Complex Hydrogeological Conditions Research Articles

Coal-Mine Water-Hazard Risk Evaluation Based on the Combination of Extension Theory, Game Theory, and Dempster–Shafer Evidence Theory

Due to the complex hydrogeological conditions and water hazards in coal mines, there are multiple indexes, complexities, incompatibilities, and uncertainty issues in the risk evaluation process of coal-mine water hazards. To accurately evaluate the risk of coal-mine water hazards, a comprehensive evaluation method based on extension theory, game theory, and Dempster–Shafer (DS) evidence theory is proposed. Firstly, a hierarchical water-hazard risk-evaluation index system is established, and then matter-element theory in extension theory is used to establish a matter-element model for coal-mine water-hazard risk. The membership relationship between various evaluation indexes and risk grades of coal-mine water-hazard risk is quantified using correlation functions of extension set theory, and the quantitative results are normalized to obtain basic belief assignments (BBAs) of risk grades for each index. Then, the subjective weights of evaluation indexes are calculated using the order relation analysis (G1) method, and the objective weights of evaluation indexes are calculated using the entropy weight (EW) method. The improved combination weighting method of game theory (ICWMGT) is introduced to determine the combination weight of each evaluation index, which is used to correct the BBAs of risk grades for each index. Finally, the fusion of DS evidence theory based on matrix analysis is used to fuse BBAs, and the rating with the highest belief fusion result is taken as the final evaluation result. The evaluation model was applied to the water-hazard risk evaluation of Sangbei Coal Mine, the evaluation result was of II grade water-hazard risk, and it was in line with the actual engineering situation. The evaluation result was compared with the evaluation results of three methods, namely the expert scoring method, the fuzzy comprehensive evaluation method, and the extension method. The scientificity and reliability of the method adopted in this paper were verified through this method. At the same time, based on the evaluation results, in-depth data mining was conducted on the risk indexes of coal-mine water hazards, and it was mainly found that 11 secondary indexes are the focus of coal-mine water-hazard risk prevention and control, among which seven indexes are the primary starting point for coal-mine water-hazard risk prevention and control. The groundwater index in particular has the most prominent impact. These results can provide a theoretical basis and scientific guidance for the specific water-hazard prevention and control work of coal mines.

Two-dimensional numerical analysis of seepage in an undersea mining area considering hydrochemical corrosion

The complex hydrogeological conditions and unique hydrochemical environment in the seabed rock often cause serious mine water inrush during undersea mining. With the exploitation of the undersea gold mining area in Sanshandao as the research background, a numerical analysis method for the seepage behavior of the surrounding rock in undersea gold mining considering the hydrochemical corrosion was put forward. A numerical simulation analysis of the undersea mining area in Sanshandao was conducted by the established method, and the results showed that mining the submarine ore body significantly changed the seepage field of the surrounding rock around the stope and water levels dropped obviously in the ore-controlling fault zone. Differences in the hydrochemical environment significantly influenced the distribution of the seepage field of the surrounding rock. The calculation results based on three fluids with different pH values show that the head variation range is the largest when pH = 2, followed by pH = 4, and pH = 7 has the smallest head variation range. The water inflow in the stope was also directly affected by the hydrochemical environment. With the change of pH, the water inflow at each boundary of the stope increases exponentially.

Regional characteristics of groundwater sulfate source and evolution in the multi-layer aquifer system of the northern Shaanxi coal mine base, northwestern China: Evidence from geochemical and isotopic fingerprints

Groundwater sulfate contamination in mining areas has attracted widespread attention. However, deciphering the source and evolution of sulfate in large-scale mining areas remains a challenge due to intense anthropogenic influences and complex hydrogeological conditions. In this study, 94 groundwater samples were analyzed by a combination of self-organizing maps, MixSiar model, multi-isotope analyses (δ34S, δ18OSO4, δD and δ18Owater) and hydrogeochemical methods to investigate the regional characteristics of groundwater sulfate source and evolution in China's largest coalfield (the Shenfuyu Coalfield). The results showed that the source and evolution of groundwater sulfate were controlled by human activities (mining and agricultural activities) and hydrogeological conditions. The groundwater sulfate primarily originated from pyrite oxidation, gypsum dissolution and human inputs. For the mining districts with shallow mining depths, pyrite oxidation and fertilizer contributed to groundwater sulfate. In addition, the ground cracks and abandoned mines controlled the BSR and pyrite oxidation processes. In contrast, the gypsum dissolution and cation exchange dominated the sulfate evolution in the mining districts with deep mining depths due to slow groundwater circulation. This study provided new insights into the source and evolution of groundwater sulfate in large coalfields, as well as references for regional water resource utilization and protection.

Assessment of soil-groundwater nitrogen cycling processes in the agricultural region through flux model, stable isotope

The nitrogen cycle in the soil-groundwater system of agricultural land is a crucial process within the global nitrogen cycle. Human activities have significantly intensified this cycling process in agricultural fields, consequently leading to substantial accumulation of nitrogen in the soil-groundwater system and giving rise to numerous ecological health issues. Quantitative assessment of soil-groundwater nitrogen cycling processes can facilitate the optimization of nitrogen management strategies in agricultural fields and the prevention and management of groundwater nitrogen pollution. However, accurately quantifying the intricate soil-groundwater nitrogen cycling dynamics in agro-irrigation areas characterized by diverse nitrogen sources and complex hydrogeological conditions poses a significant challenge. The Songhua River Basin in the Sanjiang Plain was selected as the study area for this investigation. We utilized the INCA-N model to simulate annual nitrogen fluxes in the soil-groundwater system of an agricultural watershed, and employed stable isotope and water chemistry methods to identify sources of groundwater nitrogen contamination and transformation processes. Ultimately, we conducted a comprehensive assessment of nitrogen cycling within the soil-groundwater system of the agricultural watershed. The findings revealed that atmospheric deposition, nitrogen fixation, and fertilization constituted the primary mechanisms of soil nitrogen input. Plant uptake, riverine nitrogen transport, and denitrification were identified as the three principal processes responsible for soil-groundwater nitrogen export. The results obtained from the MIXSIAR model demonstrate a substantial contribution of nitrogen fertiliser and soil nitrogen to groundwater nitrate, followed by faeces and sewage. Additionally, the annual input fluxes of nitrogen simulated by INCA-N reveal that fertiliser application is the primary contributor, which aligns to some extent with the findings of the MIXSIAR model. Soil nitrogen can serve as a relatively stable source of groundwater nitrate, while anthropogenic activities such as fertilizer application, manure deposition, and sewage discharge are likely to be the primary drivers of groundwater nitrate pollution. By quantifying the N input and output fluxes, it was determined that approximately 58% of the total annual nitrogen input has the potential to accumulate within the soil-groundwater system. The effective utilization of legacy nitrogen can contribute to the reduction of soil-groundwater nitrogen fluxes, while maintaining crop yields and mitigating greenhouse gas emissions. This study aims to optimize nitrogen management practices in agricultural areas and provide valuable insights for water conservation strategies.

Groundwater model diagnostic calibration and uncertainty analysis using information theory

ABSTRACT This study aims, as a first attempt, to establish a framework for multi-objective optimization diagnostic model calibration and uncertainty analysis based on information theory, including mutual information (MI) and variation of information (VI). Moreover, a global sensitivity analysis was performed using the information coefficient of correlation to determine the incremental contribution of each model parameter. The applicability of the proposed framework was tested in an arid region of Oman with complex hydrogeological conditions and hardrock-alluvial aquifer systems. The findings highlight the capability of the information theory approach to simultaneously calibrate the model and assess uncertainty, while providing valuable diagnostics for identifying areas of the model that require further refinement. Furthermore, the results indicate that the proposed framework successfully reproduced 96% of the observed data, demonstrating its ability to reduce parameter uncertainty and ensure an accurate match between the simulated and observed data.

Progressive Failure Mechanism of Shield Tunnel Face in Complex Urban Geological Environment

The construction of multiple tunnels across inland rivers has had a significant influence on the improvement of the transportation infrastructure. The technology for constructing tunnels is progressing towards the development of larger cross-sections, longer distances, and the ability to withstand high hydraulic pressure in complex hydrogeological conditions, including high-permeability strata. In order to ensure the face stability of shield tunnels under high hydraulic pressure that crosses a fault fracture zone, it is necessary to study the progressive failure mechanism of shield tunnel faces induced by high hydraulic pressure seepage. This paper employs finite element numerical simulation software to methodically examine the variation in the characteristics of the water seepage field, limiting support force, and face stability failure mode of shield tunnels passing through fault fracture zones with high hydraulic pressure under varying fault fracture width zones. The results show that the formation hydraulic gradient will progressively widen when the tunnel face is located within the undisturbed rock mass and is advanced towards the area of fault fracture. This will raise the likelihood of instability in the shield tunnel and progressively raise the limiting support force on the tunnel face. Moreover, as the tunnel face nears the region of fault fracture within the undisturbed rock mass, the damage range increases gradually. In addition, due to the increase in seepage force, the angle between the failure area and the horizontal plane becomes more and more gentle. On the contrary, as the tunnel’s face moves closer to the undisturbed rock mass from the region of the fault fracture, the damage range gradually decreases, and the dip angle between the damage area and the horizontal plane becomes steeper and steeper due to the decreasing seepage force in the process. The study findings presented in this work are highly significant, both theoretically and practically, for the design and management of safety.

Application of the Tracer Test in a Hydrogeological Survey for a Pumped Storage Power Station

In areas with complex hydrogeological conditions, the tracer test method is often used as an effective means in hydrogeological surveys. According to the results of tracer tests, hydrogeological parameters, including hydraulic gradient and permeability coefficient, fracture network leakage passages and their scale, and groundwater flow rate and direction can be quantitatively determined. This paper takes the upper reservoir of Yongxin Pumped Storage Power Station in Jiangxi Province as the research object, and focuses on the complex hydrogeological conditions of the upper reservoir. Three sets of tracer tests and multiple sets of single-hole flow rate and direction tests were conducted on the left and right banks of the reservoir and near surface gullies. The results showed that ZKS18 received tracers in all three tests, which indicates a close hydraulic connection between ZKS18 and the left bank, right bank, and surface gullies within the reservoir. Based on the single or multiple peak values of the tracer, it was determined that there are 1–6 leakage passages in the fractured rocks, with leakage passage sizes of 0.1–0.4 mm. According to the single-hole flow rate and flow direction tests, a self-developed instrument was used to determine the groundwater flow rate and flow direction at different depths in the test holes, which yielded results that were basically consistent with the results of the three-hole method. These results provide a basis for the use of tracer tests in hydrogeological surveys for water conservancy and hydropower engineering, and anti-seepage design of upper reservoirs.

Prediction of sulfate concentrations in groundwater in areas with complex hydrogeological conditions based on machine learning

The persistent and increasing levels of sulfate due to a variety of human activities over the last decades present a widely concerning environmental issue. Understanding the controlling factors of groundwater sulfate and predicting sulfate concentration is critical for governments or managers to provide information on groundwater protection. In this study, the integration of self-organizing map (SOM) approach and machine learning (ML) modeling offers the potential to determine the factors and predict sulfate concentrations in the Huaibei Plain, where groundwater is enriched with sulfate and the areas have complex hydrogeological conditions. The SOM calculation was used to illustrate groundwater hydrochemistry and analyze the correlations among the hydrochemical parameters. Three ML algorithms including random forest (RF), support vector machine (SVM), and back propagation neural network (BPNN) were adopted to predict sulfate levels in groundwater by using 501 groundwater samples and 8 predictor variables. The prediction performance was evaluated through statistical metrics (R2, MSE and MAE). Mine drainage mainly facilitated increase in groundwater SO42− while gypsum dissolution and pyrite oxidation were found another two potential sources. The major water chemistry type was Ca-HCO3. The dominant cation was Na+ while the dominant anion was HCO3−. There was an intuitive correlation between groundwater sulfate and total dissolved solids (TDS), Cl−, and Na+. By using input variables identified by the SOM method, the evaluation results of ML algorithms showed that the R2, MSE and MAE of RF, SVM, BPNN were 0.43–0.70, 0.16–0.49 and 0.25–0.44. Overall, BPNN showed the best prediction performance and had higher R2 values and lower error indices. TDS and Na+ had a high contribution to the prediction accuracy. These findings are crucial for developing groundwater protection and remediation policies, enabling more sustainable management.

A dynamic modeling approach to predict water inflow during tunnel excavation in relatively uniform rock masses

Karst landforms are widely distributed all over the world. With the continuous improvement of infrastructure construction, tunnelling in mountainous karst areas is inevitable. Due to the complex hydrogeological conditions in karst areas, groundwater inflow during tunnelling is usually difficult to predict and can cause huge economic losses and casualties. Therefore, finding better ways to improve the prediction of tunnel water inflow is of great significance to ensure the safety of tunnelling. In this study, three commonly used modules (CHD, DRAIN and CFPM1) in MODFLOW are selected and compared to predict the water inflow of tunnels. We find that the CFPM1 module performs better in terms of considering both tunnel size and actual water inflow dynamics during tunnel excavation, which is a continuous process rather than an instantaneous process. Secondly, we build a hypothetical case and predict the tunnel water inflows using above three different modules. We find that the CHD module yields the largest initial and stable water inflow, followed by the DRAIN module, and the CFPM1 yields the least. Besides, as the most sensitive factor in the CFPM1 module, the influence of tunnel diameter on water inflow is discussed. Finally, taking the Shizishan Tunnel as an actual field example, we compare the simulation results of different modules with the measured tunnel inflow. In general, the prediction of the CFPM1 module is the closest to the measured value, and the prediction accuracy is the highest during the conventional tunnel construction process. However, when water-saturated karst features such as underground rivers, caves or faults are exposed during tunnelling, the water level may change instantaneously, which is more consistent with the principle of CHD module. In summary, this study provides theoretical and numerical support for the safe construction of relatively uniform rock mass tunnels in karst areas.

Application of stable isotopes, mixing models, and K-means cluster analysis to detect recharge and salinity origins in Siwa Oasis, Egypt

Waterlogging, soil salinization, and groundwater depletion in non-rechargeable aquifers are among the causes endangering the sustainability of Siwa Oasis. The water resources include the tertiary carbonate aquifer (TCA), Nubian sandstone aquifer (NSSA), springs, drains, and hypersaline lakes. Geophysical logs were used to identify various aquifer systems. Stable isotopes, major ions, and heavy metals were examined. K-means cluster analysis based on principal component analysis (PCA), hydrochemistry, stable isotopes, and mixing models using NETPATH were applied in order to understand the complex hydrogeological conditions in the different aquifer systems. The results showed that all water samples were under-saturated (SI < 1) with respect to anhydrite, halite, and gypsum minerals, indicating the water's ability to dissolve more from these minerals and increase water salinity.In contrast, calcite, dolomite, Ca-montmorillonite, and illite minerals were supersaturated in most water samples (SI > 1), showing their ability to precipitate these minerals. There is no recharge for the aquifer systems, and all the groundwater resources have paleo meteoric origin, where the maximum values of δ18O and δ2H are −8.45 and −65.63, respectively. All of the springs originated from the TCA, as indicated from the K-mean cluster analysis. There is a rapid increase in the water salinity of the TCA from 1998 to 2022 due to evaporation, rock weathering, mixing with old trapped sea water, and seepage of saline water from salt lakes. The significant variations in the water salinity of the TCA aquifer are due to the mixing between fresh water of NSSA (dilution) and salt water from Zeituna and Siwa lakes through downward flow in some locations, where over-extraction of water for irrigation purposes has decreased the water pressure in the TCA. The mixing model confirmed salt lakes' contribution in increasing the TCA salinity by 2%–4%. Mixing water from TCA and NSSA could be the best management of the water resources in Siwa Oasis, as well as the application of subsurface drip irrigation.

Migration of total petroleum hydrocarbon and heavy metal contaminants in the soil-groundwater interface of a petrochemical site using machine learning: impacts of convection and diffusion.

Convection and diffusion are key pathways for the migration of total petroleum hydrocarbons (TPH) and heavy metals (HMs) from soil to groundwater. However, the extent of their influence on pollutant migration, as well as the nonlinear relationships between these processes and pollutants, remains unclear. This study investigates the spatial distribution of TPH and HMs at a petrochemical site with complex hydrogeological conditions in southwestern China. In addition, machine learning (ML) was used to assess the effects of convection and diffusion on pollutant migration at the soil-groundwater interface. The analysis identifies and reveals TPH, Co, and Ni as the primary pollutants, with soil concentrations reaching 47.427, 7.024, and 4.766 times their respective screening values. Among various ML models, Random Forest (RF) was identified as the most effective, based on R 2, and RMSE performance metrics. The RF model demonstrates that the concentrations of TPH and As are closely related to soil depth. Furthermore, importance indices calculated by RF indicate that the significance of convection and diffusion varies across different soil-groundwater systems. Specifically, at the soil-perched water interface, convection plays a more significant role than diffusion in influencing the migration of TPH and As. However, at the soil-pore water interface, diffusion more significantly influences the migration of all pollutants compared to convection. Additionally, a threshold or saturation effect was observed for the impact of the convection factor on pollutant concentrations in groundwater. These findings highlight the distinct roles of convection and diffusion across various water interfaces, providing new insights into the mechanisms governing contaminant migration and fate.

Study of a Small Robot for Mine Hole Detection

China is rich in coal resources, but complex hydrogeological conditions lead to difficulties in coal mining, including coal mine collapses, roof and water damage, and other accidents that occur frequently, resulting in many casualties and property losses. The use of coal mine hole detection technology to detect and analyze the internal environment of the coal mines in advance helps to reduce safety hazards and prevent coal mine accidents; however, the operation of existing coal mine hole detection technology is cumbersome, difficult to control, and encounters problems due to an insufficient depth of jacking. This paper designs a new type of small robot for mine hole detection. Firstly, we analyzed the function and structural design of the mine hole detection robot, designed a variable diameter function according to the characteristics of narrow and uneven mine holes in coal mines, and analyzed the mechanics of the critical parts using theoretical calculations. Secondly, using three-dimensional modeling software (Solidworks 2019), we established a structural model of the small robot for mine hole detection. After that, we designed a hardware circuit and control program for the robot and emphasized the safety design of the circuit, considering the presence of water and gas inside the coal mine. Finally, to verify the feasibility of the design program, the basic parameters and function tests of the mine hole-detection small robot were carried out. The experimental results show that the developed mine hole-detection small robot can adapt to working hole diameters from 65 mm to 100 mm and has a maximum working power of only 12 W and a maximum crawling speed of 3.96 m/min. The maximum crawling slope reaches 90°, which can meet existing mine hole inspection needs. This research provides theoretical and design guidance for developing mine hole-detection robots with substantial engineering practical reference values.

Mechanism of and Prevention Technology for Water Inrush from Coal Seam Floor under Complex Structural Conditions—A Case Study of the Chensilou Mine

Based on the complex hydrogeological conditions of the Chensilou mine, numerical simulations and field validation methods were used to study the mechanism of water inrush from the floor of the coal seam, which has faults and cracks, as well as the regional advanced grouting reinforcement technology during the coal mining process. The evolution laws of the roof stress field, displacement field, crack field, and plastic area are revealed at different mining distances. The coupling mechanism of floor water inrush channel formation under complex conditions is analyzed. Advanced grout filling reinforcement technology in the ground area is proposed, the slurry diffusion law of different grouting layers under different grouting pressures is revealed, and the grouting effect is evaluated, which provides a research basis for selecting a reasonable grouting pressure. Finally, the application of regional advanced grouting reinforcement technology was carried out at the site, and the grouting reconstruction effect was verified by the transient electromagnetic and three-dimensional DC resistivity method. The results show that the apparent resistivity of the floor after the grouting reinforcement is high, and the water yield of the verification borehole is less than 10 m3/h. The area where the three-dimensional direct current resistivity is less than 12 Ω·m only appears in the lower part of the middle of the working face, and there is no water in the verification borehole. Through our underground supplementary treatment and verification process, the initial water inflow meets the requirements of being less than 10 m3/h. It indicates that the ground regional advanced treatment project achieved significant results. The results of our research can also provide references for water hazard control in similar mines.

Performance of Prefabricated Hollow Concrete-Filled Steel Tube Bracings on Transverse Bending: Experimental and Numerical Analyses

Due to the complex hydrogeological conditions in coastal regions, the use of internal bracing systems is necessary for supporting coastal foundation pits. This paper introduces a novel prefabricated foundation pit bracing system based on Hollow Concrete-Filled Steel Tube (H-CFST) structures that can be reused, offering significant economic and societal benefits. However, there is a severe lack of research on the application of H-CFST bracing systems. Through model tests and finite element simulations, the load-displacement characteristics and failure modes of prefabricated H-CFST bracing under transverse bending were investigated. The study revealed that when a wall thickness of 1.5 d was chosen, the self-designed hoop effectively mitigated strength and stiffness reduction at the bracing connection point. When the load reached 150 kN, the outer steel tube of the H-CFST components experienced localized yielding, and when the load was increased to 300 kN, the end supports exhibited cracking. Finite element analysis provided a more accurate prediction of bracing failure at 147.18 kN, and it offered valuable insights for optimizing the bracing design. Based on the above research, theoretical methods for calculating the bearing capacity of each bracing component under transverse bending conditions have been proposed and validated against experimental results.

Isotopic identification of groundwater circulation and mixing in the Legnica-Głogów Copper District mines

Identification of the conditions of circulation, mixing, origin and age of groundwater in the area of underground mining plants is necessary for the correct design of drainage systems, directions of mining exploitation and intensity of mining works. For this purpose, isotopic studies were carried out in the mines of the Legnica-Głogów Copper District (LGCD) in Poland, characterized by complex hydrogeological conditions. The observed values of δ2H, δ18O and concentrations of tritium, as well as chlorides, sulfates and main cations in 29 water samples taken from different lithostratigraphic levels (and a few historical results) were used to explain the spatial variability of the origin of groundwater flowing into the mines. A model of groundwater mixing in the mining area of the LGCD was developed. The results of the research indicate that, depending on the region, the LGCD mines contain Holocene and/or interglacial waters, pre-Quaternary waters as well as older waters, recharged in period of very warm climate - flowing into the mining workings from deeper geological strata. Isotopic studies together with the chloride content measurements confirmed the correctness of the conceptual model of groundwater circulation within the mines. Their results will be useful in further elaboration of the strategy related to dewatering and designing further mining activities.

Analysis of reservoir slope deformation during initial impoundment at the Baihetan Hydropower Station, China

Reservoir slope deformation induced by impoundment poses a threat to the safety of high-arch dams, which has received widespread attention in recent years. With an arch dam height of 300 m class, Baihetan is the largest hydropower station under construction. However, the theory behind its reservoir slope deformation under complex hydrogeological conditions is still an open question. In this study, a numerical model was developed to describe the complex seepage field at the dam site before and after impoundment. Furthermore, the numerical simulation of reservoir slope deformation was conducted based on the effective stress principle. The monitoring data collected during the initial impoundment of Baihetan validated the numerical model. Based on that, the spatiotemporal deformation law of the reservoir slope and its main controlling factors were analyzed. The results indicate that the contraction of the upstream valley is mainly caused by the reduction of the effective stress of the reservoir slope, the high and steep topography formed by the extensive excavation, and the weakening of structural planes. The effective stress reduction caused by the bypass seepage, and the stress adjustment may be the main reason for the deformation of the downstream reservoir slope. In addition, structural planes distributed in the dam foundation play a particular control role in the deformation of the foundation slope. This study systematically characterized the impoundment-induced reservoir slope deformation features of Baihetan and discussed the possible deformation mechanism, providing an essential reference for evaluating the structural safety of the dam during operation.

Комплексная оценка геотехнических рисков в шахтном и подземном строительстве

Introduction. Projects for the construction of underground structures and mines often involve significant geotechnical risks. The uncertainty associated with geotechnical conditions implies the development of a specific approach to making design and constructive decisions. Even after a thorough geotechnical study, the ability to accurately predict the behavior of adjacent rock massif is often difficult due to the large number of engineering-geological and hydro-geological variables. Most of the identified risks can be eliminated at the design stage. Residual risks should be subjected to a comprehensive assessment, including qualitative and quantitative analysis and calculations of damage from potential risk and technical and economic efficiency of the adopted design decision. Objective. Complex estimation of geotechnical risks in mine and underground construction based on the analysis of indicators of the implementation of accidents by mining-geological and mining-technical factors, taking into account the use of special methods of construction. Methodology. A сomplex estimation of geotechnical risks was carried out on the basis of the theory of emergency risk using methods of mathematical statistics, probability theory; the method of expert assessments to obtain the values of vulnerability coefficients of the applied technologies of mine and underground construction. The developed methodology includes several stages. At the first stage of a сomplex risk estimation, it is necessary to rank the geotechnical risk factors selected for analysis, for which a concordance coefficient is introduced. When analyzing each of the emerging geotechnical figures during the construction of a specific underground or mine construction facility, one of the defining indicators is the numerical expression of the potential damage from the occurrence of an emergency situation, which represents the percentage ratio of the excess of the construction period in real practice to the same indicator laid down in the project, or the ratio of the increase in the cost of construction to the estimated cost. Next, the numerical value of each type of risk is determined and a scale of numerical values of risks is compiled, on the basis of which decisions are made on the management of each specific risk. At the end, the vulnerability of a mine or underground construction facility under construction is determined, i.e. the degree of its possible damage and destruction when exposed to abnormal situations of a natural and man-made nature. Results and discussion. A methodology has been developed for the сomplex estimation of geotechnical risk in mine and underground construction based on the ranking of risks according to the degree of vulnerability of the technologies used. Ranking of construction objects by their vulnerability to various impacts allows us to assess the correlation between the values of the parameters and the qualitative characteristics of the elements of the “mining – rock mass – construction technology” system and the factors that lead to the development of potential damage. In the course of the research, a generalized indicator of the predicted geotechnical risk was identified, which allows taking into account the impact of construction methods on the risk. Since mine workings are currently being built mainly in complex hydro-geological and engineering-geological conditions, the calculation of the generalized indicator focuses on the use of special construction methods, which required the introduction of correction factors to calculate the indicator of the predicted geotechnical risk. The values of correction coefficients for the most used special methods were obtained by the method of expert assessments. Conclusions. One of the important aspects of a сomplex estimation of geotechnical risks in mine and underground construction is to determine the vulnerability of the “mining - rock mass – technology” system. Vulnerability depends on the location of the mine, its cross-section, engineering-geological and hydro-geological conditions, mode of operation, reliability of load-bearing and fencing, etc. By the method of сomplex estimation, vulnerability coefficients of underground structures under construction and mine workings were obtained, as well as correction coefficients taking into account the construction method.

Analytical expressions of hydraulic conductivity intervals for steady flow to a single pumping well in an unconfined aquifer

Results of pumping tests are normally uncertain due to insufficient exploration capability and complex hydrogeological conditions, which poses the question of how to calculate the range of hydraulic conductivity values if the factors affecting hydraulic conductivity fluctuate within this range. In this paper, the parameters affecting hydraulic conductivity were regarded as the range, or ‘interval’. From this perspective, three analytical expressions that can quickly calculate the hydraulic conductivity interval specifically for an unconfined aquifer with a single well were derived using the Dupuit–Forchheimer formula from three universal expressions. The relative errors for the three expressions were analysed by comparing them with the equal interval continuous sampling method (EICSM). The results indicated that on the premise that the absolute value of the relative error of the hydraulic conductivity extremum was controlled within 10%, the maximums and minimums should be calculated using Expression 2 (convex model formula) and Expression 3 (Taylor expansion formula), respectively. These expressions were considered as better choices because the allowable change rate could reach 20 and 10%. At the end of the research, an actual pumping test was introduced to verify the above deduction.

A Prediction Method for Height of Water Flowing Fractured Zone Based on Sparrow Search Algorithm–Elman Neural Network in Northwest Mining Area

The main Jurassic coal seams of the Ordos Basin of northwest mining area have special hosting conditions and complex hydrogeological conditions, and the high-intensity coal mining of the coal seams is likely to cause groundwater loss and negative effects on the surface ecological environment. The research was aimed at predicting the height of the water-flowing fractured zone (WFFZ) in high-intensity coal mining in that area and gave instructions for avoiding water inrush accidents and realizing damage reduction mining during the actual mining procedure of the coal mine. In this study, 18 samples of the measured height of WFFZ in Jurassic coal seams were systematically collected. In the mining method, the ratio of the thickness of the hard rock to the thickness of the soft rock in the bedrock, buried depth, mining height, and working face length was selected as the input vectors, applied the sparrow search algorithm (SSA) to iteratively optimize the weights and thresholds of the Elman neural network (ENN), constructed an SSA-Elman neural network model. The results demonstrate that the improved SSA-Elman neural network model has higher accuracy in predicting the height of the WFFZ compared with traditional prediction algorithms. The results of this study help guide damage-reducing, water-preserving mining of the middle-deep buried Jurassic coal seams in the northwest mining areas.

ВАРИАНТНОЕ ПРОЕКТИРОВАНИЕ ФУНДАМЕНТОВ ПРОМЫШЛЕННЫХ И ОБЩЕСТВЕННЫХ ЗДАНИЙ ДЛЯ РАЗЛИЧНЫХ ГИДРОГЕОЛОГИЧЕСКИХ УСЛОВИЙ

The article considers the various foundation design for different regions of the Russian Federation. The calculation of the pile foundation was carried out taking into account the peculiarities of hydrogeological conditions in these regions for the multifunctional sport complex. The spatial frame modeling was performed using SCAD and Autodesk AutoCAD software packages. According the calculation S-5-30 5 m long with a section of 300x300 mm (by series) piles received for the Republic of Bashkortostan. For the Republic of Tatarstan: piles according to the S-3-30 series, 3 m long, with a section of 300x300 mm. According to the S-6-50 series, 6 m long, with a section of 500x500 mm piles are accepted for the Perm Territory. To define the price of building foundations, a local estimate calculation was composed based on bills of quantities. Based on the presented final price, it can be concluded that different categories of engineering and geological conditions complexity, imply additional activities in areas with more complex hydrogeological conditions. The cost of building the foundation for the Republic of Bashkortostan amounted to 93.711 million rubles, and turned out to be the largest in comparison with other regions, which is associated with a significant increase in the volume of work due to the installation of monolithic reinforced concrete belts. The authors noted, that analysis of engineering and geological conditions of the construction site is the determining factor in the choice of foundation structures for the designed building. The presented methodology allows to carry out a similar industrial and public buildings feasibility study in construction not only in the considered regions but throughout the Russian Federation.