CASE STUDY: DRILLING AND GROUTING, SCOTSWOOD EXPO
Project: Scotswood Expo
Location: Newcastle Upon Tyne
Client: Newcastle City Council.
Consulting Engineer: Halcrow.
Main Contractor: Galliford Try
Project Overview
Scotswood Expo is a £250 million residential development project covering an area of 42 Hectares west of Newcastle Upon Tyne city centre.
Originally a densely populated social housing area, the site was demolished and Galliford Try were appointed Main Contractor to carry out enabling works in preparation for the new build programme of works.
A major part of the enabling works was the location and treatment of five known coal seams and eight recorded mineshafts across the site. The coal seams sub crop at shallow depths beneath a sloping terrain rising from the River Tyne in a northerly direction.
Van Elle were appointed by Galliford Try to carry out the mine stabilisation project on an all risks basis tender valued in excess of £2 million pounds making it the largest single mine consolidation project carried out to date in the Northern Coalfield. Whilst part of the site was covered by some historical mine records the majority of the workings pre dated the legal requirement to be recorded and in preparing the bid, Van Elle carried out an extensive desk study researching available site investigation records, old mine and OS plans, archive information and extensive in-house records of previous work carried out in the area.
The works were carried out on programme during 2010-2011 utilising a variety of track and tyre mounted rigs, flushing with water and air/mist where appropriate. A primary grid to ascertain the presence of mine workings at depths shallow enough to risk surface subsidence was carried out and where at risk areas were encountered, a secondary grid of boreholes were drilled on a 3.5 metre pattern and a 10 : 1 PFA/CEMENT grout was injected.
Grout testing was undertaken under supervision from Halcrow and a staged release of consolidated areas handed back to Galliford Try.
Where mine entries were known, a series of boreholes were drilled at 1.5 metre centres to establish the exact location and diameter of the shaft which was then drilled to depth and stage grouted to consolidate the shaft fill. A reinforced concrete cap was then constructed over the treated shaft at rockhead. In some cases this involved extensive earthworks also carried out in-house by Van Elle. Eight shafts were shown on the historical records and by the end of the main works, eleven shafts had been found and treated.
Technical Information
With full time supervision by our Site Manager, an experienced Engineering Geologist, and two experienced supervisors supported by our Regional Office we were able to react and adjust borehole grids and locations on a daily basis giving optimum results to the Client.
During the course of the project Van Elle Staff and Operatives worked in excess of 50,000 accident free hours.
The following principal quantities indicate the size of the works carried out
10,000 boreholes
200,000 metres of drilling
20,000 tonnes of dry weight grout injected
25,000 cubic metres of earthworks
88 tonnes of reinforcement fixed and placed
175 cubic metres of concrete poured
A shaft cap pour at Scotswood
