The ground vibrations induced by traffic or machinery parts can propagate through the surrounding soils to adjacent buildings, causing annoyance to residents or resulting in malfunction of delicate instruments located inside. Generally, trains running on surface tracks generate vibration that propagates parallel to the ground surface as Rayleigh waves in the frequency range of approximately 4-50 Hz. This vibration may coincide with frequencies at which some buildings “bounce” or rock on the stiffness of their foundations and, in any case, lies in the frequency range for perception of whole body vibration (2-80 Hz). This type of vibration may cause disturbance to line-side residents who may also express concern about possible damage to their property. The adverse effects of such high frequency vibrations generated by railway traffic or machine foundations can be prevented through the installation of a suitable wave barrier in the ground. The wave barrier should be constructed between the source and the structure to be protected.
In this work, the effectiveness of open and in-filled trench in reducing the structural responses is investigated. The time domain coupled Boundary Element-Finite Element (BE-FE) scheme developed previously by the author is employed for the analysis. The mathematical model adopted herein is the two-dimensional profile that contains the cross section of the railway track, trench barrier, underlying soil and a nearby 6-story building frame. The building frame, the railway track and a certain region of the underlying soil that includes the trench are discretized by the finite element method. The rest of the underlying soil extended to infinity is modeled by the boundary element method where the radiation damping is directly considered without any artificial end conditions or absorbing boundaries. Therefore, unlike most of the previous works, this model completely considers the soil-structure-soil interaction effects. Moreover, the effects of the trench barrier on the structure response in terms of acceleration, normal forces, shearing forces and bending moments are directly obtained.
In the analysis, the structure foundation is considered to be as strip footings or raft foundation. The structure with raft foundation showed less response than the structure with strip footings. An extensive parameter study to find out the effects of geometric and material properties of the trench barrier on the structure response is conducted. The geometric properties include the trench depth, width and the distance to the building. For in-field trench, the backfill material is considered to be a soil bentonite mixture as a softer material than soil. The material properties include the shear modulus, Poisson’s ratio and the mass density of the filling material. Based on the obtained results, important conclusions that could be useful for the design of such vibration reduction measure are stated.
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