DFI Journal Volume 5, Issue 2
Gerald Verbeek, VMS, Tyler, TX, USA
Peter Middendorp, Allnamics, voorburg, The Netherlands
number of driven concrete piles with Embedded Data Collectors increases, it has
become possible to compare the widely used Beta Method to assess pile damage
(using the change of pile impedance) with the so-called Measured Pile Integrity
(MPI) method (a combination of two approaches using both the change of pile
impedance and the change in pile pre-stress levels). After a brief introduction of both methods,
this paper presents the outcome of that comparison based on data from more than
400 concrete piles driven in Florida, which brings into question the
reliability of any damage assessment method based solely on the change of pile
impedance (such as the Beta Method), especially to detect damage near the pile
toe. Moreover the paper demonstrates the
need to re-assess the damage classification used for the Beta Method as well as
the use of Pile Driving Analysis (PDA) to detect pile toe damage.
30th Annual DFI Conference, Chicago, October 2005
Peter Middendorp, Profound BV, Waddinxveen, the Netherlands
Gerald E.H. Verbeek, VMS-Profound, Tyler, TX, USA
This paper describes a brief history of the method of characteristics as an accurate solution of the wave equation, and the author’s experiences with the method of characteristics over a period of 30 years.
As a result of the offshore pile driving activities associated with the development of the North Sea oil fields in the 1970’s, two Dutch companies initiated extensive research efforts. Heerema started to research the dynamic behavior of soil during driving and HBG (Hollandsche Beton Groep) extended the method of characteristics with a straightforward theoretical solution for the shaft friction along the pile.
The research institute TNO started the development of the wave equation program TNOWAVE in the late 1970’s based on HBG’s friction model extension for the method of characteristics. Today the program has a worldwide application in the field of pile testing. This paper will describe its development and application over time and its relation to today’s applications for drive-ability studies for impact hammers (PDPWAVE) and vibratory hammers (VDPWAVE), signal matching for Dynamic Load Testing (DLTWAVE), Pile Integrity Testing signal matching (SITWAVE) and Statnamic simulation (STNWAVE).
The paper will highlight that these developments have been the result of multi-disciplinary and multi-national efforts and encourage geotechnical engineers to seek further developments of the wave equation program in a similar manner. Finally, the paper will indicate some areas where such further developments are required.
2005 SPE Hydrocarbon Economics and Evaluation Symposium, Dallas, April 2005
Gerald E.H. Verbeek
The recent restatements by several Oil and Gas companies of their petroleum reserves has created a lot of short-term publicity, but not a fundamental and widespread discussion regarding the process that is followed to determine a company’s reserves.
To minimize the chance of reserves misstatements in the future, some have called for the certification of the individuals preparing a company’s petroleum reserves or even the use of outside auditors to certify the reserves claimed, much like the certification of the financial reports by an independent auditor.
This paper reviews both sides of such an approach, but conclude that a solution in line with the thinking behind the Sarbanes-Oxley regulations governing a company’s financial reporting is more appropriate.
However, while this approach clearly defines the responsibility for the reserves estimate, the reporting of this estimate has to be expanded to ensure more transparency. This paper recommends that the reserves statement uses a set of probabilistic numbers rather than a single deterministic number.
Finally, the objective of this paper is not necessarily to answer all questions surrounding the process to be followed by a company for stating its reserves, but rather to ensure that there is a fundamental discussion regarding that process, and that in the end the methodology is improved in a practical manner that provides added transparency and accountability