The prevention of flooding is a major consideration for Hong Kong Engineers. The combination of tropical climate and creeping urbanisation in the New Territories creates increasing run-off problems, with downstream impact on heavily populated Kowloon.
Solutions can themselves however cause further problems as in this case, the construction of large drainage channels was at the expense of natural fauna and flora.
With advent on Environment Impact Assessment, a new approach was sought for channel design, that would provide the hydraulic capability, yet would significantly maintain the natural environment.
Such a system was available in GRASSCRETE, with a proven engineering pedigree, enabling a paving layer to be incorporated, that catered for a flow rate of over 8 metres per second, as well as withstanding the load of 30 tonne maintenance vehicles. This provided the ideal solution to satisfy both Environmentalists and Engineer and has subsequently become a benchmark design standard for drainage channels in Hong Kong.
With the advent of Environmental Impact Assessments for new projects in Hong Kong, there is an increasing desire to mitigate the loss of indigenous fauna and flora. An example of this philosophy can be found in flood storage areas in the New Territories near Lok Ma Chau.
Here a pumping station and storage pond was created together with a bund to elevate the roadway above the low-lying fields. To armour the revetments, cast-on-site GRASSCRETE was selected in GC3 (76mm thick) format. With the unbroken and reinforced structure, GRASSCRETE was easily able to accommodate the curved and variable profile of the slopes.
In consultation with Environmentalists, tree pits were also incorporated into the bund revetments and as the lower photo shows, a prolific growth was achieved within just 2 years of construction.
The autumnal storm of 1990 severely affected the South of England, many areas of historic woodland were lost to gale force winds. Badly affected by the storm was the Wentworth Golf Club in its picturesque setting of Virginia Water. The storms took place shortly before the PGA World Masters Tournament and a massive operation was called for to remove fallen trees and to bring the course up to tournament condition.
Whilst the tournament was playable, it was evident that the concentration of spectators and hospitality access, made searching demands upon the waterlogged grounds.
A particular problem was the construction of the tented village for hospitality that had hitherto been positioned in a wooded copse, with build up and breakdown access being gained by temporary excavation mats. Apart from the problems encountered for this particular tournament, this format proved to be costly for each event as well as calling for landscape reinstatement as grass died back under the mats.
A solution was achieved by the construction of a dedicated tented village area adjacent to the West Course 18th Green, with an access that was gained along the side of the adjacent East Course 18th Fairway.
To maintain a green environment, the GRASSCRETE system was selected and in particular the type GC2sc, that would cater for the 40’ articulated truck loads that would enter over the concentrated build and break down period.
The construction of the roadway proved to be challenging in itself, with the route taking it past a lake the ground conditions included sections of weak bearing alluvial soils. The challenge was however met by Grass Concrete’s laying division and the new tented village site was ready by the next tournament date.
The elevated position of Tutt Head on the picturesque Mumbles landmark provides an excellent vantage point for the construction of a Coast Guard Station. Such a location does, however, pose a number of problems in terms of accessibility.
How to maintain a theme of natural appearance whilst allowing for the problems that come with a steep access road? A grass and concrete surface was thought desirable for both appearance and self-draining nature. Stability, however, would be a problem if precast units were to be used. The steep slope would undoubtedly have led to displacement by vehicles seeking grip on the steep roadway. Additionally the curved edge of the road would have resulted in an unsightly and unstable stepping of units.
GRASSCRETE was the ideal solution with its self-draining nature resulting in a low run-off coefficient. Its reinforced structure coupled with a non-slip surface enables easy and safe use of the roadway.
It’s not always the largest jobs that are the most challenging.
Take an overgrown rear garden near the Derbyshire Peak District, introduce a landscaping scheme that includes a new steep access road leading to a car park, then add in the hurdle of a narrow bridge with a 3 tonne weight restriction along the way and…………..you have a challenge.
Pre-contract meetings with local Architect Derek Trowell formulated a design that would achieve a sustainable solution and yet maintain the natural limestone culture of the region. The design featured plateau forming dry stone walls, that enabled a car park and winding access route to be accommodated. A hint of rustic charm was introduced with the adoption of old timber railway sleepers to form the kerbed trail.
Our full range of grass reinforcement systems was considered for the access and car park, and the one that ticked all the boxes was GRASSCRETE. In particular its features provided for:
– A self draining structure
– Total felxibility in plan shape
– A level upper surface for low wheel vibration
– A non slip finish
– The ability to resist the additional wheel loads of both climbing vehicles and those braking on decent.
With a route to site that couldn’t accommodate heavy vehicles, a programme of double handling was devised. Materials including concrete were “passed” over the bridge using telescopic handlers that were then able to negotiate the incline with their four wheel drive capability.
Within the space of a few months, the garden was totally transformed and in doing so, achieved something of a celebrity status, as it became a feature in the Wirksworth Festival, a celebration of art and architecture for the region
With a phase of the light rail system passing through the prestigious Salford Quays. The aesthetic impact of a rail system was a major consideration. With a decision to increase the “greenspace” Grass Concrete Limited were called into design consultation with the Project Managing Joint Venture, Laing/Ansaldo.
Design influences were:
-To provide an access between the lines for light commercial vehicles.
-To permit natures drainage, even though a solid concrete slab was to be laid below the sleepers.
-To create a surface that could not be vandalised.
-To provide sufficient flexibility in plan profile to cater for the varying layout of the track.
In consideration of these key factors, a pre-cast system was rejected and instead cast on site, GRASSCRETE was introduced. To enable casting, a formwork system was designed that framed a box over the rail line. Crossfall drainage was catered for by a sand/gravel bedding layer between the underside of the GRASSCRETE and the lower solid concrete slab. This was contained at each line by a fluted concrete kerb under the GRASSCRETE, designed and manufactured by Grass Concrete Limited. As well as forming a clearance gap between the paving and the line, this permitted crossfall drainage collection, via French Drains.
With limited access for construction, the concrete placement and topsoiling operations were undertaken by using a road railer 360° excavator.
With Manchester’s reputation for rainfall, the establishment of a green landscape quickly followed.
A feature of a system, which is so flexible in design, is that, it is constantly being considered for unique and testing applications.
One such project is a vehicle showroom display area for Land Rover 4 x 4 vehicles. Constructed as an apparent assault course, the roadway would show vehicles in a number of demanding positions. To enable the vehicles to be positioned without continuously churning up grassland, GRASSCRETE was used to form the access itself.
With gradients of up to 1 in 1 and rolling cross-falls, the geometry of the project called for an “interesting” setting out exercise. The flexibility provided by the system easily achieved the effect with the upstands of the plastic formers throating the flow impact of high slump concrete on steep slopes.
Grass and concrete paving is often specified for use on fire and emergency access routes. In many cases, however, it is without reference to whether it will actually work and often on the premise that “it may never get used” as the justification for a low cost, low specification precast product.
We are happy to detail, therefore, GRASSCRETE under commissioning use by the local fire authority on this project. With the low lying poorly-drained ground, the self-draining capability coupled to the unique load bearing capability of a cellular reinforced concrete surface was the determining factor in design.
These advantages were, however, gained without financial penalty. By eliminating kerb edges required with precast blocks and by reducing the sub-base depth, Grasscrete proved to be more than competitive in constructed cost against precast. When considering whole life cost, this was even more the case. Precast units would undoubtedly have required rebedding after prolonged or concentrated usage particularly under those of operational equipment (see below).
The office building for Corporate Express in Broomfield, Colorado has a glass veneer and angled, out-of-vertical planes that form the walls of the building. During the landscaping phase, it was realized that cleaning of the glass on the outside of the building had not been addressed. Conventional glass cleaning systems would not work, so the preferred method for cleaning included the use of “cherry picker” type of lifts. To facilitate the use of these lifts a stable access road around the building had to be installed. About 400 linear feet (6000 sq.ft.) of that “access road” needed to run through landscape areas. We worked primarily with Valley Crest Landscape to get Grasscrete installed to accommodate both the need for landscape and the “window washer access road”. The Grasscrete was backfilled with topsoil and seeded with grasses initially specified for that area. The original install was in 1997. Photos included in this document were taken in July 2006, showing the sustainability of Bomanite Grasscrete Systems.
Within the remote location of this project lies a number of unique factors to be taken into consideration. Close to the British Army’s Otterburn Range, the road is the primary route for artillery carrying vehicles. As an area of natural beauty, it also carries a large volume of tourist traffic along this ancient arterial road between England and Scotland.
Against this backdrop a project was fashioned to create road widening at key points on the route. In addition to the need to withstand heavy loads, the environmental impact was also a major factor with the need to fully blend the lane with the natural surroundings. To achieve this, a preference for a grassed paver was identified, albeit with a brown colouring to the concrete.
The project initially commenced with a pre-cast grass and concrete block system. Early use however indicated load bearing difficulties and the bulk of the works then shifted to using cast-on-site and fully reinforced GRASSCRETE. Type GC2sc was selected using 10mm diameter (A393) mesh reinforcement. The brown pigmentation was achieved by use of a though colour in the mix supplied by Hanson Pre-Mix Limited. At the time of writing this case study works are still in progress
