P.V.D (Prefabricated Vertical Drain)
Prefabricated Vertical Drain (PVD) is a modern technique of installing a vertical drain of polyester for improving the soil properties to strengthen the soil in reclamation bed, coastal areas and marshy area where soft clay is encountered at much more depth. Installation of PVD and placing a calculated amount of surcharge fill causes the subsoil to consolidate as per ¡°Terzhaghi¡¯s Theory of Consolidation¡±. In natural consolidation with application of surcharge fill alone,it may take more than 50 to 90 years and even much more depending upon soil condition to achieve 90% consolidation where as the bed treated with PVD with surcharge fill accelerates the process of consolidation to attain the maximumsettlement within short period of time. The process involves installation of prefabricated drain in the week soil and application of calculated surcharge load to squeeze out the water through the inserted drains during the waiting period.
Application of method
- Increase water permeability to accelerate drainage and thereby accelerate foundation settlements
- Due to accelerated dissipation of excess pore pressures, increase shear strength and thereby improve bearing capacity . This allows for example a faster application of fill stages to embankment fills over clayey soils
Advantages of PVD
- PVD is relatively cheaper than Sand Drains.
- Fast Installation Method of PVD helps to reduce the time of Completion
Working Capacityg
- Normal working amount : around 20,000meter per day (N Value : under 10)
- Pre-boring is necessary, if N value is over 10
- Working amount is influenced by the operator¡¯s skill and ground condition.
