摘要
采动覆岩裂隙分布演化是防治顶板水害、实现煤矿地下水资源保护的基础,其数值结果准确性的关键在于采动覆岩连续-离散转化及其耦合力学响应特征。在纯拉、纯剪断裂模式下引入弹塑性损伤力学,结合Benzeggagh-Kenane断裂准则,得到准脆性岩石在拉、剪复杂应力下的混合型韧性断裂(MD)本构方程;构建离散块体接触状态判据,结合直剪实验数据与Sargin剪切摩擦关系,导出适用于多种法向应力下的粗糙结构面压缩-剪切摩擦(SF)本构方程。在此基础上,编制有限元V离散元(FDEM)数值计算程序,实现采动覆岩“连续”-“离散”介质转化过程。在数值计算中,分别将摩擦和断裂属性赋予结构面(接触对)、零厚度黏聚力单元,通过共享节点力的方式实现岩石断裂-摩擦耦合。采用断裂力学实验和直剪试验识别材料参数并验证MD-SF本构方程的合理性。在此基础上,模拟研究双系煤层采动导水裂隙随工作面推进的演化规律。结果表明:(1) MD-SF本构方程组及相应的FDEM数值计算方法,可实现岩体从连续介质到离散介质的转化过程,较好反映准脆性岩石混合型韧性断裂及粗糙结构面的剪切摩擦响应;(2)模拟条件下,岩层与煤层间距越小,导水裂隙总宽度随大,且开采过程中裂隙总宽度是覆岩运动稳定后的2.26~7.11倍,表明采动过程中更容易出现水害;(3)高岭土砂岩显著的韧性破坏特征能有效控制其内导水裂隙高度,但在双系煤层重复开采扰动下,覆岩裂高比为20.8,远超经验公式所得结果。采动覆岩导水裂隙高度成果在大同矿区得到应用和检验,为进一步开展采动覆岩运动、水体下安全采煤、保水采煤设计等提供理论支撑。
The distribution and evolution of fractures in coal roof under mining influence is the basis for preventing wa-ter inrush disasters and realizing the protection of groundwater resources in coal mines. The key to the accuracy of numerical results is the coupling mechanical response characteristics of continuous-discrete media of roof rock in mining advance. The elastic-plastic damage mechanics was introduced into the pure tension and pure shear fracture modes, and combined with the Benzeggagh-Kenane fracture criterion under arbitrary mixing ratio, the mixed ductile fracture(MD)constitutive equations of quasi-brittle rock under complex tension and shear stress were obtained. The contact state criterion of discrete blocks was constructed, combined with the direct shear experimental data and the shear-friction relationship proposed by Sargin, the constitutive equations of compression-shear friction(SF)applicable to the rough discontinuities under various normal stresses were derived. On this basis, the finite-discrete element(FDEM)numerical calculation program was developed to realize the “continuous” and“discrete”medium conversion process of the overburden rock. In the numerical calculation, the friction and fracture properties were respectively assigned to the discontinuities(or contact pairs)and the zero-thickness cohesive elements, and the fracture-friction coupling was realized by sharing the nodal force. Fracture mechanics experiment and direct shear test were used to identify material parameters and verify the rationality of MD-SF constitutive equations. Based on this, the evolution law of mining-induced water-conducting fractures in the Jurassic and Carboniferous coal seams with mining advances was simulated. The results show that(1) The MD-SF constitutive equations and the corresponding FDEM numerical calculation method can realize the transformation process of rock mass from continuous medium to discrete medium, and reflect the response of mixed ductile fracture and shear friction of rough discontinuities of quasi-brittle rock.(2) Under the simulated conditions, the smaller the spacing between stratum and coal, the larger the total width of water-conducting fracture, and the total width of fracture in the mining process was 2.26-7.11 times that after the movement of overburden was stable, indicating that water inrush was more likely to occur in the mining process.(3) The remarkable ductile failure characteristics of kaolin sandstone can effectively control the height of water-conducting fractures, but under the disturbance of repeated mining of the Jurassic and Carboniferous coal seams, the ratio of the height of water-conducting fracture in overburden to the coal seam height is 20.8,which is far higher than the results obtained by empirical formula. The simulation results of water-conducting fracture distribution and evolution have been tested in the Datong mining area, which provides theoretical support for further mining overburden movement, safe coal mining under water and water retaining coal mining design.
作者
李浩
白海波
马立强
康志勤
李志永
缪小成
武鹏飞
韦婕
LI Hao;BAI Haibo;MA Liqiang;KANG Zhiqin;LI Zhiyong;MIAO Xiaocheng;WU Pengfei;WEI Jie(Key Laboratory of In-situ Property Improving Mining of Ministry of Education,Taiyuan University of Technology,Taiyuan030024;State Key Laboratory for Geomechanics&Deep Underground Engineering,China University of Mining and Technology,Xuzhou221116,China;School of Mining Engineering,China University of Mining and Technology,Xuzhou221116,China;Xuzhou Zhongkuang Geotechnical Technology Co.,Ltd.,Xuzhou221116,China;Jinneng Holding Coal Industry Group,Datong037003,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2022年第12期4443-4454,共12页
Journal of China Coal Society
基金
国家自然科学基金资助项目(42102310)。
关键词
双系煤层
导水裂隙带
连续-离散介质
韧性断裂
压剪摩擦
continuous-discrete media
ductile fracture
compression-shear friction
Jurassic and Carboniferous coal seams
water-conducting fractures
作者简介
李浩(1991-),男,山西离石人,助理研究员,博士。Tel:0351-6014063,E-mail:hanlityut@163.com。
