Collapsibility in Calcareous Clayey Loess: A Factor of Stress-Hydraulic History

Abstract

ABSTRACT:The re-use of excavated loess in embankments needs a good understanding of its long-term mechanical response. Among the many collapse controlling factors, stress and hydraulic history are of significant importance as certain combination of these can alter the packing state to great extents. However, published works on stress path-packing state interaction is limited to clayey silts, underreporting the contribution of carbonates. Works on hydraulic path-packing state interaction lacks physical evidences for pore distribution, leading to disputes over the variation of air-volume over time and therefore fills' long-term behaviour. Identical artificial loess specimens were incrementally stressed on dry-, wet-, and wetting-surfaces, while microfabric, suction, particle and pore size distribution were recorded. The response of test material (moderately calcareous lightly clayey silt) showed the failure of dry-compaction in restricting the coefficient of consolidation. Wetting at any stress level improved the pore volumes and thus post-drying collapsibility. However, pre-loading to 25kPa before flooding provided the maximum degree of densification. Water-retention properties were deemed reproducible upon wetting-drying seasons for minimum content of 5-20µm size loess constituents. In short, controlled stress-hydraulic paths can guarantee the long-term response of site-won loess embankments.

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