Verification of the Repeatability of Soil Liquefaction Centrifuge Testing at Rensselaer
The Liquefaction Experiments and Analysis Projects (LEAP) is an international effort to use experimental data from physical modeling at different (international) centrifuge facilities to validate soil liquefaction numerical models and analysis tools. The goals of LEAP-2017 experimental efforts are to assess the repeatability potential at each facility, the reproducibility of centrifuge tests among different facilities, and the sensitivity of the experimental results to variation of testing parameters and conditions. A number of tests of the same (sloping deposit) centrifuge model were repeated at Rensselaer Polytechnic Institute in 2015 and 2017. This paper focuses on two specific tests to assess and demonstrate repeatability at this facility.
KeywordsLiquefaction Lateral spreading Sloping ground Dilation
The Liquefaction Experiments and Analysis Projects (LEAP) is an international effort to (1) investigate the dynamic response and liquefaction of a number of soil systems by means of centrifuge testing of small-scale physical models, and (2) use the experimental data to validate soil liquefaction numerical models and analysis tools.
In 2015, a LEAP was undertaken using a small-scale model of a sloping deposit. A number of tests were conducted at Cambridge University, Kyoto University, NCU of Taiwan, Rensselaer Polytechnic Institute (RPI), UC Davis, and Zhejiang University (Kutter et al. 2017, 2019). The data provided by these tests were used in a first validation exercise (Manzari et al. 2018). The LEAP 2017 expands and builds on the 2016 results and outcomes. Tests of the same sloping deposit were repeated in China (Zhejiang University), France (Institut français des sciences et technologies des transports, de l’aménagement et des réseaux), Japan (Ehime University and Kyoto University), Korea (KAIST University), Taiwan (National Taiwan University, UK (Cambridge University), and USA (UC Davis and Rensselaer). The tests are aimed at assessing the repeatability, reproducibility, and sensitivity of experimental results to variability in testing conditions among the different facilities.
A total of five tests of the sloping deposit were conducted at RPI. The first two tests (referred to as 2015_RPI01 and 2015_RPI02) were executed in 2015 (Kokkali et al. 2018; Abdoun et al. 2018). The LEAP 2017 three tests were aimed at repeating the LEAP 2015 tests and also assessing the soil system response to variations in input motion (i.e., presence of a 3 Hz component) and deposit relative density. Specifically, the first of this series (referred to as 2017_RPI01) was simply a repetition of the first test of 2015, and was conducted according to the same specification by two different researchers. This paper presents the 2017_RPI01 test and investigates the level of repeatability with the initial test performed in 2015 (2015_RPI01). The other LEAP 2017 tests will be published elsewhere.
19.2 Experimental Setup
19.2.1 Dry Model Preparation
Pluviation was performed manually from a specific height and at constant (lateral) velocity. This height was determined after careful calibration of the utilized pluviator and was maintained throughout the entire process of model building. The slope surface was not curved as the model longitudinal direction and direction of shaking are parallel to the Rensselaer centrifuge axis of rotation (also, curving was deemed not necessary in the transverse direction in view of the relatively small model dimension in this direction).
Sensor locations: (a) accelerometers and (b) pore water pressure transducers
Top of container
Locations of tracking targets: (a) central rows along the slope and (b) central rows across the slope
19.2.3 Viscous Fluid Preparation and Saturation Process
The dry model was first fixed on the centrifuge basket. Then, the container was sealed and put under vacuum. The dry model was thereafter saturated with CO2 which pushes air out of the voids. The process of vacuum and CO2 saturation was repeated twice, before starting saturation. The viscous fluid used for the saturation of the model was made with methylcellulose manufactured by Dow Chemical added at a specific ratio to the water to achieve a viscosity of 23.5 cp.
19.2.4 Centrifuge Equipment
The geotechnical centrifuge at RPI has a radius of 3 m and can withstand a total model weight of 150-g tons. The shaking table is installed within the centrifuge basket and can replicate dynamic (earthquake and artificial) motions in one or two lateral directions.
19.3 Recorded Response
19.3.1 Input Motion
19.3.2 Soil Acceleration
19.3.3 Pore Water Pressure
19.4 Lateral Spreading
Five LEAP centrifuge experiments were conducted at Rensselaer Polytechnic Institute in 2015 and 2017. This article presented, compared, and assessed the level of repeatability of two tests performed according to the same specification by two different researchers: the first test was conducted in 2015 (2015_RPI01) and the second was a repeat carried out in 2017 (2017_RPI01). Each test included a 0.15 and 0.25 g input excitations. The input motions were found to be highly repeatable and were consistent in frequency content and amplitude (especially for the 0.15 g motion) and showed that the two tests were subjected to practically the same loading conditions. The 2017 model building, instrumentation, preparation of the viscous pore fluid, and model saturation were performed following methodology of the 2015 test. The recorded accelerations and excess pore water pressures (of the two tests) were shown to be in very good agreement during the early phase of shaking and also during liquefaction and dilative response (including consistency in acceleration spikes and drops in pore pressure). The consistency in the pore pressure build-up between the two tests shows that the two models had comparable compressibility values. This finding along with the long-term time history of pore pressure dissipation confirmed that the two models have practically the same soil permeability. The lateral spreading displacements were also highly consistent not only in terms of the ultimate final values but also in time history of cyclic response. All these agreements are strong indicators that the two sloping soil deposits had consistent soil characteristics including stiffness and fabric.
The authors would like to acknowledge the financial support of the National Science Foundation Geotechnical Engineering Program directed by Dr. Richard Fragaszy (Grant No. CMMI- 1635040). This support is gratefully acknowledged. The authors would also like to acknowledge the contribution of the staff of the Centrifuge Center at Rensselaer to the performance of the centrifuge tests.
- Carey, T. J., Stone, N., & Kutter, B. L. (2019). Grain size analysis and maximum and minimum dry density of Ottawa F-65 sand for LEAP-UCD-2017. In B. Kutter et al. (Eds.), Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-UCD-2017. New York: Springer.Google Scholar
- Kutter, B., Carey, T., Hashimoto, T., Zeghal, M., Abdoun, T., Kokalli, P., Madabhushi, G., Haigh, S., Hung, W.-Y., Lee, C.-J., Iai, S., Tobita, T., Zhou, Y. G., Chen, Y., & Manzari, M. T. (2017). LEAP-GWU-2015 experiment specifications, results, and comparisons. International Journal of Soil Dynamics and Earthquake Engineering. https://doi.org/10.1016/j.soildyn.2017.05.018.CrossRefGoogle Scholar
- Kutter, B. L., Carey, T. J., Stone, N., Bonab, M. H., Manzari, M., Zeghal, M., Escoffier, S., Haigh, S., Madabhushi, G., Hung, W., Kim, D., Kim, N., Okamura, M., Tobita, T., Ueda, K., & Zhou, Y. (2019). LEAP-UCD-2017 V. 1.01 model specifications. In B. Kutter et al. (Eds.), Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-UCD-2017. New York: Springer.Google Scholar
- Manzari, M., Ghoraiby, M. E., Kutter, B. L., Zeghal, M., Abdoun, T., Arduino, P., Armstrong, R. J., Beaty, M., Carey, T., Chen, Y.-M., Ghofrani, A., Gutierrez, D., Goswami, M., Haigh, S. K., Hung, W.-Y., Iai, S., Kokkali, P., Lee, C.-J., Madabhushi, S. P. G., Mejia, L., Sharp, M., Tobita, T., Ueda, K., Zhou, Y.-G., & Ziotopoulou, K. (2018). Liquefaction analysis and experiment projects (LEAP): Summary of observations from the planning phase. International Journal of Soil Dynamics and Earthquake Engineering, 113, 714–743. https://doi.org/10.1016/j.soildyn.2017.05.015.CrossRefGoogle Scholar
Open Access This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.
The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.