Heave Analysis of Unreinforced Inclusion Column in Low Sensitivity Soft Clay

Abstract

The ground improvement technique with inclusions, is now widely available and used in Indonesia. Typically, it uses unreinforced concrete/mortar columns, commonly referred as rigid inclusions, for enhancing the composite ground engineering properties. Using this approach, the applied load will be distributed to both the rigid inclusions and in-situ soft soil. On the surface, this technique is analogue to compression-only cast-in-situ deep foundation element (i.e., bored pile), but with different design concept. Nonetheless, when these inclusions are installed in clay soil, either with displacement or semi-displacement method, the installed inclusions may experience heave (similar like driven pile), which is caused by ground deformation in the vicinity of installed inclusions. As these inclusions are not reinforced, mobilizing upward skin friction from excessive heave may develop into an integrity issue, specifically, when the mobilized upward force is larger than the inclusion tensile capacity. This study shows an observed heave on unreinforced inclusion columns. Retrospective soil heave prediction using shallow strain path method (SSPM), is presented. Proposed recommendations for avoiding such issue are discussed.