Full-Scale Testing of Levee Resiliency During Wave Overtopping Chris - - PowerPoint PPT Presentation

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Full-Scale Testing of Levee Resiliency During Wave Overtopping Chris - - PowerPoint PPT Presentation

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Sixth International Conference on Scour and Erosion Paris August 27-31, 2012 Full-Scale Testing of Levee Resiliency During Wave Overtopping Chris Thornton Steve Hughes Bryan Scholl Engineering Research Center Project Overview Requirements:

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Full-Scale Testing of Levee Resiliency During Wave Overtopping

Chris Thornton Steve Hughes Bryan Scholl

Engineering Research Center

Sixth International Conference on Scour and Erosion

Paris August 27-31, 2012

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Project Overview

  • Requirements:

– Simulate large wave overtopping discharges – Replicate New Orleans levee grass slopes – Test alternative slope protection products

  • Design Issues:

– Overtopping simulator design – Planter trays to simulate soil/grass/TRMs – Operating procedures – Measurements

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Principle of Wave Overtopping Simulation

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Overtopping Distribution

1000 2000 3000 4000 5000 6000 100 200 300 400 500 600 700 800 900

Number of overtopping wave, in ascending order

Overtopping volume (l/m)

0.1 l/s/m 1 l/s/m 10 l/s/m 30 l/s/m 50 l/s/m 75 l/s/m

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200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 120 130

Number of overtopping waves in descending amount

  • vertopping volume per wave

(liters per m width)

calculation simulation

1 l/s per m

56 waves with 50 l per m 40 waves with 150 l per m 10 waves with 400 l per m 6 waves with 700 l per m 3 waves with 1000 l per m

Overtopping distribution

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Wave Overtopping Test Facility

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Wave Overtopping Test Facility

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Wave Overtopping Test Facility

Physical Features

  • Full-scale testing
  • Dual test channels
  • Steady state capabilities
  • Flow measurements
  • Accommodate different tray geometries
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Wave Overtopping Test Facility

Hydraulic Features

  • Total simulator capacity – 27 m3 or 15 m3/m
  • Average wave overtopping discharge 200 –

380 l/s per m (depends on wave period)

  • Corresponds to Hm0 = 2.4 m, Tp = 9 s
  • Steady overflow – 2.5 m3/s per m (or more)
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Planter Tray Dimensions

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Tray Preparation

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Tray Cultivation

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Tray Installation

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Resiliency Testing Overview

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Overtopping Simulator in Action

Video

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Bare Clay Slope Test

Before Upper Tray Lower Tray After 1 hour at 9.3 l/s per m Total failure after 20 min at 18.3 l/s per m

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Lime-Stabilized Bare Clay Test

Before After 20 min at 370 l/s per m

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ACB Slope Protection Tests

After test at 370 l/s per m Before

New Orleans Clay

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ACB Slope Protection Tests

Failure at 370 l/s per m

Golden Soil

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Grass Slope Resiliency Tests

Bermuda Grass Slope

No damage after 370 l/s per m After 12 hrs of testing

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Grass Slope Resiliency Tests

Before No damage after 280 l/s per m

Bahia Grass Slope

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Grass Slope Resiliency Tests

Before No damage after 370 l/s per m

Bermuda Grass with TRM

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Grass with Wheel Ruts

Before After test at 370 l/s per m

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Dormant Grass Slope Resiliency Test

Before At end of 3rd hour

After 1st hour at 230 l/s per m After 2nd hour at 185 l/s per m

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Dormant Grass + Tight Weave TRM

After 3rd test at 370 l/s per m Before

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Dormant Grass + Open-Weave TRM

At end of 3rd hour

After 3rd hour at max. of 140 l/s per m

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Damage Quantification

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Cumulative Loading vs. Duration

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Dormant Grass Performance

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ACB Slope Protection Tests

Cumulative Loading ACB Soil Quality

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ACB Slope Protection Tests

Cumulative Loading ACB Soil Quality

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Levee Slope Resiliency Testing

Results

  • Healthy sodded grass surfaces did not fail
  • Damaged healthy grass surfaces survived at high loads
  • Dormant grass failed at reduced loads
  • HPTRM provided significant protection for dormant grass
  • Open-weave TRM provided little protection for dormant grass
  • Bare clay and lime-reinforced clay fail rapidly
  • ACBs effectively protected the underlying clay, but

performance dependent on soil type

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Levee Slope Resiliency Testing

Lessons Learned

  • Dense roots and thatching are critical at high overtopping

rates

  • Grass in planter trays was very good and most likely not

representative of typical grass slopes

  • Robust test protocol has been developed and vetted
  • Soil type may be key to performance
  • Steady state loading results applied to wave overwash most

likely very non-conservative

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Lessons Still to Learn

  • Effect of variations in soil type
  • Correlation between steady and un-steady loading
  • Quantification of dynamic hydraulic forces
  • Significance of:
  • Wave conditions
  • Levee geometry
  • Vegetation species
  • Resiliency of grass reinforcement
  • Implementing cumulative excess work and hydraulic

loading methodologies

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Comments or Questions?