基于光纤传感技术的三维地应力传感器

为了实现对地下岩层空间应力状态及其变化规律的有效监测,基于光纤光栅传感技术与平面应力状态测量原理,提出了一种平面应变花与光纤光栅传感技术相结合的监测方法。通过利用碳纤维层积复合材料对光纤光栅封装做成应变传感单元,九个应变传感单元分别组成两组直角应变花与一组等角应变花,三组应变花分别放置于三个圆柱形探头S1,S2,S3上,三个探头以一定的机械结构连接构成地层空间应力的监测的三维地应力传感装置。对光纤应变传感单元进行温度与应力的标定实验,在室内对整体传感装置进行了应力加载模拟实验。实验结果表明:光纤应变传感单元的应力分辨率为0.017 2 MPa;应力监测为0~60 MPa;探头S1最大主应力的监测平均误差为16.31%,探头S2最大主应力的监测平均误差为24.36%,S3探头的绝对误差为0.006 8 MPa;实际加载应力与传感器测量的应力空间角度误差平均值为1.24°。传感器的监测结果与实际加载应力的变化规律相一致,可满足对地下岩层空间应力状态连续监测的要求。

Three dimensional in-situ stress sensor based on optical fiber sensing technology

In order to realize the effective monitoring of the spatial stress state of the underground rock formation and its variation. A monitoring method combining plane strain and fiber grating sensing technology was proposed, based on the principle of fiber grating sensing and plane stress state measurement. The strain sensor unit was composed of two sets of strain sensor, which were composed of two sets of right angle strain flower and a group of equiaxed strain flower. The three sets of strain flowers were placed in three cylindrical shapes respectively by using carbon fiber laminated composite material. On the probe S₁,S₂,S₃, the three probes were connected with a certain mechanical structure to form the three-dimensional geo-stress sensor of the formation space stress monitoring. The experiment of temperature and stress of the fiber strain sensor was carried out, and the stress sensing experiment of the whole sensing device was carried out indoors. Experimental results showed that the stress resolution of the fiber strain sensor was 0.017 2 MPa; stress monitoring range of 0-60 MPa; the average error of the maximum principal stress of the probe S₁ was 16.31%, the average error of the maximum principal stress of the probe S₂ is 24.36%, and the absolute error of the S₃ probe was 0.006 8 MPa. The mean value of the stress space angle error measured by the actual loading stress and the sensor was 1.24°. The monitoring results of the sensor are consistent with the variation of the actual loading stress, which can meet the requirement of continuous monitoring of the spatial stress state of the underground rock.