Vibration isolation using open or filled trenches Part 2: 3-D homogeneous soil
University of PatrasComputational Mechanics (Impact Factor: 2.53). 02/1990; 6(2):129-142. DOI: 10.1007/BF00350518
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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[Show abstract] [Hide abstract] ABSTRACT: Reduction in traffic-induced ground vibrations by the use of barriers is investigated. The traffic load characteristics were measured for motorway traffic. The effects of parameters on various types of barriers were examined by the use of a finite element model that was calibrated to green-field measurements. The model involved a layered soil and bedrock. The depth of a trench and the elastic modulus of a solid back-fill material were found to be the most important parameters to consider. In investigation of the effects of infiltration of water into an open trench, a coupled finite element formulation of the water and the soil was applied. Infiltration of water was found to decrease the achieved reduction. At long distances from the vibration source, of around 500 m and longer, amplification in vibration level can be seen when a trench has been installed. It was also found, at long distances, that the motion of the ground surface follows the motion of the bedrock.
- "Hence, for higher frequencies the achieved reduction may be different. It should be noted that in other publications , such as [7,8,22,25], a stiff barrier has been shown to be beneficial to install. For the analyses presented in the present paper, varying the elastic modulus to a value larger than that of the top soil layer has only a slight effect on the reduction in the vibration level. "
[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.
- "The effect of such unwanted ground vibrations on the surrounding structures can be minimized by adopting various techniques such as changing the position of the source from the affected area, modifying the attenuation characteristics of the soil, using wave barriers, or using some damping devices in the form of base isolation (Celebi et al., 2009). However, properly designed active wave barriers like trenches can reduce such machine induced vibrations significantly as well as economically since the frequency associated with the machine foundations is generally not very large as compared to other vibrating sources like earthquake (Kumar and Ghosh, 2006), blasting etc. 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). "
- "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. "
Conference Paper: Capacità di mitigazione delle vibrazioni ferroviarie delle trincee piene[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.