Effect of Inclined Soil Layers on Surface Vibration from Underground Railways Using the ThinLayer Method
by Simon Jones, (corresponding author), (: Postdoctoral Fellow, McGill Univ., Dept. of Mechanical Engineering, 817 Sherbrooke St. West, Montreal, Quebec H3A 2K6. Email: simon.jones2@mail.mcgill.ca) and Hugh Hunt, (Senior Lecturer, Univ. of Cambridge, Dept. of Engineering, Trumpington St., Cambridge CB2 1PZ, U.K.)
Journal of Engineering Mechanics, Vol. 137, No. 12, December 2011, pp. 887900, (doi: http://dx.doi.org/10.1061/(ASCE)EM.19437889.0000292)
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Document type: 
Journal Paper 
Abstract: 
Noise and vibration from underground railways is a documented disturbance for individuals living or working near subways. Numerical models are used to investigate and understand vibration propagation from these underground railways, although the models commonly include simplifying assumptions (i.e., assuming the soil is a horizontally layered, homogenous halfspace). Such simplifying assumptions add a level of uncertainty to the predictions that is not well understood. The goal of the current paper is to quantify the effect of including layer inclination angles up to 5° in relation to the surface. The thinlayer method (TLM) is introduced as an efficient and accurate means of simulating vibration from underground railways in arbitrarily layered halfspaces. The TLM is an elementbased approach that uses the analytical wave equation to describe vibration in the horizontal direction, whereas assuming displacements in the vertical direction can be described by using a linear shapefunction. The method is used to simulate a halfspace with an inclined layer and is shown to be both accurate and computationally faster than a boundaryelement model in predicting surface RMS velocities. The sensitivity of surface vibrations to inclination angle is also investigated, and the results suggest that small inclination angles of 5° or less can cause significant variation in RMS response of approximately 5 dB. 
Author Keywords: 
 Ground vibration 
 Underground railway 
 Thinlayer method 
 Equivalent internal source 
 Inclined layer 
