Geomechanics of subsidence above single and multi-seam coal mining

Accurate prediction of surface subsidence due to the extraction of underground coal seams is a significant challenge in geotechnical engineering.This task is further compounded by the growing trend for coal to be extracted from seams either above or below previously extracted coal seams,a practice known as multiseam mining.In order to accurately predict the subsidence above single and multi-seam longwall panels using numerical methods,constitutive laws need to appropriately represent the mechanical behaviour of coal measure strata.The choice of the most appropriate model is not always straightforward.This paper compares predictions of surface subsidence obtained using the finite element method,considering a range of well-known constitutive models.The results show that more sophisticated and numerically taxing constitutive laws do not necessarily lead to more accurate predictions of subsidence when compared to field measurements.The advantages and limitations of using each particular constitutive law are discussed.A comparison of the numerical predictions and field measurements of surface subsidence is also provided.     

按不同开采顺序及回采率开采对路基的影响

针对采空区复杂条件,依托实体工程,利用反映实际问题的二维有限元数值分析方法,运用非线性弹塑性有限元技术,分析煤层按不同开采顺序及回采率开采对路基变形破坏的规律,为寻找防治路基出现不连续变形、沉陷,确定合理设计提供技术依据。研究表明:煤层按不同顺序开采对路基的影响是不同的。开采顺序选择不当,则对路基的危害较大;反之,改变各矿层各工作面的先后开采顺序也可以达到协调开采的目的,变形可抵消一部分。随着回采率的增加,路基竖向位移随之递增,且增加速率较快;最大水平变形也随之迅速增长;下沉盆地的范围随着开采宽度的增加而不断扩大。     

Surface subsidence prediction method of backfill-strip mining in coal mining

Intensive and massive coal mining causes a series of geological hazards and environmental problems, especially surface subsidence. In recent years, backfill-strip mining has been applied to control mining subsidence in order to realize sustainable development of the mining environment. To accurately predict the surface subsidence of backfill-strip mining, a prediction method of subsidence superposition of backfill-strip mining is proposed on the basis of the traditional probability integral method prediction model. In analyzing the distribution of the actual subsidence space, the surface subsidence problem of backfill-strip mining can be regarded as the superposition of surface subsidence caused by backfill mining and strip mining. Then, the appropriate prediction parameters will be chosen, and the surface subsidence caused by the backfill mining and strip mining will be predicted separately. The surface subsidence values of the backfill-strip mining are equal to the superposition subsidence values predicted by the backfill mining and strip mining prediction method at the same surface location. A similar material model and a numerical simulation model have been built to verify the feasibility and accuracy of the superposition prediction method. The comparison results of the surface subsidence values show that the superposition surface subsidence prediction method is reasonable. The average relative error of this superposition prediction method is less than 6.7%, and its accuracy is 3.9%~11.4% higher than that of the conventional prediction method. The superposition prediction method can satisfy the precision requirement of engineering applications. This study provides a scientific technical reference for safe mining engineering design and surface disaster protection for backfill-strip mining.

     

The influence of an abandoned goaf on surface subsidence in an adjacent working coal face: a prediction method

Historical global coal resource exploitation has resulted in goaf abandonment at most mines, which, during the life of the mine, exerts a strong influence on the ability to exploit new working faces adjacent to any abandoned goaf. Thus, the distribution law of the surface subsidence basin above the new working face differs from the general law. Given the lack of research on this distribution law, this study uses a similar material simulation method to examine the influencing mechanism(s) of abandoned goafs on the subsidence basin in the same coal seam. Synthetic aperture radar (SAR) monitoring results of the 9310 working face in the Nan Tun coal mine, Yanzhou, China, are used to verify analytical results, followed by numerical simulation to study the influence of the abandoned goaf on the subsidence basin. Finally, to accurately predict surface subsidence influenced by the abandoned goaf, inflection point deviations are selected and discussed in terms of the probability integral method. This allows for prediction of the distribution of the surface subsidence basin, and moreover, the predicted results are found to be consistent with the SAR monitoring results when the derivation of inflection points is revised.     

Improved prediction of differential subsidence caused by underground mining

Observations in the field demonstrate that there exist discrepancies between the differential movements predicted from theory and those experienced in practice. From the point of view of structural damage, such discrepancies should be eliminated in order to decrease subsidence damage associated with mining. Using non-linear geometrical field theory, the deformation factors are modified and the limitation of linear elastic theory is established. Only when the rotation angles are smaller than 4° is the application of conventional theory reasonable. A new deformation index, the mean rotation angle, is proposed. The study shows that there exists a relation between the mean rotation angle and the surface cracks. Incompatibility of rotation can initiate cracking. The outcome of the work presented will be helpful in improving the calculation accuracy of predicted differential movements, especially for steeper coal seam extraction, extraction under mountains, ‘top coal caving’ of thick seams, and mining in high relief areas.     

煤矿区土地复垦中塌陷预测分析

首先分析了煤矿区地表塌陷原理,然后对煤矿区塌陷预测模型与方法进行了研究,并以河北省峰峰集团有限公司小屯煤矿为例,采用概率积分法进行了塌陷预测。结果表明,小屯矿扩大区拟塌陷破坏土地面积为560.95 hm2,为矿区土地复垦确定了复垦责任范围。     

平缓反倾采动滑坡形成的地质力学模式研究——以贵州省马达岭滑坡为例

 马达岭滑坡是典型的采矿诱发型滑坡,自然斜坡为平缓反倾层状结构。以马达岭滑坡为原型,采用物理模拟方法,研究两层开采条件下采动斜坡的变形过程,并分析该类斜坡变形破坏的地质力学模式。研究表明：煤层开采后采空区边界上覆岩体产生应力集中,导致采动裂隙首先产生于该部位,以陡倾竖向倾倒式裂隙为主,裂隙向采空区中部扩展并逐渐形成离层裂隙和剪切裂隙;变形稳定后采空区上覆岩层弯曲,在地表形成沉陷区;受采空区上覆岩层沉陷的推挤作用,外侧坡体沿煤层向坡外滑移,导致坡体下部隆起。该类斜坡变形破坏的地质力学模式可以分为：弯曲–拉裂(“表生”改造阶段)、塑流–拉裂、蠕滑–拉裂3个阶段。     

顺层岩质斜坡开采沉陷预测模型研究

为有效预测地下采矿诱发山区顺层斜坡的沉陷变形,在分析概率积分法水平地表开采沉陷的基础上,以与岩层、矿体的倾角相同或者相近的顺层岩质坡体为研究对象,建立单元体开采和半无限开采情况下顺层岩质倾斜地表的开采下沉变形预测模型,并给出预测模型的解算过程及步骤。通过2个矿山开采沉陷实例,将预测模型的解算结果分别与现场实测数据、相似模拟试验观测数据进行对比分析,结果表明:预测结果与现场实测下沉量吻合良好,与相似模拟试验观测下沉曲线形状相似,最大下沉量基本一致,符合试验原型的实际情况,预测结果能够反映顺层倾斜地表开采沉陷的情况,预测模型具有较好的适用性。     

Combined prediction model for mining subsidence in coal mining areas covered with thick alluvial soil layer

The entire overburden stratum above a coal mining area is considered to be composed of an alluvial soil layer and a bedrock layer. In underground mining, alluvial soil has a major effect on ground subsidence. This effect is especially significant and not negligible when the alluvial soil accounts for a large proportion in the entire overlying stratum of coal mining areas covered with thick alluvial soil (CMATASs). In this study, the applicability of the most popular probability integral method (PIM) used for CMATASs was analyzed, and it was found that the PIM is not suitable for ground subsidence prediction in CMATASs for two main reasons: (1) the subsidence basin range predicted by the PIM was smaller than the measured range; thus, the predicted basin converged more rapidly than the measured basin at the edges. (2) Poor fitting results were obtained at the subsidence basin edge. The mechanism of mining subsidence in CMATASs and the reasons why the PIM is not suitable for CMATASs were investigated in terms of the internal deformation and crack (void) distribution within the rock mass induced by underground coal mining. The results indicate that the alluvial soil is compacted and then subsides under vertical compression deformation, which increases ground subsidence. The bedrock is subjected to the weight/load of the thick alluvial soil layer. Because of the vertical compression deformation inside the rock, its internal voids (spaces) are compacted; thus, the replaced voids (spaces) are transferred to the ground surface, resulting in an increase in ground subsidence. However, the effect of the alluvial soil on ground subsidence cannot be detected by the PIM; moreover, the PIM is unable to represent the mechanism of the mining subsidence in CMATASs. Thus, the PIM cannot be used for predicting subsidence in CMATASs. To precisely calculate subsidence in CMATASs, we propose a combined prediction model (CPM) for mining subsidence in CMATASs based on soil mechanics and stochastic medium theory. The new CPM was applied to the mining process in the Huainan Coal Mining Area. The calculation results show that subsidence predicted by the CPM better fits the measured subsidence values, with a relative error of 4.9%, and that the fitting accuracy is improved by 18% compared to the relative error of the PIM (6.0%). Thus, the proposed CPM is more suitable for predicting ground subsidence caused by underground coal mining in CMATASs, and can be used to provide more accurate predictions for ground subsidence in similar coal mining areas.     

采煤塌陷区环境整治与矿区可持续发展

结合我国采煤塌陷土地整治的基本情况,探讨了矿区采煤塌陷区进行环境整治的意义,着重提出了矿区采煤塌陷区环境整治的一系列措施,以提高土地整治的综合效益,同时保障矿区经济快速、持续健康发展。     

煤矿开采沉陷对地面建(构)筑物的影响

介绍了煤矿开采沉陷对地面建筑物的影响问题，从采空塌陷的一般规律、地表移动和变形等方面进行了论述，指出了煤矿开采沉陷的防治方法和措施。     

Surface subsidence due to underground mining operation under weak geological condition in Indonesia

Subsidence analysis and prediction with measured data have been conducted and applied to local strata and mining conditions worldwide. Underground coal mines chose the most suitable analysis and prediction method for them. However, there was no study based on the measured data of subsidence induced by underground mining operation in Indonesia. This paper describes the condition of underground coal mine in Indonesia and then discusses the subsidence behavior due to longwall mining operation based on measured data in Balikpapan coal-bearing formation in Indonesia.     

基于D-InSAR技术的葛亭煤矿地面沉降监测研究

为了为矿区安全开采和塌陷区环境综合治理提供科学依据,利用精细的D-InSAR技术对7景ENVISAT ASAR影像进行处理,获得了2004～2005年和2008～2009年葛亭煤矿多期地面沉降分布图。然后将D-InSAR结果导入GIS中做后处理,叠加0.25m分辨率的数字正射影像图(DOM)和开采平面图等来分析地面沉降,并以剖面图、3D可视图等进行显示。通过多期结果的相互验证,并与水准资料进行了比较。结果表明,D-InSAR结果可以清楚可靠地给出矿区沉降区域分布和演化,并且获得的矿区沉降范围和位置与实际基本吻合,沉降幅度较小的区域在数量级上和水准资料一致,而最大沉降量出现偏差,这是由于高形变梯度引起了干涉图的完全失相关,超出了D-InSAR技术形变探测的能力范围。     

Mining subsidence forecasting by structural and geomechanical analysis

Mining subsidence within Petrila coal field was surveyed since 1978 on several topographic profiles in accordance with the ongoing of the underground works. Availability of a good set of measured data on vertical and horizontal movements of the marks, correlated with detailed knowledge on lithologic and structural conditions provides for a complex modelling approach. Long time measurements are processed by a package of computer programs. Vertical movements, ground tilt and horizontal strain are computed for every year and marked on topographic profiles. Graphs of the running sums of the subsidence deformations and contour-maps are drown as main tools for quantitative prognosis. On this experimental basis, subsidence parameters are automatically forecasted for new developments of the underground coal mining during the next five and ten years. As overlays of the experimental data were tailored nummerical models to forecast the evolution of the mining subsidence. The prognosis is validated by analogy with the development of the actual observed subsidence parameters. Finaly, the forecasting package advances definit assessments on building stability risk level induced by the evolution of the ground surface subsidence.     

模糊综合评价在河南城郊煤矿地面塌陷危险性评价中的应用

本文从地质环境条件、采矿工程活动两个主要因素着手进行综合分析,选取影响城郊煤矿地面采空塌陷的9个因子,采用模糊综合评价的方法对城郊煤矿地面塌陷危险性进行评价,确定隶属函数,构建模糊评价矩阵,并利用层次分析法确定各影响因子权重,建立矿区地面塌陷危险性评价模型并将矿区地面塌陷危险性程度划分为危险性小区、危险性中等区以及危险性大区3个等级。结果表明,该评价模型能较好地应用于城郊煤矿地面塌陷危险性评价中,该评价方法是实用和有效的。     

急倾斜煤层开采岩移基本规律的模型试验

针对新集三矿急倾斜煤层开采复杂的采矿地质条件，运用实验室相似模型试验方法，对西三采区煤层开采引起的岩体移动和地表沉陷的基本规律进行了研究，总结出了新集三矿急倾斜煤层开采重复采动所引起的厚冲积层岩体移动基本特征和地表沉陷的相关参数。所得结果对现场开采及地表沉陷治理具有一定的指导作用，对于同类地质和开采条件的矿区具有重要参考价值。     

采煤塌陷区土地复垦与重构土壤质量研究

中国人多地少,土地资源短缺,再加上每年因采煤塌陷的土地甚多,矿区人地关系矛盾突出。实施土地复垦工程是缓和矿区"矿—粮"矛盾的重要措施,同时也是建立稳定煤矿区生态系统的主要措施。本文在探讨矿区土地复垦技术的基础上,研究了复垦后重构土壤的质量演变。结果表明:现有的矿区土地复垦技术主要有非充填式复垦和充填式复垦两大类;重构土壤的容重、含水量、耕作阻力,以及土壤养分和污染性状等,与自然农业土壤相比均存在相异的发展过程。     

广西大新铅锌矿地下采空区对地面沉陷的影响

针对矿体采空后对地表的影响,对采空区稳定性及地表沉陷进行了分析,结果表明,采取合理方法对浅部未充填采空区进行密实充填,实施地表水管理控制进入地下是控制地表沉降、防止地面建筑物变形和破坏的最有效措施。     

背斜构造矿层开采地面沉陷规律研究

对曲面分布矿层进行地表移动预计时，通常是把曲面分布近似地当作平面分布来处理，例如把背斜构造形式的矿层简单地分为几个斜平面，然后利用多工作面开采地表移动预计方法进行预计，这样则会降低地表移动预计精度。本文介绍一种根据概率积分基本原理、利用曲线积分建立起来的地表移动预计新方法，并讨论了积分区间划分及计算坐标确定方法。     

地面钻孔抽放采空区瓦斯及其稳定性分析

随着放顶煤开采技术在我国的迅速普及，采煤工作面及采空区的瓦斯涌出量不断增加。传统的高位钻孔、（本）煤层钻孔及穿层钻孔抽放技术有时不能完全满足现代化煤矿生产对瓦斯抽放的要求。采用地表垂直钻孔抽放采空区内的瓦斯是瓦斯治理技术的另一选择。煤层开采后，采窄区上覆岩层将发生非连续破坏和连续移动。在长壁工作面通过的过程中，地面垂直钻孔可能随岩层移动而发生破坏。据此，介绍一种进行地面抽放采空区垂直钻孔的应用及稳定性分析的方法及用于确定钻孔及套管直径的应用实例。采用提出的计算方法可避免由于受采动影响对地表瓦斯抽放钻孔引起的过大变形及其所造成的破坏。通过计算地表钻孔在不同深度的水平位移和垂直变形可确定钻孔直径和所需安设套管的直径及套管外充填材料的性能。