Experimental tests on effect of deformed prefabricated vertical drains in dredged soil on consolidation via vacuum preloading

Abstract

This study carried out an investigation into the performance of PVDs embedded in dredged soil. A new type of integrated PVDs (NPVDs), in which the filter is adhered to the core by heat melting to form an integrated body, was tested. A variety of deformation patterns were designed for the NPVDs, including straight form, natural form, S-shaped bending deformation, zigzag kinking deformation, and Z-shaped folding deformation. Vacuum-preloading tests rather than the conventional discharge capacity test were carried out to examine the effectiveness of vacuum preloading. For comparison, tests on conventional PVDs (CPVDs) in natural form were also conducted under the same test conditions. It is found that the distribution of vacuum pressure along the drain length was as a bilinear relationship after taking into account the deformation of PVDs. The Z-shaped deformation of PVDs imposed significant detrimental effects on the effectiveness of vacuum preloading. Nevertheless, the effects of the S-shaped deformation of PVDs on the effectiveness of vacuum preloading were not prominent. The deformation of the natural-from NPVDs was close to the S-shaped form; while the deformation of the natural-from CPVDs was close to the Z-shaped form. Therefore, the NPVDs possess superior performance than the CPVDs in improving dredged soil