| Popis: |
The coastal southeastern United States, from northeastern Florida to the Carolinas, is dotted with rivers and creeks that discharge into back bays and coastal marshlands of tidal brackish water. The marshes are characterized as flat lands generally covering vast areas that occasionally serve as the delta for many of these rivers and streams. River flow, tidal fluctuations, and alluvial events carry sediments to and away from these areas, but the marsh vegetation, or those areas exposed to low flow velocities, trap fines that through history have accumulated as very soft deposits. These deposits are commonly of Holocene origin and are characterized as fat clays and plastic silts with varying degrees of organics, generally normally to slightly overconsolidated. Typical infrastructure built over these types of soils include roadways and maritime or port facilities, all of which have to consider the challenges these soil deposits bring, in particular high settlement magnitudes and low bearing capacities. This paper presents relationships for determining the compression index or Cc of these deposits, developed based on data collected from multiple sites in Florida, Georgia, and South Carolina. Correlations are presented as functions of water content, organic content, and void ratio, which would permit the geotechnical engineer to make, at a minimum, preliminary estimates of anticipated consolidation settlement of these soils when lacking 1-D consolidation test results. Statistics and probability were employed to develop 95 and 99% confidence intervals envelopes to help the geotechnical design engineer with reliability-based analyses. |
