Zhang Lei, Shi Bin, Zeni Luigi, Minardo Aldo, Zhu Honghu, Jia Lixiang
School of Earth Science and Engineering, Nanjing University, Nanjing 210023, China.
Department of Engineering, University of Campania "Luigi Vanvitelli", 81031 Aversa, Italy.
Sensors (Basel). 2019 Apr 2;19(7):1591. doi: 10.3390/s19071591.
Centrifugal model tests, which can reproduce the deformation process of the slope, play a crucial role in investigating the mechanism of slope failure. The FBG-based sensors, with high precision, electromagnetic resistance, light weight and small size, have been introduced into geotechnical centrifuge monitoring. The slope evolution is a complex multi-parameter dynamic process which involves the interaction of displacement, stress and strain. However, current research is mainly focused on one or two monitoring aspects, i.e., strain or displacement monitoring to study some specific questions. To achieve multi-parameter and real-time monitoring, a comprehensive fiber Bragg grating (FBG) monitoring system including miniaturized anchors, earth pressure gauges, inclinometer pipe and retaining wall, has been designed for geotechnical centrifuge tests. Before the centrifugal test, laboratory calibrations of sensors were carried out. The calibration results indicate that the FBG-based sensors can monitor the strain, stress and displacement variation precisely. The multi-parameter information related to slope stability were captured and analyzed in detail. The stress state of the anchors, strain distribution of retaining wall together with the displacement of the inclinometer pipe indicate the progressive evolutionary process of the model slope. The test results also indicate that the critical centrifugal force for the transition of the sliding surface is 45 g, after which, a sliding surface is formed in the soil above the retaining wall. The feasibility and validity of the monitoring system is verified by a comparison between the results of FBG-based sensors and those of a numerical simulation. In summary, the innovative FBG-based monitoring system has provided a feasible multi-parameter monitoring method in geotechnical centrifugal tests so as to facilitate further in-depth analysis.
离心模型试验能够再现边坡的变形过程，在研究边坡破坏机制方面发挥着关键作用。基于光纤布拉格光栅（FBG）的传感器具有高精度、抗电磁干扰、重量轻和尺寸小等优点，已被引入到岩土离心机监测中。边坡演化是一个复杂的多参数动态过程，涉及位移、应力和应变的相互作用。然而，目前的研究主要集中在一两个监测方面，即应变或位移监测，以研究一些特定问题。为了实现多参数实时监测，设计了一种包括小型化锚杆、土压力计、测斜管和挡土墙的综合光纤布拉格光栅（FBG）监测系统，用于岩土离心机试验。在离心试验前，对传感器进行了实验室校准。校准结果表明，基于FBG的传感器能够精确监测应变、应力和位移变化。详细采集并分析了与边坡稳定性相关的多参数信息。锚杆的应力状态、挡土墙的应变分布以及测斜管的位移表明了模型边坡的渐进演化过程。试验结果还表明，滑动面转变的临界离心力为45g，此后，在挡土墙上方的土体中形成了滑动面。通过将基于FBG的传感器结果与数值模拟结果进行比较，验证了监测系统的可行性和有效性。总之，创新的基于FBG的监测系统为岩土离心机试验提供了一种可行的多参数监测方法，便于进一步深入分析。
