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现阶段岩土工程模型试验围岩变形监测多采用点式传感器,仅能获得部分测点的应变,而光纤传感作为一种迅速发展的分布式监测技术,能很好地解决这一问题。对于岩土工程室内试验,现有光纤传感技术无法满足试验对空间分辨精度的高要求。对一种新型光纤传感技术光频域反射技术(OFDR)的测量原理和优点进行介绍,并将其应用于浅埋超大断面圆形隧道十字岩柱开挖模型试验中,对整个模型不同断面进行水平向应变连续监测。根据试验结果,结合有限元分析,表明OFDR能准确记录试验过程中模型内部的应变变化,揭示围岩在十字岩柱开挖方法下的变形规律,反映十字岩柱对围岩的支撑作用,为今后隧道工程开挖提供参考。另外通过算法将应变结果转化为位移结果,并与多点位移计的监测结果进行对比分析,偏差在10%以内。结果表明,该技术可应用于岩土工程试验中的变形监测。
At this stage of geotechnical engineering model test, the deformation monitoring of surrounding rock mostly adopts point sensor, which can only get the strain of some measuring points. Optical fiber sensing, as a rapidly developing distributed monitoring technique, can solve this problem well. For geotechnical laboratory tests, the existing optical fiber sensing technology can not meet the high spatial resolution requirements of the experiment. The measurement principle and advantages of OFDR, a new optical fiber sensing technology, are introduced and applied to the excavation model test of the cross-section of shallow tunnel with large cross section. Continuous horizontal strain monitoring. According to the test results and the finite element analysis, it is shown that OFDR can accurately record the strain changes in the model during the test, reveal the deformation law of the surrounding rock under the excavation of the cross rock column, and reflect the supporting effect of the cross rock on the surrounding rock. In the future, tunnel engineering excavation provides a reference. In addition, the strain results are transformed into the displacement results by the algorithm, and compared with the monitoring results of the multi-point displacement meter, the deviation is within 10%. The results show that this technique can be applied to deformation monitoring in geotechnical engineering.