scholarly journals Surface intrusion event identification for subway tunnels using ultra-weak FBG array based fiber sensing

2020 ◽  
Vol 28 (5) ◽  
pp. 6794 ◽  
Author(s):  
Liping Xin ◽  
Zhengying Li ◽  
Xin Gui ◽  
Xuelei Fu ◽  
Minlang Fan ◽  
...  
Keyword(s):  
Event Identification ◽  
Fiber Sensing ◽  
Subway Tunnels ◽  
Weak Fbg

scholarly journals Identification of Ground Intrusion in Underground Structures Based on Distributed Structural Vibration Detected by Ultra-Weak FBG Sensing Technology

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2160 ◽  
Author(s):  
Weibing Gan ◽  
Sheng Li ◽  
Zhengying Li ◽  
Lizhi Sun
Keyword(s):  
Fiber Optic ◽  
Structural Vibration ◽  
Underground Structures ◽  
Subway Tunnel ◽  
Tunnel Wall ◽  
Sensing Technology ◽  
Detection Approach ◽  
Vibration Responses ◽  
Subway Tunnels ◽  
Weak Fbg

It is challenging for engineers to timely identify illegal ground intrusions in underground systems such as subways. In order to prevent the catastrophic collapse of subway tunnels from intrusion events, this paper investigated the capability of detecting the ground intrusion of underground structures based on dynamic measurement of distributed fiber optic sensing. For an actual subway tunnel monitored by the ultra-weak fiber optic Bragg grating (FBG) sensing fiber with a spatial resolution of five meters, a simulated experiment of the ground intrusion along the selected path was designed and implemented, in which a hydraulic excavator was chosen to exert intrusion perturbations with different strengths and modes at five selected intrusion sites. For each intrusion place, the distributed vibration responses of sensing fibers mounted on the tunnel wall and the track bed were detected to identify the occurrence and characteristics of the intrusion event simulated by the discrete and continuous pulses of the excavator under two loading postures. By checking the on-site records of critical moments in the intrusion process, the proposed detection approach based on distributed structural vibration responses for the ground intrusion can detect the occurrence of intrusion events, locate the intrusion ground area, and distinguish intrusion strength and typical perturbation modes.

scholarly journals Method of Calculating the Compensation for Rectifying the Horizontal Displacement of Existing Tunnels by Grouting

2020 ◽  
Vol 11 (1) ◽  
pp. 40
Author(s):  
Yongjie Qi ◽  
Gang Wei ◽  
Feifan Feng ◽  
Jiaxuan Zhu
Keyword(s):  
Volume Expansion ◽  
Soil Layer ◽  
Horizontal Displacement ◽  
Soil Mass ◽  
Calculation Model ◽  
Additional Stress ◽  
Corrective Effect ◽  
Engineering Data ◽  
Subway Tunnels ◽  
Good Agreement

Sleeve valve pipe grouting, an effective method for reinforcing soil layers, is often employed to correct the deformation of subway tunnels. In order to study the effect of grouting on rectifying the displacement of existing tunnels, this paper proposes a mechanical model of the volume expansion of sleeve valve pipe grouting taking into consideration the volume expansion of the grouted soil mass. A formula for the additional stress on the soil layer caused by grouting was derived based on the principle of the mirror method. In addition, a formula for the horizontal displacement of a tunnel caused by grouting was developed through a calculation model of shearing dislocation and rigid body rotation. The results of the calculation method proposed herein were in good agreement with actual engineering data. In summary, enlarging the grouting volume within a reasonable range can effectively enhance the grouting corrective effect. Further, with an increase in the grouting distance, the influence of grouting gradually lessens. At a constant grouting length, setting the bottom of the grouting section at the same depth as the lower end of the tunnel can maximize the grouting corrective effect.

scholarly journals Fast Hotspot Detection in SFCLs by Exploiting Strain Response in Optical Fiber Sensing

2021 ◽  
pp. 1-1
Author(s):  
Arooj Akbar ◽  
Nicolo' Riva ◽  
Zhisheng Yang ◽  
Luc Thevenaz ◽  
Bertrand Dutoit
Keyword(s):  
Optical Fiber ◽  
Strain Response ◽  
Hotspot Detection ◽  
Fiber Sensing ◽  
Optical Fiber Sensing
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