neoweb channel protection systems-v00

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© 2008-9 Copyright PRS. Certain products and/or applications described or illustrated are protected under

international patents. Final suitability of any information or material for use and its manner of use is the sole

responsibility of the authorized user. PRS confidential and proprietary.

NEOWEB™CHANNEL

PROTECTION

April 2009

Ver. 4.1 TECHNICAL OVERVIEW



Channel Protection Overview 2/10 PRS proprietary

Contents

NEOWEB™ Cellular Confinement System CHANNEL PROTECTION SYSTEM OVERVIEW ......................... 3

FOREWORD ............................................................................................................................................ 3

SCOPE OF THIS DOCUMENT .................................................................................................................. 3

PRS ......................................................................................................................................................... 3

INTRODUCTION TO CHANNEL PROTECTION ......................................................................................... 4

COMBINED SOLUTIONS ......................................................................................................................... 4

DURABILITY ............................................................................................................................................ 5

REDUCED PROJECT REQUIREMENTS ..................................................................................................... 5

SUSTAINABLE SOLUTION ....................................................................................................................... 5

EXAMPLES OF NEOWEB SOLUTIONS ..................................................................................................... 6

SIDE-SLOPE CHANNEL PROTECTION......................................................................................................... 7

Neoweb Protection for channel side-slopes ......................................................................................... 7

TRAPEZOIDAL CHANNEL PROTECTION ..................................................................................................... 8

Stable protection for both side-slopes and channel bed ...................................................................... 8

STEEP SIDE-SLOPES CHANNEL .................................................................................................................. 9

Protection for side-slopes/channel bed + earth retention for stability of steep side-slopes ............... 9

CHANNEL PROTECTION DESIGN FACTORS .............................................................................................10




NEOWEB™ Cellular Confinement System

CHANNEL PROTECTION SYSTEM OVERVIEW

FOREWORD

The Neoweb™ System is a soil confinement, stabilization and reinforcement solution developed,

manufactured and marketed by PRS, comprised of three-dimensional, perforated and textured

honeycombed geocells. Neoweb can be applied to a wide range of channel protection applications

subject to surface erosion, unstable slopes and hydraulic forces.

SCOPE OF THIS DOCUMENT

This document describes and illustrates typical natural and man-made hydraulic open channel

protection strategies available from PRS. These depend on the surface protection type –

soil/vegetation or non-erodible infill (hard or rigid armor) and the channel geometry and hydraulic

forces.

PRS

PRS is the world’s leading supplier of cost-effective soil stabilization solutions. Combining unique

proprietary technology with specialized engineering expertise, PRS delivers proven field-tested and

reliable solutions for load support, slope and channel protection, earth stabilization and landfills and

reservoirs. With a global network of regional offices and local distributors, PRS provides a full range

of end-to-end support services. Since its establishment in 1996, PRS has implemented hundreds of

successful projects in over 45 countries worldwide.




INTRODUCTION TO CHANNEL PROTECTION

The Neoweb Channel Protection Systems is the most advanced three-dimensional cover protection

system against channel, stream and shoreline erosion caused by flowing water. The three-dimensional Neoweb confinement enhances the performance of conventional erosion protection

materials and provides a long-term durable solution.

Channel protection systems can be divided into two types according to their surface treatment:

Erodible Channel – with soil/vegetation infill protection

Non-erodible Channel – with concrete infill protection

The infill type is determined based on the channel's hydraulics and the design of the Neoweb

protection system, depending on the following conditions:

Channel Geometry – trapezoidal, side-slope, parabolic, etc. Hydraulic Stresses – flow velocity, water level, discharge

Downstream flow creates driving forces on the channel protection system, e.g., tractive and uplift

forces, depending upon the flow velocities. Static down-slope forces imposed on side-slopes are also

a factor due to the weight of the

protection system.

Bank stabilization is maximized by the

Neoweb protection layer combined with

anchorage systems. Under turbulent/

supercritical flow, downslope tendons

may be combined with specialized

anchors to bind the system to the native

soil.

COMBINED SOLUTIONS

Solutions for a given channel are typically comprised of several different surface treatments due to

changes in the hydraulic, site and environmental conditions along the water course as well as for

cost-efficiencies. For example, a typical channel might include: Neoweb with hard concrete infill on the trapezoidal channel bed (subgrade cover);

Neoweb with soil and vegetated slope infill to protect banks subject moderate hydraulic

forces (e.g. above normal water level)

Neoweb retaining walls with aggregate infill in sections with high flow velocities or steep

slopes




DURABILITY

Neoweb is comprised of advanced polymeric alloys that make the cellular confinement system stiff,flexible and durable. In particular the Neoweb patent-pending alloys feature long term dimensional

stability, high long term design strength (creep resistance) and low reduction factors. This translates

to a longer life-span for Neoweb channel protection structures. Neoweb is non-degradable, and

resistant to weathering, extreme temperatures and water, which can affect concrete, steel and

timber solutions.

REDUCED PROJECT REQUIREMENTS

Due to the superior reinforcement of Neoweb, channel projects require less infill material and can

substitute lower quality infill without loss of long term design strength. This saves project costsduring the initial construction and the project life-time. Savings increases when concrete is used as

the infill, as the concrete thickness can be reduced or even replaced by other infill materials.

For example Neoweb can replace U-shaped designs for reinforced channels with trapezoidal designs,

thereby reducing the amount of concrete

needed by ~30%. As the Neoweb

honeycombed cells function as the forms

for pouring, the need to construct forms

is eliminated. Concrete can be poured in

one stage, making it easier, faster andmore uniform. When Neoweb is used in

channel retention walls, typically only the

outside fascia cells require concrete fill;

the inner walls cells can be filled with

local crushed stone, reducing concrete requirements even further. In fact the same Neoweb solution

can be utilized with different infill material (gravel or soil/vegetation) in sections with lower velocity

flows, to reduce project costs even further.

SUSTAINABLE SOLUTION

Neoweb is a best-available sustainable solution for long-term channel protection and erosion control

in stream banks and channels, particularly when integrated with revegetation schemes, improves the

site ecology, plant habitat and visual aesthetics. Perforations in Neoweb not only promote water

infiltration and limit the impact of hydrostatic forces. They also play a key role in soil protection by:

Preventing run-off and soil erosion

Preserving the soil structure

Enabling flow of water, nutrients and soil organisms

The perforations are also critical in promoting revegetation by providing an excellent growth stratum

for roots and plants, which is critical to the performance of the vegetated solution. This further

stabilizes the soil and slope, while facilitating the restoration of the vegetation and landscape.




EXAMPLES OF NEOWEB SOLUTIONS

Water Treatment

–

Water transport systems – Sewage treatment conduits

– Storm drainage channels

Energy Plants

–

Intake channels and outflows

–

Cooling water conduits

Stream protection

– Stream quality and ecology

– Bank (slope) erosion

– Flood water containment

Reservoirs

–

Dam and pond spillways –

Protection of hydraulic structures

Environmental protection

– Silt and sediment control /diversions during construction activities

– Pipeline and utility channel crossings

Marine

–

Port facilities and protection

–

Channel and shoreline structures

– Canals




TRAPEZOIDAL CHANNEL PROTECTION

Stable protection for both side-slopes and channel bed

SOLUTION Erosion control system

Stable protection system against sliding, tractive and uplift forces

from water action

STABILITY Side-slopes are stable at defined inclination and height

SURFACE COVER

INFILL

Topsoil + vegetation – flow velocities ranging from1.0-6.5 m/sec

Gravel – flow velocities range 1.5-3.5 m/sec

Concrete – flow velocities range 3.5-13.0 m/sec

FEATURES Easily installed on any changing/curved geometry

Enables efficient confined drainage system

INCLINATIONS Side-slopes normal inclination: 1:3 - 1:1 (18°- 45°)

ANCHORAGE

Metal stakes + Neo-Clip




STEEP SIDE-SLOPES CHANNEL

Protection for side-slopes/channel bed + earth retention for

stability of steep side-slopes

SOLUTION Erosion control system

Stable protection system against sliding, tractive and uplift forcesfrom water action

STABILITY Based on unstable native side-slopes at desired inclination and

height; retention is requiredSURFACE COVER

INFILL

Topsoil + vegetation – flow velocities ranging from1.0-6.5 m/sec

Gravel – flow velocities range 1.5-3.5 m/sec

Concrete – flow velocities range 3.5-13.0 m/sec

FEATURES Easily installed on any changing/curved geometry

Enables efficient confined drainage system

INCLINATIONS Side-slopes normal inclination: 1:1.75 – 6:1 (30°- 81°)

ANCHORAGE Metal stakes + Neo-Clip for channel bed




CHANNEL PROTECTION DESIGN FACTORS

1.

Subgrade properties – angle of internal friction, cohesion, density

2. Channel geometry – trapezoidal, site-slope, parabolic.

a. The geometry includes the vertical height and inclination of side-slopes, channel base

width and longitudinal/bed slope.

3. Hydraulics – define and calculate the following:

a.

Manning's coefficient, water level, flow unit density, hydraulic radius, flow velocity,

discharge, Froude Number (defines the flow type)

4. Surface cover infill – Type of Neoweb and soil infill properties

a.

For both side-slopes and channel bed

5. Geotextile – separation layer for both side-slopes and channel bed

6. Resistance:

a.

Design down-slope driving force – calculate the weight of the Neoweb protection

system on channel's side-slopes

b. Calculate the down-slope interface resistance

c.

Calculate the crest shoulder interface resistance

7. Down-slope anchorage system - Analyze system requirements:

a.

Metal pin stake anchors: stake density per 1 sq m, stake length and diameterb.

Defining tendons to tighten the system, if required

8. Design Tractive Driving Forces – Calculate the imposed forces on channel side-slopes and

bed.

9. Factors of safety – examine the resistance of the Neoweb cover system combined with stake

anchors to provide the required factors of safety for both side-slopes and channel bed.

10. For erodible channel – examine the infill stability retained in a three-dimensional retention

system, combined/not combined with vegetation.

neoweb channel protection systems-v00

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