基于光纤传感的隧道管片结构形态感知试验及数值模拟研究

Experimental and Numerical Simulation of Structural Shape Perception of Tunnel Segments Based on Optical Fiber Sensing

为精确感知环境荷载作用下隧道管片的结构形态,采用光纤传感技术,构建表贴式光纤传感元件纤芯层-防护层-基体层-被测层的多层力学模型,分析光纤应变传递机制,推导表贴式光纤传感元件的应变传递率公式,验证光纤传感元件对隧道管片结构形态感知的精度。采用1∶20缩尺模型开展试验研究,测量不同水压、土压力下管片的应变变化。结合ANSYS数值模拟,对比分析在有水压与无水压2种荷载工况下隧道管片结构的应变响应,揭示水-土耦合压力对隧道管片结构变形的影响机制。结果表明:1)在10 mm光栅长度下,光纤传感元件的平均应变传递率可达到95.1%;2)均布水压的存在对隧道管片结构变形具有一定的稳定效果;3)水-土耦合压力作用下,隧道管片结构拉、压应变变化呈现不同步现象,其中拱腰处压应变变化较拱顶处拉应变变化更为提前,表明拱腰区域对水-土耦合压力的作用更为敏感;4)有水压地层环境下,当地层荷载为0~1.6 MPa时,隧道管片结构位移呈现波动变化趋势;5)当荷载进一步达到1.6~2.4 MPa时,隧道管片结构位移呈线性增加趋势。

A multilayer mechanical model comprising a surface-mounted optical fiber sensing element with a core layer,protective layer,substrate layer,and measured layer is constructed using optical fiber sensing technology.The strain transfer mechanism of the optical fiber is analyzed,and a strain transfer rate formula for a surface-mounted optical fiber sensing element is derived.The accuracy of the sensing element in detecting the structural shape of tunnel segments is verified.A 1∶20 scale model is employed to perform experimental investigations by measuring the strain variations in the segments under different water and earth pressures.Numerical simulations using ANSYS are conducted to compare the strain responses of the tunnel segment structure under two load scenarios:with and without water pressure.The results also reveal the influence mechanism of water-soil coupling pressure on tunnel segment deformation.The findings are summarized as follows:(1)The average strain transfer rate of the optical fiber sensing element reaches 95.1%at a grating length of 10 mm.(2)Uniform water pressure stabilizes the deformation of the tunnel segment structure to a certain extent.(3)Under water-soil coupling pressure,the tensile and compressive strain changes are unsynchronized.The compressive strain change at the arch waist precedes the tensile strain change at the crown,indicating a higher sensitivity of the arch waist to water-soil coupling pressure.(4)In a water-pressure stratum environment,the displacement of the tunnel segment structure exhibits a fluctuating trend as the stratum load increases from 0 to 1.6 MPa.(5)When the load further increases from 1.6 to 2.4 MPa,the displacement of the tunnel segment structure follows a linear trend.