Apparatus for centrifuge modelling of top down basement construction with heave reducing piles

Abstract

The construction of deep basements in urban areas is associated with many risks and problems among Which is the possible damage to existing structures and services resulting from settlements near the excavation. A number of methods are routinely employed to attempt to control these movements (e.g. top-down construction, use of stiff diaphragm walls). This paper discusses the methodology and practicalities of a series of centrifuge model tests designed to investigate the effect of deep basement construction. Two sets of experimental apparatus are described in detail and their effectiveness in terms of robustness and generation of repeatable data are assessed. It is shown that using relatively simple techniques and equipment it is possible to model many of the features associated with top-down construction.

An experimental study into the ultimate capacity of an ‘impression’ pile in clay

“…The Geotechnical Engineering Research Group at City, University of London, makes use of an Acutronic 661 beam centrifuge, described in detail by Schofield andTaylor (1988) andMcNamara et al (2009). The package containing the model was installed on the centrifuge once the piles had been bored, impressed and cast and the loading apparatus assembled on the plane strain strongbox.…”

“…Consolidation was achieved by means of a hydraulic press over a period of 9 days including 1 day of swelling. The samples were compressed to a vertical stress of 500kPa that was then reduced to 250kPa, producing a firm, but still workable, clay sample (McNamara et al, 2009;Taylor et al, 2012;Divall and Goodey, 2015;Gorasia and McNamara, 2016).…”

Physical modelling of lime stabilisation in soft soils around deep excavations

“…An aluminium stiffener, initially developed by McNamara et al (2009) and a capping beam supported the full length of the exposed wall and pinned the top of the wall. This ensured that movements arising from the excavation process were a direct result of basal heave and not of wall movements.…”

Centrifuge modelling of the effect of base slab stiffness on long-term heave and swell pressure

“…In particular, some researchers used centrifuge modelling to investigate techniques to control the basal heave of deep excavations in clay. These techniques included soil improvement (Ohishi et al, 2000), tension piles (McNamara & Taylor, 2004;McNamara et al, 2009), compensation grouting (Halai & McNamara, 2014), and controlled flooding of the formation level (Panchal et al, 2017). However, there has been little research on how the stiffness of the basement slab itself influences the swell pressures and heave movements.…”