Application of Bayesian settlement prediction with creep on a high embankment on stabilised soft soil

Norwegian Geotechnical Insitute, Oslo, Norway

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Abstract

The Norwegian Public Roads Administration requires that future settlements of a road be less than 40 cm after its opening. This in turn requires a proper settlement prediction analysis. For road embankments on sensitive clay, material properties may be improved either by lime-cement columns, pre-fabricated vertical drains or both. The soil improvement alters the coefficient of consolidation, and as such, physics-based deterministic modelling of the settlement development is difficult. Continuous assessment of the settlements under an embankment on improved sensitive clays showed that the physics-based models underestimated the final total settlements. In his paper on an observational auto-regressive method, Asaoka included two extensions to the proposed method: a) creep effects and b) a Bayesian approach to the regression, which will output a probabilistic distribution instead of a point estimate. However, he did not include a combination of creep and Bayesian approach. The main benefit of a Bayesian model is that it allows for a probabilistic assessment of whether the final settlements will exceed a given threshold. This work extends the original work by Asaoka by including secondary settlements (creep) to the Bayesian auto-regressive method for improving settlement predictions to be used in practice where soil consolidation properties are altered or otherwise unknown.