Qiqing Wang

Effects of Coal Mining on Shallow Water Resources in Semiarid Regions: A Case Study in the Shennan Mining Area, Shaanxi, China

The Shennan mining area in northern Shanxi Province is located in a semiarid area where surface and near-surface water resources are very valuable. Mining-induced fractures can cause these shallow water resources to leak. The overburden strata were divided into engineering geology rock groups and a comparative analysis was calculated based on the height of the water-conducting fractured zone and the key stratum theory, using both an empirical formula and a fitting formula. The influence of coal mining on the shallow water resources was divided into four types: serious, moderate, slight, and no water loss. Finally, a water resource leakage differentiation graph was produced for the study area. The results can be used to guide coal extraction in the study area and to protect the area’s shallow water resources.ZusammenfassungDie Shennan Bergbauregion in der nördlichen Shanxi Provinz liegt in einer semiariden Region, in welcher oberflächliche und oberflächennahe Wasserressourcen sehr wertvoll sind. Bergbaubedingte Brüche können das Auslaufen dieser seichten Wasserressourcen bewirken. Die überlagernden Schichten wurden in ingenieurgeologische Gruppen unterteilt. Auf der Basis der Höhe der wasserleitenden Störungszone und der Schlüsseschichttheorie (key stratum theory) wurde eine vergleichende Analyse gerechnet, unter Nutzung einer empirischen und einer angepassten Formel. Der Einfluß des Kohlenbergbaues auf die seichten Wasserressourcen wurde in vier Typen beschrieben: Ernst, moderat, gering, und kein Wasserverlust. Schließlich wurde für das Studiengebiet ein Differentiationsgraph der Wasserverluste erstellt. Die Resultate können den Kohlenabbau in dem Studiengebiet lenken, um die seichten Wasserressourcen zu schützen.ResumenEl área minera de Shennan en el norte de la provincial Shanxi está localizada en un área semiárida donde las fuentes de agua superficial y las cercanas a la superficie, son muy valiosas. Las fracturas inducidas por la minería pueden causar que estas fuentes de agua se pierdan. Los estratos sobrecargados fueron divididos en grupos de rocas geológicas y se calculó un análisis comparativo basado en la altura de la zona de fractura conductora de agua y la teoría de estrato clave, usando una fórmula empírica y una fórmula de ajuste La influencia de la minería de carbón sobre las fuentes de agua superficial fue dividida en cuatro tipos: seria, moderada, ligera y sin pérdida de agua. Finalmente, se realizó un gráfico de diferenciación de la pérdida de la fuente de agua para el área de estudio. Los resultados pueden ser usados como una guía para la extracción de carbón en el área de estudio y para proteger los recursos de agua del área.

GIS-based assessment of landslide susceptibility using certainty factor and index of entropy models for the Qianyang County of Baoji city, China

The main goal of this study is to produce landslide susceptibility maps for the Qianyang County of Baoji city, China, using both certainty factor (CF) and index of entropy (IOE) models. At first, a landslide inventory map was prepared using earlier reports and aerial photographs as well as by carrying out field surveys. A total of 81 landslide locations were detected. Out of these, 56 (70%) landslides were randomly selected as training data for building landslide susceptibility models and the remaining 25 (30%) were used for the validation purposes. Then, a total number of 15 landslide causative factors, such as slope angle, slope aspect, general curvature, plan curvature, profile curvature, altitude, distance to faults, distance to rivers, distance to roads, the sediment transport index (STI), the stream power index (SPI), the topographic wetness index (TWI), geomorphology, lithology, and rainfall, were used in the analysis. The susceptibility maps produced using CF and IOE models had five different susceptibility classes such as very low, low, moderate, high, and very high. Finally, the output maps were validated using the validation data (i.e., 30% landslide location data that was not used during the model construction), using the area under the curve (AUC) method. The ‘success rate’ curve showed that the area under the curve for CF and IOE models were 0.8433 (84.33%) and 0.8227 (82.27%) accuracy, respectively. Similarly, the validation result showed that the susceptibility map using CF model has the higher prediction accuracy of 82.32%, while for IOE model it was 80.88%. The results of this study showed that the two landslide susceptibility maps obtained were successful and can be used for preliminary land use planning and hazard mitigation purpose.

A comparative study of statistical index and certainty factor models in landslide susceptibility mapping: a case study for the Shangzhou District, Shaanxi Province, China

Landslide susceptibility maps are vital for planning development activities in the mountainous areas in China. The main goal of this study was to produce landslide susceptibility mapping by statistical index (SI) and certainty factor (CF) models for the Shangzhou District of Shangluo City, China. For this purpose, a landslide inventory map with a total of 145 landslide locations was compiled from various sources such as aerial photographs and field surveys, out of which 101 (70 %) were randomly selected for training the models, while the remaining 44 (30 %) were used for validating the models. In this case study, the following landslide conditioning factors were evaluated: slope angle, slope aspect, curvature, elevation, lithology, distance to faults, distance to rivers, distance to roads, precipitation, and peak ground acceleration were considered in this study. The validation of landslide susceptibility maps were carried out using areas under the curve (AUC). From the analysis, it is seen that the CF model with a training accuracy of 70.48 % and predictive accuracy of 68.86 % performs slightly better than SI model (training accuracy, 70.19 %; predictive accuracy, 68.67 %). Overall, both of these two models showed almost similar results. The resultant susceptibility maps can be useful for general land use planning for the study area and other similar areas in the world.

Numerical simulation on crack propagation of rock mass with a single crack under seepage water pressure

The fracture characteristics of fractured rock mass have important significance in environmental geotechnical engineering. Taking a single crack rock mass with dip angle of 45° as the research object, we studied the fracture characteristics of fractured rock mass under different seepage water pressures and confining pressures based on Realistic Failure Process Analysis-Seepage. And then, the initial crack strength was derived and the effect of seepage water pressure and confining pressure on the crack propagation of fractured rock mass was analyzed. It was concluded that the mode of the longitudinal splitting failure, the upside-down capital letter “N”-type failure, and the “—”-type failure were proposed in numerical simulation, which were induced by wing cracks, anti-wing cracks, and secondary coplanar cracks, respectively. In addition, there exists the bifurcation phenomenon of cracks under the seepage water pressure. In theoretical analysis, the initial crack strength increases with the increasing confining pressure and decreases with the increasing seepage pressure, which are in good agreement with the experimental results in the literature. Confining pressure has an inhibitory effect on crack initiation. With the increase in the confining pressure, the successive order of inhibition is wing cracks, anti-wing cracks, and secondary coplanar cracks.

A comparative study on the landslide susceptibility mapping using evidential belief function and weights of evidence models

The purpose of this study is to produce landslide susceptibility map of a landslide-prone area (Daguan County, China) by evidential belief function (EBF) model and weights of evidence (WoE) model to compare the results obtained. For this purpose, a landslide inventory map was constructed mainly based on earlier reports and aerial photographs, as well as, by carrying out field surveys. A total of 194 landslides were mapped. Then, the landslide inventory was randomly split into a training dataset; 70% (136 landslides) for training the models and the remaining 30% (58 landslides) was used for validation purpose. Then, a total number of 14 conditioning factors, such as slope angle, slope aspect, general curvature, plan curvature, profile curvature, altitude, distance from rivers, distance from roads, distance from faults, lithology, normalized difference vegetation index (NDVI), sediment transport index (STI), stream power index (SPI), and topographic wetness index (TWI) were used in the analysis. Subsequently, landslide susceptibility maps were produced using the EBF and WoE models. Finally, the validation of landslide susceptibility map was accomplished with the area under the curve (AUC) method. The success rate curve showed that the area under the curve for EBF and WoE models were of 80.19% and 80.75% accuracy, respectively. Similarly, the validation result showed that the susceptibility map using EBF model has the prediction accuracy of 80.09%, while for WoE model, it was 79.79%. The results of this study showed that both landslide susceptibility maps obtained were successful and would be useful for regional spatial planning as well as for land cover planning.

Height of the Water-Flowing Fractured Zone of the Jurassic Coal Seam in Northwestern China

AbstractResearch on the height of the water-flowing fractured zone (HWFFZ) is important for mine safety and regional eco-environmental conservation in the Jurassic coal field of northwestern China. Using the Cuimu coal mine as a case study, on-site measurement, mechanical theory calculation, and numerical simulation were used to analyze the regularity of the HWFFZ in this area. A television borehole wall imaging system with a light source allowed us to examine the size and shape of fissures intuitively, allowing the top boundary of the HWFFZ to be determined. Per mechanical theory, the overlying strata in the decreasing stress zone was simplified as a clamped rectangular plate and the formula for calculating HWFFZ was obtained by comparing the value of the ultimate deflection of the thin plate and the height of the free space in the lower part of the stratum. In addition, the dynamic development of the HWFFZ was simulated using realistic failure process analysis software. The unusual characteristics of the HWFFZ were analyzed from two aspects: the inapplicability of the traditional empirical formula and the difference of the overlying strata structure of the Jurassic and the Carboniferous Permian coalfields. These strata can be divided into layered and integrated strata in the Jurassic coalfield. 导水裂隙带高度(HWFFZ) 研究对西北侏罗系煤田煤矿安全开采和生态环境保护具有重要意义。以催木煤矿为例,利用现场监测、力学计算和数值模拟方法研究了该区导水裂隙带发育规律。带光源的钻孔孔壁电视有助于观察初始裂隙大小、形状和判定导水裂隙带顶部位置。经力学分析,将应变衰减区上覆岩层简化为固支矩形板,通过比较薄板挠曲和下部地层自由空间高度获得导水裂隙带高度计算公式。利用真实破裂过程分析软件(RFPA)模拟了导水裂隙带发育的动力学过程。从两个方面分析了导水裂隙异常特征:经验公式的不适用性和侏罗系与石炭二叠系地层结构的差异。侏罗系煤田地层可被分为层状和整体两种。ZusammenfassungDie Erforschung der Höhe der wasserführenden Bruchzone (HWFFZ) ist bedeutsam im Hinblick auf Grubensicherheit und Umweltschutz im jurassischen Kohlerevier von Nordwestchina. Am Beispiel der Kohlegrube Cuimu wurde anhand von Feldmessungen, gebirgsmechanischen Berechnungen und numerischen Simulationen die Regelmäßigkeit der HWFFZ in diesem Gebiet untersucht. Ein Bohrlochkamerasystem mit Lichtquelle ermöglichte die direkte Untersuchung von Spaltengröße und -form und damit der Bestimmung der Oberkante der HWFFZ. Mittels mechanischer Theorie wurden die Deckschichten in der Stressabbauzone vereinfacht als eingespannte rechteckige Platte betrachtet, die Berechnungsformel für die HWFFZ ließ sich durch Vergleich des Werts der maximalen Durchbiegung der dünnen Platte und einem entsprechenden Abstandsmaß im unteren Schichtbereich berechnen. Zudem wurde die dynamische Entwicklung der HWFFZ mittels realistischer Versagensprozessanalyse (RFPA) simuliert. Die ungewöhnlichen Eigenschaften der HWFFZ wurden unter zweierlei Aspekten analysiert, nämlich der Nichtanwendbarkeit der herkömmlichen empirischen Formel sowie der Strukturunterschiede der Eigenschaften der überlagernden Schichten der jurassischen bzw. permokarbonen Kohlereviere. Im jurassischen Kohlerevier können geschichtete und integrierte Schichten unterschieden werden.ResumenLa investigación sobre la altura de la zona fracturada con agua fluyente (HWFFZ) es importante para la seguridad de las minas y la conservación ecoambiental regional en el campo de carbón Jurásico del noroeste de China. Utilizando la mina de carbón de Cuimu como un caso de estudio, se realizaron medidas in situ, cálculo de teoría mecánica y simulación numérica para analizar la regularidad de la HWFFZ en esta área. Un sistema de imagen de la pared del agujero de perforación con una fuente de luz, nos permitió examinar el tamaño y la forma de las fisuras intuitivamente, y determinar el límite superior de la HWFFZ. Por teoría mecánica, los estratos superpuestos en la zona de tensión decreciente fueron considerados en forma simplificada como una placa rectangular sujetada; la fórmula para calcular HWFFZ se obtuvo comparando el valor de la deflexión final de la placa delgada y la altura del espacio libre en la parte inferior del estrato. Además, se simuló el desarrollo dinámico de la HWFFZ utilizando software realista de análisis de procesos de fallas (RFPA). Las características inusuales de la HWFFZ fueron analizadas desde dos aspectos: la inaplicabilidad de la fórmula empírica tradicional y la diferencia de la estructura de los estratos superpuestos de las cuencas carboníferas del Jurásico y del Permiano. Estos estratos se pueden dividir en capas estratificadas e integradas en la cuenca de carbón del Jurásico.

Investigation on mining-induced fractured zone height developed in different layers above Jurassic coal seam in western China

The mining-induced fractured zone height (MIFZH) is of significant importance for water hazard prevention and regional eco-environmental conservation in the Jurassic coal field of western China. The paper discussed MIFZH developed in bedrock and Neogene laterite from two aspects of field measurement and theoretical analysis respectively. In theoretical analysis of MIFZH developed in bedrock, based on plate and shell theory, each stratum in bedrock above the coalface stress-decreasing zone was simplified as four clamped rectangular plates, and the value of the ultimate deflection of the thin plate and the height of the free space in the lower part of the stratum were compared to judge MIFZH. When MIFZH was developed in Neogene laterite, MIFZH was calculated by Pu’s theory and rock mass limit equilibrium theory in theoretical analysis; in on-site measurement, micro resistivity scanning imaging logging technology (MRSILT), overcoming the shortage of fluid leakage technology, was adopted to detect MIFZH, where its measured result proved the feasibility of theoretical analysis. The research results have important significance to water conservation mining and safety mining of the Jurassic coal seam in western China.

Zoning method for environmental engineering geological patterns in underground coal mining areas

Environmental engineering geological patterns (EEGPs) are used to express the trend and intensity of eco-geological environment caused by mining in underground coal mining areas, a complex process controlled by multiple factors. A new zoning method for EEGPs was developed based on the variable-weight theory (VWT), where the weights of factors vary with their value. The method was applied to the Yushenfu mining area, Shaanxi, China. First, the mechanism of the EEGPs caused by mining was elucidated, and four types of EEGPs were proposed. Subsequently, 13 key control factors were selected from mining conditions, lithosphere, hydrosphere, ecosphere, and climatic conditions; their thematic maps were constructed using ArcGIS software and remote-sensing technologies. Then, a stimulation-punishment variable-weight model derived from the partition of basic evaluation unit of study area, construction of partition state-variable-weight vector, and determination of variable-weight interval was built to calculate the variable weights of each factor. On this basis, a zoning mathematical model of EEGPs was established, and the zoning results were analyzed. For comparison, the traditional constant-weight theory (CWT) was also applied to divide the EEGPs. Finally, the zoning results obtained using VWT and CWT were compared. The verification of field investigation indicates that VWT is more accurate and reliable than CWT. The zoning results are consistent with the actual situations and the key of planning design for the rational development of coal resources and protection of eco-geological environment.

Landslide susceptibility mapping at Gongliu county, China using artificial neural network and weight of evidence models

The aim of this study was to apply and to verify the use of artificial neural network (ANN) and weight of evidence (WoE) models to landslide susceptibility mapping in the Gongliu county, China, using a geographic information system (GIS). For this aim, in this study, a landslide inventory map was prepared using earlier reports and aerial photographs as well as by carrying out field surveys. A total of 163 landslides (70% out of 233 detected landslides) were randomly selected for model training, and the remaining 70 landslides (30%) were used for the model validation. Then, a total number of twelve landslide conditioning factors, such as slope angle, slope aspect, general curvature, plan curvature, profile curvature, altitude, distance to rivers, distance to roads, lithology, rainfall, normalized difference vegetation index (NDVI), and sediment transport index (STI), were used in the analysis. Landslide hazardous areas were analyzed and mapped using the landslide-occurrence factors by ANN and WoE models. Finally the output maps were validated using the area under the curve (AUC) method. The validation results showed that the ANN model with a success rate of 82.51% and predictive accuracy of 77.31% performs better than WoE (success rate, 79.82%; predictive accuracy, 74.59%) model. Overall, both models showed almost similar results. Therefore, the two landslide susceptibility maps obtained were successful and can be useful for preliminary general land use planning and hazard mitigation purpose.

Zoning for eco-geological environment before mining in Yushenfu mining area, northern Shaanxi, China

Zoning for the eco-geological environment (EGE) aims to protect and improve the regional ecological environment. It is the basis for evaluating the ecological characteristics of a mining area prior to mining activities and has the purpose of implementing water-preserved mining according to zoning type. In this study, four EGE types were proposed following field investigation in the Yushenfu mining area: oasis type with phreatic water and bottomland in desert (OTPWBD), oasis type with surface water and valley river (OTSWVR), loess gully type with surface runoff (LGTSR), and regional deep groundwater enrichment type (RDGET). Nine EGE evaluation indices were selected: rainfall, evaporation capacity, Luohe formation thickness, surface elevation, Sara Wusu aquifer water abundance, surface lithology, topography, slope, and normalized difference vegetation index (NDVI). Remote sensing technology and geographic information systems were first used to generate the evaluation index thematic maps. Then, the weight of each evaluation index was determined based on an analytic hierarchy process (AHP). Third, the index weight was used to form an improved weighted fuzzy C s clustering algorithm, and EGE zones were assigned using the MATLAB computing platform. For comparison, the AHP was also adopted for EGE zoning and a map of zoning differences was obtained. Finally, EGE field surveys of typical mines were carried out, which verified that EGE zoning using fuzzy clustering was accurate and reasonable.