Prediction of ground vibration from trains using the wavenumber finite and boundary element methods

This paper investigates the effectiveness of a sheet pile wall to reduce railway induced vibration transmission by means of field measurements and numerical simulations. At Furet, Sweden, a sheet pile wall has been installed in the soil near the track to reduce train induced vibrations in houses close to the track. The depth of the sheet piles is 12 m with every fourth pile extended to 18 m. The efficacy of the wall is determined from in situ measurements of free field vibrations during train passages before and after installation of the sheet pile wall. The field test shows that the sheet pile wall reduces vibrations from 4 Hz upwards. Up till 16 − 20 Hz, the performance generally increases with frequency and typically decreases with increasing distance behind the wall. The performance is further studied by means of two-and-a-half-dimensional coupled finite element -boundary element models. The sheet pile wall is modeled as an orthotropic plate using finite elements, while the soil is modeled as a layered halfspace using boundary elements. The sheet pile wall acts as a stiff wave barrier and the efficacy is determined by the depth and the stiffness contrast with soil. The reduction of vibration levels is entirely due to the relatively high axial stiffness and plate bending stiffness with respect to the horizontal axis of the sheet pile wall; the plate bending stiffness with respect to the vertical axis is too low to affect the transmission of vibrations. Therefore, it is important to take into account the orthotropic behaviour of the sheet pile wall. It is concluded that a sheet pile wall can effectively act as a wave barrier in soft soil conditions provided that the wall is sufficiently deep.

Section: Introductionmentioning

confidence: 99%

Efficacy of a sheet pile wall as a wave barrier for railway induced ground vibration

Dijckmans

Ekblad

Smekal

et al. 2016

“…The corresponding two-dimensional problem is solved for each wavenumber and an inverse Fourier transform is used to recover the three-dimensional response. This so-called 2.5D method is computationally more efficient than a full threedimensional approach and has been widely used for railway vibration [22,23,26,27].…”

Section: 5d Finite Element / Boundary Element Approachmentioning

confidence: 99%

“…In the literature this has been referred to as a wave impeding block [16,17]. It is thought that vibration is reduced in this case because the stiffened block behaves like a rigid layer [22], in which case, wave propagation would only occur in the (softer) soil layer above it for frequencies higher than the cut-on frequency of waves in this constrained layer. As such, the block should ideally be infinitely wide and stiff.…”

mentioning

confidence: 99%

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Mitigation of railway-induced vibration by using subgrade stiffening

Thompson

Jiang

Toward

et al. 2015

Self Cite

Railway-induced ground vibration is often associated with sites with soft ground. Stiffening of the subgrade beneath the railway track is one particular measure that has potential to reduce the vibration level at such sites. However, the mechanisms behind this reduction are not well understood. Here, the effects are examined in the context of two alternative approaches: (i) subgrade stiffening, where the soil directly under the track is stiffened, and (ii) stiff inclusions introduced at some depth beneath the track, sometimes known as 'wave impeding blocks'. The efficacy of the measures is considered for different ground types in a parametric study carried out using a 2.5D coupled finite-element / boundary-element methodology. The soil is considered to consist of a soft upper layer over a stiffer substratum; corresponding homogeneous grounds are also considered. With a 6 m wide, 1 m thick, concrete block directly under the track, the vibration between 16 and 50 Hz was found to be reduced by between 4 and 10 dB for ground with a 3 m deep soft upper layer. For a deeper soft layer the reductions were greater whereas, for a stiffer ground without the soft upper layer, the reductions in vibration from this block were negligible. Slightly smaller reductions in a similar frequency region were observed when the block was positioned 1 m below the 2 surface, suggesting that, as with stiffening directly under the track, the reduction in vibration was primarily due to the increase of the effective stiffness of the soil beneath the track rather than the effective creation of a new, thinner soil layer. Jet grouting is considered as an alternative to concrete and, although it is found to be less effective due to its comparatively low stiffness, it may still be considered as a practical measure for existing tracks on soft soil sites. The reduction in vibration from this form of soil improvement with a depth of 3 m is similar to that for a 1 m thick concrete block. Finally, results are presented for three example sites with different soil properties which show similar trends.

“…These measures include include open trenches [11], soft and stiff buried wall barriers [12,13,14,15], subgrade stiffening [16,17] and wave impeding blocks [18,19]. Interventions on the propagation path between source and receiver have the advantage that no modifications of the track are required.…”

Section: Introductionmentioning

confidence: 99%

Mitigation of railway induced ground vibration by heavy masses next to the track

Dijckmans

Coulier

Jiang

et al. 2015

Self Cite

The effectiveness of heavy masses next to the track as a measure for the reduction of railway induced ground vibration is investigated by means of numerical simulations. It is assumed that the heavy masses are placed in a continuous row along the track forming a wall. Such a continuous wall could be built as a gabion wall and also used as a noise barrier. Since the performance of mitigation measures on the transmission path strongly depends on local ground conditions, a parametric study is performed for a range of possible designs in a set of different ground types. A two-and-a-half dimensional coupled finite element -boundary element methodology is used, assuming that the geometry of the problem is uniform in the direction along the track. It is found that the heavy masses start to be effective above the mass-spring resonance frequency which is determined by the dynamic stiffness of the soil and the mass of the wall. At frequencies above this resonance frequency, masses at the soil's surface hinder the propagation of surface waves. It is therefore beneficial to make the footprint of the masses as large and stiff as possible. For homogeneous soil conditions, the effectiveness is nearly independent of the distance behind the wall. In the case of a layered soil with a soft top layer, the vibration reduction strongly decreases with increasing distance from the wall.