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Ciria C758 Abandoned mine workings & SP32 Construction over abandoned mine workings

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Let Geoinvestigate quote for you next mine working investigation whether it’s a desk top study CMRA, site inspection or an intrusive drilling investigation. Geoinvestigate provides Coal Mine Risk Assessment CMRA, Walkover Mining & Mine Shaft Surveys & Site Inspection Reports, Intrusive Coal & Mine Working & Mine Shaft Drilling Investigations, technical advice and reporting on Mine Shaft & Mine Working Mitigation, Remediation & Stabilisation. We also investigate sinkholes and general ground instability. Let us quote for your next mine working or mine shaft investigation whether it’s a desk stop study CMRA, site inspection or a follow on intrusive drilling investigation.

Geoinvestigate Site investigation provides Mine Risk Analysis Report follow on drilling services for the investigation of all types of mine working and mine entry including Coal, Chalk, Limestone, Gypsum, Tin, Copper, Lead, Ironstone, Iron Ore, Clay and Sandstone.

We investigate and provide consultancy services on the mitigation, remediation and stabilisation of coal seam and mineral vein mine workings their associated mine shafts, mine adits, mine tunnels, adits, drifts, levels and dene hole. We also investigate opencast surface working, outcrop working, quarrying, clay, sand and gravel pitting and extraction and mine spoil heaps mine tips and slopes.

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Much of our workload is connected to the investigation of coal mining legacy as this is historically by far the largest sector of the UK extraction industry and by far the most widespread across the country extending as it does from Kent to Haverfordwest SW Wales, Neath Valley, Forest of Dean, Bristol, Birmingham, Nottingham, Stoke on Trent, Manchester, Leeds, Barnsley, Wakefield, Rotherham, Doncaster, Burnley, Bolton, Whitehaven Cumbria, Durham, Newcastle, Glasgow Edinburgh and Fife.

So it was with keen interest that we read Chapter 12 of draft Ciria publication C758 providing advice on drilling investigation.

Background

This year Ciria RP940 or C758 Abandoned mine workings replaces the seminal work by P.R. Healy and J.M. Head, Ciria SP32 ‘Construction over abandoned mine workings’ – a publication first released in 1984 and still in use 35 years later in 2019. Few if any Ciria guidance documents can claim the same longevity and continued frequent use as an important reference manual for the investigation and development of land impacted by coal mining legacy as this can. I purchased my first copy in 1988 and it disintegrated long ago with frequent use and loan. A few years ago I was lucky enough to obtain another copy, this time a 1st publication through Ebay.

Many local planning authorities (LPA’s) Building Control, coal mining consultants and the Coal Authority itself still regularly refer to this document.

Even with the introduction of C758 Abandoned mine workings this year there is no doubt that Construction over abandoned mine workings will still continue to remain a much treasured, highly respected and much used quick reference document perhaps preferred in some instances to the new document which is much expanded and now perhaps rather voluminous.

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So it was with enthusiasm that I flicked through the online draft chapters made available by Ciria last year only to be disappointed by the coverage in Chapter 12 of ‘Rotary open-hole Boreholes – unsampled’

Rotary open-hole Borehole Drilling investigation of coal mine workings  

Open-hole borehole techniques are a quick and relatively inexpensive method of intrusive coal and other mining Site investigation and locating mine working voids or disturbed bedrock referred to variously as ‘broken ground’ or ‘collapsed ground’.

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These and other features are detected by the relative progress or resistance to the drill and attached rods or drill string. The method also has applications in bedrock profiling and ‘sounding’ or probing to find the floor of a quarry or opencast surface mine. Open-hole or probing Boreholes can be used in Site investigation of mine entries for locating mine shafts and mine adits and probing their depth and diameter and establishing whether they are filled.

When drilling an increase in the rate of penetration may be indicative of potentially disturbed ground and recorded as ‘broken ground’. The drill string can also be advanced by pushing without rotation to probe ground with very low resistance to penetration. ‘Push’ may be provided by the self-weight of the drill string or hydraulic ‘pull down’ giving a qualitative impression of the collapsed strata or backfill. These actions are recorded as free fall or soft push respectively.

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There are 3 basic different types of rotary, rotary percussion (top hammer or down-the-hole hammer DTHH) giving the fastest drilling rates, rotary alone drilling and rotary percussion with advancing casing system.

All methods require drill flush of one form or another to remove cuttings from the advancing drill bit and expel them. The cuttings arising at the surface are logged for strata identification. Air, Air mist (atomised water), straight Water, Foam and Mud are all used as drill flush.

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Air and Air mist drilling are least safe as they could lead to spontaneous combustion, the production of toxic gas or the displacement of large volumes of toxic gas upwards into occupied accommodation and dwellings.

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For this reason the HSE, British Drilling and Coal Authority all agree that drilling with water is the preferred method for forming Boreholes in coal and mine workings with the CA having said that it should be mandatory. The CA themselves with regard to their own internally managed drilling investigations insists upon water flush drilling. Mud though safe is too messy.

Geoinvestigate’s new rotary open-hole microdrilling system

Chapter 12.2.5 of draft Ciria manual C758 Abandoned mine workings claim that rotary percussive is the fastest open-hole drill method producing several 20m to 30m deep Boreholes in a day and that rotary alone drilling is slower than rotary percussive.

So while rotary percussive drilling is fast, ‘rotary drilling alone’ has with the introduction in 2015 by Geoinvestigate of its new high speed small diameter Microdrilling caught-up.

Geoinvestigate Microdrill is a compact, safe, high speed, small diameter, small volume water injection drilling system suited to restricted access work in gardens, alleyways and backyards. Geoinvestigate claim their New Microdrilling system which took 3 years to develop is 3 x safer than conventional drilling with air or air mist because it uses only water flush, the smaller diameter of its drill causes less disturbance and much smaller volumes of mine gas are displaced during the drilling process. The company proudly describes Microdrill as ‘Neater, Sweeter, Faster, Safer & Cheaper’ than its market rivals. Its also quieter.

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Conventional big rig drilling is noisy, expensive and messy.

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Geoinvestigate Microdrilling is ‘Neater, Sweeter, Faster, Safer & Cheaper’

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Microdrilling was successfully demoed to the UK Coal Authority in 2015 and several hundred jobs later has established itself as the preferred method of intrusive drilling Site investigation with the public, developers, builders and astute mining consultants for development over shallow coal and mine working. Microdrill has also been used to probe Chalk sinkholes, for bedrock profiling for piling and to locate the high wall of quarries and opencasts.

The success of Geoinvestigate Microdrilling in recent years has made it the obvious and the cheapest safest choice for Coal mining risk assessment (CMRA) follow on Intrusive ground investigation drilling and probing in the UK today.

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Microdrills tilting mast allows the option of drilling raking Boreholes under buildings and avoiding obstructions and investigating mine shafts and adits from a safe stand-off distance. Last year Microdrill carried out its first inclined raking borehole investigation under a house and inaccessible restricted access back garden in Newcastle. The alternative was no investigation at all or craning the rig over the building at considerable extra expense and time. The drilling investigation followed a previous CMRA by a coal mining risk analysis consultant which had identified possible shallow mine working beneath the property.

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Later in 2018 Microdrill was once again given the opportunity to drill inclined holes on this occasion to investigate an ironstone mine while at the same time entertaining the nation on Channel 5s TV docuseries ‘Sinkholes’. Series 2 Episode 4 shows Geoinvestigate’s team using Microdrill to investigate a mine shaft which had partially subsided and collapsed and formed a mining sinkhole close to a house in Walsall.

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With the recent introduction of small volume water injection Microdrill rotary drilling alone has fast caught up and perhaps in several respects over taken rotary percussive drilling. Microdrilling is now capable of similar Borehole Drilling production rates at lesser cost with the added advantage that it is safer because it uses only water flush and it displaces very small volumes of mine gas, Its compact design and smaller size allows it access to other places larger rotary rigs cannot reach. It also causes much less site disturbance

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In direct comparison with other rotary alone rigs using water flush there is no contest as Microdrill far exceeds their drilling rates and there is not the constant delay required throughout the day to refill water tanks. Microdill also causes much less site disturbance and surface mess because much less waste water is returned to surface. Consequently Microdrill sites are tidier and safer.

Draft Chapter 12 of new Abandoned Mine Workings raises concern that Ciria C758 is published later this year in 2019 that may be out of date with regard to the advice it provides on rotary drilling un-sampled or open-hole drilling. If so this would be both disappointing and surprising given that Geoinvestigate has made most of the major contributors to this document WYG (White Young Green), Arup, Wardell Armstrong (WA) but foremost the Coal Authority aware of the considerable advances that the introduction of Microdrilling has made in recent years to the rapid and safe investigation of mine working.

Indeed the Coal Authority were present at a demo of Microdrill in 2015 and were very impressed with the performance even then at what was on this occasion its 1st field trial in the UK. Several hundred jobs later Microdrilling has become the preferred method of small developers, builders and consulting engineers for the intrusive investigation of coal mine workings. Microdrill has even been recommended by Barnsley SYMAS (South Yorkshire Mining Advisory Service) and their highly regarded coal mining consultants and mining engineers. The South Yorkshire Mining Advisory Service (SYMAS) provides an “on tap” professional and timely range of services including mineral and stability reports, planning advice, vetting of Building Regulations applications, spoil tip inspections and help with subsidence claims and is supported by Barnsley, Rotherham and Doncaster Councils.

Disappointing then that when Ciria’s new flagship publication C758 Abandoned Mine Workings replaces SP32 Construction Over Abandoned Mine Workings (the latter almost perfect in every way and hence it has stood the test of time) in 2019 it will immediately require revision to bring it up to date with major advances in rotary open-hole non-sampling Microdrilling introduced by Geoinvestigate in the UK several years ago and now in wide use for over 3 years.

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So if you’re thinking about development over abandoned mine workings? – then let Geoinvestigate quote for you next mine working investigation whether it’s a desk top study CMRA, site inspection or an intrusive drilling investigation. Geoinvestigate provides Coal Mine Risk Assessment CMRA, Walkover Mining & Mine Shaft Surveys & Site Inspection Reports, Intrusive Coal & Mine Working & Mine Shaft Drilling Investigations, technical advice and reporting on Mine Shaft & Mine Working Mitigation, Remediation & Stabilisation. We also investigate sinkholes and general ground instability. Let our experts quote for your next mine working or mine shaft investigation whether it’s a desk stop study CMRA, site inspection or a follow on intrusive drilling investigation.

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