Application of time domain reflectometer for detecting necking defects in bored piles

Lee, Jong Sub; Song, Jung Uk; Hong, Won Taek; Yu, Jung-Doung

doi:10.1016/j.ndteint.2018.09.006

Cited by 22 publications

(13 citation statements)

References 21 publications

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“…e probability of defective pile is about 9.1% for bored piles [1]. Necking pile is one of the main defects which can cause the vertical bearing capacity of piles to lose because load transmission cannot be performed effectively [2]. erefore, it is of great engineering and economic significance to study the bearing characteristics of necking piles.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Bearing Characteristics and Soil Deformation of Necking Pile with Cap Using Transparent Soils Technology

Guo

2021

Advances in Civil Engineering

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This paper will employ the transparent soil experiment technology to explore the influences of shallow necking on the vertical bearing capacity of single pile with cap. Model experiment is carried out on one intact pile and nine shallow necking piles. The load-settlement curves of all piles are obtained, which are used to study bearing characteristics of piles. The displacement fields of soil around piles are employed to investigate the reasons for the loss of vertical bearing capacity of piles with shallow necking. The vertical bearing capacity is greatly reduced which is caused by shallow necking. When the axial dimension of necking is the same, the larger the radial size is, the greater the loss of vertical bearing capacity is. When the radial dimension of necking is the same, the greater the axial size is, the greater the loss of vertical bearing capacity is. The soil near the pile shaft and under the pile cap produces a large area of vertical downward deformation, which causes the relative displacement between the pile shaft and the soil to greatly reduce. Therefore, it is easy that the necking piles with caps develop negative friction, which causes the vertical bearing capacity of piles to reduce. When the radial dimension of the shallow necking is 80% of pile diameter, the pile is easy to be damaged.

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Section: Introductionmentioning

confidence: 99%

Experimental Study on Bearing Characteristics and Soil Deformation of Necking Pile with Cap Using Transparent Soils Technology

Guo

2021

Advances in Civil Engineering

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“…The electromagnetic wave is attenuated when it encounters other areas of impedance [19]. Consequently, the technique was extensively used to understand soil behaviors, including for the measurement of the scour depth [20], internal structure change in an embankment [21], and detection of necking in a bored pile [22]. Therefore, in this study, TDR was also selected to obtain the volumetric water content and electromagnetic wave attenuation for estimating the cementation factor.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Cementation Factor of Unconsolidated Granular Materials Through Time Domain Reflectometry with Variable Saturated Conditions

2019

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The cementation factor is necessary to determine porosity via the Archie equation, and its range of values has been suggested in many previous studies. However, the cementation factors in the literature are limited to fully saturated conditions, and it may thus be inaccurate to use the same value in other saturation conditions. The objective of this study is to characterize how the cementation factor varies depending on the saturation percentage. In this study, glass beads and soil are selected as the specimens, and two relative density values, 40% and 80%, are selected. Time domain reflectometry (TDR) is used to obtain both the saturation and electrical resistivity of the specimens. TDR is installed in the cell, and fluid is continuously circulated from the bottom to the top of the porous material for 30 min. The estimated saturation increases with time and the electrical resistivity is reduced during the circulation. Finally, the cementation factor at every saturated stage is determined, and the error ratio based on the porosity is calculated to show the importance of the cementation factor. The results show that there is a high error ratio when an unsuitable cementation factor that does not consider the saturation condition is used. This study demonstrates that the method for determining the actual cementation factor using TDR and the Archie equation can be applied in various saturation conditions.

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“…In addition, the electromagnetic wave is reflected at discontinuities of the transmission line with a reflection coefficient [28,29] as:normalR=ArAi=Z2−Z1Z2+Z1 where R is the reflection coefficient, A i and A r are amplitudes of the incident and reflected electromagnetic waves, respectively, and Z 1 and Z 2 are impedances of the media that make a discontinuity of the transmission line. Therefore, if relative permittivity of the transmission line is known, such as telecommunication lines, power lines, and uniform metal bars, locations of discontinuities can be accurately evaluated based on the travel time of the reflected electromagnetic waves [30,31].…”

Section: Time Domain Reflectometrymentioning

confidence: 99%

Dynamic Cone Penetrometer Incorporated with Time Domain Reflectometry (TDR) Sensors for the Evaluation of Water Contents in Sandy Soils

Hong

Kim

et al. 2019

Sensors

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Ground moisture content and strength properties are the most important factors for a proper assessment of ground stability. This study developed a dynamic cone penetrometer incorporated with time domain reflectometry (TDR) sensors (TDCP). The TDCP is composed of an anvil, a driving rod, and a TDCP probe. Three wave guides and a K-type thermocouple are installed on the TDCP probe. For utilization of TDCP, relationships between relative permittivities measured by TDCP and those measured by standard TDR probe, temperature, and volumetric water content of the soils were investigated. In addition, the relationship between penetration indices by TDCP (TPI) and by standard dynamic cone penetrometer was established. In the field application test, relative permittivity, ground temperature, and TPI were measured along the depth. Moreover, gravimetric water contents were also measured for comparison. The experimental results showed that volumetric water contents compensated by ground temperature showed good agreement with the volumetric water contents estimated from the gravimetric water contents of the soil samples and TPI. This study suggests that the TDCP may be effectively used for the evaluation moisture contents and for the strength characterization of the subsurface.

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Application of time domain reflectometer for detecting necking defects in bored piles

Cited by 22 publications

References 21 publications

Experimental Study on Bearing Characteristics and Soil Deformation of Necking Pile with Cap Using Transparent Soils Technology

Experimental Study on Bearing Characteristics and Soil Deformation of Necking Pile with Cap Using Transparent Soils Technology

Characterization of Cementation Factor of Unconsolidated Granular Materials Through Time Domain Reflectometry with Variable Saturated Conditions

Dynamic Cone Penetrometer Incorporated with Time Domain Reflectometry (TDR) Sensors for the Evaluation of Water Contents in Sandy Soils

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