168
boreholes advanced
Sandwell & Wednesbury: Coal Mine Workings Ground Investigation & Remediation
We were commissioned to undertake desk-based assessments, develop and supervise ground investigations at two sites in the West Midlands. The aim was to identify risks posed through significant shallow historic coal mine workings and support the development of the sites.
Key details
Project name
Sandwell & Wednesbury: Coal mine workings
Client
Quinbrook Infrastructure Partners
Location
Sandwell and Wednesbury, West Midlands
Services provided:
- Coal Mining Risk Assessments
- Ground Engineering
- Consultancy
- Site Identification
- Assessment
Challenge
Risks from disused mine shafts and workings involve the sudden collapse of material that may occur, resulting in settlement of the overlying non-consolidated materials into the void. This can be caused through degradation of the shaft lining, hanging wall or footwall or settlement of the fill materials, which can result in migration of the settlement to the surface to form a crater.
The initial ground investigation and remedial works were required to prepare the site for development. This involved managing the risks posed from coal mine workings and the risks surrounding specific site constraints. These constraints comprised Victorian Sewers, an adjacent metro line embankment, and high voltage overhead cables with pylons founded adjacent to one of the sites.
Solution
By successfully liaising with the authorities and stakeholders, we devised and implemented remedial works with a treatment programme of the coal seams and mine shafts through grouting.
Following a Phase 1 desk-based assessment, we conducted a Phase 2 ground investigation comprising trial pitting, rotary preclusive boreholes, probing and windowless sampling to provide information on the presence and condition of the mine shafts, coal seams and ground profile.
The investigations positively identified a total of five shafts and coal mine works spanning four seams. Following the investigations, we developed Coal Mining Risk Assessments and Geo-environmental Assessments for both sites to ensure a robust engineering solution was identified and was sufficient to enable discharge of planning conditions relating to legacy mine works at the sites. Through ongoing liaison and agreement with the Coal Authority, we developed Grouting Strategy Assessments and a specification for the treatment works for the proposed development.
During the remedial works, two unrecorded mine entries were encountered and our site staff and management team allowed us to quickly implement a revised strategy to delineate, interpret and agree a revised treatment package with the Coal Authority.
Project statistics
> 80 tonnes
of grout injected
5
mineshafts successfully treated
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Key contacts
Glynn Jones
Principal – Environment Compliance and Ground Engineering