Application of Nanofiber to Enhance the Anti-Clogging property of Prefabricated Vertical Drainage (PVD)

Prefabricated vertical drains (PVD) are one kind of geotextile filter for the consolidation of soft soil before the building of structure. This consists of a plastic core with grooves on both sides along its length, surrounded by a geotextile filter. The formed groove acts as water channel even at large lateral pressure whereas, surrounded geotextile filter maintain the hydraulic capacity of the grooves preventing clogging by soil intrusion. When the pore size of surrounding filter is larger than the fine soil particle, internal water flow paths of PVD gets clogged by fine soil particles under lateral soil pressure. Intrusion of many fines could reduce the PVD discharge capacity and increase the filter resistance. This filter jacket with appropriate pore size can be used to prevent the clogging and maintain the hydraulic capacity of the grooves. To achieve the appropriate small pore size, thin nanofibrous membrane has been deposited on spun bond nonwoven filter jacket membrane using needle less electrospinning system. During electro spinning, parameters were optimized to get uniform bead less nanofiber layer with required diameter. Further, thickness of nanofiber mat was standardized to keep the pore size less than the soil particle size present in the marshy land soil. Anti-clogging property and water permeability of the membrane with nanofiber layer were investigated after continuous use for a long time in presence of soil. Results showed that use of nanofiber membrane rather than only nonwoven membrane, significantly improves anti-clogging property and maintain constant water flow. The intrusion of soil particles in the membrane pores has been observed by Scanning Electron Microscope (SEM) after use.