Abstract
A novel fiber-optic based earth pressure sensor (FPS) with an adjustable measurement range and high sensitivity is developed to measure earth pressures for civil infrastructures. The new FPS combines a cantilever beam with fiber Bragg grating (FBG) sensors and a flexible membrane. Compared with a traditional pressure transducer with a dual diaphragm design, the proposed FPS has a larger measurement range and shows high accuracy. The working principles, parameter design, fabrication methods, and laboratory calibration tests are explained in this paper. A theoretical solution is derived to obtain the relationship between the applied pressure and strain of the FBG sensors. In addition, a finite element model is established to analyze the mechanical behavior of the membrane and the cantilever beam and thereby obtain optimal parameters. The cantilever beam is 40 mm long, 15 mm wide, and 1 mm thick. The whole FPS has a diameter of 100 mm and a thickness of 30 mm. The sensitivity of the FPS is 0.104 kPa/με. In addition, automatic temperature compensation can be achieved. The FPS’s sensitivity, physical properties, and response to applied pressure are extensively examined through modeling and experiments. The results show that the proposed FPS has numerous potential applications in soil pressure measurement.
Highlights
As much of the world’s infrastructure, such as high buildings, tunnels, dams, and subways, is built on soil, an understanding of soil pressure is essential to safety design and perform evaluation.Many disasters have occurred due to a lack of understanding of soil pressure during construction, such as the collapse of Nicoll Highway in Singapore on 20 April 2004 [1]
The results show that the proposed fiber optic based earth pressure sensor (FPS) has numerous potential applications in soil pressure measurement
The proposed fiber Bragg grating (FBG) sensor is ideally suited for strain measurement
Summary
As much of the world’s infrastructure, such as high buildings, tunnels, dams, and subways, is built on soil, an understanding of soil pressure is essential to safety design and perform evaluation. Soil pressure is responsible for the long-term deformation, such as the settlement of the Pisa Tower, and caused a tunnel excavation collapse in Borràs Square, Spain [1]. These cases of geotechnical structural failure indicate that consideration of soil pressure is essential to design and construction. A dual diaphragm design has been proposed to improve measurement accuracy [20,22] To address the above-mentioned limitations, a new type of fiber optic based earth pressure sensor (FPS) for earth pressure measurement is proposed, fabricated, and analyzed. The results of these tests are presented and discussed, and the major findings highlighted
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