A New Experimental Approach Toward A Unified Theory of Time-Dependent Consolidation

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9812106 DeGroot "A New Experimental Approach Toward a Unified Theory of Time- Dependent Consolidation" This research involves an innovative experimental approach to help resolve a fundamental issue in geotechnical engineering: the role of time-dependent creep deformations during consolidation. The original consolidation theory for fine-grained soils cannot predict the influence of creep deformations that occur under constant effective stress levels. This has led to significant practical problems, including difficulty in predicting field consolidation settlements based on laboratory tests. It has also led to research and debate on the nature of creep during consolidation. One hypothesis predicts no influence of creep deformations until after all loading- induced pore water pressures are dissipated; the other hypothesis includes creep throughout the consolidation process. There are substantial data and prominent researchers supporting each of the two theories, but little agreement between them. This research will investigate the validity of a consolidation model that can potentially unify the two hypotheses and explain both sets of apparently conflicting data. This research is not aimed at proving one of the hypotheses, but toward measuring the contribution of each consolidation component (due to pore pressure dissipation and due to creep) to the overall behavior. The research will be executed through a partnership between Northeastern University and the University of Massachusetts- Amherst. The UMASS- Amherst partner will obtain high quality block samples of four natural soils, each with its own particular structure, and will perform short- and long-term conventional, incrementally loaded tests to evaluate creep behavior and conventional consolidation parameters. At Northeastern, a computer-automated, specially instrumented consolidation cell was developed under a prior NSF award. This device will be used to perform controlle d gradient tests with feedback provided by mid-specimen pore pressure probes. ***