Shiliang Liu

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.

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.n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.

Risk Evaluation of Bed-Separation Water Inrush: A Case Study in the Yangliu Coal Mine, China

Water that accumulates in the void space where overburden strata separate can be an inrush source. We established an engineering geology model of bed-separation water inrush, and chose five factors (hard rock thickness, coal seam thickness, aquifuge thickness, aquifer thickness and hydrostatic head) as risk factors. Additionally, based on an analysis of hydrogeological and engineering geological conditions at two areas in the Yangliu coal mine, the comprehensive weight values of these factors were found to be 0.32, 0.24, 0.18, 0.15, and 0.11, respectively, using fuzzy analytic hierarchy process and entropy method. Finally, the data were normalized, and a zoning map for risk evaluation was created using the space superposition function of GIS. This method was further used to evaluate the risk at the Haizi coal mine, and the results were in accordance with an inrush disaster that occurred at the 745 working face at that mine. This validated the model’s practical applications. This provides mines with strategies to prevent and control bed-separation water inrush.ZusammenfassungWasser, das sich in Hohlräumen sammelt, an denen sich Abraumschichten voneinander trennen, kann eine Quelle für Wassereinbrüche sein. Wir haben ein ingenieurgeologisches Modell für Wassereinbrüche aus Aufblätterungszonen erstellt und fünf Faktoren als Risikofaktoren gewählt (Mächtigkeit des Festgesteins, der Kohleflöze, der Aquifuge, des Aquifers sowie hydrostatischer Druck). Basierend auf einer Auswertung der hydrogeologischen und ingenieurgeologischen Bedingungen in zwei Bereichen der Kohlegrube Yangliu wurden mit Hilfe eines Fuzzy-Hierarchieanalyseverfahrens und der Entropie-Methode die umfassenden Wichtungswerte dieser fünf Risikofaktoren zu 0,32, 0,24, 0,18, 0,15 bzw. 0,11 bestimmt. Schließlich wurden die Daten normalisiert und eine Zonierungskarte für die Risikobewertung mit Hilfe der Raumüberlagerungsfunktion von GIS erstellt. Dieses Verfahren wurde weiter verwendet, um das Risiko in der Haizi-Kohlemine zu bewerten, und die Ergebnisse stimmten mit einer Wassereinbruchskatastrophe überein, die bei der Arbeitsebene 745 in dieser Mine auftrat. Dadurch konnte das Modell für die praktische Anwendung validiert werden. Bergwerken stehen damit Strategien zur Verhinderung und Kontrolle von Wassereinbrüchen aus Aufblätterungszonen zur Verfügung.ResumenEl agua que se acumula en el espacio vacío donde se separan los estratos puede ser una fuente de irrpución. Establecimos un modelo geológico ingenieril de la entrada de agua de separación de lecho y elegimos cinco factores (espesor de roca dura, espesor de la veta de carbón, espesor de la capa acuífera, espesor del acuífero y cabeza hidrostática) como factores de riesgo. Además, en base a un análisis de las condiciones geológicas hidrogeológicas y de ingeniería en dos áreas en la mina de carbón Yangliu, se otorgaron pesos a estos factores de 0,32, 0,24, 0,18, 0,15 y 0,11, respectivamente, utilizando el proceso de jerarquía analítica difusa y el método de entropía. Finalmente, los datos se normalizaron y se creó un mapa de zonificación para la evaluación de riesgos utilizando la función de superposición espacial de GIS. Este método se usó posteriormente para evaluar el riesgo en la mina de carbón Haizi y los resultados concordaron con los correspondientes a un desastre de irrupción de agua que ocurrió en el frente de trabajo 745 en esa mina. Esto validó las aplicaciones prácticas del modelo. Esto proporciona estrategias para prevenir y controlar la entrada de agua por separación de lecho en las minas.摘要积聚在上覆离层空腔中的水可以形成突水的水源。本文建立了离层水害评价的工程地质模型, 选取了5个评价因素,包括硬岩厚度、煤层厚度、隔水层厚度、含水层厚度和静压水头。基于对杨柳煤矿两个采区水文地质和工程地质条件分析,利用模糊层次分析法和熵权法,得出5个因素的综合权重分别为0.32, 0.24, 0.18, 0.15, 0.11。利用GIS的空间叠加功能,将数据进行归一化处理,得到研究区离层水害危险性评价分区图。运用这种方法对海孜煤矿进行危险性评价,结果与745工作面发生的水害事故吻合,证明该方法具有实用性,为矿山防治离层突水提供了对策。

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.

Numerical simulation for groundwater distribution after mining in Zhuanlongwan mining area based on visual MODFLOW

With large-scale coal resources being discovered and mined in mid-west China, latent environment problems gradually come into view. In arid and semi-arid region, environmental impact assessment of mining on groundwater distribution is a vital mission before mining works. In Zhuanlongwan Mining Area (ZMA), data of surface elevation were performed by remote sensing information and ArcGIS. The study area was divided into clayey fine sand, aeolian loose sand, weathered fracture, and low permeability zones, according to hydrologic conductivities and borehole data. By simplifying as a single-layer system of phreatic groundwater and optimizing with geological parameters in each unit zone, a reasonable model of the groundwater distribution in steady state was then found and calibrated. Combined with local climate, variable groundwater behavior was discussed in relation to different precipitations which reduced the loss of the drain in degrees. The study results may give benefit and safety to management in mining, as well as beingxa0refined in the future.

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.