Investigation of Grouted Helical Pier based Foundation Rehabilitation
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Abstract
This data report describes the centrifuge test that was performed in June 2006 on the UC Davis geotechnical centrifuge. The purpose of the test was to develop the instruments and materials for in-flight grouting and simulate and study the working mechanisms and properties of grouted helical pier systems (GHPS). The testing procedures, methods, and observations during the testing series are described in this report. Prior to centrifuge testing, 1-g bucket tests were also performed to develop suitable materials and tools for the piers planned for placement in the centrifuge and these 1-g tests are also summarized in this report. Additional data analysis may be found in Bian (2006).
The soil used to construct the model was air pluviated #30 sand, which was obtained commercially from White Cap Construction Supply. A series of seven spin up and down cycles were performed to either grout or load the piers in flight. In total, one plain (non- grouted) pier, one helical (non-grouted) pier and 16 grouted helical piers were placed. The most important data from these experiments was post-test excavation observations.
General configuration parameters for the test are as follows:
Centrifuge: Model Container: Centrifuge Acceleration:
9-m-radius centrifuge at UC Davis Flexible Shear Beam (FSB-1) Soil Container
15-g
The centrifuge allows modeling of prototype soil stresses and thus captures the strength and deformation characteristics of the soil. A model specimen subjected to N-g is dimensionally N times smaller than its prototype size at 1-g. Therefore, in an N = 15 (15-g) centrifuge experiment, the dimensions of the model pier are scaled by N (=15); density and stress at the prototype is equal to the model scale; force is scaled by 1/N2 (=1/152) and acceleration is scaled by N (=15). Basic scaling laws adopted for this experiment are those presented in Table 1.1, reproduced from Kutter (1992).