Simplified Design Procedure for Piles Affected by Lateral Spreading Based on 3D Nonlinear FEA using OpenSees

Project # NCTRPA

Research Team

  • Pedro Arduino, Associate Professor, University of Washington (PI)
  • Peter Mackenzie-Helnwein, Research Assistant Professor, University of Washington (co-PI)
  • Christopher McGann, Graduate Student, University of Washington

Research Abstract

A simplified procedure for the analysis of deep foundations affected by liquefaction-induced lateral spreading is developed using nonlinear 3D finite element analysis. The 3D finite element model considers a single pile in a soil continuum. This model is used to simulate lateral spreading and two alternative lateral load cases, as well as to compute p-y curves representative of the soil response for various soil-pile systems.

The affects of pile kinematics on computed p-y curves are evaluated and a computational procedure for p-y curves is proposed. The computed curves are compared to p-y curves defined by existing methods commonly used in practice to evaluate the applicability of these methods to the analysis of piles subject to lateral spreading.

The 3D finite element model is used to compute p-y curves for homogenous and layered soil profiles in which a weaker (liquefied) layer is located between two stronger (unliquefied) layers.
Comparison of the resulting sets of p-y curves identifies reductions in the ultimate lateral resistance and initial stiffness of the unliquefied soil due to the presence of the liquefied layer.

The identified reductions are characterized in terms an exponential decay model. A simplified procedure utilizing dimensionless parameters is proposed as a means of implementing appropriate reductions for an arbitrary soil profile and pile diameter. Beam on nonlinear Winkler foundation (BNWF) analyses of lateral spreading are conducted to validate and demonstrate the use of the proposed reduction procedure. A recommended analysis procedure using a BNWF approach is proposed based upon the results of this study.

Research Outcomes

Fig. 1: OpenSees 3D Finite Element Model and considered pile cross-sections.

Fig. 2: Considered pile kinematic cases and example reduction in ultimate lateral resistance due to the presence of the weaker liquefied layer.

Fig. 3: Reductions in ultimate lateral resistance and initial stiffness due to the presence of the weaker liquefied central layer for a 1.37 m diameter pile. Markers are computed values from 3D FEA and lines show the fitted exponential decay function.


PEER reports:

  • COMING SOON: PEER Report 2012/XX – Development of Simplified Analysis Procedure for Piles in Laterally Spreading Layered Soils by Christopher McGann, Pedro Arduino, and Peter Mackenzie-Helnwein

Journal Papers:

  • McGann, C.R., Arduino, P., and Mackenzie-Helnwein, P. (2011). “Applicability of conventional p-y relations to the analysis of piles in laterally spreading soil.” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 137(6), 557-567.
  • McGann, C.R., Arduino, P., and Mackenzie-Helnwein, P. (2011). “Simplified procedure to account for a weaker soil layer in lateral load analysis of single piles.” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, (under review).

Papers in Conference Proceedings:

  • McGann, C.R., Arduino, P., and Mackenzie-Helnwein, P. (2010). “Lateral resistance reduction for static analysis of lateral spreading.” Joint Conference Proceedings, 7th International Conference on Urban Earthquake Engineering (7CUEE) & 5th International Conference on Earthquake Engineering (5ICEE), Tokyo Institute of Technology, Tokyo, Japan, March 3-5, CD-ROM, Paper ID 02-387.

Master’s Thesis:

  • McGann, C.R. (2009). “Analysis and evaluation of single piles in laterally spreading soil,” Master’s thesis, University of Washington.

Research Impact

Deep foundations (piles and drilled shafts) are used extensively to provide support for bridges and wharf facilities in seismically active areas. Due to the nature of these types of structures, they are often located in areas with high liquefaction potential, and are susceptible to lateral spreading events. It is difficult to obtain reasonable estimates of the bending moment and shear force demands placed upon a foundation body due to the complexity of the lateral spreading load case. Analysis approaches therefore rely on simplifying assumptions which can lead to over-conservative solutions. An analysis procedure which better captures the essential elements of the liquefaction-induced lateral spreading load case may lead to more realistic and cost-effective foundations for these critical facilities.