Geologic Control of Sand Boils Along Mississippi River Levees
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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A common problem during floods along the lower Mississippi River is the formation of sand boils on the landward sides of levees. If the hydrostatic pressure in the pervious substratum landward of a levee becomes greater than the submerged weight of the topstratum, the uplift pressure may cause heaving and rupture at weak spots with a resulting concentration of seepage flow in the form of sand boils. This, in turn, can lead to piping and instability of the levees during critical high-water periods. The disposition of pervious versus impervious floodplain deposits beneath the levee and the angle at which such bodies are crossed by the overlying levees are controlling factors in the localization of sand boils. Thus recognition of alluvial landforms forming the riverbanks, the types of soils association with them, and their detailed mapping in plan and profile are important factors in levee design. Corrective design involves a detailed delineation of the surface and subsurface geology b careful selection of borrow pits to avoid stripping critically thin topstratum deposits, and c the use of riverside of landside berms of blankets andor the installation of relief wells.
- Geology, Geochemistry and Mineralogy
- Hydrology, Limnology and Potamology
- Civil Engineering