研究论文 正式出版 版本 2 Vol 9 (3) : 291-297 2018
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倾斜工作面底板破坏深度计算方法研究
Formula derivation of calculating depth of failing zone in floor of inclined working face
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: 2018 - 05 - 15
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摘要&关键词
摘要:煤层倾角是影响底板破坏带深度的一个重要因素,为深入研究煤层倾角对底板破坏带深度的影响。采用断裂力学理论建立了煤层倾角对底板破坏带深度影响的计算模型,得出由于煤层倾角的存在,倾斜工作面上部破坏带深度小于下部破坏带深度。收集我国大量的突水案例与煤层倾角统计数据,以及破坏带深度与煤层倾角统计数据,从突水案例数据可以看出倾斜工作面下部由于底板破坏造成的突水次数明显多于上部,从破坏带深度与煤层倾角变化趋势可以看出随着倾角增大破坏带深度也在增大。统计得到数据的结论与应用断裂力学模型分析得到的结论一致。最后对建立的破坏带深度计算模型井下质量检验,检验,检验结果显示该计算模型的精度较高,符合现场应用的要求。
关键词:底板破坏带;破坏带深度;煤层倾角;工作面斜长;断裂力学
Abstract & Keywords
Abstract: Background, aim, and scope In recent years, mining technology and technology level has been rapid development, the number of long working face and deep mining face is increasing, and the problem of water damage of floor in our country is increasing. This problem has been paid more and more attention by many experts and scholars in the industry. The Wu Qiang academician applied the vulnerability index method and GIS system to study the causes and prediction of the floor water damage, and put forward the "three graph double prediction" method, which has received great attention in the industry and site application effect has also been unanimously praised. Professor Jiang Zhenquan and Professor Wang Lianguo have also made some achievements in the research on the developmental characteristics and distribution of the failure zone in the floor, and put forward the method of judging the water inrush from the floor. Professor Shi Longqing and his team have made an in-depth study on the influencing factors of the depth of the failure of the floor, and established the prediction model of the depth of the failure zone of the floor according to the influence degree of each factor. This paper mainly studies the influence of coal seam dip angle on the depth of failure zone in floor. Materials and methodsThe stress distribution characteristics of the posterior floor of the inclined working face are analyzed by using the fracture mechanics, and the failure zone calculation model of the lower edge and the upper edge of the inclined working face is established based on the fracture mechanics model. Results From the above calculation model of the failure zone, the damage zone of the upper and lower edges is the same when the dip angle of the coal seam is 0 °, and the depth of the failure zone of the lower edge is larger than that of the upper edge when the dip angle of the coal seam is not 0 °. The depth of the failure zone at the upper edge of the working face decreases with the increase of the inclination angle of the working face, and the depth of the failure zone of the lower edge increases with the increase of the inclination angle. DiscussionFrom the case of water bursting in China's coal mine and the depth of the inclination working face can be seen: The location of the water burst occurs mostly at the lower edge of the inclination working face, and the depth of the failure zone of the bottom plate is increasing with the increase of the inclination angle of the coal seam. ConclusionsThe results of theoretical analysis and statistical data can be concluded that the dip angle of the coal seam has a significant effect on the depth of the failure zone of the floor. With the increase of the dip angle of the coal seam, the depth of the lower edge of the inclined working face becomes larger and the depth of the upper edge is smaller. Recommendations and perspectivesThe established failure zone depth calculation model was subjected to quality inspection. The model is used to calculate the depth of the failure zone under actual conditions, and compared with the observed failure zone depth. The average error between the calculated result and the measured result is 1.20m, which indicates that the model has high accuracy and meets the requirements in engineering application.
Keywords: failing zone of floor; depth of failing zone; dip angle of coal seam; inclined length of working face; compressive strength
随着我国采矿技术和科技水平的发展,超长工作面,大采深工作面的数量连年增多,在我国出现的底板水害问题也不断增加,问题也受到了业内众多专家学者的关注和重视(彭赐灯,2015)。在底板水害预测预报方面,经过众多专家学者多年的努力和研究,我国的底板水害研究取得了丰硕的成果。武强教授应用脆弱性指数法和GIS系统等,提出了“三图双预测”方法(武强等,2000;武强等,2007),姜振泉教授和段宏飞等提出了带压开采底板突水的评判方法(段宏飞,2014;段宏飞等,2011;段宏飞,2012),王连国教授和孙建等对倾斜煤层底板破坏特征及突水机理进行了深入的研究(孙建等,2011;孙建,2011)。底板破坏是造成水害的一个最重要原因,对底板破坏深度的预测尤为重要。繆协兴教授、姜耀东教授和刘树才等对采动底板破坏规律进行了深入研究(刘树才等,2009;刘树才,2008;姜耀东等,2011;吕春峰等,2003;张平松等,2006),施龙青教授和于晓鸽等对底板破坏深度进行了多因素分析,建立了多因素底板破坏深度计算模型(施龙青等,2005;施龙青等,2013;于小鸽,2011;于小鸽等,2009),郭文兵等建立了基于BP神经网络的底板破坏深度预计模型(鲁海峰等,2014;郭文兵等,2003)。
以上专家学者在破坏带深度确定方法方面取得众多突破,但在确定底板破坏带深度的研究道路上还有很多的事情要做,提高底板破坏带的计算精度仍然是我们不断改进追求的一个方向。
1   底板破坏范围
分析工作面采后底板破坏和应力分布,一般可以应用断裂力学的分析方法,采后底板应力分布如图1所示。工作面的底板由于采动影响,使得应力重新分布,应力集中在煤壁两侧,使得煤壁处支承压力增大,在采空区形成一个应力降低区。图1中①区为主动主应力区,②区为过渡区,③区为被动应力区。由于支承压力影响而形成的破坏深度增加,在煤壁两侧的破坏深度要远大于工作中间位置,最大的破坏带深度一般都集中在过渡区内。


图1   底板应力分布及破坏范围示意图
Fig.1 Sketch map of stress distribution in floor and broken range
2   底板破坏深度计算公式建立
当煤层倾角在0°~30°之间时,开采后采场形成如图2所示的力学模型,在煤壁处形成应力集聚,由于煤层倾角的存在,应力场的分布与水平工作面应力场有很大的区别,倾斜工作面上部和下部的应力场也存在着差别。


图2   煤层倾角不为0°时底板受力模型
Fig. 2 Mechanical model of floor in inclined coal seam
采用westergard应力函数对工作面采后的应力场进行分析,应力场函数为:
(1)
式中,为一个复变函数的解析式;的一阶导数;为一个考虑了倾角影响的应力系数。
通过式1可以求得倾斜上方处应力函数和倾斜下方处的应力函数
(2)
对式2进行求解,得到倾斜上下位置应力场边缘函数:
(3)
式中,为岩体平均容重,单位为采深,单位为工作面斜长,单位为破坏带深度,单位
根据mohr-coucomb破坏准则,在平面应力状态下为岩体抗压强度)时底板破坏。可得到倾斜下方边缘破坏深度和倾斜上方边缘破坏深度:
(4)
通过上式可以看出破坏带深度与岩体容重、采深、工作面斜长成正比,与岩体抗拉强度成反比。为分析煤层倾角对断裂带深度的影响,假设为定值1时,煤层倾角对断裂带深度的影响如图3所示,从图中可以看出煤层倾角的变化范围是0°~30°时,倾斜上方的破坏带深度随倾角增大而减小,倾斜下方的破坏带深度随倾角增大而增大。当工作面为水平工作面时上方和下方的破坏带深度相同,当为倾斜工作面时倾斜下方的破坏带深度要大于倾斜上方的破坏带深度,而且倾角越大现象越明显。


图3   破坏带深度与煤层倾角变化曲线
Fig. 3 Varying curve of depth of failing zone vs dip angle of coal seam
3   突水点位置分析
倾斜工作面的上下位置虽然存在着标高差,但由于埋深比标高差要大得多,而且地表标高也存在着差异,所以视倾斜工作面上下位置的原岩应力相等。收集全国范围内的突水点与煤层倾角的统计数据进行分析,统计突水点时只选择由于底板破坏造成的突水案例进行分析。由于工作面的长度不同,按照突水点“比例位置”进行分析,0为倾斜工作面的最下部,1为倾斜工作面的最上部,0~0.3视为工作面下部,0.3~0.7视为工作面中部,0.7~1视为工作面上部,分析数据整理列于图4,横坐标为突水点的位置,纵坐标为煤层倾角。从图中可以看出突水事故的突水点位置72%集中在工作面的下部,而且当煤层倾角大于10°小于30°时突水点位置79%的突水点集中在下部位置,说明下部破坏带深度较大,倾角变大对破坏带深度的影响更为明显。


图4   突水点位置分布图
Fig.4 Distribution of water inrush point
4   实测数据分析煤层倾角对破坏带深度影响
收集全国各矿区的43组破坏带深度与煤层倾角的统计数据,其中测得的破坏带最大深度都是在倾斜工作的下方。破坏带深度随着煤层倾角的变化关系,如图5所示。从图中可以看出当煤层倾角的变化范围是0°~ 30°时随着煤层倾角的变大,破坏带的深度呈现递增的规律。


图5   实测数据煤层倾角对破坏带深度影响曲线
Fig.5 Influence curve of measured dip angle of coal bed on depth of broken zone
5   计算公式质量检验
收集破坏深度实测数据,并对收集的数据进行挑选,选择的数据都是无断层影响、无原生裂隙影响和无重复采动等影响。破坏带深度都是工作面测量的最大值,并且测量到的最大值位置都是位于倾斜工作面的下方。整理《三下规程》和《煤矿防治水规定》中记载的国内矿井破坏带深度及地质采矿煤岩参数统计数据[20,21],共10组样本数据,见表1。
表1   样本数据影响参数与破坏带深度统计表
编号
number
采深/m
mining depth/m
工作面斜长/m
Inclination length of working face/m
底板岩体平均容重/kN/m3
average volume weight of floor rock mass/ kN/m3
抗压强度/MPa
compressive strength/MPa
倾角/°
dip angle/°
破坏带深度/m
destruction belt depth/m
1峰峰三矿
1 fengfeng three mine
1301350.0276.71512.00
2肥城曹庄矿
2 feichengcaozhuang mine
148950.0277.4189.00
3肥城白庄矿
3 feichengbaizhuang mine
2251300.02913.8149.75
4淄博双沟矿
4 ziboshuanggou mine
2871300.02614.2109.50
5韩城马沟矿
5 hanchengmagou mine
2301200.02510.11013.00
6鹤壁三矿
6 hebi three mine
2301800.02310.22620.00
7邢台矿
7 xingtai mine
2591600.02713.02216.40
8澄合二矿
8 chengtai two mine
320600.02911.349.70
9井陉一矿
9 jingjing one mine
400340.02712.598.00
10吴村矿
10 wucun mine
227300.0277.2127.00
用式4中计算的公式对各组数据的破坏带深度进行计算,将破坏带深度的计算结果和实测结果对比,见表2。
表2   公式计算误差对比
Tab. 2 Error comparison of formula
 
编号
number
计算值/m
Calculated/m
实测值/m
Measured/m
绝对误差/m
Absolute error/m
编号
number
计算值/m
Calculated/m
实测值/m
Measured/m
绝对误差/m
Absolute error/m
1峰峰三矿
1 fengfeng three mine
13.6912.001.696鹤壁三矿
6 hebi three mine
20.2320.000.23
2肥城曹庄矿
2 feichengcaozhuang mine
10.739.001.737邢台矿
7 xingtai mine
18.8016.402.40
3肥城白庄矿
3 feichengbaizhuang mine
10.559.750.808澄合二矿
8 chengtai two mine
11.529.701.82
4淄博双沟矿
4 ziboshuanggou mine
11.999.502.499井陉一矿
9 jingjing one mine
8.288.000.28
5韩城马沟矿
5 hanchengmagou mine
12.9913.000.0110吴村矿
10 wucun mine
7.597.000.59
用式4计算的误差平均值为1.20m,从表3的对比结果可以看出,最大误差为2.49m,最小误差为0.01m,说明式4的计算精度较高,符合工程应用的要求。
6   结论
1)通过分析我国各个矿区的突水点位置的统计数据,得出突水点多集中在倾斜工作面的下部位置,而且煤层倾角越大,突水点位置集中在下部的概率越大,说明了底板破坏带的深度受到了煤层倾角的影响;
2)分析收集的煤层倾角与破坏带深度的数据,得出当煤层倾角在0°~30°范围内时,破坏带深度随着煤层倾角的增大而增大;
3)通过力学模型推得,建立了当工作面倾角在0°~30°范围内时倾斜工作面上方和下方的破坏带深度计算公式,当煤层倾角逐渐增大下方的破坏带深度变大,上方破坏带深度变小,下方破坏带深度大于上方的破坏带深度。并进行实测数据的检验,得出该公式的计算精度较高,符合现场应用的要求。
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稿件与作者信息
沈浩
吴伟宁
张波
出版历史
出版时间: 2018年5月15日 (版本2
参考文献列表中查看
地球环境学报
Journal of Earth Environment