Research Team:
Armin Stuedlein
Arijit Sinha
Hao Wang
Project Duration:
2017-2019
2017-2019
Introduction & Background
Soil liquefaction is the tendency of loose soils to lose their strength and stiffness in response to forces such as earthquake movements.
Liquefaction caused damage to 25,000 homes in the 2011 Tohoku earthquake in Japan and $15 billion in losses in Christchurch in 2010-11. This project investigated design guidelines for the use of timber piles, a timber product widely used for structural support of buildings, to mitigate liquefaction hazards. This approach has application in protecting a broad range of other structures, including port and harbor facilities, bridge approach embankments, and bridge foundations. . The results of this research can be used by engineers to judge the parametric effects of design variables on design criteria and develop appropriate liquefaction mitigations.
Research Methods
This project sought to formalize design procedures for engineers that wish to use the economically driven timber pile ground improvement alternative for the mitigation of earthquake-induced liquefaction but have dismissed this alternative owing to the lack of availability of such procedures. Specifically, the objectives were to:
- Develop and validate sophisticated numerical models that have been calibrated to the data from the aforementioned tests;
- Use the calibrated numerical model to perform nonlinear effective stress site response analyses and deformation analyses of typical ground improvement arrangements and acceleration time histories;
- Conduct parametric analyses to determine which parameters are most critical for optimization of ground improvement methodologies; and,
- Condense the work in (1) through (4) to formalize specific design guidance in the form of parametric effects of design variables.
Key Findings
This study used linear and nonlinear numerical modelling approaches to accompany the results of previous experimental work on how effective timber piles are in reducing soil liquefaction and movement in seismic events. Pile spacing, depth, and density were all considered in a parametric study in order to establish a more in-depth model of timber pile behavior, given their unique shape and characteristics.
Example simulation results for comparable unimproved and 22 m long timber pile-improved liquefiable soil subjected to earthquake shaking: (a) ground surface acceleration time histories, (b) ground surface acceleration response spectrum, (c) ground surface and pile displacement time histories; performance of unimproved ground, including (d) shear strain vs. shear stress, (e) excess pore pressure ratio time histories, and (f) effective stress paths for various depths; performance of improved ground, including (g) shear strain vs. shear stress, (h) excess pore pressure ratio time histories, (i) effective stress paths at different depths; and pile responses including the variation of (j) lateral displacement, (k) shear force, and (l) moment with depth.
Publications & Presentations
Wang, H., Stuedlein, A. W., & Sinha, A. (2021). Dynamic response of timber pile ground improvement: 3D numerical simulations. Soil Dynamics and Earthquake Engineering, 143, 106614. https://doi.org/10.1016/j.soildyn.2021.106614
Wang, H. (2023). Liquefaction Mitigation Using Timber Pile-Improved Ground. PhD Thesis, School of Civil and Construction Engineering, Oregon State University, Corvallis, OR.
Funding & Acknowledgements
USDA Agricultural Research Service in cooperation with the TallWood Design under grant #58-0204-6-002
Deep Foundations Institute (DFI) under grant CPF-2018-GRIM-1
