The 2010-2011 Canterbury, New Zealand, Earthquake Sequence (CES) resulted in 185 fatalities and approximately $NZ40 billion in damage, much of which was due to liquefaction and related phenomena. As a result, an extensive soil improvement field testing program was initiated and Rammed Aggregate Piers� (RAP) were shown to be a feasible method to mitigate the risk from liquefaction during future events. To better design and more fully assess the efficacy of reinforcement techniques against liquefaction, pre- and post-treatment in-situ test data are compiled, to include results from cone penetration tests (CPT), direct-push crosshole tests, and vibroseis (T-Rex) shaking tests. The data are used to evaluate the capabilities of numerical tools to predict the liquefaction response of unimproved and improved sites. A finite difference (FD) numerical model is developed in a FLAC platform and a coupled analysis using the Finn model with Byrne (1991) formulation is conducted. The FD model calibrated for top-down shakings similar to the vibroseis tests succeeded in qualitatively reproducing the general observed behavior without quantitatively matching the in-situ values for shear strains and excess pore pressure ratios. The introduction of the RAP elements to the FD model reduced the shear strain, but slightly overestimated that reduction. Considering more advanced constitutive models that better simulate the complexity of the soil behavior under dynamic loading would likely increase the accuracy of the predicted response. / MS / During earthquakes, a significant loss of strength in soil can occur. This phenomenon, known as liquefaction, can have a devastating impact on the area affected. The 2010-2011 Canterbury, New Zealand, Earthquake Sequence (CES) resulted in 185 fatalities and approximately $NZ40 billion in damage, much of which was due to liquefaction and related phenomena. Consequently, the New Zealand Earthquake Commission implemented a field testing program in order to investigate the efficiency of ground improvement techniques in reducing soil liquefaction potential. One of the tested techniques was Rammed Aggregate Piers™ (RAP) and was shown to be a feasible method in mitigating the risk from liquefaction during future events. The focus of this study is to develop a numerical model capable of predicting the liquefaction response of unimproved and RAP-improved sites. Pre- and post-treatment test data are therefore compiled and used to calibrate the model. The numerical model calibrated for shakings similar to the on-site tests succeeded in qualitatively, but not quantitatively, reproducing the behavior observed in the field. The introduction of the RAP elements to the model revealed an improvement against liquefaction hazard; however, the improvement was overestimated compared to the field results. Considering more advanced numerical features that better simulate the complexity of the soil behavior under dynamic loading would likely increase the accuracy of the predicted response.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/99375 |
| Date | 24 January 2019 |
| Creators | Saade, Angela Charbel |
| Contributors | Civil and Environmental Engineering, Yerro Colom, Alba, Green, Russell A., Castellanos, Bernardo Antonio |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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