Settlement for Construction on Soft Clay Improved Using Floating Rigid Inclusions Considering the Installation Effect

Abstract

This paper presents a novel approach to predicting induced deformations in clay deposits that have been improved by a system of floating rigid inclusions. The improvement of clay deposits is a complex process that is governed by a wide range of factors, making it challenging to accurately predict the expected settlement. The proposed approach aims to address this issue by developing reliable and user-friendly charts that estimate the settlement improvement factor (N), which is defined as the ratio of settlement values after soil improvement to those before improvement. To achieve this objective, the paper employs the cavity expansion method to model the installation process of the rigid inclusions in soft clay formations. A comprehensive parametric study is conducted using numerical modeling to investigate the variation in the improvement factor for a 15.00m thick clay deposit, where inclusions may be stopped before penetrating the firm stratum below the considered soft deposits. The study considers the variation of the treated soil stiffness and the geometry of the rigid inclusion system. The analyses are performed for a case study of a zone loading test conducted at New Mansoura city in Egypt, using the finite element software (PLAXIS 3D). The comparison of settlement associated with loading both the improved and unimproved soils is conducted for each studied condition in the parametric study to determine the improvement factor (N). The findings of the study demonstrate that the rigid inclusions have a significant impact on reducing the settlement associated with construction on the improved soft clay. The achieved improvement factor varies between 2.31 and 8.23, with an average value of about 4.65. The paper's contributions are twofold. Firstly, it presents a reliable approach for predicting the induced deformations in clay deposits improved by a system of floating rigid inclusions. Secondly, it provides a straightforward tool for predicting the settlement values associated with construction on improved soft clay formations with rigid inclusions under different conditions. This tool can be used to improve the design and construction of infrastructure projects built on soft clay deposits, leading to more cost-effective and sustainable solutions.