Pile Integrity Test (PIT) is a tool from Pile Dynamic Inc. (PDI), consisting of a mini-computer, accelerometer, and hammer. Integrity testing on piles using PIT equipment is carried out by analyzing ...one-dimensional wave propagation provided by hammer blows on the pile head. An accelerometer sensor installed on the pole will read the reflection that occurs during wave propagation on the pole head. The wave propagation speed that occurs in concrete will range from 3,500 m/s to 4,200 m/s. The PIT test results indicate the reduction in impedance in the pole by the BTA value, which compares the theoretical impedance value to the residual impedance. From the results of the Pile Integrity Test carried out at three pile points, it was found that all samples experienced a reduction in impedance around a depth of ± 3.0 meters below the sensor with BTA values of 75%, 78%, and 72% and fell into the damaged category. The reduction in impedance at a depth of 3 meters is most likely part of the connection between piles because one pile point uses 2–3 spun piles, with the length of 1 spun pile being 9 meters. From the results of visual observations, it can be seen that the condition of the existing spun pile and pile cap is still quite good.
•An innovative non-axisymmetric pile-soil interaction model is proposed.•Radial motion of the pile body under eccentric hammer impact is considered.•Testing signals of pile integrity test under ...non-axisymmetric condition are analyzed.•Optimal testing location for PIT under non-axisymmetric condition is summarized.
A simplified model of non-axisymmetric pile-soil interaction (NPSI) that considers both vertical and radial motions of the pile body is developed and applied to the investigation of pile integrity test (PIT) with eccentric hammer impact. The pile is treated as a simplified three-dimensional (3D) continuum and the soil along the pile shaft is simulated as a series of independent thin soil layers, while the soil under the pile base is defined by the fictitious soil-pile model. Theoretical solution of the velocity-time history of each point on the pile top section is deduced by integral transformation technique. Based on the NPSI model, characteristics of test signals of PIT for large-diameter piles under non-axisymmetric condition are analyzed. The optimal testing position for acquiring signals, which minimizes the influence of high frequency (HF) interference resulting from the pile body 3D effect, is identified. Findings from this study provide the basis for accurate interpretation of the PIT of large-diameter piles with eccentric hammer impact.
An innovative theoretical model of non-axisymmetric vibration of pipe pile (NVPP) is proposed in this paper to investigate the three-dimensional effect in the pile integrity test (PIT) for open-end ...pipe piles. A new dynamic equilibrium equation of the pipe pile is established based on the stress simplification assumption. It overcomes the inaccuracies of existing three-dimensional models in predicting the longitudinal wave velocity of pile material. The surrounding soil and soil plug conform to the classical plane strain assumption, while the pile end soil is simulated by the fictitious soil annular pile developed from the traditional fictitious soil pile. Theoretical solutions for the velocity response of each point on the pipe pile top are deduced and validated against existing solutions and FEM results. The NVPP model is then applied to analyze the characteristics of testing signals of PITs for thick-wall and thin-wall pipe piles. Problems concerned in actual PITs for pipe piles are settled and practical recommendations for acquiring high-quality testing signals with minimal interference are provided.
•A new dynamic equilibrium equation of the pipe pile under vertical loads is established.•Fictitious soil annular pile is developed to simulate the pipe pile end soil.•Three-dimensional effect in pile integrity tests for thick-wall and thin-wall pipe piles is investigated.•Eeffectiveness of the multi-point sampling method is discussed.
This paper presents a non-destructive method for detecting necking defects in bored piles using electromagnetic waves. Small-scale laboratory experiments are conducted with a defective model pile ...with diameter of 0.6 m and length of 1.0 m. Four artificial necking defects are introduced on three different sides of the model pile. One necking defect is introduced at the upper position on one side of the model pile, another one is introduced at the lower position on other side of the model pile, and the other two are introduced at both the upper and lower positions on the same side of the model pile. Electrical wires are installed alongside the main rebars of a reinforcement cage to configure a two-conductor transmission line. Electromagnetic waves are generated and detected using a time domain reflectometer. The experimental results indicate clear detection of the reflected electromagnetic waves at the necking defects and pile end. In addition, the calculated defect locations are similar to the actual locations. This study demonstrates that electromagnetic waves can be effective in detecting necking defects at various positions in bored piles.
The in-hole multipoint traveling wave decomposition (MPTWD) method is developed for detecting and characterizing the damage of cast in situ reinforced concrete (RC) piles. Compared with the results ...of MPTWD, the results of the in-hole MPTWD reconstruction technique are found ideal for evaluating the lower-part pile integrity and are further utilized to establish a data-driven machine-learning framework to detect and quantify the degree of damage. Considering the relatively small number of field test samples of the in-hole MPTWD method at this stage, an analytical solution is employed to generate sufficient samples to verify the feasibility and optimize the performance of the machine learning modeling framework. Two types of features extracted by the distributed sampling and statistical and signal processing techniques are applied to three machine-learning classifiers, i.e., logistic regression (LR), extreme gradient boosting (XGBoost) and multilayer perceptron (MLP). The performance of the data-driven machine-learning framework is then evaluated through a specific case study. The results demonstrate that all three classifiers perform better when employing the statistical and signal processing techniques, and the total of 24 extracted features are sufficient for the machine-learning algorithms.
A new simplified model for defective pile-soil interaction (DPSI) is developed to account for the three-dimensional (3D) effect in the pile integrity test (PIT) for large diameter piles. To account ...for the 3D effect, the defective pile is treated as linear continuum rather than the conventional 1D rod model. The surrounding soil is simulated employing the classical plane strain model and the soil resistance at the pile base is represented by the fictitious soil pile model. Theoretical solutions for the velocity field of the defective pile under vertical half-sine excitation are derived by integral transformation technique. The developed DPSI model and solutions are then used to investigate the 3D effect in the PIT for defective pile considering four common pile defect types. The obtained results provide important insights into the high-frequency (HF) interferences on the velocity-time history of the defective pile top caused by the 3D effect. Recommendations to minimize the HF interferences in the actual PIT are consequently provided. Application of the DPSI model in interpreting PIT measurements can improve accuracy of pile defect diagnosis.
This paper presents the velocity wave of concrete spun piles with welded splice. The stress wave velocity was recorded using Pile Integrity Test. Two specimens were prepared in the experiment. The ...first sample was prepared visually no gap between the two end-plates of connected piles, while the second specimen was prepared by inserting 5mm thick steel plate into the splice to create a gap in its connection. The results show that a spike of reflecting stress wave still develops at the splice with and without gap, regardless the splice was welded in full circle. The relatively high spikes of reflecting waves at pile toe are noticed for both specimens with and without gaps. It shows that the full welded splice able to transfer stress wave velocity. A good quality of welded splice can be indicated by the reflecting wave at the pile toe, regardless the reflecting wave development at the splice.
The integrity of extended pile shaft is paramount for ensuring safe and acceptable performance of supported bridge structures. However, it is difficult to conduct the vertical excitation low-strain ...integrity test for an extended pile shaft that supports an existing bridge. This paper investigates the feasibility of employing lateral low-strain test to predict the pile length of an extended pile shaft. An analytical model is developed to simulate the behavior of a pile, partially embedded in soil, with a pile cap and superstructure under a lateral low-strain excitation. Considering the frequency spectrum of an impulse excitation, the developed model employs the modified Timoshenko beam theory to accurately simulate the lateral pile vibration accounting for both rotary inertia and shear. The analytical solution is then utilized to analyze the dispersion of the pile-soil system when subjected to the lateral excitation. The effects of pile and soil properties on the pile dynamic response and wave propagating velocity are investigated through a comprehensive parametric study. A simplified method is proposed to approximately evaluate the pile length of this case on site.
•This paper investigates the feasibility of employing lateral PIT to predict the pile length of an extended pile shaft.•An analytical model is developed to simulate the behavior of a pile under a lateral low-strain excitation.•The dispersion of the developed model has been investigated.•We proposed a lateral PIT on site: the excitation is imposed at pile near the ground, the sensor is placed near the pile top.
Defects of concrete piles can occur at any point during the construction of piles. Most common types of pile integrity issues are; presence of voids, inconsistency in concrete mix, entrapped ...groundwater or slurry, and geometric dislocation. These defects can be categorized based on the place in the construction sequence at which the defect occurs. This research introduces several numerical models of defected piles with various scenarios in order to identify, locate, and quantify the necking occurring in these piles. The finite element software (ADINA) is used to simulate the studied models. The soil domain is modeled as an axisymmetric space around the concrete pile. Five diameters of piles (40, 60, 80, 100 and 120 cm) are studied. Necking is modeled at three different locations along the pile namely; upper, middle, and bottom third. Four ratios between the necking diameter and pile diameter are also studied. The dynamic force used in this research is that simulating the pile integrity test (PIT) case, with 2.5 N impact load applied at the pile head, half wave of sinusoidal pattern, and 0.5 kilo hertz frequency. The time domain of the dynamic force analysis is equal to 0.0175 sec, and applied in 450 steps.
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