ABSTRACT

A crushed quartzitic slate, used in previous investigations on rockfill behavior, was tested to study the effects of the previous loading and the hydraulic history on material delayed deformations. Typical tests involved loading-unloading samples at constant relative humidity-or total suctionand at different OCRs, as well as soaking-drying paths at constant and elevated stress, which were performed in special large diameter oedometer cells (300 mm in diameter). A finding is that preloading the crushed slate at increasing OCRs leads to the progressive vanishing of creep deformations, following a behavioral response similar to soils. An equivalent response was observed at overconsolidated states after the soaking-drying paths. The reduction has practical applications, since the long term settlements of rockfill materials could be controlled by pre-compression and pre-soaking technique at elevated stress. If at each point of the rockfill embankment an OCR = 1.1 is ensured by pre-loading, a reduction to 22% of the normally consolidated long-term settlement would be expected.