Tight timeframes on microtunnelling installations can increase the difficulty of a project as unforeseen circumstances can cause delays. The key to managing these challenges and ensuring a pipe installation is completed within the specified timeframe is pre-planning. Here, Stuart Harrison, Managing Director at Edge Underground, looks at four complications that can arise on projects, and how pre-planning can help mitigate them.
Changing ground conditions
Knowing the prevailing ground conditions at a site before beginning to drill is paramount to achieving a successful pipeline installation without time blowouts. However, it is not uncommon for contractors and subcontractors to arrive on site and start drilling only to find that the ground conditions are somewhat different to the geotechnical information provided.
According to Mr Harrison, this is one area where pre-planning is of great benefit to completing the installation on time.
“Pre-planning is important in two key ways: having the equipment to check the ground conditions before starting, and having a selection of cutters on hand,” Mr Harrison said.
“The best chance of completing a job within a tight timeframe, is to identify any discrepancies between the geotechnical information and the actual conditions at the site as early as possible.
“If you’re lucky, the difference will be picked up before drilling begins, during the excavation of the entry and exit pits. This will give the opportunity to change the approach to the microtunnel before it is launched, but this is not always the case.”
This still leaves the risk of ground conditions changing during the microtunnel.
“Traditional microtunnelling machines can only move forward, they can’t retract, so if ground conditions change mid-installation, you’re guaranteed to lose time excavating the head. Using a machine such as the Vermeer AXIS that can retract, means contractors can perform a pilot line through the ground, inspect it and change the drill head to one that best suits the prevailing conditions,” Mr Harrison said.
“To further reduce any impacts on time, it is good to prepare a selection of cutters suited to a range of different ground conditions to allow for changes during the drilling process, so you’re not having to try and get the right cutter head to site after the pilot has been completed.”
Mechanical failure is another problem for projects that need to be completed in a tight timeframe as emergency maintenance and fixes will stall the project and can be very costly.
“If you’ve got a project coming up that needs to be completed in a short timeframe, it’s recommended to have all your equipment serviced, tested and made ready for operation prior to construction. It’s also good practice to have spare parts available, and a backup drilling machine should also be on standby in case there machinery does breakdown,” Mr Harrison said.
“Having the most appropriate and effective tools for a job is a straightforward decision, and makes a big difference when working on projects with tight time constraints.”
For projects with tight timeframes, having a backup plan for bad weather must also be considered.
“Heavy rain can quickly wash away access roads, making the site inaccessible, so having backup equipment on hand such as earthmoving machinery will allow you to quickly continue operations,” Mr Harrison said.
“You should also arrange to have all-weather access to a tipping facility to dispose of drilling mud.”
Supply of materials
Pre-planning is also essential to ensure that you have all the materials on site when required.
“Once a project has started there is no time to modify anything on site, so everything needs to already be measured and trialled before beginning, including steel jacking bands, concrete jacking pipe, joint packers, centralising brackets and carrier pipework,” Mr Harrison said.
“If a project is taking place after hours or over a weekend, facilities such as concrete batching plants for grout supply should be pre-booked.”
Getting the job done quickly
“Pre-planning is top priority when it comes to completing projects within a strict deadline. Thinking ahead to consider any complications that may occur, and taking steps to have a contingency plan in place will ensure the project can be completed within time and safely.”
This partner content is brought to you by Edge Underground. For more information, visit edgeunderground.co.