File Name: undcut01.cri, undcut02.cri ...

Specification Manual Reference: 225-1 (C) Undercut Excavation

Undercut Excavation
Undercut Excavation consists of the excavation, placement, and compaction and/or satisfactory disposal of materials removed from a location below the finished grade roadway cross section, except for the following:

(1) Rock in the bottom of roadway cuts that has been excavated 1 foot or less
below the roadbed and ditches.
(2) In cut areas, excavation removed below the outside slopes of roadway ditches.

Required Definition Files: standard

The undercut criteria files are designed to allow the designer to draw the area of undercut to the cross sections after the proposed templates have already been run. The process to draw undercut on cross sections begins with a Geotechnical Recommendation letter.

Typical Geotechnical Recommedation for Undercut

Once the proposed template has been drawn in the XSC file, the Undercut Criteria can be used to draw the area designated as undercut excavation. The Undercut Criteria extracts two important features from a completed proposed template, the subgrade edge of pavement point directly below the blue proposed finished pavement inside and outside edge of pavement (EOP) points and the pink subgrade line. The Undercut Criteria will always start from the Centerline and start tracing toward the outside EOP. Then with the addition of a user definable offset distance from the outside subgrade EOP point, the Undercut Criteria will establish the outside subgrade edge for undercut excavation. With a user definable undercut depth variable, the Undercut Criteria will trace the subgrade line (copy parallel) at the depth specified to (1) where the subgrade line ties to existing ground, (2) to an optional user definable inside subgrade EOP offset distance point, or (3) to the Centerline. Finally, the inside and outside edges are drawn to close the area designated as undercut excavation. This starting point can either be on the pink subgrade line or the existing ground line depending on the undercut depth. This is the main difference between NCDOT definition for undercut versus Geopak's definition. Criteria will draw the undercut line to the subgrade line or existing ground line.

Features of this criteria include the designer's ability to control the following:

• The offset distance from the outside subgrade EOP point
• The offset distance from the inside subgrade EOP point
• The depth of undercut

Special Note: The Undercut Criteria will only work with cross section files (XSC) drawn on the correct standard NCDOT level name.

User Defined Variables

"UNDERCUT XS DGN" (required)
The name of the cross section file (XSC). If the XSC file and the Criteria input file are not in the same folder, then the directory path to the XSC file must also be included with the XSC file name. For example; C:\Myfolder\R2008_rdy_xsc_l.dgn.

"UNDCUT01 OUTSIDE EOP OFFSET"
Define the offset distance from the outside subgrade edge of pavement point. Paved shoulders are considered part of the edge of pavement. A positive offset value is applied toward the outside of the template (toward the side slopes). A negative offset value is applied toward the inside of the template (toward the Centerline). If not defined, a default value of 1 foot (or 1 meter) is used.
Default definition = 1.

"UNDCUT01 INSIDE EOP OFFSET"
Define the offset distance from the inside subgrade edge of pavement point. Paved shoulders are considered part of the edge of pavement. A positive offset value is applied toward the inside of the template (toward the Centerline) . A negative offset value is applied toward the outside of the template (toward the side slopes). If not defined, a default value of 1 foot (or 1 meter) is used.
Default definition = 1.

"UNDCUT01 DEPTH"
Define the depth from the subgrade line to the bottom of the undercut limit. The undercut depth is always positive. If not defined, a default value of 3 feet (or 1 meter) is used..
Default definition = 3 (or 1 (m)).

Example:

DEFINE "UNDERCUT XS DGN" u3326_geo_xsc_l.dgn
DEFINE "UNDCUT01 OUTSIDE EOP OFFSET" 1
DEFINE "UNDCUT01 INSIDE EOP OFFSET" 1
DEFINE "UNDCUT01 DEPTH" 1

GEOTECH STRATIGRAPHY

Geotech stratigraphy is automatically considered by the Undercut Criteria. Red dashed line elements on levels "Prop Road Sect: Material - Contact (Rec Bottom - Major)" and "Prop Road Sect: Material - Contact (Rec Bottom - Minor)" are considered geotechnical stratigraphy elements. Below are the various geometry and locations of the stratigraphy line elements (red) and demonstrates how undercuts (green) are drawn accordingly.

1) Stratigraphy Line Above Subgrade - No undercut drawn.

2) Stratigraphy Line Below Subgrade - Greater Than Undercut Depth

3) Stratigraphy Line Below Subgrade - Less Than Undercut Depth

3) Other Oblique Stratigraphy Geometry

3A.

3B.

3C.

3D.

3E.

3F.

3G.

3H.

3I.

3J.

3K.