Abstract
In recent decades, the provisions of new challenges to railway track demanded for a better understanding of the track dynamic, especially to track geotechnical dynamics. For geotechnical problems the presence of water in the void of soils has influence on the behavior of the soil effects such as temporarily development of excess pore water pressure of the soil or even liquefaction and mud pumping can occur. To account these effects considering the soil as two-phase material would be helpful to better understand the saturated railway line failures. Hence, this paper describes the pore fluid analysis of fully saturated railway embankment response subjected to train induced vibrations using three-dimensional finite element package ABAQUS. The modelized 3D track consists of train loads, rail, pads, sleeper, sub-ballast, ballast, saturated sub-grade, saturated subsoil layer and semi-infinite bedrock. The water-saturated soil layers modeled as poroelastic and the infinite bed rock as elastic medium. To this end, the influence of relative density, hydraulic conductivity, un-drained Young’s modulus and depth of embankment on excess pore water pressure development are compressively studied. The predicated results show that hydraulic conductivity, un-drained Young’s modulus and depth of embankment have quite significant effect on the induced excess pore water pressure; while the influence of relative density is very small. The result also shows that positive excess pore water pressure mainly distributes on the soil and this will permit fine grain soils to flow out from interior to exterior region of the model. Hence, mud pumping and liquefaction is developed not in specific type of soil instead can be developed in any type of soil with low hydraulic conductivity, high depth of embankment and low un-drained Young’s modulus.
Highlights
A number of failure of railway embankments have been attributed to the liquefaction and mud pumping of the saturated sub-grade surface caused by vibrating or seismic loading, since moving train load is recognized as source of ground vibration [1], and resulting upward flow of water frequently turns the soil in to liquefied condition and mud pumping
It’s easy to say that the direct influence of relative density on excess pore water pressure is very small, increasing relative density has a minor influence on transfer of loading from the pore water to the solid phase
Mud pumping and liquefaction is not depending on the type of the soil instead it depends on the parameters such as relative density, hydraulic conductivity, un-drained Young’s modulus and embankment height
Summary
A number of failure of railway embankments have been attributed to the liquefaction and mud pumping of the saturated sub-grade surface caused by vibrating or seismic loading, since moving train load is recognized as source of ground vibration [1], and resulting upward flow of water frequently turns the soil in to liquefied condition and mud pumping. The dynamic responses of saturated sub-grade railway structures induced by moving train loads are fundamental to alleviate liquefaction and mud pumping disturbance in a number of engineering fields such as transportation engineering. The excess pore water pressure distribution of the railway saturated sub-grade layers under different key parameters such as relative density, hydraulic conductivity, un-drained young's modulus and depth of embankment are comprehensively investigated. The goal is to identify the parameters that cause high excess pore water pressure development and evaluate the variations in the predicated value in each parameters required
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