The isolation of structures from ground transmitted waves by open and infilled trenches in a three-dimensional context is numerically studied. The soil medium is assumed to be elastic or viscoelastic, homogeneous and isotropic. Waves generated by the harmonic motion of a surface rigid machine foundation are considered in this work. The formulation and solution of the problem is accomplished by the boundary element method in the frequency domain. The infinite space fundamental solution is used requiring discretization of the trench surface, the soil-foundation interface and some portion of the free soil surface. The proposed methodology is first tested for accuracy by solving three characteristic wave propagation problems with known solutions and then applied to several vibration isolation problems involving open and concrete infilled trenches. Three-dimensional graphic displays of the surface displacement pattern around the trenches are also presented.
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"Trenches can be installed in different form like open or infilled trenches (Woods, 1968; Richart et al., 1970; Segol et al., 1978; Haupt, 1981; Beskos et al., 1986; Dasgupta et al., 1990; Ahmad and Al-Hussaini, 1991; Saikia and Das, 2014) rows of piles (Liao and Sangrey, 1978; Kattis et al., 1999; Tsai et al., 2008), gas membranes (Massarsch, 2005). However, the usage of EPS geofoam as in-filled trench material in vibration screening technique is limited (Wang et al., 2006; Alzawi and El Naggar, 2009; Murillo et al., 2009). "
[Show abstract][Hide abstract] ABSTRACT: The application of open as well as in-filled trenches as vibration screening technique has been considered in several situations.
However, very few works have included the Expanded Polystyrene (EPS) geofoam as an in-filled material for the trench. The current
study focuses on the effectiveness of the intermittent geofoam in-filled trench as vibration barrier in presence of machine induced
ground vibration, where the geofoam blocks and the open air pockets are arranged alternately to form an effective vibration screening
material. The screening efficiency of the geofoam in-filled trench is determined in terms of Amplitude Reduction Factor (ARF). The
effect of the soil non-linearity under the propagating waves is also emphasized in the present study. Hyperbolic non-linear elastic
Duncan and Chang (1970) soil model has been implemented in time domain finite element analysis. A parametric study is performed
considering the geometric parameters of trench, excitation frequency, and stiffness of the soil.
Full-text · Article · Nov 2015 · KSCE Journal of Civil Engineering
"L'uso di trincee assorbenti come sistema di mitigazione delle vibrazioni ferroviarie è diffuso in molti Paesi e pertanto diversi autori hanno studiato l'efficacia di tali elementi    in diverse condizioni di impiego, quali ad esempio differenti tipologie di terreni e caratteristiche della sorgente. I principali aspetti da definire per l'utilizzo delle barriere assorbenti, riguardano soprattutto il loro dimensionamento, con particolare attenzione alla scelta della larghezza e della profondità , e la loro posizione in relazione alla sorgente ed al ricevitore. "
[Show abstract][Hide abstract] ABSTRACT: The use of trenches as railway vibration mitigation system is spread out in many countries. The design process complexity of the intervention depends by several parameters that can influence its efficacy, in particular, the main ones are: the geometric dimensions (length, width, depth); the section shape; the in-filled material and the distance between source, trench and receiver. This paper deals with the mutual influence between the length of the trenches and the type of filled material used. The analysis is realized using an FE model, previously calibrated through a comparison with in-situ measurements. The effectiveness of each tested configuration is assessed calculating the amplitude reduction ratio Ar, and analyzing the attenuation capacity both in time and frequency domain. In agreement with the results of other studies, it is found that increasing the length of the trenches, an improvement of the mitigation effect is obtained, but this improvement seems to be strongly influenced by the in-filled material type used.
L'uso di trincee assorbenti come sistema di mitigazione delle vibrazioni ferroviarie è diffuso in molti Paesi. La complessità del processo di progettazione dell'intervento dipende dal numero di parametri che influenzano la sua efficacia, tra cui in particolare: la dimensione geometrica (larghezza, profondità, lunghezza); la forma della sezione; il tipo di materiale utilizzato per il riempimento; la distanza tra sorgente, trincea e ricevitore. Questo articolo tratta dell'influenza reciproca tra la lunghezza delle trincee e il tipo di materiale di riempimento utilizzato. L'analisi è stata sviluppata utilizzando un modello EF, precedentemente calibrato attraverso il confronto con misurazioni in-situ. L'efficacia delle diverse configurazioni considerate , è stata valutata mediante il calcolo dell'indice di riduzione dell'ampiezza Ar e analizzando la capacità di attenuazione delle vibrazioni sia nel dominio del tempo sia nel dominio della frequenza. In accordo con quanto osservato da altri ricercatori, si è riconosciuto che, aumentando la lunghezza delle trincee, si ottiene un migliore effetto di isolamento, ma tale miglioramento sembra essere fortemente influenzato dal tipo di materiale usato per il riempimento.
"The numerical techniques including finite element method (FEM) and boundary element method (BEM) have been widely used to understand the isolation mechanism of wave barriers. Beskos et al. , Al-Hussaini , Kattis et al. , Tsai and Chang , Wang et al , Zoccali et al. , Saikia and Das  employed numerical methods in order to evaluate the effect of both geometrical properties and type of wave barriers on screening performance. They concluded that open trenches provided better performance for vibration isolation compared to in-filled trenches. "
[Show abstract][Hide abstract] ABSTRACT: The isolation of ground-borne vibrations caused by heavy traffic, construction activities and railway transportation has gained importance in recent years with rapid urbanization. Open or in-filled trenches have commonly been used as wave barriers in reducing unwanted vibrations. There only few experimental data concerning the effects of frequency of excitation, soil layering, material type and dimensions of the wave barrier on vibration control and isolation. In the present study, a series of full scale field experiments were conducted in order to investigate the screening efficiency of open, water filled and geofoam filled trenches. The attenuation of ground borne vibration was examined to determine the effects of frequency, distance and complex behavior of layering and irregular geometry of soil profile. Moreover, the results obtained from the experimental tests were compared with the numerical and experimental findings available in literature. Consequently, the field tests confirmed that the geofoam filled trench can be used as an efficient isolation system for reducing the transmission of ground-borne vibrations.
Full-text · Article · Jul 2015 · Construction and Building Materials