Dewatering Rate Saltation Problem in PHD-Treated Slurry and a Theoretical Explanation

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 (Δ h ). 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.