基于弱光纤光栅传感技术的围岩变形监测研究

Research on deformation monitoring of surrounding rock based on weak fiber grating sensing technology

煤矿深部地层高地应力与围岩低强度间的突出矛盾导致巷道开挖后极易发生大变形失稳灾害。为及时掌握巷道开挖支护前后围岩内部的变形情况,研究基于弱光纤光栅传感技术,研制了一种准分布式大量程应变传感器光缆,实现了围岩内部变形测点的1 m级间距布置。通过室内标定试验掌握了传感器光缆的测试性能,测试结果表明:研制的应变传感光缆应变量程不低于0.04,灵敏度为1.23 pm/με,精度等级为0.5,属于高精度传感器并具有良好的重复性和线性度。依托平煤股份四矿深部岩石巷道开展了现场工业性试验,试验结果表明:巷道围岩应变随孔深增加而减小,4 m范围内围岩应变数值较大,7 m外应变数值较小且渐趋稳定;巷道围岩应变激增主要发生在前30 d内,随后巷道围岩应变增加量逐渐减小并趋于稳定;取应变速率迅速向0收敛位置作为围岩松动区边界,确定巷道帮部和顶部松动区边界为5 m,肩部松动区边界为4 m。该应变光缆通过弱光纤光栅技术与时分复用技术的综合应用,极大地提高了光纤传感网络的复用容量,满足了煤矿深部巷道围岩变形监测的大量程、精细化在线监测需求。通过技术应用,可及时掌握煤矿深部巷道围岩内部变形特征及松动圈时空演化规律,为深部巷道围岩稳定控制决策提供科学基础数据。

The prominent contradiction between high ground stress and low strength of surrounding rock in deep strata of coal mine leads to large deformation and instability disaster after roadway excavation.In order to grasp the internal deformation of surrounding rock before and after roadway excavation and support in time,this study developed a quasi-distributed large-range strain sensor cable based on weak fiber grating sensing technology,and realized the 1 m-level spacing arrangement of deformation measuring points in surrounding rock.The test performance of the sensor cable is mastered through the indoor calibration test.The test results show that the strain range of the developed strain sensing cable is not less than 0.04,the sensitivity is 1.23 pm/με,and the accuracy level is 0.5.It belongs to the high-precision sensor and has good repeatability and linearity.Field industrial test was carried out in deep rock roadway of No.4 Coal Mine of Pingdingshan Tian’an Coal Shares The results show that:The strain value of surrounding rock decreases with the increase of hole depth.The strain value of surrounding rock within 4 m is larger,and the strain value outside 7 m is smaller and tends to be stable.The strain of roadway surrounding rock mainly occurs within 30 days after roadway repair,and then the strain increase of roadway surrounding rock gradually decreases and tends to be stable.Taking the rapid convergence position of strain rate to 0 as the boundary of surrounding rock loose zone,the boundary of roadway side and top loose zone is 5 m,and the boundary of shoulder loose zone is 4 m.Through the comprehensive application of weak fiber grating technology and time division multiplexing technology,the strain optical cable greatly improves the multiplexing capacity of optical fiber sensing network and meets the large range and fine online monitoring requirements of surrounding rock deformation monitoring in deep roadway of coal mine.Through technical application,the internal deformation characteristics of surrounding rock of deep roadway in coal mine and the spatio-temporal evolution law of loose circle can be mastered in time,which provides scientific basic data for the stability control decision of surrounding rock of deep roadway.