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Haley & Aldrich, Inc. The Use of Wire Mesh/Cable Net Drapes to Control Rockfall: Case Study and Guidelines Dr. Martin J. Woodard, PG [email protected]
Haley & Aldrich, Inc.
The Use of Wire Mesh/Cable Net Drapes to Control Rockfall: Case Study and Guidelines
Dr. Martin J. Woodard, [email protected]
Haley & Aldrich, Inc.
Mohican State Park
Haley & Aldrich, Inc.
Project Location
Haley & Aldrich, Inc.
Park Activities
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
ASH-97-4.1 circa 1999
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Resource Guide
• Washington Department of Transportation Guideline Report
• Balasingam Muhunthan, Shanzhi Shu, NavaratnarajahSasiharan, Omar A. Hattamleh, Thomas C. Badger, Steve M. Lowell, John D. Duffy
• DESIGN GUIDELINES FOR WIRE MESH/CABLE NET SLOPE PROTECTION
• April 2005
• WA-RD 612.2
Haley & Aldrich, Inc.
Types of Rock Slope Failures
Large-Scale
Haley & Aldrich, Inc.
Friction CircleCritical Zone
Slope Orientation
SR 2 Leavenworth, WA
Kinematic Analysis
Types of Rock Slope FailuresLarge-Scale Planar Failures
Haley & Aldrich, Inc.
Types of Rock Slope FailuresLarge-Scale Wedge Failures
Smart Road Blacksburg, VA
Haley & Aldrich, Inc.
Large Block on Slope: SR2/97 MP137.46-137.55
Block in Question
30 ft
8 ft
15 ft
3-4 inch separation
Types of Rock Slope FailuresLarge-Scale Topple Failures
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Large vs. Small Scale Failures
Global Concern
Rockfall Concern
Haley & Aldrich, Inc.
Structurally Controlled Small FailuresRockfall
Large blocks that free-fall from steep cliffs
Haley & Aldrich, Inc.
Rock Slope Engineering and the Public
As geologists and engineers,
our responsibility is to ensure public safety.
Virginia, USA Near Sacramento, CA
Haley & Aldrich, Inc.
Rockfall Containment
Haley & Aldrich, Inc.
Roadway Relocation
Haley & Aldrich, Inc.
Steps in Mesh Design
• Site Reconnaissance
• Slope Characteristics and External Loads
• Fabric Selection
• Anchor Loads for Mesh
• Factor of Safety for debris and impact loads
• Anchor Capacity and Spacing
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Fabric Selection
Fabric Block Size
Double‐twisted hexagonal mesh < 2 ft
Cable net < 4‐5 ft
Haley & Aldrich, Inc.
Anchor Loads
• Weight of drape (40 kips)
• Weight of debris (150 kips)
• Impact loads (13 kips)
• Colorado Rockfall Simulation Program
• Snow and Ice Loads (assumed to be 0)
• Total loads = 203 kips Assume 250 kips
1 ft4 ft
Debris load
Haley & Aldrich, Inc.
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4567891011121314
Lateral East
Lateral west
D
D
12Approximate location of anchors. Anchor locations not surveyed.
Distance between anchors is approximately 36 feet with the exception of lateral anchors.
Slope Height (ft) Anchor Spacing (ft)
< 100 50
100 – 200 25
200 – 300 20
Haley & Aldrich, Inc.
Anchor Design
• Development Length
• Bar/cable to grout
• Bond Length
• Grout to rock
• Rock Mass Reaction
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
Haley & Aldrich, Inc.
