ABSTRACT
This paper presents the design of a railway embankment composed of silts with steep slopes at 3H/2V, protected against imbibition by capillary barriers above the highest water level and beneath the subgrade layer, in order to consider suction in the design. This embankment configuration was developed as part of a competition for Lot G of the Grand Paris Express railway line. Possible failure modes were studied: skin failure due to imbibition and overall failure (embankment body and foundation). The paper demonstrates that capillary barriers ensure that, for overall failure, the most unfavorable calculation scenario is the end of construction. The tests to be included in a compaction study conducted to account for suction are presented: Proctor test with immediate bearing capacity index at 2 or 3 energies (at least Normal and Modified Proctor) and measurement of suction at all points; for densities and water contents encompassing the chosen compaction target from the Proctor test: double oedometer tests with measurement of initial and final suction; CD triaxial tests on saturated specimens. The saturation of ambient air, which creates an average suction at the soil surface, is taken into account in this approach. A stability analysis shows that for the retain compaction target stability is reached for 20 meters high fill with slope at 3H/2V and a berm each 10 meters.
