and preventing water inrush disasters in tunnel construction. The tunnel water inrush problem involves solid–fluid interactions. The coupling of the parallel three-dimensional discontinuous deformation analysis (3-D DDA) and 3-D smoothed particle hydrodynamics (3-D SPH) is suitable for analyzing this problem. The critical condition of a block under water pressure was first investigated to check the validity of the 3-D coupled DDA-SPH method. Further, a tunnel water inrush phenomenon was reproduced, and the mechanical behaviors of tunnels were explained with respect to the thickness T of the rock wall, the initial water height H, and the presence and location of a water outlet. The simulation results show that the tunnel deformation increases as T decreases and as H increases. The tunnel deformation was found to be larger when there was a water outlet; however, the location of the outlet had a slight effect on the deformation.

Evolution Mechanism of Water-Conducting Fissures in Overlying Rock Strata with Karst Caves under the Influence of Coal Mining

There are a large number of karst caves in the limestone rock strata in the karst mining area, and the karst water in rock strata seriously restricts the safe and efficient recovery of coal resources. In order to reveal the influence law of karst caves of rock strata on the evolution of water-conducting fissures in coal seam mining, the numerical simulation method in UDEC software is employed to analyze the development characteristics of water-conducting fissures in coal seam mining under the conditions of karst caves of different sizes. By comparing and analyzing the development characteristics of overlying fissures in rock strata and the displacement fields in coal seam mining under the conditions of different karst caves, the evolution law of water-conducting fissures in coal seam mining is obtained. The research results show that the size of karst cave directly affects the maximum height of the water-conducting fissures in the overlying rock strata in coal seam mining; when the thickness of the coal seam is 3.0 m, the larger the radius of karst cave is, the higher the development height of water-conducting fissures in the overlying rock strata is, and the greater the overall sinking displacement in the Yulongshan limestone is. When the radius of karst cave is between 10 m and 15 m, a through-type water-conducting channel is formed between the working face and the karst cave after the coal seam is mined, and the numerical simulation results are consistent with the field monitoring results. The research results provide an important reference for the prevention and treatment for water inrush disaster in karst mining areas.