Correlation of Soil Parameters and Bearing Capacity Analysis of Piled Raft Foundation for Dhaka - Chittagong Elevated Expressway

Abstract

Determination of soil parameters is one of the important tasks in geotechnical engineering. Sometimes, in many projects only basic soil parameters such as index properties of soils are determined through laboratory tests. In such cases, correlations of soil parameters available in literature are used in getting the other necessary soil parameters. In many soils, parameters determined by using available correlations significantly differ from the test results. In this research the validity of the correlations of soil parameters available in literature has been checked for the ground where Dhaka-Chittagong expressway will be constructed. Here, the correlation of compression index (Cc) which is an important soil parameter for clayey soils is taken into consideration. There are many empirical formulae that relate compression index to other soil parameters such as void ratio (e0), liquid limit (LL), natural water content (wn) and many others. Several different tests have been carried out to determine compression index (Cc), void ratio (e0), liquid limit (LL), and natural water content (wn). It is found the available correlations of the compression index cannot properly express the test results for the ground investigated in this research. Therefore, three correlations for soil parameters relating compression index and liquid limit, compression index and void ratio, compression index and natural water content have been proposed in this study. Elastoplastic constitutive model parameter identification is an important task

for proper modeling of any soil. In this research, subsoil characteristics of study locations are presented based on field and laboratory test results. Elasto-plastic constitutive model parameters of study locations soil has been determined for extended sub-loading tij model. Using these parameters, bearing capacity of piled raft has been estimated for 0.05% settlement of soil section. Considering the effect of settlement in 2D Finite Element analysis have been conducted. It is found that bearing capacity determined by the conventional methods match well with the results of the numerical simulations.