The Hyson Cells “double liner” system comprises a layer of bitumen that is sandwiched between two layers of Hyson Cells interlocking block paving that is cast in-situ and is “soil nailed” to the underlying material. The system is patented.
The Department of Water Affairs have reported that the cast-in-situ Hyson Cells lining used on its own without the bitumen exhibits approximately the same seepage properties as a conventional concrete canal liner. The conventional “single-layer” liner is therefore adequate for many applications. However, possible subsidence could cause the joints between the cast blocks to open and so cause leaking that would be unacceptable for applications such as for toxic ponds.
With the “double liner bitumen sandwich” (a) the bottom layer serves as a flexible surface on which the bitumen emulsion is applied, the encapsulated bitumen provides the require waterproofing, and (c) the top layer of Hyson Cells provides physical protection, distributes the wheel loads of vehicles used for mechanical removal of silts, and also prevents UV degradation and drying out of the bitumen..
Case Study
The 570,000 m³ Havercroft dam at Lebalelo is reported to be completely leak free seven years after construction
Havercroft Dam - Lebalelo Water Scheme
2 x 300 mega litre storage dams for Anglo Platinum mines
11.5 metres deep
Lined with Hyson Cells “trafficable double-liner”- bitumen layer sandwiched in Hyson Cells armouring
100% waterproof
Labour-intensive construction
Second need for cleaning in three years
This would not be possible with a plastic membrane liner
The Lebalelo scheme serves five mines of the Eastern Limb Bushveld complex as well as the demand of 1,304,000 rural people. The scheme comprises a 570,000 m³ off-channel storage dam and five smaller dams of 11 000 m³ to 28 000 m³. Design was by Peter Labrum of SRK.
The project achieved a tight deadline even though construction of the liner had been subcontracted to local “newly emergent contractors” as part of the social upliftment commitment requirement.
Malcolm Sales of Lebalelo confirms that the Havercroft Andalusite dam is still completely free of leaks after having been in operation for seven years (as at 2010) and after having been trafficked by heavy equipment for removal of silts.
More information
Full case studies on cleaning and repair are obtainable from our office.
Send an email to mshot@hysoncells.co.za with document number "WL03" as the subject and they will be sent by autoresponder.
Case Study 2
The Client
Phalaborwa Mining Company
Project
Relocation of Raw & Potable Water Reservoirs
Key issues
Existing water storage facility threatened so rapid construction of new facility needed
Limited space available requires small footprint
Waterproofing essential because of adjacent mine workings and infrastructure
Trafficable for maintenance
Chosen solution was patented Hyson Cells® “bitumen sandwich” system
Consulting engineers
Knight Piesold
Construction
L A Crushers – Main contractor
Süllwald Bouers Bk – Sub-contractor for Hyson Cells®liner
Background
The existing water reservoirs at Phalaborwa mine (Limpopo Province, South Africa) were constructed fairly close to the old open cast workings. The slopes of the pit were rapidly retreating and the integrity of the mine’s existing water supply was threatened.
It was required to urgently construct a new reservoir. Only limited space was available because of adjacent infrastructure and mine workings. The reservoir was to be constructed above natural ground level and had to be waterproof.
Although Havercroft dam at Lebalelo had mainly been constructed with slopes of 1:3 (because it had originally been intended to use a plastic liner), it was known that Hyson Cells® had constructed the liner on walls of 65 - 70 degrees at their pilot trial on the Wasserman dairy farm at Bethel in Mpumalanga. The dam was therefore constructed with 60 degree walls to achieve a smaller footprint.
Speed of construction
Self levelling slump used on floor
A slump of 100mm was used for the grout used for the floor of the dam. This was placed directly from the Ready Mix truck. The discharge chutes were swung from side to side to help distribute the fill over as wide an area as possible. The mix had good flow characteristics because of the use of riversand with no other aggregate and was largely self-leveling.
Installation speeds of 400 m² per day were achieved on the floor of the dam.
Liner constructed concurrent with earthworks
As soon as the bottom of the dam had been prepared it was possible to commence constructing the waterproof liner on the floor concurrent with the earthworks construction of the sidewalls.
More information
The full case study is obtainable from our office.
Send an email to mshot@hysoncells.co.za with document number "WL01" as the subject and it will be sent by autoresponder.
