The intricacies of restricted access drilling

28th July 2020
Posted By : Lanna Cooper
The intricacies of restricted access drilling

Most people don't link geotechnical drilling to an urban setting, but sometimes, the connection needs to be made. There are plenty of scenarios where a regular rig won’t work, making restricted access drilling the perfect option. It’s natural to think of busy towns and cities when considering a site with restricted access, but this form of drilling is frequently used in more rural settings too. If it’s difficult to access the site, then a specialist, restricted access rig is the answer.

John Rodgman, Managing Director of UK-based geotechnical drilling company, Borehole Solutions, has provided his professional insight on the things to consider when looking at a restricted access site. He has also detailed the surprisingly extensive list of ways a restricted access rig can be applied - from window sampling to cable percussion drilling - as well as gone into detail of how all these things can be achieved in such a small space, whilst keeping safety in mind.

The many applications of restricted access drilling

The staggering versatility of the smaller, more portable rigs make them an excellent addition to any drilling company’s fleet. The applications of restricted drilling rigs include, but are not limited to:

  • Cable percussion drilling
  • Open borehole sampling
  • Sonic drilling
  • Micro-piling
  • Window sampling
  • The installation of retrofit geo-exchange units
  • Hollow stem augering
  • Ground anchors and soil nails
  • Water wells

Urban settings

Drilling deep into the ground in a town or city, with no more than a few square metres to work with, does sound rather far-fetched. With the limited space that hotel lobbies or underground transport tunnels (to name a couple of examples) provide, it simply doesn’t sound feasible to introduce and operate heavy machinery. The portability of many restricted access drilling rigs, however, make the prospect of getting it to the desired drilling spot much more realistic. If need be, it can always be dismantled and then reassembled on-site.

Mounted rigs are an option when the issue presented to the drill operator is one of width. The adjustable capabilities of many mounted rigs allow them to move seamlessly through tight spaces, such as narrow alleyways, in a way that was until recently thought impossible.

Useful from head to toe

A form of restriction often forgotten, amidst all the narrow spaces and densely packed environments of both rural and urban settings, is the restriction of height. When it comes to checking the appropriateness of the ground in preparation for clearing, or more serious construction work, this may involve working in a space with very little headroom.

These kinds of site investigations may take place anywhere from a building with low ceilings to a forest with a low-hanging canopy. These kinds of settings are no place for a conventional rig, but instead require a restricted access drilling rig that can utilise telescopic masts to allow for drilling in spaces with only a couple of metres of headroom.

Restricted access drilling rigs do have a place in wide open spaces, however. Even if the site presents no issues of narrow spaces or minimal headroom, sometimes the environmental features of the site will mean a smaller rig is the only option. To avoid damaging rare plant life or threatening the habitats of a particular species, leaving the smallest rig ‘footprint’ possible is essential.

This includes the carbon footprint, as well as the physical one. Although some level of disturbance is inevitable, a portable and modular rig allows for minimal damage caused when accessing and leaving the site, as well as the smallest possible impact on the patch of ground in need of investigation. Being environmentally conscious is hugely important when undertaking any site investigation.

Restricted and limited: know the difference

Restricted and limited access drilling are often thought to be one and the same. This is not the case. Whilst limited access refers to the drilling space impeding a drill operators ability to work with regular equipment under normal circumstances, restricted access refers to the ease (or lack thereof) of getting the rig to the site in the first place.

Most companies that are able to offer restricted access drilling rigs will also be able to cater to limited access situations too.

Safety is a priority

Safety is often doubly important to those working on a restricted access site. Hydraulic breakout clamps are fitted to most restricted access rigs, in an effort to combat the risk of personal injury. It is vital to utilise these in particularly cramped conditions, as they alleviate the need for any drill operators to get too hands-on when operating the rig.

Whilst the safety of the general public is always a huge factor to consider in any drilling scenario, many restricted access situations take place in towns and cities, making public safety an even greater factor to consider. Companies engaging in restricted access drilling must be responsible for setting up sufficient parameters to ensure no member of the public can come into contact with any dangerous machinery. Even the smallest restricted access drilling rigs present an element of risk, especially to those who aren’t used to dealing with them.

In the modern world, geotechnical drilling companies, like Borehole Solutions, have no need to force their traditionally larger equipment into unsuited sites, as restricted access drilling rigs provide the ability to cater to the specifics of the site. This ultimately means that there are very few situations where drilling can’t be done to the best possible standard.


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