Centrifuge Modelling of Compaction Grouting

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9622399 Compaction grouting is the injection under high pressure of stiff cement-based grout into soil. There is existing and clear evidence that the technique works as a method to halt or reverse the effects of ground settlement, and to modify and improve characteristics of existing soils and in situ stress conditions. The application is overwhelmingly in the hands of specialized consultants and contractors, but even among them, questions persist about the details of soil and grout mechanics. This project will answer questions on the interrelationship between injection depth, grout pressure, grout mix, soil conditions and in situ stress, and the resulting effects on soil compaction, shear deformation, and soil displacement. Preliminary centrifuge indicates that this test technique with small, 1-g models can demonstrate general mechanisms of behavior. However, stress-correct centrifuge models are necessary to develop reliable representation of full-scale field response. There is a commitment in this work for cooperative interaction with on- going NSF-sponsored research on FEM modeling and full-scale field testing of grout injection at North Carolina State University, and with the U.S. Army Corps' Waterways Experiment Station. The centrifuge models completed for this award will be highly complimentary to address questions relating to the design of grout and injection schemes, including variable parameters such as injection depth, pressure, grout injection angle, and surface surcharge. Commitment has also been made by grouting contractors to advise on this project, and plans are included for practical training of researcher teams. ***