City Research Online

Abstract

In recent years development is at premium in many European cities. With life cycles of 25-30 years of buildings in financial cities and about 40 years in regional centres the
ground is becoming more and more congested with redundant foundations. As the underground development of services and infrastructure already confines the location of building foundations, redundant foundations only add to this problem.

The research described in this thesis, using centrifuge model testing, describes how the existing pile foundations in overconsolidated clay are likely to behave when their loading conditions are changed by unloading caused by demolition and subsequent reloading. This is done with the view to re-use the existing pile foundations for the new redevelopments. The influence of the new foundations on the existing foundations is also described. By re-using the foundations, the use of raw materials is reduced, the energy consummation for construction is reduced, the volume of soil from foundation construction is eliminated and the construction time significantly reduced, consequently
reducing the whole costing of a structure.

Experimental data was obtained from series of twenty one centrifuge model tests undertaken at 60g. The geometry of the model was such that it was possible to test two sets of foundations with each test. The performance of piles in overconsolidated clay when subjected to load/unload/reload cycles and the influence of supplementary piles used to achieve the required capacity were investigated. The model tests include comparison of the behaviour of bored piles when supplemented with mini piles of different length, number and spacing (centre to centre distance between the mini piles and the existing centre pile).

An increase in capacity was observed when single piles were subjected to load cycles. It was found that this increase in capacity is dependent on the previous loading
conditions of the pile. The behaviour of enhanced piles was characterised using a single pile test as datum test. The influence of these novel pile groups on the existing pile was dependent on the number, length of the mini-piles in the group and centre to centre spacing between the existing and new pile foundation.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering Doctoral Theses School of Science & Technology > School of Science & Technology Doctoral Theses

Export

Downloads