predicting erosion impact on highway and railway bridge ... · department of civil engineering...
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Charles T. Swann, R.P.G.Mississippi Mineral Resources Institute
111 Brevard Hall
University, Mississippi
Christopher L. MullenDepartment of Civil Engineering
University of Mississippi
P.O. Box 1848
University, Mississippi
2015 University Transportation Center
Conference for the Southeastern Region
Birmingham, Alabama
March 26, 2015
Predicting Erosion Impact on Highway and
Railway Bridge Substructures
Predicting Erosion Impact on Highway and Railway Bridge
Substructures
Project Goals
1) To evaluate bridge condition and the present status of stream erosion beneath
existing bridges.
2) Relate this erosion potential to the geological unit on which the bridge is
founded.
3) To identify any additional factors that may accelerate stream erosion beneath
the bridges.
4) To identify erosion sources other than stream erosion that may influence
bridge well-being.
5) To evaluate any stream erosion mitigation measures.
6) Determine the implications present erosion may have during a major
earthquake event in North Mississippi.
7) Transfer the results to engineering and geological professionals.
Predicting Erosion Impact on Highway and Railway Bridge
Substructures
Bridge Condition Survey
Modern Construction
*Appropriate amount of well
placed rip-rap
*Stream is located between
piers
*No structural discontinuities
*Small-scale erosion features
Older Construction
*Some lack rip-rap mitigation
*Piers within stream flow
*Structural discontinuities are
present
*Erosion concerns are present to varying degrees, some significant
* Construction dates back to the 1930’s
Predicting Erosion Impact on Highway and Railway Bridge
Substructures
Stream Erosion Conditions
Identified concerns include: 1) lateral migration of channel; 2) rapid downward
erosion of stream channel; 3) local scour caused by debris dams; and
4) erosional vulnerability of the substrate.
Predicting Erosion Impact on Highway and Railway Bridge
Substructures
Erosion and Geological Unit
Some geological Units
more vulnerable to
erosion than others,
most vulnerable are:Ripley Formation – particularly
the Transitional Clay, Coon
Creek Members
Least Vulnerable Units:Ripley Formation – Chiwapa
Member, Demopolis Chalk
Predicting Erosion Impact on Highway and Railway Bridge
Substructures
Channelization Impact On Erosion Vulnerability
Predicting Erosion Impact on Highway and Railway Bridge
Substructures
Vulnerability to Seismic Events
• FEA (ABAQUS) modeling
• Predicting effect of Earthquakes on eroded substructure
• Soil-Substructure Interaction (use of Infinite Elements)
Predicting Erosion Impact on Highway and
Railway Bridge Substructures
Soil Profile per Original Drawings (1936)
Predicting Erosion Impact on Highway and
Railway Bridge Substructures
Soil Profile per Current Field Observation (2014)
Predicting Erosion Impact on Highway and
Railway Bridge Substructures
Original Soil Profile and Current Observed Soil
Profile Overlay
Predicting Erosion Impact on Highway and Railway Bridge
Substructures
Preliminary Conclusions
1) Erosional concerns are time-dependent features. The Highway 178 bridges
provide insight into the future concerns likely to develop on the new U.S 78
corridor.
2) Stream erosion, both lateral and vertical, is a significant stability factor at the
older bridges.
3) Bridge drainage openings and expansion joints can initiate erosion in addition
to the stream channel erosion.
4) Rip-rap provides only short term mitigation. Condition of the rip-rap should
be monitored and renewed as needed.
5) Misalignment of channelized streams and bridge piers can initiate rapid scour
and downcutting.
6) Erosion and geological units can be correlated providing geotechnical insight
to future bridge design.
7) Bridges are frequently used well beyond its intended designed life span.