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Cable jointing and jointing pits construction methodology 2.7
The construction of a jointing pit typically requires the following:
2.8 2.9 Polyethylene plastic membrane between the ground and concrete floor
A flat level reinforced concrete foundation and additional sump pit at a lower level to facilitate drainage and dewatering
Adequate wall shoring or sheet piling on all sides of the excavation to prevent collapse of soil
Sufficient space to facilitate the cable jointing process Safe access and egress including provision of steps Generator with lighting
Temporary Heras security fencing around the site to prevent unauthorised access At least 300m2 for laydown area
Jointing pit floor at least 150mm thick.
There is no requirement for permanent hard standing to support excavators and pulling gear for plant for construction of jointing.
The assumed plant is listed in Table 1.1.
2.10 The quantity of excavated material would be approximately 65m3 per jointing pit. Half of this material is likely to be reused as backfill materials with the excess disposed of offsite. The jointing pit would also contain bedding sand.
If a permanent manhole access was to be constructed, then, blockwork walls and cover slab would also be required.
2.11 The estimated duration of the works is 3-4 weeks per jointing pit with simultaneous operations along the route.
3 3.1 Cable drum transport – both Options
Each section of cable installed between jointing pits would be delivered to the jointing pit on a cable drum, transported to the site by low loader or cable trailer along public highway to nearest access point, then, where necessary, across agricultural land to the jointing pits. The particular low loader dimensions would depend on the cable length on the drum and thus the drum size.
3.2
For significant cable lengths, in excess of 900m, specialist hauliers might be required with rear wheel steering low loaders and/or tandem tractor units that could be used to navigate steep inclines. A photograph of a typical drum transport low loader and cable trailer is provided in Plate 1.
3.3
No abnormal loads to the sites would be considered in the cable pulling process, and therefore no temporary works would be required along the public highway for abnormal loads.