Trend analysis of leap 2020 experimental results and validation of numerical predictions
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Authors
Sepulveda Guatecique, Alejandro
Issue Date
2024-05
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Civil engineering
Alternative Title
Abstract
The current landscape of geotechnical engineering benefits from abundant computational power and advanced numerical modeling platforms capable of analyzing the dynamic response and liquefaction of saturated granular soil systems. In this regard, an important step involving the validation of soil constitutive models and numerical platforms is need to foster a greater acceptance and utilization of numerical modeling in geotechnical engineering design and analysis. Recent efforts under the Liquefaction Experiments and Analysis Projects (LEAP) are aimed at promoting the validation of numerical models developed for soil liquefaction. LEAP are a series of international research collaborations aiming to produce high quality experimental data to validate soil constitutive models and modeling techniques for dynamic geotechnical systems involving soil liquefaction. The focus of this thesis is to analyze the LEAP 2020 experimental data and develop a validation methodology of numerical simulations of dynamic geotechnical systems involving soil liquefaction using centrifuge experimental data. The thesis is a collection of journal articles from chapter 2 to chapter 5. The abstracts of each chapter are presented below: Chapter 2: Miniature cone penetration tests (CPTs) were conducted during the LEAP 2017 and LEAP 2020 centrifuge experiments to characterize and quantify the soil deposit properties. All experiments were performed using Ottawa F-65 Sand and used the same CPT tool model. The CPTs showed consistent results below a critical depth, with tip resistance affected by overburden pressure and soil density. The (experiment) container widths were found to affect the CPT results when the used container is narrow. The cone (tip) penetration resistance was normalized to account for overburden pressure and corrected to address the potential effects of container width. An empirical relation was developed to estimate soil relative density from the corrected and normalized tip resistance. The obtained relation provides an estimate of relative density profile and associated standard deviation (as a measure of uncertainty) from measured CPT tip resistance of Ottawa sand deposits. Chapter 3: This chapter and compares the results of the LEAP 2020 centrifuge experiments. The centrifuge model consisted of a saturated Ottawa sand deposit supported by a cantilever sheet-pile wall that is practically rigid. Experiments were conducted at eight facilities with deposits having a relative density varying from about 50 \% to 80 \%. The models were subjected to an input base acceleration with a reference consisting of a ramped sinusoidal motion with five cycles at peak value. The achieved input accelerations varied from a (practically) monoharmonic 1 Hz motions to motions with significant 3 Hz and 5 Hz components. Peak accelerations ranged from 0.09 g to 0.27 g. The models were monitored in terms of deposit accelerations, pore pressures, surface lateral displacements and settlements, and retaining wall lateral displacements and rotations. The obtained experimental results cover a wide range of conditions and provide valuable information and insight into the response characteristics of the soil-retaining wall system. Chapter 4: The LEAP-2020 comprised a series of 23 centrifuge experiments of a saturated Ottawa sand (backfill) deposit supported by a cantilever wall. The experiments covered a comprehensive range of experimental conditions. The deposits had a relative density that varied from 49\% to 76\% and the centrifuge models were subjected to input motions that varied in amplitude and frequency content. The experimental results were consequently marked by a broad spectrum of response characteristics. A Gaussian Process Regression (GPR) was employed to investigate and assess the trends and response mechanisms of permanent lateral displacements, settlements, wall rotation and pore pressure buildups of the tested soil-retaining wall systems. The conducted analyses showed a high level of consistency among the experimental results and shed light on a number of salient response characteristics. Chapter 5: Recent efforts under The Liquefaction Experiments and Analysis Projects (LEAP) are aimed at promoting the validation of numerical models developed for soil liquefaction. LEAP are a series of international research collaborations aiming to produce high quality experimental data to validate soil constitutive models and modeling techniques for dynamic geotechnical systems involving soil liquefaction. This chapter presents a validation methodology of numerical simulations of the dynamic response and liquefaction of a soil-retaining wall systems using centrifuge experimental. The methodology includes the following steps: (1) A regression analysis is implemented to assess response characteristics and patterns in the experimental data, (2) A surrogate model of the computational model is developed based on a limited number of numerical simulations and (3) A probabilistic validation metric is implemented to assess the computational model performance. An implementation of the methodology is presented as an example for numerical simulations of a finite element model using two different soil constitutive model calibrations. The validation quantified the performance of the finite element models with respect to the centrifuge experimental data.
Description
May 2024
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY