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

研究进展：基于本构模型的细粒冰沉积试验研究。简森，P.U. Clark， C.S. Desai & D.N. contractoj [r],[0229907, -0229513, -0229513， - 0229883]本项目将为约束和检验关于沉积物变形、滑动和犁耕在影响软沉积物床上冰盖行为中的作用的假设提供更完整的经验基础。了解冰盖动力学及其与地球气候系统的联系，需要对冰下丘的变形行为进行准确和完整的描述。结合气候模型，这样的冰盖模型可以用来研究冰盖的稳定性——包括更新世和现代——以及它们与全球气候的相互作用。这个由冰川地质学、土壤力学和材料工程以及地球物理建模专家组成的合作项目将通过对劳伦泰德冰盖沉积的两个具有代表性的细粒沉积物的力学特性进行全面评估来解决这一重要问题。具体来说，pi提出的实验室计划将应用一个包容性的通用模型，使我们能够通过这些沉积物的整个变形历史，从应变开始到后期行为，全面评估其行为。对于每个till， 15个力学参数将根据高度通用的本构模型进行量化，该模型已成功地应用于各种岩土工程和其他材料工程应用。这些实验将包括在大约30个月的时间里进行80次或更多的测试，使用经过验证的设备和方法，以及研究小组一名成员最近开发的一些创新技术。为了帮助验证实验确定的参数，该项目包括开发非线性反向预测模型，该模型将用于验证实验确定值与预测值的一致性，给定物理条件和实验中观察到的响应。

COLLABORATIVE RESEARCH: TESTING & CONSTITUTIVE MODELINGOF FINE-GRAINED TILLS DEPOSITED BY THE LAURENTIDE ICE SHEETJ.W. Jenson, P.U. Clark, C.S. Desai & D.N. ContractorEAR-0229907, -0229513, -0229889This 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.