Field Study on the Vacuum Preloading of Dredged Slurry with Wheat Straw Drainage: Fid-Bau Portal

Field Study on the Vacuum Preloading of Dredged Slurry with Wheat Straw Drainage

Liu, Chao / Xu, Guizhong / Xu, Bing

Abstract In this paper, a new shallow reinforcement technique for dredged fill was proposed. In which wheat straw was used as vertical and horizontal drains in lieu of materials applied in the traditional vacuum preloading method. This was not only helpful to avoid permanent environmental damage caused by prefabricated vertical drains but also helpful to relieve the sand shortage and handle the problem triggered by noncontinuous sand cushion layer. On the other hand, this proposal was able to reduce the side effect to the environment triggered by improper handling method on agricultural associated waste greatly, for instance incineration and disposal. Based on prior indoor experimental findings, the feasibility and suitability of the vacuum drainage system composed by straw roller and straw blanket through field test was verified. After doing the comparison between new reinforcement technique and traditional method, it has been found that both the straw blanket and sand cushion performed good in vacuum transmission. Secondly, the vacuum degree of straw roller and prefabricated vertical drains decayed gradually along the depth, but the vacuum attenuation rate of straw roller was slightly smaller than PVD. Thirdly, the performance on the settlement, water content of reinforced soil and undrained shear strength of dredged fill obtained from new reinforcement technique were similar with that generated from traditional vacuum preloading method. Besides, as an agricultural associated waste, the wheat straw had great advantage on financial benefit. Most importantly, unlike PVD, this material is eco-friendly and degradable. Based on these findings, it was suggested that the new reinforcement technique is worth popularizing in real engineering projects.