ABSTRACT:

A case study is presented of the geotechnical design, construction and construction monitoring of the drained basement of the Airport Central Sheraton Hotel building at Mascot, Sydney.

INTRODUCTION

This paper provides brief details of the geotechnical design and construction monitoring carried out for the basement of the Airport Central Sheraton Hotel at Mascot, Sydney (Figure 1). The building is 12 stories high with down to 4 levels (depth of excavation about 12.5m) of basement parking and contains commercial premises as well as a five star hotel. The design and construct tender to build the hotel was won in 1990 by Concrete Constructions, now Walter Constructions who, with Douglas Partners, geotechnical consultants, proposed a drained basement. This nonconforming design eliminated the need for tanking and permanent anchors to resist hydrostatic uplift. It facilitated an accelerated construction program using the "top down" method, the first time this technique was used in Australia. In "top down" construction the external diaphragm wall, load bearing barrettes and piles are installed and the basement floors and internal building structure used for lateral support allowing excavation of the basement and construction of the superstructure to proceed together.

SUBSURFACE CONDITIONS

The site is a relatively level, approximately egg shaped area of about 7800 square metres, bounded to the north and east by major streets with a railway embankment forming the southern boundary. Geotechnical investigations by Douglas Partners and others meant results from 16 test bores and 10 cone penetration tests were available to characterise the site. Hydraulic conductivities (k) of the various strata were estimated from experience in similar conditions and the results of numerous borehole permeability tests, including rising and falling head tests in piezometers with screens in the sands and clays, and packer tests in the shale/laminite.

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