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The utilization of a mechanically stabilized earth wall (MSE wall) is prevalent due to its stability and cost-effectiveness compared to conventional earthwork construction methods. In addition, the railway transportation infrastructure has played a vital role in connecting Thailand's numerous regions. The behavior of a 6-m-high MSE wall constructed on a hard ground foundation, which was reinforced with high-density polyethylene on one side and a metallic strip on the other side, was studied in this research. The purpose of this MSE wall is to support the railway structure under dynamic train loads at 100, 150, and 200 km/h. The three-dimensional finite-element method was used to simulate and investigate the behavior of the MSE wall in terms of lateral displacement, settlement, and strain of reinforcement materials. The findings of the study demonstrate that there is a positive correlation between train speed and both lateral displacement and settlement. This relationship is most pronounced at the top of the MSE wall, which is primarily attributable to the influence of surface waves. The MSE wall's behavior under the influence of dynamic train loads was most prominently displayed by the surface waves, which were a curved wavefront at 150 km/h and a Mach cone at 200 km/h. The settlement profile increased when the speed of dynamic train loads increased. The impact of velocity fluctuations on the strain of the reinforcement material was insignificant. Due to the hard ground foundation, the behavior of the MSE wall on both types of reinforcement materials exhibited similar tendencies. Moreover, it was observed that the maximum tension lines closely follow the bilinear coherent gravity method with a standard distance of 0.3H from the facing, where H represents the equivalent height of the MSE wall. [ABSTRACT FROM AUTHOR]

This paper proposes a novel optical fiber sensor-based nondestructive method, namely, the long-gauge fiber Bragg grating (LGFBG) method, for integrity assessment of cement-grouted soil nails. This LGFBG sensor was developed by encapsulating a number of straight, bare FBG sensors inside an aluminum tube, and then mounting them on a steel bar surface for monitoring average strain distributions of soil nails subjected to tension force. Measured strain distributions of LGFBG sensors were finally used for the prediction of effective elastic modulus (EEM) distributions along the soil nails and the assessment of soil nail integrity in terms of the predicted EEM. A number of pullout tests of soil nails with different defects in the laboratory were performed to verify the feasibility of this proposed method. Pullout test results indicate that the elongation contributions of defective soil nail sections are 1.5 to 3 times the intact soil nail sections, whereas the related EEM values of the two defective soil nail sections are around 0.3 to 0.5 times that of intact soil nail sections. The statistical hypothesis Student’s t-test was used to determine the magnitude ranges of the modulus ratio leading to a rejection of the null hypothesis for a prespecified level of significance. In this study, a significance level of 0.01% is suggested for the integrity evaluation of cement-grouted soil nails. [ABSTRACT FROM AUTHOR]