Erosion Controlling erosion on

soil and rock slopes

Tel: +44 (0)1254 262431

Fax: +44 (0)1254 266868

E-mail: info@tensar.co.uk

www.tensar-international.com

Tensar International Limited

New Wellington Street

Blackburn BB2 4PJ

United Kingdom

Your local distributor is:

Contact Tensar International or your local distributor to receive further

literature covering Tensar products and applications.

Also available on request are product specifications, installation guides

and specification notes.

The complete range of Tensar literature consists of:

• Tensar Geosynthetics in Civil Engineering A guide to the products

and their applications

• Ground Stabilisation Reinforcing unbound layers

in roads and trafficked areas

• Tensar Structural Solutions Bridge Abutments - Retaining Walls -

Steep Slopes

• Foundations over Piles Constructing over weak ground

without settlement

• Basal Reinforcement Constructing embankments over

weak ground

• Railways Reinforcing ballast and sub-base layers under railway track

• Asphalt Pavements Reinforcing asphalt layers

in roads and trafficked areas

• Erosion Controlling erosion on soil and rock slopes

©Copyright Tensar International Limited

Printed April 2006 Issue 7, 79010013

The information in this brochure is supplied by Tensar International free of charge. Tensar

International do not assume any duty of care to you or any third party. No liability for negligence

(other than for death and personal injury) can arise from any use of or reliance on the information

in this brochure or use of any Tensar International product mentioned. Tensar International will

not be liable if this brochure contains any misrepresentation or misstatement. Determination of

the suitability for any project of the information and any Tensar International product mentioned in

it must be made by your engineer or other professional advisor who has full knowledge of the

project. You, together with any such engineer or advisor, must assume all risk of loss and damage

of any kind arising from use of the information or any product of Tensar International other than

the risk of death and personal injury. If you or any third party subsequently purchases a product

referred to in this brochure or any other Tensar International product the entire terms of the

contract of purchase and the entire obligation of Tensar International relating to the product or

arising from its use shall be as set out in Tensar International's Standard Conditions in force at the

time of purchase, a copy of which may be requested from Tensar International.

Weathering and freeze-thaw action can often lead to

fracturing and spalling on rock slopes, creating the hazard

of falling rock fragments and ongoing erosion. These falls

are particularly dangerous when close to public areas.

TENSAR BIAXIAL GRIDS - THE LONG-TERM SOLUTION

Tensar biaxial grids can be draped over the face and

secured with rock anchors to act as a cladding to control

loose rock fragments and remove the hazard of bouncing

projectiles. This can allow topsoil and scree to be retained

and facilitates the subsequent development of vegetation

which in turn improves stability of the surface.

The fixing details including the length and spacing of

bolts is site specific and primarily governed by the nature

of the rock, slope geometry and the purpose of the

protection. Adjacent grid rolls are overlapped and stitched

with a high density polyethylene (HDPE) braid to form

secure vertical joints. Typical installation details are

available on request.

Controlling erosion on rock slopes

Tensar Biaxial grids - the benefits

■ Cost-effective solution ■ High impact resistance ■ Easy to install, wide, lightweight rolls

■ Non-corrodible, durable ■ High resistance to weathering ■ High resistance to ultra-violet light

■ Aids establishment of vegetation ■ Environmentally safe

Chalk highway cutting immediately after Tensar

installation

Chalk highway cutting showing vegetation taking hold.

The grid controls the fall of rock fragments.

Tensar rolls are wide and light, aiding installation. Protecting a railway cutting.

Q 05288BS EN ISO 9001:2000

EMS 86463BS EN ISO 14001:2004

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Unsurpassed experience

and reliability

Tensar International is the world leader in erosion and

geogrid technology and has over 20 years experience in

providing high performance ground stabilisation, erosion

and reinforced soil solutions.

Tensar offers a broad variety of cost-effective and efficient

options for construction projects to combat erosion,

which require retaining walls or slopes.

Tensar’s experienced civil engineers are available to

provide design and on-site construction support for your

erosion project - from concept to completion.

By combining our specialist knowledge of erosion,

materials, application technologies and geotechnical

design techniques, we are able to offer the complete

solution for structural integrity and long-term reliability.

Natural vegetation can provide good soil erosion

protection. However, this may not be adequate on steep

slopes (including those strengthened with soil

reinforcement, ground anchors or soil nails).

Areas prone to temporary water inundation, wave run-up

or intermittent high velocity flows, such as river banks,

shorelines, ditches, flood bunds and dam spillways, can

also suffer from soil erosion.

In these cases, an additional permanent erosion

protection layer is needed to enhance the resistance of

the vegetation - but one which visually becomes part of

the slope.

■ Rivers ■ Lakes

■ Reservoirs ■ Drainage ditches

■ Flood bunds ■ Overspill ponds

Controlling erosion on grass slopes

The Tensar Mat range is used to control soil erosion. It

consists of a flexible three-dimensional polymer mat which

initially stabilises the surface whilst assisting vegetation to

establish. It then goes on to provide long-term, tenacious

reinforcement of the root system.

The mats have a flat, high tensile modulus base layer

bonded to an upper cuspated surface which provides an

array of pockets and traps for topsoil retention.

The thick, dimensionally-stable matrix of filaments presents

an ideal medium for anchorage and reinforcement of a

root system. Reinforced grass slopes have been shown to

have an erosion resistance able to withstand current

velocities in excess of 4m/sec.

Tensar Mats have unsurpassed drape qualities, which allows

them to closely conform to, and maintain intimate contact

with, the soil surface. This can be critical to prevent uplift of

a mat as well as to control soil erosion below. In addition,

roots will not be able to penetrate through to the soil

surface if voids exist underneath a mat.

Tensar Mat - the permanent solution

Once vegetation becomes established the

use Tensar Mat is inconspicuous.

Tensar Mats are manufactured from polyethylene - a

polymer that is chemically inert and therefore non-

corrodible. Polyethylene is not susceptible to water

absorption and deterioration and non-polluting to its

installed environment. It is also microbiologically inert and

therefore not attacked by bacteria and provides no

nutrient for animals.

There are two standard grades of Tensar Mat: Tensar Mat

200 for routine erosion control applications and Tensar

Mat 400 for the more critical applications such as very

steep slopes/high flow forces.

■ Cost-effective long-term solution for erosion control

■ Easy, quick and economic to install

■ Natural, attractive appearance

■ Environmentally safe

■ May replace some obtrusive and expensive traditional

revetments

■ Maintains close contact with the soil profile for

maximum root anchorage

■ Aids establishment of initial vegetation growth

■ Avoids topsoil creep on slopes

■ Protects against ‘bald spots’ on grass slopes subject to

high wear

■ May be used with hydraseeding and soil nails

1 Prepare the slope to be treated by trimming the profile.

2 Place 50-70mm of topsoil on the prepared slope (this is

optional depending on the soil type and uniformity of

the prepared slope).

3 Unroll the mat down the face of the slope flat side

down, lapping adjacent strips by a minimum of 100mm.

4 Fixings (either Tensar Pegs or approved mild steel pins)

should be at around 1m centres (depending on the

slope angle) along the laps.

5 Bury the top and bottom ends of each strip at the

shoulder and the toe, respectively, in shallow trenches

typically 450mm wide by 250mm deep.

6 Sow grass seed into the mat.

7 Brush friable soil into the full depth of the mat.

8 Re-sow the slope and apply (optional) fertiliser.

9 Lightly tamp the soil surface.

Omit steps 6 to 9 for planted slopes. The soil-filled mats

can be slit longitudinally to accommodate planting.

Railways and highways Installing Tensar Mat on

grass slopes

Tensar Mat - the benefits

The problem: gully erosion of railway slope.Tensar Mats are used to control erosion on the banks of

lakes and reservoirs.

Installing Tensar Mat on the slopes of a stilling pond. The top of the mat is buried in an anchor trench.

Tensar Mat installed over the slope. The solution: Tensar Mat fully vegetated.

Mats are unrolled down the face of the slope. Typical section showing Tensar Mat on a highway slope.

Pegs

Tensar Mat

ShoulderTrench

Railway application of Tensar Mat

Highway application of Tensar Mat

Tensar grids and mats are often used as a facing to

soil-nailed slopes.

Tensar Technology - proven

practical solutions and the

know-how to get them built

Based on the unique properties of Tensar geogrids,

Tensar Technology is widely adopted for ground

stabilisation and soil reinforcement problems.

Tensar Technology delivers real savings in cost and

time to your projects. We can help you apply Tensar

Technology to improve the bottom line on your

project.

Q 05288BS EN ISO 9001:2000

EMS 86463BS EN ISO 14001:2004