Estimation of embankment settlement caused by deterioration of soft rock grains

Embankments made from crushed soft rock grains can be susceptible to additional settlement caused by a deterioration of the grains inside the embankment. This additional settlement is not caused by the change of the stress state inside the embankment and cannot be predicted by standard calculating methods using the embankment modulus of deformability measured after compaction of the embankment. The deterioration of the grains is mainly caused by the weathering process, which, in soft rocks such as marl, is mainly induced by the wetting and drying processes. If marl grains in an embankment are subjected to the wetting and drying process, the result is breakage of the grains, as well as decomposition into soil material. Disintegrated material then fills the macro-pores of the embankment grain structure and gradually causes additional settlement. This process in soft rock material lasts from a few months to a few years. We propose a calculation procedure to estimate the possible value of the additional settlement, based on measured settlements gained from examples of laboratory-weathered samples. The samples were made of crushed marl in laboratory conditions. A test was conducted with a modified oedometer apparatus. In the proposed model, the deformation is calculated based on possible volume changes due to the deterioration of the grains and transport of the detached material into the macro-pores; this is done with the intention of estimating the settlement without measuring the deformation modulus change caused by the weathering.