摘要
采用水岩相似材料模拟试验研究了不同荷载、岩层性质及开采速度等因素影响下煤层开采后覆岩垮落及裂隙演化特征。基于分形理论,得到了采动裂隙随开采进程在采煤工作面不同分区内的分形演化规律,并根据采动裂隙分布推导了裂隙岩体分形渗流公式,得到了渗透系数随开采进程及裂隙扩展的关联性演化规律及其相应的理论公式。在此基础上,利用大型相似材料物理模型试验,通过对采动影响下上覆岩层垮落后的裂隙网络物理模型进行钻孔电视成像,得到采动裂隙分布,并应用推导的渗透系数关联演化理论公式计算出含裂隙网络的模型试验介质的渗透系数,同时,利用钻孔注水试验验证了渗透系数理论模型的正确性。研究表明,采动裂隙在水平方向分布类似“W”形;而在垂直方向,总体上分形维数随高度增加而减小,减小幅度为4.32%~11.40%。然而在裂隙带与弯曲带交接部位,由于离层裂隙的存在,使分形维数较垮落带增大约3.47%。采动裂隙渗透系数与采动裂隙分布相关,在水平向上大体呈“V”形分布,总体上中间分区渗透系数相对较低,两端分区渗透系数相对较高。随着竖向分区增高,渗透系数逐渐减小,在裂隙带和弯曲带交接部位离层裂隙发育,使该区域渗透系数显著增大。本文推导的采动裂隙渗透系数关联演化理论公式,是定量研究采动影响下上覆岩层的渗透特性变化有益尝试。
The water-rock interaction similar material models were employed to simulate the stress variation,cyclic breaking and the cracks formation and distribution status of the overlying strata with different loading conditions,rock properties and mining process.It was found that the fractal dimension of cracks varied with mining advancing.The evolvement laws of crack network with mining advancing and different mining advancing footage were obtained.According to the distribution of mining fractures,the fractal seepage formula of fractured rock mass was derived,and the evolution law of the correlation of the permeability coefficient with the mining process and fracture expansion and the corresponding theoretical formula were obtained.On this basis,by using large-scale similar material physical model test,through the borehole television imaging of the physical model of fracture network of overlying strata under the influence of mining,the distribution of mining fracture was obtained,and the permeability coefficient of model test medium with fracture network was calculated by using the derived permeability coefficient correlation evolution theoretical formula.At the same time,the correctness of the theoretical model of permeability coefficient was verified by the borehole water injection test.By establishing the relationship between the fractal dimension with the mining length in different horizontal and vertical zones,it demonstrates that the fractal dimension in horizontal and vertical zones have a self-similar characteristic,and the spatial distribution of mining induced cracks may be saddle shaped,the horizontal zone H 3 and H 6 have a relative low fractal dimension and H 1,H 4 and H 7,oppositely have a relative high fractal dimension.At the meanwhile,the fractal dimension reduces with the increase of the caving height,at a rate of 4.32%to 11.40%.In the transition zone between the fractured zone and sinking zone,on the contrary,has an increase of 3.47%,taking the caving zone as the reference standard.The permeability distribution of mining induced cracks may be“V”shaped in horizontal direction,with a relative low permeability in the middle zone and relative high at the ends.The permeability de-crease gradually with the increase of vertical height and the permeability increase dramatically due to the separation fractures at the transition region of fractured zone and bending zone.
作者
梁涛
刘晓丽
王思敬
LIANG Tao;LIU Xiaoli;WANG Sijing(Aerospace Architecture Design and Research Institute Co.,Ltd.,Beijing 100162,China;State Key Laboratory of Hydroscience and Hydraulic Engineering,Tsinghua University,Beijing 100084,China;Institute of Geology and Geophysics of the Chinese Academy of Sciences,Beijing 100029,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2019年第12期3729-3739,共11页
Journal of China Coal Society
基金
国家重点研发计划资助项目(2016YFC0501104)
国家自然科学基金优秀青年基金资助项目(51522903)
国家自然科学基金资助项目(51479094)
关键词
采动裂隙
裂隙演化
分形维数
物理模型试验
渗透特性
mining induced cracks
crack evolution
fractal dimension
physical model test
permeability
