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U.S. Army Corps of Engineers
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US Army Corps of EngineersInstitute for Water Resources, Risk Management Center
Internal Erosion Suite

Horizontal Crack

Method of Analysis​

The method of analysis is the same as that described for the Cylindrical Pipe worksheet in the Method of Analysis section.

Critical Shear Stress and Initial Crack Dimensions​

The critical shear stress and initial crack dimensions are very similar to that described for the Cylindrical Pipe worksheet in the Critical Shear Stress and Initial Pipe Diameter section. Instead of entering an initial pipe diameter, input the initial crack width. In addition, step 2 includes an input for the crack width parallel to the embankment centerline (X) as Figure illustrates.

Horizontal crack geometry.
Figure: Horizontal crack geometry.

Core Geometry​

The core geometry is the same as that described for the Cylindrical Pipe worksheet in the Core Geometry section.

Hydraulic Shear Stress​

The hydraulic shear stress on the surface of the horizontal crack from flow of water in the crack is the same as that described for the Cylindrical Pipe worksheet in the Hydraulic Shear Stress section, but using a different equation and crack width instead of pipe diameter. The hydraulic shear stress on the rectangular surface of the horizontal crack is calculated using Equation.

τ=γwiWX(2W+2X)\tau = \gamma_{w}i\frac{WX}{(2W+2X)}

where:

W = initial crack width
X = crack width parallel to the embankment centerline

Likelihood of Initiation of Concentrated Leak Erosion​

The likelihood of initiation of concentrated leak erosion is the same as that described for the Cylindrical Pipe worksheet in the Likelihood of Initiation of Concentrated Leak Erosion section, but using crack width instead of pipe diameter.

Headwater Level for Initiation of Concentrated Leak Erosion​

The headwater level for initiation of concentrated leak erosion is the same as that described for the Cylindrical Pipe worksheet in the Headwater Level for Initiation of Concentrated Leak Erosion section, but using crack width instead of pipe diameter.

Critical Crack Width for Initiation of Concentrated Leak Erosion​

The critical crack width for initiation of concentrated leak erosion is the same as that described for the Cylindrical Pipe worksheet in the Critical Pipe Diameter for Initiation of Concentrated Leak Erosion section, but using a different equation and crack width instead of pipe diameter. Equation calculates the critical crack width for initiation of concentrated leak erosion for each headwater level.

Wcr=−2LτcX2Lτc−γw(H1−H2)XW_{cr} = \frac{-2L\tau_{c}X}{2L\tau_{c} - \gamma_{w}(H_{1}-H_{2})X}
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