Pore-water pressures in soft to firm clay during driving of piles into underlying dense sand

Abstract

During driving of steel piles through soft, sensitive clay into very dense sand and gravel, pore-water pressure responses were monitored. As a result of the large length of the piles and also because of the high sensitivity of the soft clays, the piles were driven in two stages. During the initial stage of driving in the soft clay, only very small pore-water pressure increases were recorded together with very low pile driving resistances; however, during the second stage of driving, high pore-water pressure increases were observed in the clay as soon as the piles penetrated into the underlying very dense sand and gravel. It was concluded that the clay deposit was loaded from below, as the piles were driven into very dense sand. The total stress changes and the resulting pore-water pressure changes in the clay were analyzed, assuming that the pile driving load was equivalent to a flexible load acting on the surface of an elastic half-space, which represents the soft clay deposit. This interpretation of the pore-water pressure increases is important for the assessment of the bearing capacity of engineering structures affected by piles driven through soft soils into very dense deposits. The potential for high pore-water pressure increases in the clay during undrained loading as well as for volume increases in the dense sand due to pile driving can be predicted from piezocone test data. Key words: pile driving, pore-water pressure, piezocone testing, soft sensitive clays, dense sand deposits.

Archives of Civil Engineering

“…Pore-water pressures were measured by inserting two piezometers at 9 and 18 meters below the ground surface during the inspection of piling activities [36]. Prior to the piling operations, readings from all piezometer were taken on a regular basis, at least once a day.…”

Pore Water Pressure Development in Soft Soil due to Installation and Loading of Controlled Modulus Columns

“…The most important mobilization of EPWP can be expected for driven piles due to the induced large soil displacement and high number of impacts applied during their installation (Eigenbrod and Issigonis 1996;Ng et al 2013;Pestana et al 2002;Randolph et al 1979). It can be also important in the case of jacked piles (Gavin et al 2010;Rahardjio 2017) and screw auger piles (Larisch 2014;Prezzi and Basu 2005).…”

Ground response during offshore pile driving in a sandy slope

“…Several studies exist which examine pore pressures induced during pile driving in fine-grained soils. Among them Bjerrum & Johannessen (1960); Lo & Stermac (1965); Airhart et al (1969); and Eigenbrod & Issigonis (1966). Many of these studies are motivated by the determination of pile set-up after installation by considering a disturbed zone, or zone of excess pore water pressure, as studied by Randolph and Wroth (1979).…”