Collaborative Research: Testing and Constitutive Modeling of Fine-Grained Tills Deposited by the Laurentide Ice Sheet

University Of Guam, Mangilao GU

Investigators

Abstract

COLLABORATIVE RESEARCH: TESTING & CONSTITUTIVE MODELING OF FINE-GRAINED TILLS DEPOSITED BY THE LAURENTIDE ICE SHEET J.W. Jenson, P.U. Clark, C.S. Desai & D.N. Contractor EAR-0229907, -0229513, -0229889 This project will provide a more complete empirical basis for constraining and testing hypotheses regarding the role of sediment deformation, sliding, and ploughing in influencing ice-sheet behavior over soft sediment beds. An accurate and complete description of the deformational behavior of subglacial tills is required for understanding ice sheet dynamics and their linkages to the Earth's climate system. In conjunction with climate models, such ice sheet models may be used to investigate the stability of ice sheets-both Pleistocene and modern-and their interaction with global climate. This collaborative project by specialists in glacial geology, soil mechanics and materials engineering, and geophysical modeling will address this important issue by obtaining a comprehensive evaluation of the mechanical properties of two representative fine-grained tills deposited by the Laurentide Ice Sheet. Specifically, the PIs proposed laboratory program will apply an inclusive general model that will enable us to comprehensively evaluate behavior through the entire deformation history of these sediments, from the onset of strain to late-stage behavior. For each till, fifteen mechanical parameters will be quantified in terms of the highly general constitutive model that has been successfully applied elsewhere in a variety of geotechnical and other materials engineering applications. The experiments will encompass 80 or more tests over about 30 months utilizing proven equipment and methodologies, as well as some innovative techniques recently developed by one of the members of the research team. To help validate the experimentally determined parameters, the project includes development of a non-linear back-prediction model, which will be used to verify the consistency of the experimentally determined values with predicted values, given the physical conditions and responses observed during the experiments.