Abstract

In geotechnical and road engineering, it is quite common to encounter ground represented by a layered system consisting of a thin upper subgrade layer overlaying a deep natural soil deposit. Structures built on such type of ground usually experience low bearing capacity and, consequently, large settlement. In order to achieve better results, the subgrade layer is compacted using the conventional techniques. The level of the densification achieved is influenced not only by the compacting effort applied on soil surface, but also by the strength of the underlying soil deposit. In the literature, several reports can be found dealing with the subject matter. The majority of these reports have ignored the contribution of underlying soil on the compression of the upper thin layer. The objective of this thesis is to develop a numerical model using the finite element technique, to examine the compression of a thin subgrade layer overlying a deep deposit. In this model all the parameters believed to govern the compression of the subgrade layer will be incorporated. The compression of the subgrade layer under various applied loads will be evaluated. The results are presented in the form of charts and tables in order to determine the total settlement of the foundation and the compression of the upper layer. Empirical formula is proposed to predict the compression of the upper subgrade layer for practicing use.

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