基于光纤光栅的地基土瞬态应变响应试验研究

为掌握冲击荷载下一定范围内地基土的应变发展、分布和变化规律,采用光纤布拉格光栅(FBG)技术,通过在级配连续的均匀密砂地基中水平埋设三层传感光纤,获得了不同落球高度条件下土体内部应变的动态响应。试验结果表明,各组试验中土体应变经历了幂律增长、线性增长、幂律减小(回弹)和残余应变(稳定)的四个阶段。土体达到峰值应变的时刻存在高度一致性,试验中测得约为100 ms;冲击荷载的影响深度在20 cm左右,为钢球直径的4~5倍。在相同FBG埋深条件下,土体应变随钢球落高增加呈近线性增长;在相同钢球落高条件下,土体应变随FBG埋深增加呈指数减小。研究成果对揭示土体应变发展机理、估算地基土体强度参数和快速测定含水率的进一步探索具有一定的指导意义。

Experimental Study on Transient Strain Response of Foundation Soil based on Fiber Bragg Grating

In order to understand the development, distribution and variation law of strain developed in a certain range of foundation soil near impact load, the dynamic response of the soil strain caused by balls falling from different heights was obtained by using fiber Bragg grating (FBG) technique. In the tests, the FBG strain sensors were horizontally embedded in a homogeneous continuous sand foundation with three layers. The results show that the soil strain experienced four stages: power law growth, linear growth, power law reduction (rebound) and residual strain (stability). The peak strain moment in each group is highly consistent, which is about 100ms. The influence depth of the impact load is about 20cm, which is 4 to 5 times of the ball diameter. Under the condition of the same FBG depth, the soil strain increases linearly with the increase of the falling height. Under the condition of the same falling height, the soil strain decreases exponentially with the FBG depth. The research results have certain guiding significance for revealing the mechanism of soil strain development, estimating the strength parameters of soil and further investigating on rapid determination of soil water content.