G-Octopus: Adding value to projects with pile driving monitoring
What’s covered in our webinar?
In this webinar, presented by Emilio Nicolini, Technical Director of G-Octopus, we’ll introduce you to the business, our expertise and our global reach followed by an in depth look at pile driving monitoring (PDM). We’ll cover an overview of what PDM entails, it’s benefits and why it shouldn’t be overlooked as well as the value it can add to your next project. Then, to help bring it all to life, there’s three great case studies followed by an excellent Q&A session with great questions from the audience.
You can see the questions and answers below:
Q: What are the advantages of your PDM system compared to the system of any competitors?
There are actually several. Two key advantages are: how we install the sensors and the quality of those sensors. We use high quality instrumentation, cables and sensors, at the origin and over the years we’ve developed our own way of carrying out the installation. In many cases, electrical problems occurring during driving actually reduce the quality of the signals and reduce the precision of the test. We’re dedicated to providing a precise and well planned service, we make sure the connection is guaranteed and the instruments are performing at their theoretical (laboratory proven) maximum and we also take care of the regular certification of the instruments.
Q: Is there any limitations for pile diameter (L:D) to use PDM?
No there aren’t any limitations, PDM is a very flexible methodology and can be adapted to your specific project. We can carry out PDM on all piles regardless of their diameter. For example, traditionally offshore monopiles piles have a very large diameter of up to 8m.
Also, by instrumenting your piles at different levels you can measure how the energy is distributed along the pile to see if any energy is reflected before it reaches the soil.
Q: How accurate are the bearing capacity predictions?
The bearing capacity predictions can be between 90-100% accurate however it depends on how accurately the methodology is applied. As experts in PDM we will always work with our clients to make sure all instrumentation is applied precisely, allowing them to achieve the most accurate results. A long, public track record is available to prove this.
Q: Is PDM recommended in standards for offshore wind?
PDM is not strictly recommended by standards, but it is very often required by the certification authorities which require you to prove the pile is designed, as required, for the lifetime of the structure.
Currently, we believe that only the BSH in Germany requires pile testing for jacket or tripod piles (normally not for monopiles, at least for Wind Tower Generators). If dynamic tests are undertaken in Germany, they should be ideally calibrated against static tests in similar conditions, otherwise the uncertainty factor will be very high. It seems that Poland is following Germany’s route (i.e. design approach following Eurocode), therefore, pile testing may also become a requirement in this country as well.
Q: Do you know if marine warranty surveyors request PDM for some pile installation in challenging soil conditions?
The marine warranty surveyor (MWS) only deals with installation aspects not design aspects. Therefore, it’s unlikely that any MWS would asks for pile tests however certifiers may ask if they consider that the design is not safe enough.
Q: Based on your experience on offshore wind, how many piles do you instrument on an offshore wind farm?
Depending on which standard you use, you’d usually instrument 5-10% of piles in an offshore wind farm. Eurocode specifies an absolute number of tests (i.e. not a proportion of piles to be tested). The lowest uncertainty factors correspond to more than 20 tests per soil province. Dynamic tests on 20 piles is obviously a lot. Therefore, the approach that is generally followed is to indicate that pile driving data (blowcount and hammer energy) are available for all piles and selected piles are dynamically tested in each soil province (say 3 Wind Tower Generator positions).
Q: Roughly what percentage of offshore pile driving projects use PDM?
The percentage of offshore pile driving projects varies by country and depends on engineering traditions and they types of piles used. In some cases, PDM / Pile Dynamic Testing is not welcome due to “bad reputation” of this technique or bad experience had by a client. When solicited by asking our clients to share the results which caused this, we always discover that the method was not applied properly and carried out by non professionals. Although we cannot share these as case histories due to confidentiality, we were able to change clients’ opinions to prove they cant rely on this method.