A nine-year case history of monitoring a wide pile group part I

This is the first of two papers on a wide pile group. The geology and a geotechnical model of the site are presented, along with the design of a single pile, analysis of a static loading test, and some dynamic tests. Response of the piled foundations comprising 399 bored piles supporting three 70-storey towers on a common mat was monitored. Records consist of results of a static loading test, dynamic tests of four piles, the development of load in 15 piles, and settlement of 40 points during construction and nine years following. At end of construction, the perimeter piles received more load from the towers than did the interior piles and the mat settled on average 90 mm. By the end of the monitoring period, due to the general subsidence, the average settlement of the mat had increased by 50 mm. Most of the settlement is considered to originate from the compression of the soil layers below the pile toe level. A subsequent paper will present the analysis and design of the wide pile group, and the numerical analysis of the static loading test on a single pile and of the wide pile group.