Prefabricated horizontal drains (PHD) exhibit lots of priority against vertical drains in treatment of high moisture slurry. However, recent research reported a significant dewatering rate saltation (DRS) problem in PHD-treated slurry, and theoretical explanation and quantitative analysis are lacking. This research first reanalyzed the recently reported tests of PHD-and flocculant-treated slurry, where the DRS problem was studied through water discharge rate and soil-water height difference (Δh). Then, a 1D consolidation solution was proposed considering vacuum boundary and critical flow gradient. Relationship between consolidation time and height of the forward flow line was established to predict the vacuum transmission in the model test. In addition, the proposed method was used to back-analyze the time when the DRS occurs. Last, with assumed critical gradient and consolidation coefficient considering the flocculation effect, the DRS problem was theoretically investigated for different cases and the predicted results are reasonable compared with the test data.

Soft foundations of high embankments exhibit significant time-dependent effect on deformation in decades after construction, and there is a lack of simple method for predicting the creep rate of over-consolidated soft clay under plain strain condition. In this paper, laboratory creep tests under plain strain consolidation with different principal stress ratio were shown. The variation of stress in zero strain direction (σ y ) under different degree of consolidation was analysed. Linear relationship between (σ y ) and the applied principal stress σ x (or σ z ) was found. And then, the creep rate of volumetric strain (C α ) and vertical strain (β) were calculated and linked to volumetric stress defined ratio of over-consolidation (OCR p ) and stress ratio (K). Finally, the new parameter K•OCR p was found to have a good correlation with the creep rate (C α or β).

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