predicting erosion impact on highway and railway bridge ... · department of civil engineering...

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.


Substructures

Study Area


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


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.


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


Substructures


Substructures

Other Erosion Sources


Substructures

Channelization Impact On Erosion Vulnerability


Substructures

Vulnerability to Seismic Events

• FEA (ABAQUS) modeling

• Predicting effect of Earthquakes on eroded substructure

• Soil-Substructure Interaction (use of Infinite Elements)



Soil Profile per Original Drawings (1936)



Soil Profile per Current Field Observation (2014)



Predicted Soil Profile (2045)



Original Soil Profile and Current Observed Soil

Profile Overlay


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.


Substructures

QUESTIONS?

predicting erosion impact on highway and railway bridge ... · department of civil engineering...

Documents