采动覆岩导水裂隙发育光纤感测与表征模型试验研究

Optical fiber sensing and characterization of water flowing fracture development in mining overburden

随着国家生态文明建设标准的日益提高,我国西部干旱半干旱地区赋存的浅埋煤层开采引起的生态环境问题愈发严峻。导水裂隙带发育高度探测是与保水开采密切相关的科学问题,是矿山生态损害监测与评价、生态修复策略制定的重要依据。将分布式光纤感测技术应用于相似模型试验,探究采动岩体导水裂隙带发育与光纤检测数据的内在响应关系。针对以往研究中对光纤与采动覆岩在不同开采阶段耦合作用关系分析不足的问题,提出传感光纤与采动岩体的耦合关系量化指标“光纤-岩体耦合系数”,通过耦合系数对采动引起的覆岩垂直分带区进行合理划分。研究表明:与光纤接触的不同受力状态岩层介质包括5种:顶部未受采动影响的稳定岩层、稳定关键层上受采动影响存在下移趋势的岩层、离层空域区、采空区矸石区及煤层底板;基于监测数据将覆岩分为4部分:已破坏区、强烈影响区、微弱影响区和未影响区。已破坏区即导水裂隙带,强烈影响区为受采动影响内部应力集中程度极高但结构完整的岩层,即弯曲下沉带。试验得出断裂带与弯曲下沉带分界处耦合系数阈值为0.65;建立了应变曲线形态、导水裂隙带发育高度与关键层活动的内在联系,实现光纤感测表征覆岩分带特征。将光纤传感技术应用于采动引起的覆岩变形监测为导水裂隙带发育高度探测提供了新的研究思路。

With the increasing improvement of national ecological standards,the eco-environmental problems caused by shallow coal seam mining in arid and semi-arid areas of western China are becoming more and more serious.The development height detection of water conducted fracture zone is a scientific problem closely related to water-preserved coal mining,and it is an important basis for mine ecological damage monitoring and evaluation,and ecological restoration strategy.The distributed optical fiber sensing technology is applied to the similarity model test to explore the internal response relationship between the development of fracture zone and optical fiber detection data.In view of the insufficient analysis of the coupling relationship between optical fiber and mining rock mass in previous studies,the quantitative index of coupling relationship between optical fiber and mining rock mass,“optical fiber-rock mass coupling coefficient”,is put forward.The vertical zoning area of overlying strata caused by mining is divided reasonably by coupling coefficient.The study shows that there are five kinds of rock mass in contact with optical fiber:the stable strata at the top which are not affected by mining,the strata with downward movement tendency on the stable key stratum,the abscission layer empty area,the gangue area,and the coal seam floor.Based on the monitoring data,the overburden is divided into four parts:damaged area,strongly affected area,weakly affected area and unaffected area.The damaged area is the water conducted fracture zone,and the strong influence area is the strata with high internal stress concentration but complete structure,namely bending subsidence zone.The threshold value of coupling coefficient between fracture zone and bending subsidence zone is 0.65.The internal relationship between the shape of strain curve,the development height of water conducted fracture zone and the activity of key stratum is established,and the zonation characteristics of overburden are characterized by optical fiber sensing.The application of optical fiber sensing technology in monitoring the water conducted fracture zone caused by mining can promote the construction of intelligent mining and green mine.