Abstracts

Measurements of Physical Characteristics of Earthen Levees for Small Lakes in Mississippi

Author(s): Andrews, W.; Ozeren, Y.; Wren, D.

The state of Mississippi has many aging earthen levees, but the current status of the levee system is unknown. Many of the levees in Mississippi have exceeded their 50-year design life, and the possibility of a critical failure on one of the levees is increasing with time. The overall goal of this project is to create a computer model to simulate a critical failure of a levee and analyze how it would affect the surrounding area and the surrounding population. However, a computer model cannot be created without knowing the mechanical properties of each levee. Through a grant from MDEQ, the National Center of Computational Hydrological Engineering (NCCHE) was tasked with finding these mechanical properties by performing in-situ tests and to collect soil samples from fifteen levees throughout the state of Mississippi. The soil samples were taken at three different locations near the middle of each levee. At each location, one 6-in diameter sample was collected for jet erosion testing, and two 2-in diameter samples were collected for bulk density measurements and soil texture analysis. It was found that the range of the critical shear stress varied from 10 Pa to 130 Pa. The older dams had a higher critical stress due to longer amount of time for the soil to consolidate. The 2-in samples showed the soil texture of each levee. For example, the levee at Lake Druid in Meridian, MS, was composed of 30% clay, 41% silt, and 29% sand. With this information on the mechanical properties of each levee, more accurate simulations of levee breaches can be made, leading to better understanding of the aging levee system in the state of Mississippi.

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