Installation procedures of TENAX TENWEB geocells, Tenax geosynthetics

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Installation procedures of TENAX TENWEB geocells

The installation of TENAX TENWEB geocells on slopes is relatively simple and can be easily performed by unskilled labourers. The procedure is as follows:

1. Site preparation: Clear and grub the site. Site should be brought up to grade as specified by designer. The surface should be as smooth as possible.

2. Placement of the geocell panels: Geocell panels shall be expanded to the full open dimension, parallel to the flow direction. Each panel shall be first anchored at the top of the slope in a trench whose dimensions are determined by design. If it is possible, the anchorage trench at the top can be filled with concrete (to reduce the embedded length). Along the slope the geocells shall be anchored with pins. The spacing between the pins shall be determined by the design engineer. Pins have shape and length depending on the soil characteristics. Pin diameter shall be 8 mm minimum. Each pin shall be placed at the junctions of the panel. Pins are placed in staggerd pattern, that is like the number 5 on a dice.

Scheme of the anchorage trench filled with soil

Scheme of the anchorage trench filled with
concrete having 4 cells inside the trench

3. Junction between panels: Adjacent panels shall be fixed by pins, one pin every 2-4 cells (see drawing).

4. Infill: Infill in the geocells is influenced by hydraulics, soil conditions, aesthetics. The geocells can accommodate infills and finishes such as soil/grass, gravel. Infill can be placed by the use of a front endloader, backhoe, bottom dump bucket, conveyor system or ready mix truck. Soil or granular infill material shall be about 2 cm above the top of the cells and compacted to the required density

5. Finishing details: Seeding with suitable essences allows a fast vegetation. Seeded areas may be protected with synthetic or natural fibre blankets (jute).

particular conditions

Anchorage at top
TENAX TENWEB, anchorage at top

Anchorage at top
If it is not possible to provide a proper anchorage at top, or if the anchorage length is not sufficient, the geocells panel begin to slide downward; the only resistance is given by the fixing pins. Localised stresses transmitted by the pins to the junctions (particularly the upper cell junctions) may plasticize (and break) the junctions. The surrounding cells then open, thus reducing soil confinement; then localised erosion may occur. This can be avoided by increasing the number of pin when the anchorage length is insufficient.

Anchorage at toe
TENAX TENWEB, anchorage at toe

Anchorage at toe
It is important to fix carefully the lower cells (in a base trench or by pins). When this is not properly done, the lower cells row may raise in "crocodile mouth shape". Infiltration water, passing through the cells apertures, will then empty the cells from the bottom. When the first row of cells is empty, the second one begins to raise, and so on. Erosion continues up to the first pin, able to avoid cell raise. Obviously, if the first row of cells is properly fixed, the problem will not occur.

Intense runoff
TENAX TENWEB, intense runoff

Intense runoff
If there is a long slope upstream, or there is any possible cause of intense runoff, the top rows can be subject to intense erosion. The change of slope angle, in fact, causes a local increase in water flow speed. To avoid the consequent erosion, it is necessary to cover the zone with a bio-mat or, better, with a geomat. It is strongly recommended to excavate a draining ditch immediately upstream the surface to be protected, thus reducing the runoff.

Lack of pins
TENAX TENWEB, lack of pins

Lack of pins
Finally, if the number of pins is less than required or if the pins used are not properly chosen, the localised stress transmitted by pins to the junctions can break them. The failure of a junction transmits an over-stress to the adjacent junction, thus producing a progressive failure.

products

TENAX TENWEB

TENAX International B.V. • Geosynthetics Division
Via Ferruccio Pelli, 14 CH-6900 Lugano, Switzerland • Tel +41+91.9242485 • Fax +41+91.9242489

geo@tenax.net

TENAX SpA - Geosynthetics Technical Office (GTO)
Viale Monza, 1- 20125 Milano (MI), Italy • Tel. +39 02.26113532 • Fax +39 02.28971107

gto@tenax.net

TENAX SpA • Divisione Geosintetici
Via dell'Industria, 3 • I-23897 Viganò (LC), Italia • Tel +39 039.9219307 • Fax +39 039.9219200

geo@tenax.net