Estimating strength of stabilized dredged fill using multivariate normal model

Abstract

Various empirical equations have been proposed to estimate the unconfined compressive strength (qu) of cement-treated soils based on the proportions of water, cement, and clay or based on measured early strength. Most equations provide only a point estimate of qu and no measure of uncertainties associated with the estimation. As the design's safety level is governed by the uncertainties involved, it is essential to quantify uncertainties associated with the estimation. The coefficient of variation (COV) is taken as a measure of uncertainties. It is straightforward to estimate the mean and COV of qu based on a single parameter. Similar estimation based on multiple parameters, which may be intercorrelated, is not as straightforward. This paper aims to integrate multiple parameters (water-to-cement ratio, cement content, and 7-day strength) that may contribute to the estimation of 91-day strength using a multivariate normal distribution. The multivariate normal model can be used to derive the mean, COV, and the 95% confidence interval of 91-day qu at given values of the governing parameters. This confidence interval provides richer information on qu than the single value provided by most empirical equations. Results show that incorporating more parameters in the estimation of qu reduces the bias and the COV; thus, a more accurate estimate is obtained. Data of stabilized dredged fill (SDF) from a real land reclamation project are used to demonstrate the approach. © 2013 American Society of Civil Engineers.