Proceedings of DFI-India 2017: 7th Conference on Deep Foundation Technologies for Infrastructure Development in India, (DFI)
Use of Porous Concrete in Secant Bored Pile Walls
Markus Herten, Matthias Pulsfort, Claudia Fierenkothen and Rolf Breitenbücher
Secant bored pile walls are frequently used as retaining walls in watertight excavations to cut off ground water aquifers and are subsequently exposed to ground water pressure loading in addition to earth pressure loads. To avoid extra loading from ground water pressure in soils with limited permeability, it can be useful to arrange drainage windows within secant bored pile walls by means of single primary piles filled with porous concrete without reinforcement cages, which usually have to be placed within casings in submerged conditions. This concrete may serve as a horizontal arch between the reinforced secondary piles, but it must however enable vertical draining between load carrying construction beams and the bottom of the excavated pit. In the present submission, the results of several material tests with different mix designs of porous concrete with certain admixtures are presented together with first and important experiences with a wellsuited placement technique for porous concrete casings in small- and large-scale laboratory tests. It can be shown that the usual placement technique of employing a tremie pipe is not suited for this type of unsaturated concrete. Instead, pouring with a particular kind of cone and an open conductor pipe has proven successful. Additionally, special testing methods are currently developed for judging the suitability of the desired concrete mix design in preparation for an upcoming real-scale experimental pile installation in Germany.
|article #2745; publication #1035 (India2017)|