Sonic Echo Method Research Articles

Improved sonic echo method with multiple receivers and amplifier to evaluate the length of capped piles

ABSTRACT Using nondestructive testing techniques to evaluate the length of a pile in a capped pile group is always an important issue for its high value of potential applications. One of the applicable occasions is to decide whether the underneath piles of a capped pile group are broken after the attack of severe earthquakes. There seems no economically feasible way at current stage to achieve this goal for capped piles. In this paper the essence of this difficulty is further illustrated with the results of the sonic echo tests carried out before and after a pile was capped. Then a new method utilizing the traditional sonic echo test incorporated with multiple receivers is proposed to approach the solution of this kind of problems. The idea of this method is to calculate the difference of the response signals obtained in the receivers so that the interferences from the pile cap may be reduced or eliminated and then the differenced result is exponentially amplified for identifying possible reflections from the pile toe. Numerical simulations using finite element models and a field test on a miniature pile group were carried out to study the feasibility of this new method.

Limitations of Sonic Echo Testing on Buried Piles of Unknown Bridge Foundations

ABSTRACT Nondestructive Sonic Echo (SE) field tests have shown that this method does not have a satisfactory performance in determining the depth of piles fully buried underneath pile caps. In the current study, we endeavored to investigate the possibility of improving SE methodology to obtain interpretable results leading to determining the depth of buried piles in such foundations. The results obtained from the investigated numerical models indicated that the location of the pile toe could be determined when the height of the pile cap is less than 1 m. However, this value is questionable since it has been concluded in the absence of surrounding soil damping. In real bridge foundations with surrounding soils, the SE method may only be able to detect the length of a pile located beneath a cap with a height significantly smaller than 1 m. In summary, our simplified models show that the SE test is not a proper method to determine the length of fully buried piles supporting caps due to the limitations and difficulties discussed in the article.

Improved sonic echo method with multiple receivers and amplifier to evaluate the length of capped piles

Improved sonic echo method with multiple receivers and amplifier to evaluate the length of capped piles

Estimating the Depth of Concrete Pier Wall Bridge Foundations Using Nondestructive Sonic Echo

This application paper outlines procedure developed for conducting nondestructive sonic echo (SE) tests to determine the depth of unknown concrete pier wall foundations. The National Bridge Inventory recognizes that more than 86,000 bridges in the US have no foundation data on record. An unknown percentage of these could also be highly vulnerable to scouring and subsequent failure. A series of field tests using the SE method were conducted on concrete pier wall foundations in the current research. Finite element models were used to understand the effect of the duration of impact, superstructure and upward striking on the pier caps on the waveform detected at the sensors. Good agreement were identified between the field tests and simulated models. Finally, practical recommendations were made to improve the SE methodology based on laboratory and field tests.

Use of the Impact-Echo Method for Analyzing the Integrity of Driven Reinforced Concrete Piles

The limitations of using the sonic echo method for evaluating the integrity of driven concrete piles with near-surface flaws are examined. Criteria for detecting pile flaws in a compact region are obtained. It is shown that it is possible to use the multiplicative impact-echo method for determining the length of a pile with a near-zone flaw.

Numerical and experimental study on evaluating the depth of caisson foundation with Sonic Echo method

Using nondestructive testing techniques to evaluate the length or depth of an existing foundation is an important issue with potential high application values. One of these is to evaluate whether the foundation is broken after severe earthquakes. In this aspect, academic research related to nondestructive evaluation for caisson foundations is rarely reported. The objective of this paper is to study the feasibility of using Sonic Echo method to evaluate the depth of caisson foundations. Two types of caissons, simple cylindrical caisson and compound caisson with chambers, were studied for their responses to the Sonic Echo tests. The study was carried out in numerical simulation with finite element method and experimental way with in-situ tests. A bridge system which spans over Sofong Brook in Taiwan was selected for the tests in situ. The bridge system is still under construction and therefore the effect of different construction stages on the testing results may be studied. In this paper, the parameters to be varied for the studies include the testing locations and the existence of chamber plates, the bottom plate and the top plate. Finally some preliminary conclusions can be reached for a successful test.

Experimental study for the evaluation of stress wave approaches on a group pile foundation

This paper investigates the relative performance of the sonic echo (SE), impulse response (IR), and parallel seismic (PS) tests using a field constructed pile foundation incorporating simulated defects. Tests were performed before and after the construction of a pile cap. According to the experimental results, the SE method has the best performance with regard to defect detection in an isolated pile. The results of the PS test were more consistent with regard to the length determination of the piles with a cap than those obtained using the SE and IR methods. The pile length estimated from the PS method increases with increasing borehole-to-pile distance, but this over-estimation can be reduced by applying length correction factors, thus providing more conservative estimations of the pile length. The two length correction approaches for the PS test produced similar results.

Rational Alternative to Positive Discovery of Pile-Supported Bridges with Unknown Foundation Depth

Bridges with unknown foundations have been a burden on the transportation agencies across the United States because of the lack of funding and availability of rational methods to determine the risk of failure of these bridges from scour. The embedment of unknown foundation bridges is a key to proceed further with any risk-based management approach and/or the widely used Federal Highway Administration (FHWA) guidelines on the methods of evaluation of unknown foundations. The need for a practical, cost-effective, and rational approach to positive discovery of bridge foundations and to reclassify bridges with unknown foundations is greater than ever. This technical note presents an assessment of the predictive capability of various methods currently in use to determine the embedment of unknown foundation bridges. The methods discussed in this paper include sonic echo method (or pile integrity tester) as non-destructive testing (NDT), inference (IM) and/or back calculation (BC) [i.e., reverse engineering (RE)], and static/back calculation (S/B-C). The well-documented case histories presented in the paper illustrate the usefulness of using the S/B-C method in determining the embedment of unknown foundations. The S/B-C also can be used to assess/validate NDT results and embedment estimates made by IM and/or BC (RE) approaches. For high priority unknown foundation bridges, the S/B-C reasonable minimum embedment and the embedment required for stability considering the scour can be used to plan and efficiently implement any future NDT for these bridges. It can significantly reduce the cost of treating unknown foundation bridges by optimizing the use of NDT, if warranted. The three case histories presented in the paper also suggest that, in general, the sonic echo (i.e., pile integrity tester)/NDT tends to be conservative whereas the IM and/or BC (RE) methods tend to be unconservative. This would lead to high cost or high risk, respectively, if such estimates are used to assess the stability of unknown foundation bridges impacted by scour.

Evaluation of Unknown Foundation Depth Using Different NDT Methods

Many of the older bridges in the United States have no original contract documents available, and about 26,000 bridges that are rated as scour critical have unknown foundation conditions. Thus, no information is available regarding the type, depth, geometry, or material of these scour critical bridge foundations. The unknown bridge foundations pose a significant problem to bridge owners because of safety concerns. This paper presents the determination of an unknown bridge foundation depth at Forth Worth, Texas. The bridge was supported by driven steel H-piles. Three nondestructive testing (NDT) techniques were utilized: (1) the parallel seismic (PS) method, (2) the sonic echo (SE) method, and (3) resistivity imaging (RI). The main objective of this present study was to compare the suitability of NDT techniques to determine the unknown bridge foundation depth. Based on the field test results, both PS and RI methods provided foundation depth close to actual foundation depth. However, the SE method was determined to be unsuitable for determining the unknown steel H-pile depth.

Assessment of identifiable defect size in a drilled shaft using sonic echo method: Numerical simulation

The purpose of this paper is to study the capabilities of the sonic echo method in assessing the location of defects and the minimum possible detectable defect size in a drilled shaft. Three-dimensional axisymmetric finite element models were performed to investigate the effects of the defect size, defect depth-to-shaft diameter ratio, and shaft-to-soil stiffness ratio on the response of the sonic echo test. According to the results from the numerical simulations, a useful formula for defect size assessment in a shaft based on the sonic echo method is proposed, considering these factors simultaneously. Furthermore, a formula for predicting the detectable length-to-diameter ratio of a shaft was also recommended which correlates with the shaft-to-soil stiffness ratio and it varies from 10 to 32.

Time–Frequency Signal Analysis for Nondestructive Evaluation of Pile with Cap

As stress waves decay as they pass through the pile foundation system, it is extremely challenging for all nondestructive testing methods to evaluate the pile integrity of a shaft underneath a structure. In this study, time–frequency signal analysis (TFSA) is used for signal processing and adopted to interpret the pile integrity testing signal. An experimental case with pile lengths of 58m with caps, were tested by the low strain sonic echo method. Traditional time domain analyses can not identify the pile tip response signals 58m lengths. After time-history curves are transformed into a time–frequency domain distribution, the results indicate the pile tip can be located more easily and clearly than the traditional time-domain analyses of pile integrity testing allowed for.

NONDESTRUCTIVE INTEGRITY EVALUATION OF PC PILE USING WIGNER-VILLE DISTRIBUTION METHOD

Nondestructive evaluation (NDE) techniques have been used for years to provide a quality control of the construction for both drilled shafts and driven concrete piles. This trace is typically made up of transient pulses reflected from structural features of the pile or changes in its surrounding environment. It is often analyzed in conjunction with the spectral response, mobility curve, arrival time, etc. The Wigner-Ville Distribution is a new numerical analysis tool for signal process technique in the time-frequency domain and it can offer assistance and enhance signal characteristics for better resolution both easily and quickly. In this study, five single pre-cast concrete piles have been tested and evaluated by both sonic echo method and Wigner-Ville distribution (WVD). Furthermore, two difficult problems in nondestructive evaluation problems are discussed and solved: the first one is with a pile with slight defect, whose necking area percentage is less than 10%, and the other is a pile with multiple defects. The results show that WVD can not only recognize the characteristics easily, but also locate the defects more clearly than the traditional pile integrity testing method.

Nondestructive Evaluation of In-Isolation Pile Shaft Integrity by Wigner-Ville Distribution

AbstractThe Wigner-Ville Distribution is a new numerical analysis tool for signal process technique in the time-frequency domain and it can offer assistance and enhance signal characteristics for better resolution both easily and quickly. Time-frequency transform can describe how a spectrum of signals changes with time owing to defects and boundary conditions. In this study, five single pre-cast concrete piles have been tested and evaluated by both sonic echo method and Wigner-Ville distribution (WVD). The appropriateness of time-frequency domain analysis is discussed. Furthermore, two difficult problems in nondestructive evaluation problems are discussed and solved: the first one is with a pile with slight defect, whose necking area percentage is less than 10%, and the other is a pile with multiple defects. The results show that WVD can not only recognize the characteristics easily, but also locate the defects more clearly than the traditional pile integrity testing method.

Nondestructive Evaluation of Installed Soil Nails

This paper presents the findings from a research study that evaluated nondestructive test (NDT) methods that may be useful for quality assurance purposes during construction of soil nail retaining walls. More specifically, the new NDT procedure will be used to evaluate the integrity of the grout column surrounding the steel tendon and to measure the grouted length of the installed soil nail. A preliminary evaluation of the existing NDT methodologies was undertaken to identify candidate NDT methods. The selected NDT methods, sonic echo and impact echo, were subjected to a detailed evaluation through three series of full-scale field NDT testing. The findings from the sonic echo tests are presented in this paper. The field studies demonstrated that the sonic echo method can be used successfully to detect major defects in installed soil nails. The nail condition predictions from sonic echo tests were confirmed by actual nail conditions observed after all the soil nails were exhumed.

Nondestructive Evaluation of Installed Soil Nails

This paper presents the findings from a research study that evaluated nondestructive test (NDT) methods that may be useful for quality assurance purposes during construction of soil nail retaining walls. More specifically, the new NDT procedure will be used to evaluate the integrity of the grout column surrounding the steel tendon and to measure the grouted length of the installed soil nail. A preliminary evaluation of the existing NDT methodologies was undertaken to identify candidate NDT methods. The selected NDT methods, sonic echo and impact echo, were subjected to a detailed evaluation through three series of full-scale field NDT testing. The findings from the sonic echo tests are presented in this paper. The field studies demonstrated that the sonic echo method can be used successfully to detect major defects in installed soil nails. The nail condition predictions from sonic echo tests were confirmed by actual nail conditions observed after all the soil nails were exhumed.