Numerical investigations on vibration screening by in-filled geofoam trenches

Ashref Alzawi, M. Hesham El Naggar

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Shallow Foundations

ABSTRACT: In-filled concrete and bentonite trenches have been used in practice for many years as wave barriers to control the transmitted surface steady-state ground vibration induced by machine foundations. On the other hand, experimental investigations conducted by the authors showed that in-filled geofoam trenches can be used as an effective wave barrier to reduce the transmitted surface waves. In this paper, numerical models were developed to further investigate the effectiveness of geofoam trenches as wave barriers. The developed numerical models have been verified by comparing the numerical results with those obtained from the field experiments and a favourable agreement was observed. A comprehensive parametric study has been performed to examine the influence of various geometrical and material parameters on the protective effectiveness of geofoam trenches as wave barriers. The results are analyzed, interpreted and some guidelines regarding the design of geofoam wave barriers are outlined.

RÉSUMÉ: En béton rempli et tranchées de bentonite ont été utilisés dans la pratique depuis de nombreuses années comme des obstacles à la vague de la surface de contrôle transmis vibrations du sol l'état d'équilibre induite par des fondations de la machine. D'autre part, des études expérimentales menées par les auteurs ont montré que les tranchées geofoam en-rempli peut être utilisé comme une barrière d'onde efficace pour réduire la transmission des ondes de surface. Dans cet article, les modèles numériques ont été développées pour étudier plus avant l'efficacité des tranchées geofoam que les obstacles d'onde. Les modèles développés numériques ont été vérifiées par la comparaison des résultats numériques avec ceux obtenus à partir des expériences de terrain et un accord favorable a été observée. Une étude paramétrique exhaustive a été réalisée pour examiner l'influence de divers paramètres géométriques et des matériaux sur l'efficacité de protection de tranchées geofoam que les obstacles d'onde. Les résultats sont analysés, interprétés et des lignes directrices concernant la conception des écrans d 'ondes geofoam sont décrites. 1. INTRODUCTION The use of geofoam material in vibration wave screening has been the focus of a few studies. Davies (1994) carried out a series of 20-g centrifuge tests to explore the screening effect of the expanded polystyrene (EPS) wall, concrete wall and their composites on adjacent buried structures. The centrifuge test results indicated that barriers containing low acoustic materials were highly effective in the attenuation of stress wave propagation. Wang (2008) has conducted numerical investigations on the performance of EPS geofoam barriers to protect buried structures against the effect of blast-induced ground shock. An open trench, an inundated water trench, three in-filled geofoam walls with different densities, and a concrete wall have been included in the numerical simulation. The numerical model simulated the prototype dimensions of a centrifuge test carried out by Davies (1994). Based on the numerical model findings, the geofoam barriers were found to significantly reduce the blast-induced stress waves. Moreover, Wang (2008) noted that the geofoam barrier is considered to provide flexibility in design that can be easily and efficiently implemented in the field. However, it should be noted that vibration sources in the above-mentioned two studies were blast-induced ground shock. Murillo et al. (2009) performed centrifuge tests to simulate the traffic vibration and investigate the effectiveness of EPS barriers in scattering this type of ground borne vibrations. The centrifuge tests involved a parametric study to examine the EPS barriers performance in terms of the barrier dimensionless geometry and its distance from the source of disturbance. The results showed that the barrier performance depends mainly on its depth and location from the vibratory source. Also, it was concluded that the barrier width had a minor influence in the case of deeper barriers. On the other hand, a remarkable influence of the barrier width was observed for the case of shallow barriers. The above mentioned studies demonstrated that geofoam wave barriers can be used as an effective tool to screen ground-borne vibrations, and that geofoam polymers provide an attractive construction material for these barriers. Alzawi and El Naggar (2009) conducted a comprehensive parametric study to investigate, numerically, the behavior and effectiveness of the geofoam material under periodic harmonic loadings as active and passive wave barriers in the form of box-wall, single-continuous wall, double-continuous and double-staggered wall systems. The finite element method (FEM) has been adopted as a numerical tool to simulate the problem of wave propagation in soil medium. The results showed that all the proposed configurations performed well in scattering the surface waves; however, the single-continuous wall system was considered the economic and practical alternative for wave scattering. Alzawi and El Naggar (2011) investigated, in a field study, the constructability of a single-continuous wall

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Ashref Alzawi; M. Hesham El Naggar (2011) Numerical investigations on vibration screening by in-filled geofoam trenches in GEO2011. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GEO11Paper549,author = Ashref Alzawi; M. Hesham El Naggar ,title = Numerical investigations on vibration screening by in-filled geofoam trenches,year = 2011}