Analysis on the efficiency of water collection and drainage according to different installing methods of prefabricated horizontal drain (PHD) in ground improvement works

Soil improvement using PVD (Prefabricated Vertical Drain) is the most frequently used and very common dewatering method in large-scaled soil improvement works. Usually, sand or gravel blanket is used in order to discharge the pore water, drained from PVD. However, securing good quality natural materials is getting more difficult, because collecting natural materials causes serious environmental de-struction, and rapid increase in demand causes jump in prices. This is the reasons that Prefabricated Hori-zontal Drains (PHDs) are being increasingly preferred to replace natural materials.
The common installation of PHD is done by aligning PHD with pre-installed PVDs stapled together with PVD on top. But when PVD is stapled on top of PHD, the pore water from PVD could be lost while it is going into the drainage channel of PHD from PVD. This loss of pore water could cause the delay of dis-charge, which consequently would cause the delay of settlement. This problem must be improved.
In this paper, the efficiency of water collection and drainage will be studied and analyzed with compar-ing different connecting methods of PVD with PHD. And based on this analysis, the ideal method and structure of PHD will be suggested.