Publication Abstract

Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations, 2014, Stockholm, Sweden, (DFI)

New Method for Reduction of Settlement Drilling Casings for Steel Core Piles
Håkan Bredenberg, Bredenberg Teknik AB, Sweden; Rani Isa, BESAB AB, Sweden; Martin Jönsson, Atlas Copco Mining and Rock Excavation Technique, Sweden; Mats Larsson, Verctura, Sweden; Lars-Erik Larsson, Tyrens, Sweden

Steel Core Piles are used extensively in Scandinavian countries, where hard rock is found within reasonable depths. A steel core is cast into a drilled steel tube casing and a rock hole is extended below the casing. This pile type is considered a very reliable type of pile, and for urban environment it has several advantages compared to other types of piles. One critical phase of the installation is the drilling of the casing. Usually a DTH (Down The Hole) hammer is used. Drilling in fine grained soils, e g silt, below the ground water level, may give rise to an excessive volume of soil material flushed up from the point of the casing, resulting in unacceptable settlements around the pile installation area. Using a new method for drilling of the casings, the ELEMEX-method has proven to significantly reduce the risk for such problems. In the paper a case record from a ground improvement project in central Stockholm is described. Ground settlements around the drilling area were carefully monitored over a longer period. Both the new drilling method and the conventional DTH casing drilling method where used, so that the corresponding ground settlements could be compared. Settlement records and comments are included in the paper. The paper also gives a description of the project. The installation of new piles and foundation constructions cover a whole city block in Stockholm downtown. The reason for the replacement of the old, damaged wooden piles were due to their destruction caused by a long time lowering of the ground water table. The paper gives a description of the new drilling method as well as an overview of usual urban foundation issues and their solution in Sweden, Finland and Norway.

 article #1977; publication #100 (IC-2014)