COMBINING HARD AND SOFT ENGINEERING by sdsdfqw21

VIEWS: 17 PAGES: 2

									                                                                                                                    EDITORIAL
                                                                                           ZAF / ED / 014: Eng - Rev. 03, Nov 2007

                                COMBINING HARD AND SOFT ENGINEERING
                                                                                                    GREEN TERRAMESH™
GEOTECHNICAL ENGINEERING
Reinforced soil slopes
Editorial published in:
Urban Green File, May/June 2002




Imagine satisfying the needs of the environmentalist
and the civil engineer simultaneously. Fiction you
think? Perhaps not. This article aims to introduce a
system, which is not only environmentally friendly
and aesthetically pleasing, but also satisfies the
engineers’ design criteria. It a soil reinforcement
system referred to as Green Terramesh™.

Green Terramesh™ is an environmentally friendly modular
system used for soil reinforcement in mechanically stabilised
earth slopes and embankments. The system units made of a
continuous double twist wire mesh are heavily galvanised and
PVC coated. The units together with a geosynthetic or
biodegradable erosion control blanket, a welded steel panel
and two pre-formed steel brackets are assembled at the factory
(Fig. 1). Wire characteristics comply with SANS 675:1997
whilst PVC extrusion is in accordance with SANS 1580:2005.              Corresponding advert


• The double twist wire mesh has been used successfully for
    reinforced soil structures worldwide. With over 500 000 m²                                              welded steel panel
    of facing area installed, it has proved its reliability and                                              slope angle
    performance in many different conditions.                                                                    pre-formed steel brackets
•   The durability and performance of the mesh is guaranteed                height
    by the double protection of the wire, first by the heavily
    galvanised coating, 275 g/m2 and secondly by the nominal                               length                    width
    0,5 mm thick PVC layer.
•   Stress transfer from the soil to the double twist mesh is           Geosynthetic or Biodegradable         Fig.1: Green Terramesh™ unit.
                                                                        Erosion Control Blanket
    immediate. The double twist wire mesh has an ultimate
    stress of 43 kN/m at only 2% strain.                                Fig.1 Green Terramesh™ unit
•   Reinforcement is continuous in the horizontal plane over
    the whole width of the layer allowing for a superior system
    and easier installation.
•   All the testing and assimilation of technical data and
    performance has been undertaken and verified by
    internationally accepted testing centers and laboratories.
    Green Terramesh™ soil reinforced structures follow the
    most recent Codes of Practice and are based on industry
    accepted earth pressure theories and design methods.
•   The quality of the materials and their compliance with the
    most rigid international regulations are guaranteed by an
    ISO 9001:2000 Certified Company.
•   Computer software, MacStars 2000™ (Fig. 2) together with
    technical support from our regional offices is readily
    available to assist in the design of Green Terramesh™
    structures.     The MacStars 2000™ program performs
    internal and external stability checks of the reinforced
    structure and provides a brief report detailing the
    calculations, cross sections and stability analyses.
                                                                        Fig. 2 MacStars 2000™ stability analysis software




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Installation involves using in situ soils for the backfill,
compacted using standard techniques in accordance with the
design. To allow for fast and effective vegetation growth of
the completed structure, a soil wedge extending 0,3-0,5 m
behind the front face is filled with vegetative soil and hand
compacted. The vegetative soil can be manually pre-seeded
during the installation. For high works (>7-8 m) such soil can
be blended with expanded clay. Shrubs and cuttings may be
horizontally inserted at the interface between two units or
into apertures in the biodegradable blanket. Alternatively, a
hydro seeding treatment may be used to green the front
face.
The appropriate choice of greening technique should be
made in relation to the local rainfall-climatic situation, sun
exposure, slope of the external facing, soil conditions and to
the natural plant population of the site.                                          La Lucia Ridge Office Park - Green Terramesh™ structure

Case Studies:
La Lucia Ridge Office Estate, KwaZulu-Natal
Important site-specific conditions that had to be considered
in the design were:
• The occurrence of collapsible soils - Berea Red Sands in
      the area.
• The structures had to be flexible yet monolithic.
• The structures needed to be durable and resistant to
      corrosion, due to being in a fluvial environment and in
      close proximity to the ocean.
•     The structures needed to handle a 1,5 m flow depth in
      the watercourse. (The flow in the watercourse is partially
      controlled by an attenuation dam upstream).
•     The structures had to be cost effective.                                     Imola F1 Race Track, Italy - Immediately after construction
•     The structures needed to be environmentally friendly and
      be able to blend into the natural surroundings.

The Imola Formula 1 Race Track, Italy
The use of a double twist wire mesh solution at the
Formula 1 Race Track in Imola, Italy has allowed for:
• The construction of an 11 m high reinforced structure,
      whose safety factor under seismic conditions is 1:39.
• The greatest simplicity in setting up the structure by re-
      using and improving the soil located on the site.
• Installation of 1600 m² of facing surface (that is 12 400 m²
      of reinforcing mesh) in 20 days using a standard team
      (4 men plus the foreman).
•     The creation of a completely grassed 70° slope, 170 m
      long, ensured that the stringent tolerances and maximum
      stability for a Formula 1 circuit were met.

                                                                                   Imola F1 Race Track, Italy - After vegetation

    Maccaferri SA (Pty) Ltd
    HEAD OFFICE - DURBAN, SOUTH AFRICA
    P O Box 15777, Westmead, 3608 Tel: +27-31-700 8456 Fax: +27-31-700 8469 e-mail: dbnsales@maccaferri.co.za
    JOHANNESBURG, SOUTH AFRICA
    P O Box 2285, North Riding, 2162 Tel: +27-11-704 0160 Fax: +27-11-704 0159 e-mail: jhbsales@maccaferri.co.za
    CAPE TOWN, SOUTH AFRICA
    P O Box 22150, Fish Hoek, 7974 Tel: +27-21-702 1416 Fax: +27-21-702 2977 e-mail: cptsales@maccaferri.co.za
    MADAGASCAR
    BP 168 Antananarivo 101, Madagascar Tel: +261-20-22-231 02 Fax: +261-20-22-553 90 e-mail: maccaferri@moov.mg
                                                       www.maccaferri.co.za



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