Experimental validation of a simplified numerical model to predict train-induced ground vibrations

This study evaluates the effect of high-speed train (HST)-induced environmental vibrations using simplified computational models and validates the test results in full-scale field conditions. Experimental investigations and in-situ measurements were performed at the Istanbul-Ankara high-speed railway section to examine the effect of ground vibrations from HSTs on the surrounding residential lands. In this study, ground-borne free-field surface motion at different distances from the railway track was realized using accelerometers. The experimental results of vertical and horizontal ground vibration accelerations induced by HSTs with a velocity of 250 km/h were analyzed. In the first part of the study, a two-dimensional (2D) numerical model based on finite element method (FEM) was used to investigate ground vibrations and validate the experimental results. To minimize artificial reflections and dissipate vibrational energy at the boundaries, the lateral extension of an infinite domain was modeled with viscous absorbing boundaries. A dynamic analysis of the proposed railway-soil coupled model was performed in the time domain under plain-strain conditions using Plaxis 2D, a commercial FEM software. For the verification, the experimental results were compared with those obtained from the numerical analysis. The simplified computational model validated by the test results may help researchers determine further investigation strategies to develop cost-effective mitigation measures for structures with sensitive devices near the railway track and significantly contribute to understanding complex wave propagation problems. In the second part of the study, train-induced environmental ground vibrations were analyzed for different types of soil conditions using a 2D FE model. Computational analyses were performed with four types of soil: soft, medium, dense, and rock, based on the Turkish Earthquake Code. The HST was used as a dynamic source to observe the differences in vibration generation and wave transmission in different types of soil. The HST load on the slab track was simulated to study the effect of operational loads on ground-borne vibrations. Based on the dynamic analysis results, the response of the free-field motion was investigated to obtain the relative acceleration time histories for different points of soil. According to the results, the peak acceleration values of train-induced vibrations at soft, medium, and dense soil sites increased dramatically when compared to the rock site. Vibration measurement data collected from parametric experiments with a simple numerical model for various soil characteristics can be particularly useful when planning residential and industrial facilities at new locations near railroads, to avoid the adverse effects of environmental vibrations caused by HSTs.