This particular section of the works runs from the existing rail bridges near Ashton Gate Underpass through to Ashton Avenue Swing Bridge, all behind Paxton Drive. With the main access for the works located at Jessops Underpass.
Section 2b is a typical civil engineering based project with the following works to be carried out;
Surface water drainage; including pipework up to 450mm diameter
Installation of pumping stations and rising main
Earthworks; importing and exporting of materials
Constructing a new road/guided bus route; working to Highway Standards (MCHW)
The surface water drainage is located throughout the section, running either side and through the middle of the route itself. Drainage running North to South and on the East will come into close contact with the existing residential buildings.
Works involved are simply excavating a trench along the route of the drainage, installing large trench boxes where necessary and installing the required drainage pipes and manholes for the specific route. Once installed the trench is backfilled and, due to Highways Standard regulations, the material must be compacted using either a roller or plate compactor.
All the surface water drainage is carried to the 3no pump station we’ll be constructing on site; these pumping stations in turn then pump the surface water north and discharge in to the river Avon.
We have a tunneling sub-contractor who will be sinking shafts 6m deep to construct the main ‘wet well’ where the water will flow into and then get ‘pumped’ up the line.
The earthworks process for this section involves our sub-contractor excavating down to the design ‘dig’ level which is known as the ‘sub-formation’ level of the proposed bus route. Material specified in our design is then imported and placed to a specific level.
Our method of compacting this material is defined by the Specification for Highway Works issued by the Dept. of Transport. We have a degree of latitude in the choice of equipment, ranging from heavy vibrating rollers, smaller vibrating rollers and in some cases dead weight rollers which do not use vibration, but takes many more passes. We are currently trialling dead-weight rolling and will test the formation on completion. If this proves satisfactory, we will complete the works immediately adjacent to Paxton Drive in that fashion, if further compaction is required, we will investigate the use a smaller roller, but this will increase the duration of the operation.
Once we have completed the earthworks and the imported material has been installed to the correct level, we then have to install a Cement Bound Material (CBM); this ensures that our levels are within tolerance.
The CBM is then compacted which then provides a stable base for us to install the concrete road and the guided bus route sections. The concrete will be installed using plant/equipment similar to that of what is used to install asphalt roads.
The guided bus route sections will be constructed using traditional concrete shuttering to form the shape.