Proceedings - Fifth International Conference & Exhibition on Piling and Deep Foundations, 1994, Bruges, Belgium, (DFI)
Survey of the realisation, detection of anomalies and grouting of large bored piles
Y. Zaczek & P. Debauche
An industrial complex of buildings has been founded on more than one thousand large bored piles (0.75 to 1.10 m in diameter). According to the geotechnical investigations, the site is made of about 10 m of backfill followed by sandy gravel alluvium, with lenses of peaty clay, covering the shally bedrock. During the piles construction, anomalies such as water expulsion from the fresh concrete at the top of the pile and overconsumption of concrete have been detected. This water circulation has caused progressive increases in the water content of the concrete of the upper end of some piles, leading to concrete weakening with formation of excessive laitance, and the washing of some reinforcement bars. Coreborings into the pile shafts have been decided to control the integrity and the quality of the shaft concrete. These coreborings have been realized together with bore parameters recording to quantify the anomalies. Inadequate contacts between the pile bases and the supporting rock have been shown by the high penetration speed of the boring rods on some centimetres to some decimeters. Although a general good quality of the shaft has been revealed. The grouting of the lower end of some piles of the settlement-sensitive structures has been decided to fulfill the voids and to strengthen the disturbed rock discovered by the borings. Due to difficulties in boring and grouting through the center of the pile shafts, a more complex methodology has been elaborated to grout these anomalies through external borings.
|article #819; publication #36 (IC-1994)|