Sonic Echo Tests Research Articles

Application of non-destructive geophysical methods for testing concrete structures

Non-destructive testing of reinforced concrete structures is of utmost importance in construction and civil engineering, where many factors can cause internal and external deterioration of reinforced concrete structures: the environment, nuclear radiation, and structural defects, among others. Geophysical non-destructive testing methods such as ultrasonic and radar have been increasingly used in civil engineering in recent years. Improvements in the ultrasonic testing of concrete have produced detailed images of the interiors of even the most complex structures and allowed for the earliest possible detection of deterioration. In this study, three geophysical methods were applied to inspect concrete structures: parallel seismic, sonic echo, and ultra-seismic. These three testing methods are applied to concrete foundations of two depths, namely 5, and 7 m; the deep foundation has a fracture at a depth of 4.5 m. The collected data are processed using a low-pass filter to remove the higher frequencies. These results of parallel seismic tests accurately predict foundation depths of 5.0 and 6.6 m and P-wave velocities of 2551 and 1097 m/s, respectively. Sonic echo tests yield depth predictions of 5.07 and 7.01 m for the tested foundations and 4.44 m for the depth of the crack. Meanwhile, ultra-seismic tests give depth predictions of 7.1 and 4.6 m for the foundation and fracture, respectively, while clarifying the P-wave velocities of the corresponding reflections: 3447 m/s exiting the 7-m foundation and 2668 m/s exiting the embedded fracture. Depth estimates based on each method show strong agreement with true depths. In conclusion, these three geophysical methods have great potential to provide quantitative data to drive quality assurance and remediation for concrete structures.

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.

Study of the Effect of Source Application on Sonic Echo Tests in Timber Piles

The long-term effects of scour have been identified as one of the primary reasons for bridge failure. To evaluate the performance of the bridges against scour, it is essential to assess the conditions of the bridge foundation including the depth of the piles. Sonic Echo (SE) has been a favorable nondestructive method to evaluate the condition of unknown bridge foundations in the recent decades. Previous studies have shown that the results obtained from SE tests can be affected by a variety of factors such as the pile-to-soil stiffness ratio, length-to-diameter ratio of the pile, presence of defects and anomalies near the pile head, striking method, and hammer type. Although previous studies have discussed such affecting factors, there is a lack of comprehensive investigation regarding the effect of striking method and hammer tip type specific to wood piles supporting bridge decks. In the current study, the effect of striking method and hammer type on the success of SE tests conducted on wood piles has been scrutinized by investigating various options of striking methods and hammer tip types. After comparing different options, superior ones were identified and recommendations for better conducting the SE tests on unknown wood bridge foundations were presented. Numerical simulations were also performed to support some of the conclusions.

Integrity Testing of Model Pile with Embedded Accelerometers

Non-destructive testing (NDT) techniques based on surface reflection of stress-wave have been successfully used for the integrity testing of newly-built individual piles. However, for piles with pile cap, previous studies have shown that the stress-wave reflected from the boundary of pile cap may cause difficulties in determining their integrity. In order to minimize the effects of stress-wave reflected from pile cap, three model piles (one is intact and the other two are with defects) were constructed with embedded accelerometers inside the pile in this study. Conventional Sonic Echo test and tests with embedded accelerometers were performed to assess their integrity. Results of these tests indicate that, in comparison to the surface reflection NDT method, testing with embedded accelerometers is more accurate in assessing the integrity of these model piles.

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.

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.

Sonic echo and impulse response tests for length evaluation of soil nails in various bonding mediums

The objective of this paper is to present the results of research for evaluating the installed lengths of soil nails with nondestructive testing methods. Two closely related methods, the sonic echo test and the impulse response test, both of which had been widely applied to assess the integrity of drilled shafts and driven piles, were evaluated to test their capabilities on soil nails. To carry out this study, soil nails of various lengths were embedded in different surrounding materials in the laboratory and then tested with both methods to predict their lengths. The surrounding materials studied in this research included soil and cement grout. Finally, field tests for in situ soil nails were carried out. The results indicated that the relative stiffness of the soil nail to the bond material plays a very important role in the success of testing. It is hoped that through this kind of study, the capability and limitation of using these nondestructive testing techniques to determine the installed lengths or to evaluate the bonding conditions of soil nails can be better understood.

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.

The De‐Noising of Sonic Echo Test Data through Wavelet Transform Reconstruction

This paper presents the results of feasibility study into the application of the wavelet transform signal processing method to sonic based non‐destructive testing techniques. Finite element generated data from cast in situ foundation piles were collated and processed using both continuous and discrete wavelet transform techniques. Results were compared with conventional Fourier based methods. The discrete Daubechies wavelets and the continuous Mexican hat wavelet were used and their relative merits investigated. It was found that both the continuous Mexican hat and discrete Daubechies D8 wavelets were significantly better at locating the pile toe compared than the Fourier filtered case. The wavelet transform method was then applied to field test data and found to be successful in facilitating the detection of the pile toe.