Modified Time Factor to Estimate the Duration of Pile Setup
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ORIGINAL PAPER
Modified Time Factor to Estimate the Duration of Pile Setup Murad Y. Abu-Farsakh
. Md. Nafiul Haque
Received: 14 November 2018 / Accepted: 27 May 2020 Springer Nature Switzerland AG 2020
Abstract Pile setup is defined as the increase in pile capacity with time. This increase in pile capacity starts immediately after end of driving (EOD). Majority of the setup conducted during the consolidation period followed by a small amount during the post-consolidation period. However, there is no available methodology to estimate the duration of setup during the consolidation period, and to establish a theoretical upper time limit for pile setup capacity beyond which pile setup capacity can be neglected. This paper examines or focuses to develop a methodology to estimate the time duration of pile setup. Three instrumented test piles (TPs) were driven mainly in clayey soil in Louisiana besides regular bridge construction projects. The piles were instrumented with sister bar strain gages to measure the load transfer along the piles’ length, and four sets of pressure cells and piezometers were installed on each pile face to measure the total stress, effective stress and excess pore water pressure (PWP) with time. Dynamic and Static load tests were performed for a duration of 6 months after EOD and hence study setup. Piezocone dissipation tests were performed at each TP locations at different M. Y. Abu-Farsakh (&) Louisiana Transportation Research Center, Louisiana State University, Baton Rouge, LA 70808, USA e-mail: [email protected] Md. Nafiul Haque Geotechnical Engineer, Kleinfelder, Greensboro, NC 27410, USA
depths to measure the horizontal coefficient of consolidation (ch) besides the regular laboratory and in situ cone penetration test (CPT) to characterize the subsurface soil condition. The piezometers that were installed on the pile face showed that the dissipation continued from 2.5 h to 90 days after EOD depending on the soil properties. The equation that was proposed by Teh and Houlsby (Geotechnique 41(1):17–34, 1991) for dissipation test of piezocone was adopted to calibrate the time factor for pile. A new modified time factor for pile (Tpile*) was proposed in this study to estimate the duration of pile setup. Keywords Pile setup Time factor Consolidation Dissipation test Time period
1 Introduction Piles driven into fine-grained soils usually exhibits increase in capacity (mainly skin friction) over time. This increase in capacity, known as ‘‘setup’’, has been studied by many researchers over a long time in an attempt to predict the actual pile capacity at a specific time after pile driving, and to incorporate its effect into pile design (e.g., McVay et al. 1999; Paikowsky et al. 2005; Bullock, 2012; Fellenius, 2008). Experimental studies (e.g., Ng et al. 2013; Seo et al. 2013) and numerical modeling studies (e.g., Fakharian et al.
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2013; Basu et al. 2013) have been conducted on fullscale load tests for piles driven into
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