Out Of Sight...Out Of Mined
When a Mining Risk Assessment or other feasibility study highlights a potential risk from shallow mining, the next step is often to carry out an intrusive shallow mining investigation.
We do this to look for any signs of possible shallow mine workings and assess whether the minerals or workings are shallow enough to be a potential risk should they collapse in the future.
Do You Have Questions About Shallow Mining Investigations? We Have Answers!
Why Is Shallow Mining Investigation Needed?
We do this to look for any signs of possible shallow mine workings and assess whether the minerals or workings are shallow enough to be a potential risk should they collapse in the future.
The most significant of these is usually the potential for collapse of shallow depth underground mine workings - this can lead to instability if the collapse migrates to the surface.
How Do We Carry Out Shallow Mining Investigations?
To do this we drill down to confirm the depth, thickness and state of the coal or mineral seams or any associated workings that might be present. Most often we drill boreholes using rotary open-hole methods just to confirm the above, but rotary coring techniques can also be used where lots of information about the bedrock is needed.
What Are The Benefits Of Shallow Mining Investigation?
By getting the information that you need to understand what’s happening in the ground beneath your site, we can assess the extent of areas that need treatment if there could be a risk of land instability at the surface, or areas where the risks are lesser if mineral seams or mine workings have enough rock cover above them.
But before any intrusive fieldwork is undertaken we liaise with regulatory authorities such as The Coal Authority to get permission to drill through any coal seams or mine workings, and get their agreement for the proposed works to be undertaken. Health and safety should always be at the forefront of a shallow mining investigation.
Old shafts and mine entries
Where old mine shafts or mine entries are identified or suspected, a shallow mining investigation can also locate recorded mine entries and confirm their position. Shafts and adits can pose a significant risk to land stability if they haven’t been infilled properly in the past!
Once they’ve been located, there’s often more investigation needed at a later stage to probe drill any shafts, to confirm if they’ve been filled to the bottom, or only partially infilled.
Locating a mine shaft can also be useful to help make adjustments to design out some of the inherent risks from buildings over or near to mine shafts. Ideally if lower risk activities can be designed to be over mine entries then their potential impact is lessened.
What happens next?
The data collected from a shallow mining investigation determines if remediation works need to be undertaken to stabilise any shallow mine workings or treat mine entries as part of the development of a site. Often shallow mine workings needs to be “drilled and grouted” to consolidate the works and substantially fill any remaining voids. This reduces the potential of the workings settling further in the future and causing ground movements if this were to happen.
If located, mine entries will also need to be probe drilled and either grouted to consolidate any existing infill, or filled with a suitable material, and then often a concrete cap is placed over the shaft at bedrock level to allow building on top of the shaft afterwards.
Making adjustment to a proposed site layout can be one of the most effective ways to reduce the potential risks from mining legacies. That’s why we like to work with our clients and get involved with projects as soon as possible in the feasibility and design process. By relocating buildings or using certain areas for lesser risk activities can reduce the potential risks a lot.
At Abbeydale Geoscience we’re experienced in producing drilling and grouting strategies and scopes of treatment works for mine entries, and we work closely with our clients and their designers to provide robust and cost-effective treatment solutions to ensure that the risks of historical mining legacies are understood and can be mitigated.
