Large Fill Shrinkage and Instrumentation Along a Levee Enlargement

摘要

In this paper, the causes for the significant 40% borrow to fill shrinkage in a levee enlargement project in western Mississippi is analyzed and presented. In-place moisture-density tests, as well as laboratory tests such as Atterberg limit, unconfined compression, compaction, CBR, unconsolidated undrained triaxial, and one-dimensional consolidation tests were conducted to characterize the soil properties required for the shrinkage and fill stability analyses. The shrinkage analysis of the characterized soil was conducted by considering both the immediate and time-dependent settlement of foundation soil, the compaction of levee material and the levee construction history. Since settlement plates were specified for settlement and volume loss measurement, the fill volume loss was also calculated using plate settlement and specified volume loss calculation method in the construction documents. It is shown that the specified method in the contract significantly underestimated the shrinkage even if the expected construction schedule could be achieved. The conducted fill stability analyses using lab and field test results determined that the material which was compacted following the specified compaction procedure would be unstable. The fill instability resulted in significantly extending the construction time and consequently resulted in more consolidation of levee foundation soils. These difficulties resulted in much greater levee enlargement costs than anticipated.