Volume 8, Issue 2 June 2023

Young Members

Load-Settlement Behavior of Precast Jacked Concrete Pilesfrom Static Load Tests and High-Strain Dynamic Pile LoadTests in the PhilippinesBenjamin B. Buensuceso III
Managing Director, BRB Solutions Inc.
MS Civil Engineering - Geotechnical Engineering specialization of the University of the Philippines Diliman
I graduated Cum Laude in BS Civil Engineering, also from the University of the Philippines Diliman. I
am also currently Managing Director at BRB Solutions Inc. My areas of expertise and research include
high-strain dynamic load testing and pile integrity testing.

Installing precast displacement piles by pile jacking is a relatively new technique but growing in
popularity because of the reduced noise and vibration compared to traditionally driven piles.
Estimating the ultimate capacity and settlement of jacked piles for specific subsurface conditions is ofinterest to piling stakeholders. The jacked pile installation method allows for the measurement of astatic capacity during the installation, which in some cases can be a reliable estimate of the pile’s ultimate capacity asmeasured by a compressive static load test (SLT) [1]. SLTs and high-strain dynamic compressive pile load tests (HSDPTs)
can also be performed after a certain amount of time has elapsed since installation to estimate the increase in skin friction
due to pile “set-up”. While SLTs have been referred to as the most reliable predictor of long-term pile capacity andbehavior [2], HSDPTs are more commonly used in the Philippines for evaluating the capacity of jacked piles and in somecases, have completely replaced SLTs. HSDPTs, while providing a good approximation of results from SLTs, are typicallymore affordable to conduct, less time-consuming, and can be done on a greater number of piles at a project than SLTs[3]. An estimated pile top load-settlement curve can also be generated from an HSDPT, similar to what is measured in aSLT. However, a common limitation encountered when conducting HSDPTs is the incomplete mobilization of ultimate
capacity relative to what can be obtained in an SLT. Nevertheless, there remains uncertainty regarding which load test touse for certain projects, as well as the equipment and load required to fully mobilize ultimate capacities in test piles,
particularly because of significant increases in pile capacity due to pile setup in certain types of soils.
Presented here are SLT and HSDPT results of tests conducted on ten (10) prestressed, jacked, square concrete piles with45 cm width, 30 m length, and a specified allowable capacity of 750 kN installed with a hydraulic static pile driver in silty
clay in the Luzon, Philippines region. Final jacking forces applied on the piles during installation ranged from 456 to 2018
kN. Four (4) piles were subjected to SLTs following the “Quick Test” procedure, while six (6) piles were subjected to HSDPTs.
These tests were conducted as non-destructive proof tests to prove that the piles can support at least a certain multipleof a provided allowable capacity. SLTs were conducted up to 2.5 times the allowable capacity, while a target capacity of
2.0 times the allowable capacity was used for the HSDPT. Signal matching analysis was conducted on HSDPT data togenerate ultimate capacity estimates and estimated load-settlement behavior.
Significant capacity increases, or pile setup, were found between the date of installation and the date of load tests for all
10 piles tested. All target capacities were attained during both SLTs and HSDPTs. Additionally, the measured capacities
were 1.19 to 5.43 times the final jacking force measured during
installation, indicating that capacities had increased. However, using
the Davisson Offset Limit Method, a widely used method for static load
capacity estimation [4], capacity estimates from HSDPTs were found to
be closer to actual ultimate capacities compared to estimates fromSLTs, despite smaller target capacities used during the HSDPT. Loadsettlement curves from the HSDPTs (also called PDA tests) and SLTs, aswell as the Davisson-Offset Line, can be seen in Fig. 1. This is likely
because of the relative ease in mobilizing additional capacities duringa HSDPT, which typically requires increased hammer drop heights.
Additional reaction piles or dead loads are typically needed to increaseloads in a SLT. As such, HSDPTs may be a superior option forFig. 1. Load-settlement curves of jacked piles
maximizing measured capacities when a significant and uncertainfrom SLTs and estimated by HSDPTs
amount of capacity increase is expected in a project.
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Volume 8, Issue 2 June 2023
References[1] Yetginer, A.G., White, D.J. and Bolton, M.D. (2006). Field measurements of stiffness of jacked piles and pilegroups. Geotechnique, 56(4): 349-354.
[2] Likins, G. E., Rausche, F., Thendean, G. and Svinkin, M. (1996). CAPWAP Correlation Studies. Fifth International
Conference on the Application of Stress-wave Theory to Piles (STRESSWAVE ’96): Orlando, FL; 447–464.
[3] Komurka, V. E., & Theiss, A. G. (2018). Savings from Testing the Driven-Pile Foundation for a High-Rise Building. InIFCEE 2018 (pp. 87-101).
[4] Fellenius, B. H., & Tech, P. (2001). What capacity value to choose from the results a static loading test.

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