How to plan and execute a successful pile testing campaign

Testing and monitoring piles may only take a few hours on the day of installation but the preparation that goes into each project is complex and can take weeks or even months to make sure all the potential issues and scenarios have been anticipated. In this article we explain the procedure involved to prepare for a project which allow us to help guarantee good quality signals and data, avoid damage to the equipment and, most importantly, avoid loss of barge time for clients.

How much preparation time should be accounted for?

The amount of time required for preparation time can vary depending on many factors. For example, preparing to test piles installed on land is likely to be simpler than testing XL monopiles installed at an offshore wind farm out at sea. While it is not unusual for the team to be called onto a project at short notice, we would always prefer to be involved from the early stages.

Project awarded – what’s next?

As soon as the contract is awarded, preparation starts. And the earlier we’re involved in the process the better, especially for offshore projects.
To make sure the team are fully prepared, a method statement is developed, which covers all the operational procedures and a detailed description of all the operational phases. This includes mobilization and demobilization of personnel, details on sensors installation, offshore acquisition, and data analyses.

Working closely with our client

Client input is vital in creating a thorough method statement, so we will often implement regular calls at agreed intervals with our clients. This allows us to anticipate the critical path of the installation procedures, potential limitations and the environment in which the operations will take place, as well as highlight if there is likely to be any issues or interference during the different stages of the operations.
There are three main phases that require attentive planning and organization which are:

• Preparing the pile
• Installing the sensors
• Data acquisition during pile installation.

It is fundamental to anticipate all the details of each of the above phases during the project preparation.

Preparing the pile

Pile preparation covers all the activity that needs to be done to the pile before the sensors and cables are installed and is discussed in detail with the client. Our aim is to understand:

• Which section(s) of the pile will be instrumented
• The number of sensors required and their position to guarantee suitable measurements
• The possible interactions and clashes during the different phases of the operations
• Whether the sensors will be recovered after driving
• If there are any structural limitations to consider.

The G-Octopus team would always prefer to carry out the pile preparation , however it could be carried out using the agreed procedure by the company in charge of fabrication. It’s important this is done as accurately as possible as the tolerance for the equipment can be very limited (+/- 1mm in some cases).

To make sure everything has been prepared correctly, the G-Octopus team will often follow up with a site visit. This helps to make sure the signal will not be affected, and we have the best chance at gathering the data accurately for our client.

Installing the sensors and preparing the cables

Sensor installation is a key element for a successful offshore pile monitoring campaign. It is also vital to understand the vessel layout and installation procedure so the team know if there will be access to the pile and how the cable can be retrieved.

These elements are anticipated during the project preparation and form the basis of our method statement. This document contains the procedures and technical drawings for sensors installation, detailing how sensors and cables are mounted/secured to anticipate all the potential issues that could be faced during the offshore operations. Our experts will then carry out the installation of the cables and sensors onto the piles in the yard, prior to load out (for smaller piles, it is possible to do this on deck or cargo-barge in some cases). A strict quality check (QC) follow-up is implemented during this phase: the sensors installation phase is fully documented, and as-built characteristics of the installed equipment is shared with the client together with integrity tests performed at the end of sensors installation.

This planning helps to make sure everything can be installed correctly and accurately on the day, avoiding damage and interference to the sensors, and most importantly that and no barge time is lost.

Data acquisition

In order to analyse the data, the cables must be successfully recovered on deck and connected up to the acquisition unit in the acquisition room which is why understanding the vessel layout and cable route is so important.

The other key considerations in this final phase focus on anticipating any issues that may occur once the pile is upended and driving has started, as well as contingency measures for damaged or broken sensors and how the cables and, where possible, sensors can be recovered at the end of driving. To support this activity and monitor and recover the cables, it’s common for a G-Octopus technician to be on deck throughout.

By carrying out each of the phases above thoroughly and working closely with our client, we have the best chance of collecting accurate data while minimising barge time lost.

The G-Octopus team have years of experience in testing and monitoring deep foundations onshore, nearshore and offshore and underwater. Get us involved early by discussing your project with us today.