Ground Improvement for Enhanced Seismic Performance of Rocking Footings on Sand
Bibliographic record
Abstract
This work details a centrifuge modeling investigation of the performance of rocking footings supported by various ground improvement strategies with the aim of controlling their performance before, during, and after earthquake shaking. The rocking footings investigated in this study are modeled after the shallow foundations supporting a two-span highway bridge (Hwy 108 at Sanguinetti Road) in Sonora, California which served as the archetypal bridge in previous centrifuge studies. Where these earlier studies proved that under-designed foundations re-center themselves reliably while dissipating energy, the present study focuses on the capacity of ground improvement to preserve these beneficial traits while also limiting the foundation’s settlement and residual rotation, even when it is relatively heavily loaded to begin with.By developing a strategy to control the detrimental kinematics of rocking footings during plastic hinge development, geotechnical engineering practice can move towards embracing a natural, cost-effective solution and its implementation in performance based engineering (PBE) of transportation infrastructure. Based on case histories and advice from geotechnical practitioners in California, ground improvement for the centrifuge testing program revolved around soil-cement columns in medium dense Ottawa F-65 sand. Soil-cement mixing was selected as it is a well-known technique to reduce liquefaction hazard that is widely used in practice, and also has the potential to reduce settlement of shallow footings on loose-medium sand which is the focus of the present study.A baseline case was first developed for a rocking footing without ground improvement by subjecting it to shaking at a level that caused it to settle and rotate much more than would be tolerable by any performance criteria. This baseline case was established reliably through repeated tests before being compared to other cases with a variety of soil-cement column configurations. Foundation performance in all tests was assessed based on settlement accumulation against cumulative rotation demand, and a correlation diagram relating re-centering and energy dissipation. Ideal ground improvement configurations were identified with minimal settlement and maximum energy dissipation and re-centering. The centrifuge testing results have been organized in a manner allowing their seamless integration into the existing FoRDy database of rocking foundation tests. Ultimately, the expanded database will increase the engineering community’s receptiveness to adopting the rocking foundation design. Such a design reduces risk to infrastructure in the event of severe earthquakes, limiting potential service disruptions and costly repairs to transportation systems.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".