SuperPile 2017 Online Proceedings, (DFI)
Construction risks associated with drilled displacement columns
Martin D. Larisch, Ph.D.
Drilled displacement columns (DDC) are used for the improvement of soft or loose soil formations where a closely spaced array of concrete columns is installed to reduce settlements and increase stability. Over the past decade, the DDC method has been used with great success all over the world, allowing embankments and structures to be constructed efficiently in poor ground conditions without the creation of spoil. However, there are different ways of designing DDCs and some uncertainties exist regarding which approach to adopt. Installation effects of DDCs are often not understood and therefore not incorporated into designs, which can add significant risk to projects. The construction of DDCs also bears some significant risks and especially ground heave and lateral displacements caused by the installation effects of DDCs adjacent to structures or freshly installed columns is not uncommon and often causes issues with cracked concrete shafts or necking. This raises concerns about the subsequent performance of the columns if the wrong construction sequences and methodologies were adopted. A discussion about the fundamentals of DDC design and construction methods are presented in this paper. Several case studies, based on the authorís personal experience, are included in this document, describing examples of the design, construction and subsequent performance of embankments and structures constructed on DDCs in Australia and Europe over the past decade.
|article #2663; publication #1031 (SP-2017)|