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Holding Back the Earth
Designing attractive, sustainable and cost effective
earth retaining systems by Peter Wills, Earth
Retaining Systems Specialist, Tensar International
N
ew building sights, for a range of BBA certificated systems and Professional £320 million Modernisation of Acute Services in
uses from hospitals and colleges to Indemnity backed designs, developers can assure Central Nottinghamshire project, completed in
affordable housing, often have to themselves of the optimum results. 2009 by Skanska.
use more marginal ground than As a bonus, earth retaining systems using The new car park was constructed on the
previously considered cost geogrid technology can be very versatile. sloping area in front of the new Pavilion Building
effective. This makes more efficient use of For example, well engineered systems can be by creating a level site, bounded at one end by an
available land, especially in industrial and used to construct load bearing embankments with ellipsoid retaining wall with a maximum height of
urban areas. heights beyond 20 m and with a choice of face 4 m. The proprietary soil reinforcement and
In addition, construction must demonstrate its angles and finishes. These structures may take a retaining structure comprises compacted site won
low ecological impact and minimal carbon variety of aesthetic finishes, from soft vegetated fill material which is stabilised by layers of uniaxial
footprint credentials, so the use of proven yet faces at angles up to 70
0
or high quality split faced geogrid fixed to specially-designed modular
sustainable construction practices should always and dry laid concrete blocks which may be concrete blocks using a unique polymer
be considered. supplied in a variety of colours or alternatively with connector. Use of site-won material reduced the
Many of these marginal sites also require a tied masonry fascia skin. The vertical concrete impact of imported quarried stone, and of the
construction over ground with low bearing faced walls and vegetated steep slopes may be transport required to bring it to site.
capacity. Conventional techniques for building combined in terraces to enable planting for both The blocks are dry laid by hand, so eliminating
earth retaining structures over such ground have durability and aesthetic effect. time for curing mortar. This enabled the wall to
included concrete retaining walls, whether Sites also need good access for both the carry its full design load straight away and for the
reinforced cast in-situ or precast and often with the contractor’s plant and, eventually, for the end car park to be completed immediately, without
need for piled foundations. users; over poor ground this can load the cost of waiting for an in-situ concrete wall to gain
However, as well as the unattractive aesthetics development. Geogrid technology can also be structural strength, thus saving contract time.
of reinforced concrete facings, these techniques used here to mechanically stabilise the road As well as using local stone facings for this client,
are often expensive, take considerable time and foundation and significantly reduce the amount of the wall is capped with granite copings and
require heavy plant and specialist skills; for aggregate fill needed. incorporates feature lighting and stainless
example in the steel fixing and formwork, steel handrails.
with associated cranage or in the construction of Hospital Car Park Soil reinforcement and earth retaining geogrid
piled foundations. Conventional techniques may A typical example is a recent new car parking technology are also widely used for constructing
also require high grade expensive imported fills area for 77 cars at Mansfield Community Hospital, fully vegetated embankments and slopes, whether
and materials that add to the environmental which has been constructed with major savings in for landscaping or as part of load bearing
impact through transportation costs, as well as the time, cost savings in materials and has made a structures. This can offer additional advantages
impact and cost of quarrying mineral aggregates. reduced environmental impact, with proprietary for enhancing the surroundings for civic or
earth retaining structure technology. public developments and creating a pleasing
Sustainable, Cost-Effective Alternative “Using the reinforced soil retaining wall solution local environment.
A proven alternative to these techniques is the saved more than 50 % in materials and time costs Slope and retaining wall solutions using
use of earth retaining technology using high over the conventional reinforced concrete, certificated geogrid technology combine proven
strength, polymer geogrids to reinforce the soil fill. buttressed retaining wall structure originally long-term performance, excellent cost savings,
As a geotechnically designed solution this can proposed,” commented Vince Hackett, Director of a wide choice of aesthetics, either textured
offer contractors and clients many advantages. groundwork contractors North Midland concrete, masonry or vegetated finishes and low
Particular benefits include the speed of Construction. “Additionally, the site is very environmental impact over conventional reinforced
construction as no specialised skills or equipment, constrained and creating formwork and pouring or mass concrete facings. Specifiers considering
such as cranes are required during installation; concrete would have been extremely difficult in projects where slopes and poor ground bearing
and potentially the use of site-won materials as the such a tight space, while the soil retaining solution performance are factors should be aware of
structural fill rather than high-priced imported has minimal plant requirements.” reinforced soil solutions and the considerable
aggregates. The geogrids are supplied in rolls The car park project is part of the advantages that they offer.
and simply placed by hand on top of compacted redevelopment and upgrade of Mansfield
layers of fill. In addition, by insisting on use of Community Hospital, and is included in the
Enquiry N
o
146
Enquire via:
Our online database Post using See inside back cover and
at www.cpbsonline.eu Enquiry Card Fax to 01435 863897
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