TDOT Rockfall ManagementSystem

Saieb Haddad

Geotechnical Engineer

Geotechnical Engineering Section

Tennessee Department of Transportation

Old Approach: Falling Rock signs

History/Background

• Most of the “Easy” routes have been developed.

• Meanwhile, the previously lightly traveled, more challenging routes have seen increased traffic.

• In addition, weathering of rock slopes along existing routes continues…

New Approach:

• Develop a systematic method of identifying and repairing problem slopes.

Tennessee RMSDeveloped as a collaboration between TDOT, the

University of Tennessee, and Virginia Tech

Research Project Goals

Identify Hazardous Sites Develop a Rockfall Hazard Rating System

Statewide Coverage of TDOT Roadways

Ability to prioritize remediation

Inclusion of photos

Database and GIS System

Hazard Rating Components• Slope height• Ditch effectiveness• Average Vehicle Risk (AVR)• Roadway Width• Decision Site Distance (%DSD)• Geologic characteristics

(Structural/weathering modes)• Block size/volume per event• Presence of water on slope• Rockfall history

Rockfall Hazard Management System Training Manual

Rockfall Hazard Rating System

Preliminary Ratings:

A – High Hazard

B – Moderate Hazard

C - Low Hazard

Failure Modes

• Planar Sliding• Wedge Sliding• Toppling• Differential Weathering• Raveling

Planar Sliding

Wedge Sliding

Toppling

Differential Weathering

Raveling

RMS WebMap Application

There are just under 2000 A and B SitesApproximately 49% are A Sites

Remedial MeasuresOften used in combination

• Removal – Blasting, scaling, trimming• Restraint – High capacity anchors, rock

bolts, anchored wire mesh, retaining walls• Containment – High energy fencing• Control – Draped wire mesh• Widening of ditch/catchment area

RemovalBlasting

RestraintHigh Capacity Anchors

RestraintBolts/Dowels

Pile and Lagging WallRock Socket Drilling

RestraintPile & Lagging Wall

Pile and Lagging WallLagging in Place

ContainmentHigh Energy Fencing

ControlWire Mesh Drape

Catchment Area/Ditch Improvement

Challenges

• Developing/selecting the most cost-effective remedial measures (maintaining traffic is a critical factor).

• Producing construction plans/contract documents

• Funding• Keeping database up-to-date

Civil Engineers, Infrastructure, Highways, and Public Safety

• Highway Engineers traditionally have needed a working knowledge of route geometry/surveying, construction methods, structural design, hydraulics, hydrology, soils and materials.

Return to office or laptop

Data synchronization

Database & GIS interface

Field datacollection

QA/QC

Technical Response

Rock Fall/Rock Slide reported to the Geotechnical Staff

• Site inspection.• Stability assessment.• Highway closure or maintain partial traffic (important decision).

• Geotechnical Investigation and Analyses.(could include drilling and testing).

• Perform repair design and contract document/ emergency contract.

Contractors Prequalification

Award Contract Start Construction

Skilled labor

Roadway closed due to traffic safety and work space.

The end