Distinct element modeling and analysis of mining-induced subsidence

Summary The influence of rock discontinuities on mining-induced subsidence is addressed in this paper. A two-dimensional rigid block computer model was used to simulate discontinuities within strata overlying a longwall coal mine. Input for the model was available from a previous field study and numerical experiments were performed by varying the simulated joint stiffness, joint roughness, and vertical joint density. A comparison of simulated and measured displacements both within the overburden and on the surface provides insight into the influence of rock discontinuities. For the case in which all contacts had a relatively low stiffness, the maximum simulated subsidence was 293 mm whereas the case involving variable, but higher contact stiffness produced a maximum subsidence of only 73 mm reflecting the influence of increased overall stiffness. By comparison, the maximum measured subsidence was 580 mm. Consequently, the model behaved more stiffly than the actual rock mass but still provided a reliable simulation of block caving and strata separation. A comparison of simulated and observed displacements within the overburden suggests that horizontal discontinuities not included in the rigid block mesh above the zone of caving controlled rock mass compliance.List of Symbols c joint stiffness ratio [dimensionless] - d strata thickness ratio [dimensionless] - e strata modulus ratio [dimensionless] - E _a modulus of stratum a [MPa] - E _b modulus of stratum b [MPa] - E _equiv equivalent rock mass modulus [MPa] - E _u unconfined compression modulus of intact rock [MPa] - F _n contact normal force [N] - h overburden thickness [m] - k _a normal spring stiffness of stratum a [N/m] - k _b normal spring stiffness of stratum b [N/m] - k _equiv equivalent rock mass spring stiffness [N/m] - K _n normal material stiffness of joint [MPa/m] - K _s shear material stiffness of joint [MPa/m] - m mined thickness of coal seam [m] - q _u unconfined compressive strength of intact rock [MPa] - Sh shale - Ss sandstone - Sh/Ss shale/sandstone interbeds - S _max maximum subsidence [m] - SLEX Slope Indicator inclinometer/Sondex extensometer - T _a thickness of stratum a [m] - T _b thickness of stratum b [m] - T _j joint thickness [m] - u _a compression of stratum a [m] - u _b compression of stratum b [m] - u _j compression of joint [m] - u _total total compression of strata and included joint [m] - w width of longwall panel [m] - _n normal stress [MPa]     

东庞矿突水陷落柱三维地震处理效果与对比

以东庞矿2903工作面突水陷落柱为例,利用三维地震的纵横剖面、联井剖面、等时切片与沿层切片对陷落柱进行了对比解释,并对偏移速度90%、95%和103%的3个不同地震数据体上陷落柱边界的控制效果进行了分析。结果表明:偏移速度95%的地震处理效果较好,地震沿层属性切片技术对陷落柱的解释精度最高。     

A GIS-based landslide susceptibility evaluation using bivariate and multivariate statistical analyses

Bivariate and multivariate statistical analyses were used to predict the spatial distribution of landslides in the Cuyahoga River watershed, northeastern Ohio, U.S.A. The relationship between landslides and various instability factors contributing to their occurrence was evaluated using a Geographic Information System (GIS) based investigation. A landslide inventory map was prepared using landslide locations identified from aerial photographs, field checks, and existing literature. Instability factors such as slope angle, soil type, soil erodibility, soil liquidity index, landcover pattern, precipitation, and proximity to stream, responsible for the occurrence of landslides, were imported as raster data layers in ArcGIS, and ranked using a numerical scale corresponding to the physical conditions of the region. In order to investigate the role of each instability factor in controlling the spatial distribution of landslides, both bivariate and multivariate models were used to analyze the digital dataset. The logistic regression approach was used in the multivariate model analysis. Both models helped produce landslide susceptibility maps and the suitability of each model was evaluated by the area under the curve method, and by comparing the maps with the known landslide locations. The multivariate logistic regression model was found to be the better model in predicting landslide susceptibility of this area. The logistic regression model produced a landslide susceptibility map at a scale of 1:24,000 that classified susceptibility into four categories: low, moderate, high, and very high. The results also indicated that slope angle, proximity to stream, soil erodibility, and soil type were statistically significant in controlling the slope movement.     

Application of a fuzzy operator to susceptibility estimations of coal mine subsidence in Taebaek City,Korea

Quantitative determination of locations vulnerable to ground subsidence at mining regions is necessary for effective prevention. In this paper, a method of constructing subsidence susceptibility maps based on fuzzy relations is proposed and tested at an abandoned underground coal mine in Korea. An advantage of fuzzy combination operators over other methods is that the operation is mathematically and logically easy to understand and its implementation to GIS software is simple and straightforward. A certainty factor analysis was used for estimating the relative weight of eight major factors influencing ground subsidence. The relative weight of each factor was then converted into a fuzzy membership value and integrated as a subsidence hazard index using fuzzy combination operators, which produced coal mine subsidence susceptibility maps. The susceptibility maps were compared with the reported ground subsidence areas, and the results showed high accuracy between our prediction and the actual subsidence. Based on the root mean square error and accuracy in terms of success rates, fuzzy γ-operator with a low γ value and fuzzy algebraic product operator, specifically, are useful for ground subsidence prediction. Comparing the results of a fuzzy γ-operator and a conventional logistic regression model, the performance of the fuzzy approach is comparative to that of a logistic regression model with improved computational. A field survey done in the area supported the method’s reliability. A combination of certainty factor analysis and fuzzy relations with a GIS is an effective method to determine locations vulnerable to coal mine subsidence.     

A new GIS-based data mining technique using an adaptive neuro-fuzzy inference system (ANFIS) and k-fold cross-validation approach for land subsidence susceptibility mapping

In this paper, we evaluate the predictive performance of an adaptive neuro-fuzzy inference system (ANFIS) using six different membership functions (MF). In combination with a geographic information system (GIS), ANFIS was used for land subsidence susceptibility mapping (LSSM) in the Marand plain, northwest Iran. This area is prone to droughts and low groundwater levels and subsequent land subsidence damages. Therefore, a land subsidence inventory database was created from an extensive field survey. Areas of land subsidence or areas showing initial signs of subsidence were used for training, while one-third of inventory database were reserved for testing and validation. The inventory database randomly divided into three different folds of the same size. One of the folds was chosen for testing and validation. Other two folds was used for training. This process repeated for every fold in the inventory dataset. Thereafter, land subsidence related factors, such as hydrological and topographical factors, were prepared as GIS layers. Areas susceptible to land subsidence were then analyzed using the ANFIS approach, and land subsidence susceptibility maps were created, whereby six different MFs were applied. Lastly, the results derived from each MF were validated with those areas of the land subsidence database that were not used for training. Receiver operating characteristics (ROC) curves were drawn for all LSSMs, and the areas under the curves were calculated. The ROC analyses for the six LSSMs yielded very high prediction values for two out of the six methods, namely the difference of DsigMF (0.958) and GaussMF (0.951). The integration of ANFIS and GIS generally led to high LSSM prediction accuracies. This study demonstrated that the choice of training dataset and the MF significantly affects the results.     

昆明盐矿三维建模及溶通性分析

针对地下盐矿在开采过程中,随时可能会因为溶通状况的改变而发生坍塌地质灾害,本文利用矿山数字管理软件Quanty Mine,确定昆明盐矿的三维模型,以期监控盐矿开采不同阶段溶通的变化规律,为避免盐矿过度开采导致地质灾害的发生。     

三维数字矿山信息系统的集成与研发

以四川拉拉铜矿山为例,集成三维建模技术、信息技术、虚拟现实技术等高新技术,构建了一套集三维地质模型、虚拟场景漫游、数据查询及二维、三维联动等功能于一体的完整的三维数字矿山信息系统。该系统为矿山管理、生产和科研服务提供了有效的综合平台,具有面向公众的矿山查询、浏览、科普教育的公益性。     

Positive and negative impacts of longwall mine subsidence on a sandstone aquifer

 Subsidence due to longwall underground coal mining changes the hydraulic properties, heads, yields, and in some cases the groundwater chemistry of overlying bedrock aquifers. A 7-year study of a sandstone aquifer overlying an active longwall mine in Illinois has supported a comprehensive model of these impacts. Subsidence caused increases in permeability and storativity over the longwall panel. These changes initially caused a major decline in water levels in the sandstone, but the aquifer recovered slightly within a few months and fully within several years after mining. The enhanced hydraulic properties combined with potentiometric recovery resulted in a zone of greater well yield. However, at sites with very poor transmissivity and inadequate recharge pathways, recovery may not occur. Also, at the study site, the physical enhancement was accompanied by a deterioration in groundwater quality from slightly brackish, sodium bicarbonate water to more brackish water with increased sulfate levels. Received: 17 March 1997 · Accepted: 9 September 1997     

基于模型的3D3C采集设计与评价

对目前三维三分量(3D3C)地震勘探数据采集设计的方法进行了系统分析,利用聚焦射束分析技术(CFP),提出了基于模型的3D3C采集设计方法及其评价的参数。从模型出发的设计方法,能够使3D3C的采集结果更加真实可靠。     

Sustainable development and utilization of groundwater resources considering land subsidence in Suzhou,China

Suzhou is located at the lower reaches of the Yangtze River in southeastern Jiangsu, China. It is part of the Su-Xi-Chang area including Suzhou, Wuxi and Changzhou. As one of the most developed areas in China, this region has suffered from severe land subsidence caused by extensive groundwater exploitation since 1980s. The land subsidence was controlled by prohibition of groundwater exploration in the past several years. However, the surface water pollution prompted a new task of how to sustainably utilize the groundwater resource, especially to satisfy the emergency demands of water supply. In this paper, we took Suzhou as a representative case to discuss how to develop groundwater resources while controlling the land subsidence. The relationship between the deformation and the groundwater level was analyzed, with focus on the deformation features after the period of groundwater exploitation ban. The results confirmed the conclusion by Shi et al. (2007, 2008a): even in the period of rising groundwater level, same units may manifest different deformation characteristics, such as elasticity, elasto-plasticity, and visco-elasto-plasticity, at different locations of the cone of depression. A land subsidence model that couples a 3-D groundwater model and a 1-D deformation model was developed to simulate the groundwater level and deformation. A high-resolution local grid (child model) for Suzhou was built based on the regional land subsidence model of Su-Xi-Chang area by Wu et al. (2009). The model was used for a number of predictive scenarios up to the year of 2012 to examine how to develop sustainable use of groundwater resources under the conditions of land subsidence control. Our results indicated that about 3.08 × 10⁷ m³/a groundwater could be provided as emergency and standby water source while meeting the land subsidence control target of 10 mm/a.     

GIS地表塌陷计算的有限棱柱法及三维数据模型

具有强大信息管理和可视化功能的GIS已在地下硐室开挖、矿山采掘、边坡等许多工程领域中得到了广泛应用。笔者给出了一种用于地下开挖变形描述和应力分析的方法——有限棱柱法，并就该方法与GIS集成中的数据模型和数据组织方法进行了探讨，建立了基于GIS的虚拟地质体地下开挖变形描述与评价计算的三维可视化系统，并对多语言集成模式和数据可视化方法进行了探讨。同时还给出了该方法的工程应用实例，对该方法的可靠性和有效性进行了验证。     

孙村煤矿深部区的三维地震勘探

针对新汶矿业集团孙村煤矿深部三维地震勘探区目的层埋藏深、地表条件复杂、钻孔资料少的特点,阐述了野外数据采集、资料处理和资料解释过程中所采用的主要技术措施及取得的地质效果。经矿井生产实际验证,三维地震资料的精度较高。     

考虑三维形貌特征粗糙裂隙加卸载渗流规律研究

裂隙岩体在天然地质因素和人工扰动作用下处于加卸载环境是普遍存在的,裂隙面的几何特征和加卸载环境对裂隙渗流特性的影响在实际工程中不可忽视。采用试验和数值模拟相结合的方法,利用热-流-固三场耦合渗流试验系统,开展了应力加卸载作用下不同粗糙度裂隙岩芯试件的渗透试验,自主开发程序将激光扫描裂隙面的三维形貌信息导入到ABAQUS软件,模拟应力作用下的粗糙裂隙渗流。试验和数值模拟一致表明,粗糙裂隙的宽度和渗透率都随载荷的增加而减小,随着载荷的增加,裂隙接触刚度增大,裂隙的宽度和渗透率对载荷变化的敏感性降低;由于点接触产生的塑性变形不可恢复,卸载阶段的裂隙宽度和渗透率增加幅度减小,且小于加载阶段同载荷条件下的宽度和渗透率;裂隙渗透率、宽度与粗糙度呈正相关关系,且粗糙度越大,接触应力分布越不均匀;裂隙内流场符合群岛流,粗糙度越大群岛流现象越明显。     

考虑变井阻和涂抹效应的真空预压三维有限元分析

真空预压工程中塑料排水板等竖井通水量随地基深度和固结时间而变化,即变井阻效应已经证明是实际存在的。另一方面,在真空预压工程三维有限元分析中,由于竖井和涂抹区在有限元模型中的划分使得三维有限元模拟较为困难。为真实模拟真空预压工程实际情况,在有限元分析中引入变井阻数学模型,并给出变井阻无量纲参数A_1、α_2。另外,为降低三维有限元建模难度,选用合适的网格单元简化竖井区,并用等效方法简化涂抹区,实现了考虑涂抹、变井阻效应的三维有限元分析。以天津港某围海造陆工程为例,建立三维有限元模型进行分析计算,对比分析计算值与实测数据,验证了程序的合理性,为以后软基加固工程三维有限元模拟提供了一种有效方法。     

Assessment of shallow landslide susceptibility using the transient infiltration flow model and GIS-based probabilistic approach

This study proposes a probabilistic analysis method for modeling rainfall-induced shallow landslide susceptibility by combining a transient infiltration flow model and Monte Carlo simulations. The spatiotemporal change in pore water pressure over time caused by rainfall infiltration is one of the most important factors causing landslides. Therefore, the transient infiltration hydrogeological model was adopted to estimate the pore water pressure within the hill slope and to analyze landslide susceptibility. In addition, because of the inherent uncertainty and variability caused by complex geological conditions and the limited number of available soil samples over a large area, this study utilized probabilistic analysis based on Monte Carlo simulations to account for the variability in the input parameters. The analysis was performed in a geographic information system (GIS) environment because GIS can deal efficiently with a large volume of spatial data. To evaluate its effectiveness, the proposed analysis method was applied to a study area that had experienced a large number of landslides in July 2006. For the susceptibility analysis, a spatial database of input parameters and a landslide inventory map were constructed in a GIS environment. The results of the landslide susceptibility assessment were compared with the landslide inventory, and the proposed approach demonstrated good predictive performance. In addition, the probabilistic method exhibited better performance than the deterministic alternative. Thus, analysis methods that account for uncertainties in input parameters are more appropriate for analysis of an extensive area, for which uncertainties may significantly affect the predictions because of the large area and limited data.     

GIS-based 3D prospectivity mapping: A case study of Jiama copper-polymetallic deposit in Tibet,China

This paper reports a deposit-scale GIS-based 3D mineral potential assessment of the Jiama copper-polymetallic deposit in Tibet, China. The assessment was achieved through a sequential implementation of metallogenic modelling and 3D modelling of geology, geochemistry and prospectivity. A metallogenic model for the Jiama deposit and 3D modelling workflow were used to construct multiple 3D layers of volumetric and triangular mesh models to represent geology, geochemistry and ore-controlling features in the study area. A GIS-based 3D weights-of-evidence analysis was then used to estimate the subsurface prospectivity for Cu (Mo) orebodies in the area, which led to the identification of three prospective deep-seated exploration targets. Additionally, the geochemical modelling indicates three potential fluid flow pathways based on the 3D zonation of major geochemical elements and their ratios, particularly the Zn/Pb ratios, which support the results of the weights of evidence model.     

基于GIS技术的皖南地区钨钼矿资源评价与预测

近年来,皖南地区在钨钼矿找矿方面取得了重大突破,具有较大的找矿潜力。应用GIS技术对皖南地区的地质、矿产、物化遥等综合信息建立地学空间数据库,在此基础上综合分析区内各类成矿信息和找矿信息,借助计算机处理各类数据,进行成矿信息空间综合分析,建立评价预测模型。选用证据权法对矽卡岩型、斑岩型和热液型钨钼矿资源进行空间定位评价和预测,在四级成矿远景区内圈定了23个Ⅴ级成矿区和68个重点区块,并对这些重点区块进行分级与评述,为该地区的钨钼矿勘查提供参考。     

岩盐水溶开采沉陷新概率积分三维预测模型研究

开采沉陷的准确预测是减小和杜绝开采沉陷灾难发生的前提，传统概率积分法难以应用于岩盐水溶开采复杂条件下的地表沉陷预测。因此，充分考虑上覆岩层在复杂地质条件下可能表现出来的各向异性、岩盐溶腔的不规则性，建立了新概率积分三维预测模型；并从力学角度，对三维预测模型的参数进行了研究，获得了模型参数与上覆岩层力学参数之间的关系。该模型能够对复杂地质条件和不规则采空区引起的地表沉陷进行较为准确地预测。     

A study of surface subsidence and coal pillar safety for strip mining in a deep mine

Some villages and bridges are located on the ground surface of the working district no. 7 in the Wanglou Coal Mine. If longwall mining is adopted, the maximum deformation of the ground surface will exceed the safety value. Strip mining is employed for the working district no. 7 which is widely used to reduce surface subsidence and the consequent damage of buildings on the ground surface. To ensure the safety of coal pillars and improve the recovery coefficient, theoretical analysis and numerical simulation (FLAC 3D) were adopted to determine the coal pillar and mining widths and to discuss the coal pillar stress distribution and surface subsidence for different mining scenarios. The results revealed that the width of coal pillars should be larger than 162 m, and the optimized mining width varies from 150 to 260 m. As the coal seam is exploited, vertical stress is mainly applied on the coal pillar, inducing stress changes on its ribs. The coefficient of mining-induced stress varies from 2.02 to 2.62 for different mining scenarios. The maximum surface subsidence and horizontal movement increase as the mining width increases. However, when the mining width increases to a certain value, increasing the pillar width cannot significantly decrease the maximum subsidence. To ensure the surface subsidence less than 500 mm, the mining width should not be larger than 200 m. Considering the recovery coefficient and safety of the coal pillar, a pillar width of 165 m is suggested.