11stst NORTH AMERICAN LANSLIDE CONFERENCENORTH AMERICAN LANSLIDE CONFERENCE

ROCK FALL SHEDSROCK FALL SHEDSAPPLICATION OF JAPANESE DESIGNS IN APPLICATION OF JAPANESE DESIGNS IN

NORTH AMERICANORTH AMERICAJune 5, 2007June 5, 2007

Dr. H. YoshidaDr. H. YoshidaToshimitsu NomuraToshimitsu Nomura

Duncan C. WyllieDuncan C. WyllieAnthony J. MorrisAnthony J. Morris

Kanazawa University, Kanazawa, JapanKanazawa University, Kanazawa, JapanProtec Engineering, Niigata, JapanProtec Engineering, Niigata, Japan

Wyllie & Norrish Rock Engineers, Vancouver, CanadaWyllie & Norrish Rock Engineers, Vancouver, CanadaCanadian Pacific Railway, Calgary, CanadaCanadian Pacific Railway, Calgary, Canada

Opening of Protec Engineering new

office buildingMay 22, 2007

Summary of TopicsSummary of Topics

1.1. Rock fall sheds in JapanRock fall sheds in Japan2.2. Rock fall analysisRock fall analysis3.3. Principles of rock shed design and testingPrinciples of rock shed design and testing4.4. Design impact energies and forcesDesign impact energies and forces5.5. North American rock fall sheds:North American rock fall sheds:

Kicking Horse Canyon Shed, CanadaKicking Horse Canyon Shed, CanadaPitkins Curve Shed, CAPitkins Curve Shed, CAFerguson Rock Slide Shed, CAFerguson Rock Slide Shed, CA

ROCK FALL MITIGATION STUDYNIIGATA AND KANAZAWA

JAPAN

OCTOBER 20 TO 25, 2003

Niigata

To Tokyo

Kanazawa

Sea of Japan

Rock Sheds

Fence “Rock Keeper”

Concrete Barrier

Rock Shed

MSE Barrier

Sand Cushion

Styrofoam

5 10 20 50 100 200 300 500 1000

Rel

ativ

e C

onst

ruct

ion

Cos

t

5

10

5

0

100

2

00

500

Impact Energy Capacity (tf.m)

Styrofoam cushionSand

cushionSuper shed

SHEDSSHEDSRock Shed

Pre-cast concrete shed

“Super Rock Shed” – high ductility shed, capacity 800 tf m

Test loading:Mass = 44,000 lbHeight = 120 ft.

Summary of TopicsSummary of Topics

1.1. Rock fall sheds in JapanRock fall sheds in Japan2.2. Rock Rock fallfall analysisanalysis3.3. Principles of rock shed design and testingPrinciples of rock shed design and testing4.4. Design impact energies and forcesDesign impact energies and forces5.5. North American rock fall sheds:North American rock fall sheds:

Kicking Horse Canyon Shed, CanadaKicking Horse Canyon Shed, CanadaPitkins Curve Shed, CAPitkins Curve Shed, CAFerguson Rock Slide Shed, CAFerguson Rock Slide Shed, CA

Rock fall modeling programsRock fall modeling programs

Objective of modeling is to determine:Objective of modeling is to determine:Velocity of rock falls, which is used to determine impact Velocity of rock falls, which is used to determine impact energy on protection structureenergy on protection structureTrajectory of rock falls to determine dimensions of Trajectory of rock falls to determine dimensions of protection structure protection structure

Common modeling programs:Common modeling programs:CRSP CRSP –– Colorado Rockfall Simulation ProgramColorado Rockfall Simulation ProgramRockFall RockFall –– RocScienceRocScience

ModelledModelled trajectories are often too hightrajectories are often too high..

Typical computer simulation of rock falls

α

x

y

Impact point

Impact point

Velocity, V

Calculation of rock fall trajectoryCalculation of rock fall trajectory

⎟⎟⎠

⎞⎜⎜⎝

⎛⋅+⎟

⎠⎞

⎜⎝⎛

⋅⋅−= α

αtanx

cosVxg.y

2

50

Rolling rock hazard -boulder travelled ~1 km from source

Impact marks on slope and bounce heights on trees used to calculate trajectory and velocity

Skagway, AK

Source of rock falls –blocks break up as they

impact the slope

Impact points on dockImpact points on dock

Trajectory calculationsTrajectory calculationsRock fall trajectories at base of slope

32 ft. high rock fall net

Measured Rock Fall Trajectories Measured Rock Fall Trajectories (Japan)(Japan)

No. of tests: 212Rock sizes: 300, 500, 700 mmShape: spherical, tabular

Energy Loss during Rock FallsEnergy Loss during Rock Falls

⎟⎟⎠

⎞⎜⎜⎝

⎛−⋅⋅=

ftanHgV

ψμ12

ψf

μ – friction coefficient at impact points

HgV ⋅⋅= 20

Free fall velocity:

Fall velocity, V

Rock fall velocitiesRock fall velocities

0

50

100

150

200

250

0 10 20 30 40 50 60 7

V e lo c it y (m/s)

Free fall velocity

Bare rock faces:Slope = 45°μ = 0.40 (impact)

Talus slopes:Slope = 31°μ = 0.35 (rolling)

Rock fall velocity, V (m/s)

Fall

heig

ht, H

(m)

Energy loss due to impacts

on slope

Skagway

Swiss test

Big Sur

Term

inal

vel

ocity

?

⎟⎟⎠

⎞⎜⎜⎝

⎛−⋅⋅=

ftanHgV

ψμ12

Summary of TopicsSummary of Topics

1.1. Rock fall sheds in JapanRock fall sheds in Japan2.2. Rock fall analysisRock fall analysis3.3. Principles of rock shed design Principles of rock shed design

and testingand testing4.4. Design impact energies and forcesDesign impact energies and forces5.5. North American rock fall sheds:North American rock fall sheds:

Kicking Horse Canyon Shed, CanadaKicking Horse Canyon Shed, CanadaPitkins Curve Shed, CAPitkins Curve Shed, CAFerguson Rock Slide Shed, CAFerguson Rock Slide Shed, CA

Weight impact force –mass x deceleration

Rock mass

Transmitted force distribution

Cushion material

Rock shed roof

Transfer of impact energy into shed structureTransfer of impact energy into shed structure

Weight impact force –mass x deceleration

Transmission impact force –integration of transmitted

pressure on distributed area

Cushion material

Instrumented shed to measure weight impact and transmission impact forces

W = 10kN

Span length

12m10m8m

0 5 10 15 200

2

00

400

60

0

Fall Height (m)M

axim

um re

actio

n fo

rce

(kN

)

Test Setup (plan view)

Load cell(Unit: mm)

2H-390X300X10X16 (Base beam)

Beam A

Beam B

250

Sand Tank

3175

Span length

Displacement meter

Earth pressure gauge

650

170

150 2H-390X300X10X16 (Main beam)

250

Test Setup (plan view)

Load cell(Unit: mm)

2H-390X300X10X16 (Base beam)

Beam A

Beam B

250

Sand Tank

3175

Span length

Displacement meter

Earth pressure gauge

650

170

150 2H-390X300X10X16 (Main beam)

250

Variation of weight and transmission impact forces with

time, full-scale tests

Span length (m)

Deformation

Styrofoam

Sand

Rubber tires

Forc

eRelationship between

force and deformation for three cushioning materials

Deformation

Pre-cast concrete shed

Hinge in column

Rigid connection between column and roof beam

Longitudinal connection between roof beams

Pinned connection

Hinge at base of column

Column

Roof beam

Post tensioned

cables

Rigid connection

between roof beams and

columns

Post tensioned cables joining

roof slabs

Summary of TopicsSummary of Topics

1.1. Rock fall sheds in JapanRock fall sheds in Japan2.2. Rock fall modelingRock fall modeling3.3. Principles of rock shed design and testingPrinciples of rock shed design and testing4.4. Design impact energies and Design impact energies and

forcesforces5.5. North American rock fall sheds:North American rock fall sheds:

Kicking Horse Canyon Shed, CanadaKicking Horse Canyon Shed, CanadaPitkins Curve Shed, CAPitkins Curve Shed, CAFerguson Rock Slide Shed, CAFerguson Rock Slide Shed, CA

Design Impact Load, Design Impact Load, PP

15352321082 −= βλ /// H)mg(.P

Japanese Rock Fall Protection Measures Handbook (2000)Japanese Rock Fall Protection Measures Handbook (2000)

m = rock fall mass (tonnes)λ = Lame constant, 1000 kNm-2 for soft sand cushioning material H = fall height, mβ = factor defining the relationship between the thickness of cushioning layer (T, m) and the diameter of the impacting rock (D, m)

580.

DT −

⎟⎠⎞

⎜⎝⎛=β

Relationship Cushion Thickness (T), Rock Fall Dimension (D) and Factor β

ββ

T/D

Large value for T adds

weight with little increase

in energy absorption

Distribution of impact load through Distribution of impact load through cushion on to roof of shedcushion on to roof of shed

Sand cushion, thickness T

Effective area of transmitted force on

roof, A

4

2TA π=

Roof

Summary of TopicsSummary of Topics

1.1. Rock fall sheds in JapanRock fall sheds in Japan2.2. Rock fall analysisRock fall analysis3.3. Principles of rock shed design and testingPrinciples of rock shed design and testing4.4. Design impact energies and forcesDesign impact energies and forces5.5. North American rock fall sheds:North American rock fall sheds:

Kicking Horse Canyon Shed, Kicking Horse Canyon Shed, CanadaCanadaPitkins Curve Shed, CAPitkins Curve Shed, CAFerguson Rock Slide Shed, CAFerguson Rock Slide Shed, CA

Kicking Horse Canyon

Rock falls are concentrated in gulliesRock falls are concentrated in gullies

Rock shed location19 m

Clearance envelope

“Crash” wall with socket connection to column

Column (pre-cast)

with flexible hinge

Granular fill Rock anchor

with tie-back through wall

Sand cushion 900 mm thick

Rigid connection – post-tensioned cables

Footing supported with rock socketed

pilesRock fill

supporting track

Roof beams (pre-cast) with ducts for longitudinal

connection cables

Retaining wall (cast in place)

Footing dowelled to

rock foundation

Pinned connection with rubber pad

Clearance envelope

Top of “crash” wall with sockets for lower ends of

columns.

Valley-side

columns, 1500 O.C.

Concrete blocks to

retain sand

cushion

Elevation view

Roof beams

Summary of TopicsSummary of Topics

1.1. Rock fall sheds in JapanRock fall sheds in Japan2.2. Rock fall analysisRock fall analysis3.3. Principles of rock shed design and testingPrinciples of rock shed design and testing4.4. Design impact energies and forcesDesign impact energies and forces5.5. North American rock fall sheds:North American rock fall sheds:

Kicking Horse Canyon Shed, CanadaKicking Horse Canyon Shed, Canada

Pitkins Curve Shed, CAPitkins Curve Shed, CAFerguson Rock Slide Shed, CAFerguson Rock Slide Shed, CA

Pitkins Curve, Highway 1, CAPitkins Curve, Highway 1, CA

Pitkins Curve Shed• 45 m high rock face• Design rock fall ~2.5 m

Artists rendering of completed project

Roof protection –Styrofoam with sand covering

Widely spaced columns to maximize view of ocean

Summary of TopicsSummary of Topics

1.1. Rock fall sheds in JapanRock fall sheds in Japan2.2. Rock fall modelingRock fall modeling3.3. Principles of rock shed design and testingPrinciples of rock shed design and testing4.4. Design impact energies and forcesDesign impact energies and forces5.5. North American rock fall sheds:North American rock fall sheds:

Kicking Horse Canyon Shed, CanadaKicking Horse Canyon Shed, CanadaPitkins Curve Shed, CAPitkins Curve Shed, CA

Ferguson Rock Slide Shed, CAFerguson Rock Slide Shed, CA

Slide has blocked highway- temporary

bridges by-pass route traffic on to right bank

Ferguson Rock Slide Highway 140 between

Mariposa and Yosemite National Park, CA

Pre-fabricated steel shed constructed after removal

of slide debris

Steel shed design based on technology to protect

aircraft from missile attack

Steel shed under

construction

ConclusionsConclusions1. Rock fall modeling can produces excessively high

trajectories based on observations of actual rock falls2. Information needed on impact friction coefficients

related to slope surface conditions3. Extensive testing of rock fall sheds in Japan provides

reliable information on design impact forces4. Rock sheds constructed with flexible components that

absorb impact energy5. Properties and thickness of cushioning material (sand

and/or Styrofoam) influences magnitude of transmitted impact force

Thank you

Impact positions of rock falls on Impact positions of rock falls on roof of shedroof of shed

ψP′ P

Envelope of Rock Fall Envelope of Rock Fall TrajectoriesTrajectories

Source

Trajectory envelope

Trajectory height, h

Angular velocity

Translational velocity

ψf

Steel shed

Ferguson Rock Slide Highway 140 between

Mariposa and Yosemite National Park, CA

Deflection sheds

Measured Rock Fall TrajectoriesMeasured Rock Fall Trajectories

Fall

heig

ht, H

(m)

Trajectory height, h (m)

90% envelope