schnabel-eng.com

Controlling Seepage Along

Penetrations Through Dams and

LeveesJoseph S. Monroe, PE

Levee and Embankment Workshop

International Commission on Large Dams

Seattle, Washington

Cause of Failure?

Background

� Types of Penetrations

� History Seepage Control Measures

� Design Considerations

� Construction Considerations

Types of Penetrations

� Conduits

� Spillways

Types of Penetrations

� Transportation Facilities

� Utilities

Historic Seepage Control Measures

� Anti-Seep Collars

Historic Seepage Control Measures

� Anti-Seep Collars

� Relatively Simple Design

� Extensive Manual Labor

� Difficult to Achieve Desired Results

Historic Seepage Control Measures

� Anti-Seep Collars

Historic Seepage Control Measures

� Use of Anti-Seep Collars Rescinded

� 1974 - USACE Technical Letter 1110-2-180

� 1974 - USACE Technical Letter 1110-2-192

� 1987 - USBR Assistant Commissioner Engineering and Research Technical Memorandum Number 9

� 2005 – Federal Emergency Management Agency Document 484

Historic Seepage Control Measures

� Rescinding Use of Anti-Seep Collars –

Alternatives to Reduce and Control

Seepage

� Filters

� “Cement Slurry in Haunch Areas of Pipe” or Concrete Cradle

Design Considerations

� Cradles for Pre-Cast Conduits

� Battered/Sloping Walls for Cast In-place

Construction

� Rigidly Behaving Structures that

Articulate with Embankment Movement

� Filters

Cradles

� “Cement Slurry in Haunch Areas of

Pipe” or Concrete Cradle

Battered Walls

Battered Cradles

Conduit and Cast-in-Place Concrete

Design Considerations

� Rigidity

� Conduits Should be Designed to Act Rigidly Under Loads Imposed – Three Edge Bearing Loads for Conduits

� Design for At-Rest Pressure to Limit Potential for Movement and Separation to Occur

� Allow for Articulation at Controlled

Locations

Conduit and Cast-in-Place Concrete

Design Considerations (continued)

� Durability

� Select Materials With Anticipated Life Spans Greater than 100-years

� Consider Bond between Selected

Materials and Soil

� Concrete versus Plastic

� Filters

� Use Accepted Criteria to Properly Design Filters to Prevent Movement of Soil Particles

Conduit and Cast-in-Place Concrete

Design Considerations (continued)

� Cradle/Battered Wall Geometry

� Facilitate Placement of Concrete

� Facilitate Placement and Compaction of Soil

� Improve Contact Between Soil and Concrete

� Articulation

Filters

Construction Considerations

� Use of Mud Slabs

� Concrete Placement

� Placement and Compaction of Soils

� Moisture Content

� Compaction Methods

� Equipment Selection

Construction Considerations

� Mud Slabs

� No Wider than Base Width of Structure

� Joints at each Construction Joint

� Rough Finish Perpendicular to Flow

Mud Slabs

Mud Slabs

Mud Slabs

Construction Considerations

� Concrete Placement

� Use Reasonable Slump Concrete

� Too Dry Prevents Adequate Movement and

Contact with Foundation and Conduits

� Too Wet Inhibits Strength and Increases

Shrinkage

� Use Vibrators to Consolidate Concrete

� Place Concrete from One Side Only To Prevent Creation of ‘Air Lock’

Concrete Placement

Construction Considerations

� Soil Placement and Compaction

� Wet of Optimum

� Control Particle Size

� Selection of Material Type

� Selection of Compaction Method

Soil Placement and Compaction

Soil Placement and Compaction

Cause of Failure???

Backfill, Design, Concrete Placement?

Concrete Placement

Thank-You