Instrumented Pile Load Testing With Distributed Optical Fibre Strain Sensor

Distributed Optical Fibre Sensor (DOFS) is a versatile sensor considering that it can be used to measure various parameters, such as detection of small strains over large areas and long distances. The application of DOFS is currently being explored as an early warning system, particularly for slope movement detection. In this paper, an embankment slope at Sungai Rual, Jeli, Kelantan, Malaysia was selected to determine the best monitoring layout for landslide detection. Two methods of installation for vertical Fibre Optic (FO) inclinometers (using conventional casing with a special grove) were installed to monitor subsurface horizontal ground movements. The first method of FO inclinometer installation uses concrete (grade 35) grouting, and the second method uses a bentonite mixture. It was found that the first method was unsuccessful due to the fibre breakage during the hardening process of concrete and hence not recommended. However, the measurement was successfully taken for the bentonite mixture method. The displacement reading was taken using both the FO and conventional inclinometer probe. The reading for the 9.5 m depth of the inclinometer casing were recorded for the comparison between FO and conventional inclinometer probes. A comparison between FO and conventional systems showed almost similar results to the conventional method. The FO inclinometer developed in this project shall provide vital information to assist designers and operators, as well as inform stakeholders on the integrity of their structures.

“…The method described in Eq. ( 1) for transforming bending strains into traversal displacements was previously demonstrated by [18]:…”

Section: Banding Strain To Lateral Deflection Conversionmentioning

confidence: 95%

Slope Monitoring of a Road Embankment by Using Distributed Optical Fibre Sensing Inclinometer

Ghazali,

Mohamad,

Nasir

et al. 2023

“…DOFS adoption as an instrumentation method for pile load tests had gained the construction industry's faith. Numerous publications available express the acceptance trend including [8][9][10][11][12][13][14][15][16][17][18] to name a few. BOTDA outrun commonly used conventional instrumentation, e.g., vibrating wire strain gauge (VWSG), in such a way, provides continuous data measurement along the pile shaft, better data reliability, easy installation procedure, no electromagnetic interference and mechanical faulty.…”

Section: Dofs Instrumented Pile Load Testmentioning

confidence: 99%

Instrumented Pile Load Test: Analysing Measurement Anomaly at the Pile Head

Beddelee,

Mohamad,

Tee

et al. 2024

Loading activity during Distributed Optical Fibre Strain Sensor (DOFS) instrumented pile load test prevails the strain disparity within the pile’s initial depth and converges at a certain depth. This work aims to determine the strain convergence (SC) depth: investigate the influence factor of the SC and propose a standard empirical model for SC depth determination. The strain profile variation at any point within the pile diameter is examined using PLAXIS 2D. A set of test cases are simulated starting with defining influence factors of SC depth and further analysis of the cogent factor. The proposed model is validated to a few real field projects. This work is significant to determine the real start (RS) depth of the plotted strain profile and will improve data processing for the pile load transfer analysis of the DOFS instrumented pile load test. The cogent factor that influences the SC depth is the jack area coverage to pile area and an empirical model is proposed to determine the SC depth. The model is validated to a few real field projects with nominal differences of SC by the model to the field measured at ±0.05 sensitivity, comply the model goodness of fit at 0.9492 (R-square).

“…It is vital to have a full strain profile of a pile as it enables to yield an accurate soil interaction interpretation includes unit shaft friction that guarantees a better pile analysis [5][6][7][8]. Furthermore, this instrumentation offers the ability to be embedded into a solid (e.g., concrete), immune to electromagnetic interference, and inert to various chemical and adverse temperatures [4,9,10].…”

Section: Introductionmentioning

confidence: 99%

Instrumented pile load tests in limestones and granite formations - case studies with optical fibre strain sensors

Mohamad,

Beddelee,

Tee

2024

In instrumented pile load tests, obtaining a reliable strain profile is crucial to interpret the load-transfer behaviour of the test pile. For conventional instrumented pile load tests, an extensive quantity of point-based sensors such as vibrating wire strain gauges and tell-tale extensometers were installed to measure strains and pile deformation especially when the test pile is long and with large variation in soil stratum. The advancement of distributed fibre optic sensor (DFOS) technology, has significantly improved the conventional instrumented pile load test method. DOFS based on Brillion Optical Time Domain Analysis (BOTDA) is a novel technique for measuring strains in a continuous manner that outweighs the conventional point-based sensors. A full continuous pile length strain profile minimised misinterpretation of the load-transfer and mobilised shaft friction of the test pile, especially the cast-in-situ pile. This paper discusses two case studies of instrumented pile load tests performed using BOTDA technology for the Klang Valley Mass Rapid Transport (KVMRT) project found in limestones and granite formations. The interpreted results in terms of load transfer response, average unit shaft resistance, and elastic shortening of rock socketing piles are in exceptional agreement with conventional instrumentations such as Vibrating Wire Strain Gauges (VWSG) and Linear Variable Displacement Transducers (LVDT) at 6% difference. The maximum unit shaft friction acquired in the granitic layer was about 2,200 to 2,500 kN/m2 whereas the pile founded in limestones achieved maximum unit shaft friction of 1,800 to 1,900 kN/m2.