The problem of structural isolation from ground transmitted vibrations by open or infilled trenches under conditions of plane strain is numerically studied. The soil medium is assumed to be linear elastic or viscoelastic, homogeneous and isotropic. Horizontally propagating Rayleigh waves or waves generated by the motion of a rigid foundation or by surface blasting are considered in this work. The formulation and solution of the problem is accomplished by the boundary element method in the frequency domain for harmonic disturbances or in conjunction with Laplace transform for transient disturbances. The proposed method, which requires a discretisation of only the trench perimeter, the soil-foundation interface and some portion of the free soil surface on either side of the trench appears to be better than either finite element or finite difference techniques. Some parametric studies are also conducted to assess the importance of the various geometrical, material and dynamic input parameters and provide useful guidelines to the design engineer.
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"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.
"Several studies have underlined the better vibration reduction capacity of open trenches than the filled ones     but, considering the limited application of the first ones, in the present paper, through the development of a Finite Element(FE) model that represents a straight section of an high speed railway, the influence of the filled trench extension and the type of in-filled material on the reduction of perceived vibrations has been investigated. The model validation was achieved through comparison with in-situ measurements results performed during a previous experimental research. "
[Show abstract][Hide abstract] ABSTRACT: The use of trenches as vibration mitigation action is widespread in many countries. The complexity of the intervention design process depends on the high number of parameters that influence its efficacy, such as trench geometry size (width, depth, length), section shape, used in-filled material, distance among source-trench-receiver and frequency content of the source. This paper focuses on the study of the mutual influence between trenches length and in-filled material type considering several fixed observation points. The analysis was realized using a finite element model that was calibrated through comparison with in-situ measurements, and the evaluation of the effectiveness of each configuration taken into account was performed calculating the amplitude reduction index Ar and analyzing the vibration attenuation capacity both in time and frequency domain. As found by several other authors, it was found that increasing trenches length, a better isolation effect is performed, but the improvement amount seems to be strongly influenced by the kind of material to be used to fill trenches. This aspect must be taken into account in the optimization process of vibration isolation actions performed using trenches.
Full-text · Article · Jan 2015 · Construction and Building Materials
"To decrease or eliminate the effects of vibration on infrastructures and facilities, two types of vibration isolation methods have been proposed, which are active vibration isolation and passive vibration isolation. Regarding the passive vibration isolation, open or filled trenches and piles are employed as wave barriers [Beskos et al., 1986; Liao and Sangrey, 1978]. Trenches are often used to isolate vibrations for shallow structures, while piles are much more widely utilized due to their capabilities to be exempted from the influence of high groundwater level and to enhance the capacity of ground simultaneously. "
[Show abstract][Hide abstract] ABSTRACT: The isolation of surface wave-induced vibration using periodically modulated piles in soil is investigated. We demonstrate through simulations the dependence of complete bandgaps on the lattice symmetries, geometric parameters of the piles and material properties of the soil. The simulated results suggest that the piles modulated with square and hexagonal lattices are much more favorable for the formation of complete bandgaps than those modulated with honeycomb lattice. The height of the piles also plays a significant role in governing the evolution of complete bandgaps. Besides, complete bandgaps can be tuned by tailoring the volume fraction of the piles and the geometries of the pile cross section. Our results indicate that the contrast in the Young's modulus and the density is vital for the evolution of complete bandgaps and the viscosity of the soil should be considered as well. The analysis of surface wave propagation in a finite number of piles confirms the simulated complete bandgaps and also reveals that the complete bandgaps stem from Bragg interferences. This paper not only demonstrates the promising application of periodically modulated piles as wave barriers but also provides design guidelines for civil engineers.
Full-text · Article · Aug 2014 · International Journal of Applied Mechanics