An experimental study: Fiber Bragg grating–hydrothermal cycling integration system for seepage monitoring of rockfill dams

Abstract

In order to make up defects liable for the conventional monitoring of rockfill dam seepage in spatial inconsequence and low efficiency, a new monitoring system is proposed based on the heating technique incorporated in the temperature tracer method, that is, the integrated system of fiber Bragg grating temperature sensing and hydrothermal cycling. The system has a boiler as its heating device, and heated water from boiler is admitted through redistributor and circular warm pipelines, in which fiber Bragg grating sensors are embedded in advance for measuring the water temperature, thereby the seepage behavior is identified from the correlative fields of temperature and seepage. A coefficient ζv, according to Newton’s law of cooling, is then fitted out by pipeline cooling curves and used as a new way to identify the seepage state. The temperature–time–travel curves for the cooling period have proved by calibration tests to be, in general, consistent with the mathematical model of temperature variations under Newton’s law of cooling, thereby to inverting the seepage velocity through the fitting formula of it with ζv. With the test model of concentrative leakage established in regard to the location, amount of leakage passages, and leakage rate, multi-condition tests have been conducted which conclude that the proposed method is capable of positioning leakage and quantifying seepage velocity; therefore, it is valid for seepage monitoring and identification.

A Laboratory Experimental Study: An FBG-PVC Tube Integrated Device for Monitoring the Slip Surface of Landslides

“…The reflected light wavelength λ B of FBG varies with the change of temperature and strain, so its wavelength shift ∆λ B versus the increment of strain ∆ε and of temperature ∆T can be expressed as: ∆λ B = K ε ∆ε + K T ∆T where K ε and K T denote the strain sensibility coefficient (nm/µε) and the temperature sensibility coefficient (nm/°C), respectively [ 14 , 18 ]. It needs to be noted that all the tests have been completed under normal temperature level, and time for data collection is very short.…”

“…Fiber optical sensors (FOS) have the advantages of anti-corrosion, being waterproof, tiny size, high sensitivity, immunity to electromagnetic interference and long-term stability, so they have been widely used to monitor structural health [ 14 , 15 ] and geological hazards [ 16 , 17 , 18 ]. For slip surface monitoring using the FOS technique, two typical FOS-based modes including the internal displacement monitoring method [ 19 , 20 ] and strain monitoring method [ 21 ] were adopted.…”

Crack width identification for underwater concrete structures using temperature tracer method

“…There are also coupling effects between many physical quantities and temperature, such as the coupling between stress field and temperature field [24], and the coupling between seepage field and temperature field [25]. Temperature tracer method is a method to indirectly measure other physical quantities by measuring temperature based on the thermal coupling effect, among which the temperature tracer technologies for seepage [26][27][28][29] and soil moisture monitoring [30][31][32] are the research highlights. Chen et al [33] applied this technology to monitor cracks in underwater concrete structure.…”

Application of Miniature FBG-MEMS Pressure Sensor in Penetration Process of Jacked Pile

“…With the continuous development of urban construction and the gradual improvement in jacked pile technology, jacked pile is more widely used in soft soil areas and densely populated cities [ 1 , 2 , 3 , 4 ]. In recent years, fiber Bragg grating (FBG) technology has been continuously developed and has gradually become an effective test method for civil engineering health monitoring, and many beneficial results have been achieved [ 5 , 6 , 7 , 8 ]. Therefore, how to obtain the mechanism of jacked pile penetration in viscous soil foundation has become a hot topic in the research of jacked pile [ 9 , 10 ].…”