Deformation Behavior of Lime/Cement Column Stabilized Clay
Doctoral thesis, 2000
Deep stabilization of clay with lime/cement columns has lately become one of the most frequent methods for improvement of soft clays. The method is cost effective, as it results in a drastic reduction of settlement.
The theories used for design were originally developed for lime columns. Traditionally, a relatively simple method has been used to calculate the long-term and consolidation settlements occurring in lime/cement stabilized soil.
The objective of this study was to investigate the mechanical and hydraulic properties of lime/cement stabilized clay. Furthermore, the study was aimed at developing a settlement prediction method that takes into account the effect of the stiffness difference between the column and the surrounding soil on the rate of consolidation.
Three mathematical models are presented in this study, two of which are numerical and one is an analytical elastic model. In-situ field tests were carried out to determine the stiffness and the hydraulic conductivity of the treated soil at three sites.
It was shown that the rate of consolidation is accelerated as the stiffness ratio between the lime/cement column and the surrounding soil increases. Furthermore, the vertical stress in the untreated soil below the stabilized block can be evaluated by distributing the applied load from the ground surface using Boussinesq's elastic solution. It was also shown that the secant Young modulus, E50, evaluated from in-situ tests, is in general higher than that evaluated from unconfined compression tests. The hydraulic conductivity of the lime/cement columns is considerably lower than traditionally assumed in the calculation of rate of settlement.