Comparison between the Behaviour of Coated and Uncoated Lightly Loaded Piles in Swelling Soils

In the last four decades significant effort has been devoted to designing piles in swelling soils. Nevertheless, only a scant effort has been devoted to the elimination of heave forces acting on the upper part of lightly loaded piles. For this purpose, an investigation site was established in Karmiel in Northern Israel. On this site sixteen unloaded cast-in-situ piles, both uncoated and coated, were installed in a moderately expansive clay soil in the end of summer 1996. The piles were executed to different depths ranging between 2.0 m and 7.0 m and were observed over a period of 27 months. Another nine unloaded cast-in-situ bored piles, both coated and uncoated, were installed at the end of summer 1998 for carrying out pullout tests. These piles were embedded two meters from the ground surface. Results obtained from observations and from full-scale static pull out tests showed that separating the piles from the surrounding clay in the active zone by a twin walled plastic sleeve eliminated the heave forces significantly. The scope of the work is, determining of the elimination degree of the heave forces due to the provision of the above sleeve.