多煤层开采覆岩结构演化的光纤感测

发布时间：2018-09-11 12:49

【摘要】：为进一步开发煤炭资源而采用多煤层开采的方式,随着累计采厚的增大,多煤层开采过程中主关键层经历多次采动影响,主关键层结构的破坏将引起采场上覆岩层整体的变形破坏,同时决定上位岩层整体的结构形态。因此本文从多煤层开采过程中主关键层的受力变形出发,采用理论分析、数值模拟和相似材料模型实验相结合的研究方法,以乌苏海则井田2、3号煤层相距46.9m且覆岩中含有主关键层为工程背景,利用光纤传感技术对多煤层开过程中覆岩结构演化特征进行研究。计算并判别出上覆岩层中主关键层的位置,通过分析2、3号煤层顶底板岩性计算得出两层煤开采后导水裂隙带发育的最大高度,并建立了两层煤开采覆岩结构演化模型。采用FLAC3D软件对2、3号煤层开采过程中覆岩应力状态及塑性区的分布特征进行模拟。将FBG和PPP-BOTDA光纤传感技术联合应用于相似材料模型实验中,模型实验中首次采用温度补偿方法对FBG和BOTDA测试系统进行温度补偿,合理解决了温度变化对实验测试精度的影响;采用铁砂加载方式代替铁砖加载,有效控制了加载的准确性及连续性;此外,采用加热法对模型内部的光纤进行了定位,保证了光纤测试的有效性。在2m模型内埋设4根传感光纤和2个光纤光栅应变传感器,对多煤层开采主关键层由弯曲下沉发育至断裂过程中的应力应变进行感测。研究表明,2号煤层开采后主关键层及上位岩层处于弯曲下沉带中,连续变形未破断的主关键层阻碍裂隙向上位岩层发展;3号煤层开采后主关键层破断导致上覆岩层整体处于断裂带中,裂隙向上位岩层蔓延,导水裂隙带发育至洛河组含水层。模型实验中需要采用温度补偿方法对FBG光栅和BOTDA光纤测试结果进行补偿,铁砂加载方式相对铁砖加载更具有准确性,PPP-BOTDA分布式光纤感测技术能很好的监测岩层整体的运动规律和发展趋势,FBG传感器可以监测岩层关键点的运动情况,实现了对覆岩主关键层结构演化过程中整体及局部的实时监测,为乌苏海则井田安全生产提供依据。
[Abstract]:In order to further develop the coal resources, the method of multi-seam mining is adopted. With the increase of cumulative mining thickness, the main key strata in the process of multi-seam mining experience multiple mining effects. The failure of the main key layer structure will cause the deformation and failure of the overlying strata in the stope, and determine the structural form of the upper strata as a whole. Therefore, starting from the stress and deformation of the main key layer in the process of multi-seam mining, this paper adopts the research method of combining theoretical analysis, numerical simulation and similar material model experiment. Based on the engineering background of coal seam No. 2 and No. 3 in Wusuhaizi mine field with 46.9 m distance and the main key layer in overburden rock as engineering background, the evolution characteristics of overburden structure in the process of multi-seam opening are studied by using optical fiber sensing technology. The position of the main key strata in the overlying strata is calculated and distinguished. By analyzing the lithology of the roof and floor of coal seam 2 and 3, the maximum height of the fracture zone developed after the mining of the two layers of coal is obtained, and the evolution model of the overburden structure of the coal mining in the two layers is established. The stress state of overburden and the distribution characteristics of plastic zone in coal seam No. 2 and No. 3 are simulated by FLAC3D software. The FBG and PPP-BOTDA optical fiber sensing technology are combined in the model experiment of similar materials. In the model experiment, the temperature compensation method is used for the first time to compensate the temperature of the FBG and BOTDA test system, which reasonably solves the influence of the temperature change on the precision of the experiment. The accuracy and continuity of the loading are effectively controlled by replacing the iron brick loading with the iron sand loading method, in addition, the optical fiber inside the model is located by the heating method, which ensures the validity of the optical fiber testing. Four sensing fibers and two fiber Bragg grating strain sensors were embedded in 2m model to detect the stress and strain of the main critical layer in multi-seam mining from bending subsidence to fracture. The results show that the main key strata and upper strata are in the bending subsidence zone after coal seam No. 2 mining. The main key layer without continuous deformation hinders the development of fracture upward rock layer, and the main key stratum after coal seam No. 3 mining results in the whole overlying rock layer in the fault zone, the fissure spreading upward, and the water-conducting fracture zone developing to the Luohe formation aquifer. In the model experiment, the temperature compensation method is used to compensate the test results of FBG grating and BOTDA fiber. Compared with iron brick loading, iron sand loading mode is more accurate. PPP-BOTDA distributed optical fiber sensing technology can monitor the movement law and development trend of strata as a whole. FBG sensor can monitor the movement of key points of rock strata. The real-time monitoring of the whole and part of the structure evolution of the main key strata in the overburden is realized, which provides the basis for the safe production of the Wusu Haize mine field.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TD326

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