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This paper explores the stabilisation of dredged lakebed sediments with ordinary portland cement and fly ash to repurpose the sediment as road pavement construction material. Data are obtained from previous studies on sediments collected from Phayao Lake and Huai Mae Phong Reservoir in Phayao province, and Mae Sab Reservoir in Chiang Mai province in Thailand. Empirical correlations are established between strength and stiffness parameters of the chemically stabilised dredged sediments intended for transportation and geotechnical applications. The strength and stiffness parameters considered in this study include unconfined compressive strength, the California bearing ratio, and the resilient modulus. The influence of curing period on strength development is determined. New strength and stiffness correlations are proposed and presented to describe stabilised soils based on the extensive experimental data. Optimised sediment/cement/fly ash mixtures which proved to be most effective in generating appropriated material strengths for road construction are reported.

Recently, random field copulas have been deployed to characterise the dependent structures of spatially variable soil parameters. This study expands on this concept by implementing finite element limit analysis (FELA) with adaptive meshing alongside the copula approach to perform reliability assessment of a geotechnical problem. A hypothetical slope with drained and undrained soil conditions was used as an example. First, adaptive FELA was carried out on the hypothetical slope. Second, single and multiple dependency soil parameter structures were represented by several selected copulas (Gaussian, Frank and Clayton). Finally, random adaptive FELA was implemented to explore the effects of copula selection on slope stability and reliability analyses. Results show that considerably different slope failure probabilities are produced by different copula approaches, and that failure probabilities reduce for simulating multiple dependency structures. In addition, failure probability exhibits different tendencies between drained and undrained soil conditions as soil parameter crosscorrelations become stronger. Failure probabilities are also different when performing lower and upper bound (UB) random adaptive FELA with each of the selected copulas.

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