An experimental study on discharge capacity for prefabricated horizontal drains

Discharge capacity test is carried out to find out influencing factors on discharge capacity of prefabricated horizontal drains (PHD) to improve weak dredged clay. Six representative PHD are selected based on the size of drain as well as the shape of core. Test is carried out for 10 days at each three level of confining pressure for all drains. Effects of elapsed time, confining pressure, hydraulic gradient and strength of filter and core on discharge capacities are examined. It is found that discharge capacity of drain, which has deformable core or has a possibility of squeezing filter into core, decreases more with time due to its low strength. As confining pressure increases, discharge capacity decreases due to squeezing filter into core. To verify the compatibility of the selected drains in the field, the test results are compared with the required discharge capacities proposed for assumed field conditions. Type-E drain, which has low strength of core, does not satisfy the required discharge capacity at given hydraulic gradients. All other drains satisfy the proposed criteria.