Intrusive UXO surveys
On construction sites where a desktop or non-intrusive survey has identified a risk of encountering deep buried unexploded ordnance (UXO), and where intrusive works such as piled foundations are planned, intrusive surveys can enable detection and clearance of the risk - ahead of piling or borehole drilling.
Intrusive UXO surveys also enables exploration at depths not achievable by non-intrusive methods, and can be used on land unsuitable for non-intrusive methods such as surface ferro-contaminated ground.
What is an intrusive UXO survey? Drilling down into the details:
Intrusive surveys for unexploded ordnance (UXO) are normally undertaken using magnetometers. SafeLane has two proprietary methods for conducting intrusive surveys for its clients.
It either pushes magnetometers into the ground using hydraulic rams; this is known at SafeLane as the BXP methodology.
Alternatively, intrusive UXO surveys are undertaken by lowering magnetometers into non-ferrous tubes which are inserted into boreholes formed using a rotary drill or other hole forming method. This is referred to as the TFG methodology at SafeLane.
If you’re planning deep intrusive works such as piling (more than 4 meters below ground level), then a non-intrusive survey will not be suitable for your project. You will need an intrusive survey to ensure that any risks from unexploded ordnance are identified.
SafeLane most often conducts intrusive surveys for its clients ahead of planned piling works.
Upon receipt of pile layout plans from a client site, SafeLane geophysicists calculate how many surveys will be required to clear all the proposed piles.
The deepest survey carried out by SafeLane will be to bomb penetration depth (BPD). This is the maximum depth that an airdropped unexploded bomb (UXB) could be present at.
This depth varies depending on the geology of a site.
BXP rigs – understanding this intrusive survey methodology:
- BXP uses a survey rig with hydraulic rams to penetrate the ground with a magnetometer probe to bomb penetration depth.
- This probe records live data and the geophysics experts at SafeLane process and analyse the results.
- If there isn’t UXO present, a clearance radius of up to 2m is provided for every survey.
- In optimal conditions, BXP rigs can achieve a maximum of 20 intrusive surveys per day.
TFG intrusive UXO survey methodology:
- A TFG intrusive survey is conducted using a drill rig that creates a hole into which non-ferrous tubes and probes are inserted.
- Probes record live data and SafeLane geophysics experts process and analyse the results.
- In optimal conditions, TFG rigs can achieve around 8 surveys per day.
Which survey method is right for your site – TFG vs BXP?
BXP rigs are bigger and can cover more ground faster than a TFG rig, but TFG rigs can get through harder ground and can be used in confined spaces.
Your SafeLane consultant will assess your site and make the most appropriate recommendation, taking into account all considerations including your project timelines and and financial constraints.
Combination of TFG and BXP rigs
Combining both intrusive survey methodologies is possible, and you could benefit from the speed of the BXP with the TFG’s ability to penetrate harder ground surfaces.
The combination of these methods is called pre-drill BXP. This involved using a TFG drill rig to drill the first few meters – then once the softer ground beneath has been accessed, the BXP rig will complete the survey.
The experts at SafeLane will assess your project, the ground types and the extent of the risk to formulate a logical, commercially appropriate methodology that is right for you. They will also underwrite your risk and ensure you remain on schedule.
Contact the team for a free consultation today.
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