Doctor of Philosophy
Civil and Environmental Engineering
M. Hesham El Naggar
A significant amount of numerical and experimental research has been conducted to study the vibration isolation by wave barriers considering open trenches, in-filled concrete or bentonite trenches, sheet-pile walls, and rows of piles. A few studies have investigated the use of expanded polystyrene (EPS) geofoam material as wave barriers, which indicated that in-filled geofoam trenches can be used as effective wave barriers. However, no engineering design method is available to date for the design of such type of wave barriers. This dissertation presents comprehensive experimental and numerical investigations on the use of in-filled geofoam trench barriers to scatter machine foundations vibration, in order to provide some recommendations and design guidelines for their implementation in design.
Two- and three-dimensional time-domain finite element models have been developed utilizing the finite element package ABAQUS. The numerical models have been verified and then used to study the effectiveness of different configurations of in-filled geofoam wave barriers. All the proposed configurations performed well in scattering surface waves. However, the single-continuous wall system was considered to be more economic and practical alternative for wave scattering.
Based on the findings of the preliminary numerical investigations, a full scale field experimental study has been conducted to investigate the performance of in-filled geofoam trenches. An innovative approach to construct geofoam trenches involving hydro-dig technology was utilized. A series of experimental tests have been conducted to evaluate the performance of both open and in-filled geofoam trench barriers considering their geometry and distance from the source of disturbance. The results of the field experimental investigations were analyzed and interpreted to provide recommendations for implementation in design. Experimental results confirmed that in-filled geofoam trench barriers can effectively reduce the transmitted vibrations and its protective effectiveness is comparable to the open trench barrier.
An extensive numerical parametric study was conducted to investigate the behaviour of in-filled geofoam wave barrier under different soil conditions and to point out the key parameters that dominate the performance of in-filled geofoam trench barriers. The influence of various key parameters on the screening performance were carefully analyzed and discussed. A model using Multiple Linear Regression (MLR) analysis was developed for design purpose. Finally, an artificial neural network (ANN) model has been developed, which aims at extrapolating the parametric study results to predict the in-filled geofoam wave barrier protective effectiveness in different soil profiles with different geometric dimensions.
Alzawi, Ashref Mohamed A., "Vibration Isolation Using In-filled Geofoam Trench Barriers" (2011). Electronic Thesis and Dissertation Repository. 265.