Three-dimensional numerical simulation of the geometrical dimension pile group effects on the critical speed of high-speed railway track (Case study: Tehran- Isfahan high speed railway track)

Abstract

Existence of soft soil layers and high ground water level in the Qom Salt Lake area have caused deflection more than allowable limitation in Tehran- Isfahan high speed track railway. Due to reduce deflection of track railway in this area, improving the stiffness and strength of the soil beneath will be done by means of concrete pile group. But also, due to the high speed of train, resonance phenomenon is expected to happen. Despite conducting some researches on the effect of improving soft ground by pile in recent years, but there are ambiguities about performance of pile on the increasing critical speed of the track-ground system which track has been experienced large dynamic amplification as the train speed approaches that speed. So first, the bearing capacity of pile and soil layers geotechnical parameters have been determined by comparing the numerical modeling results of single pile with data obtained from in situ compressive loading test on that in this paper. Afterwards, the effect of the geometrical dimension pile group on the dynamic behavior and critical speed of track-ground system has been investigated under various speed of train (60–450 km/h) using 3D finite element model. The results indicate that resonance phenomenon has been occurred at speed of 100 km/h, which is equal to Rayleigh speed of first subgrade layer. However, improving of soil layers by pile group increases the value of the critical speed to 250 km/h.