Nonlinear amplification is typically done on velocity signals from low-strain pile integrity tests to enhance weak echoes and superimpose any peak reflections. This conventional method may sometimes fail to untangle the hidden information within the signal that is obscured by the presence of noise. In this study, a pile defect identification system based on the conventional nonlinear amplification method and the wavelet packet transform (WPT) was proposed to easily detect the presence of any geometric or material defects by identifying feature parameters. Diagnostic rules, which have been lacking in the literature, were presented to serve as a guide in interpreting decomposed signals and in analyzing various characteristics of peak waveforms that are associated with certain types of defects. In this study, the finite element method was used to simulate the impact echo test of nine cases of defective piles. To verify the proposed scheme, six data sets of the nine cases of defective piles were made, in which a total of 54 piles were analyzed. The results of the study showed that the identification method based on WPT could detect defects 87.04% of the time compared to the conventional method, which only detected defects 64.81% of the time.
In planning and designing geotextile tubes, predicting the consolidation characteristics is very important to ensure that the capacity and deformation of the tubes are well regulated during construction. Design and construction parameters, such as dewatering time and permeability, must be evaluated considering the interaction of the soil and geotextile during filling and consolidation. In this study, field scale tests, such as the hanging bag test and geotextile tube demonstration tests, were performed as a geotechnical design approach in determining the equivalent soil-geotextile consolidation parameters. In the hanging bag test, seepage pressure was applied to simulate the effect of filling pressure in the actual construction site. Procedures to determine the required slurry volume, soil-geotextile consolidation parameters, tube geometry, and consolidation characteristics were introduced in this study. The procedures were proposed on the basis of the areal method, which considers the vertical and lateral movement of the tube, and the large strain consolidation theory, which considers finite strain and the change of the coefficient of consolidation. Finally, using the proposed procedures and obtained consolidation parameters, a parametric study was performed to show the applicability of the areal method and large strain consolidation theory.
The performance of geotextile tubes is affected by many factors such as the pumping pressure, fill material and geotextile properties, and so on. Hence, obtaining hydraulic compatibility between geotextiles and fill materials containing a variety of coarse and fine particles – that is, silty sand – is complex. For this reason, the modified geotextile tube (MGT) was invented to optimize the filling and dewatering or consolidation performance of geotextile tubes. To assess the behavior of MGTs, experimentation and theoretical analysis were conducted. The MGT retention performance, filling time, and water pressure were evaluated through a geotextile bag experiment while the MGT geometry, tension force, strain, water content distribution, and consolidation performance, were investigated through a parametric study. The two-dimensional MGT solution presented in this study is based on a combination of various modeling concepts that were modified or extended to be able to sufficiently describe the MGT behavior. Results showed that the performance of geotextile tubes can be optimized in a variety of ways by interchanging the geotextile placement, by changing the circumferential lengths, and by using geotextiles with different properties. With the methods presented in this study, modified geotextile tube design is made possible.
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