Posted on May 17, 2022
A DredgeWire Exclusive
By Judith Powers
Based on conversations with Prof. Miedema and Robert Ramsdell
Dr.ir. Sape Andries Miedema will retire in June after 42 years of involvement in dredging as an MSc student, then PhD and finally professor of dredging engineering at Delft University of Technology (DUT) in the Netherlands.
At DUT he is Associate Professor of Dredging Engineering and Mechatronics; Educational Director of the Offshore & Dredging Engineering MSc Program; and in the past Educational Director of the Mechanical Engineering &Marine Technology MSc Program.
His retirement coincides with the 100 year anniversary of the founding of DUT’s Chair of Dredging Technology, and he will give a presentation on the history of the Chair at the World Dredging Congress (WODCON XXIII)in Copenhagen the week of May 16th through 20nd.
He decided on dredging engineering as a student at Delft in the early 1980s, and was the first ever PhD in Dredging, studying under Prof. ir. Jan de Koning. Through the years he has contributed invaluable research and information on the scientific and engineering processes involved in cutting and transporting bottom material of every description.
Prof. ir. at WODCON XXII in Shanghai in 2019 indicating his signature on a wall of signatures. He will retire in June after more than four decades in dredging technology education, research, and technical writing.
Dr.ir. Miedema obtained his M.Sc. degree in Mechanical Engineering with honors from DUT in 1983, and his Ph.D. degree in 1987 with a dissertation topic of the basics of soil cutting in relation to ship motions. He was offered and accepted a tenured professorship upon receipt of his Ph.D., and from 1987 to 1992 he was assistant professor at the chair of Dredging Technology.
In 1992 and 1993 he was a member of the management board of Mechanical Engineering & Marine Technology at DUT, and in 1992 was appointed associate professor with the chair of Dredging Technology. From 1996 to 2001 he was educational director of Mechanical Engineering and Marine Technology in conjunction with his associate professorship of Dredging Engineering. In 2005 he was appointed Educational Director (Director of Studies) of the MSc program of Offshore & Dredging Engineering, and in April 2013 was appointed director of Studies of DUT’s MSc Marine Technology program, remaining Associate Professor of Dredging Engineering.
Prof. Miedema in 1989 receiving the IADC Best Paper by an author under 35 at WODCON XII in Orlando, presented by WEDA President Charles Hummer.
Contributions to Dredging Education
During his career, he has taught courses on soil mechanics and soil cutting, hopper sedimentation, mechatronics, applied thermodynamics, drive system design principles, mooring systems, and mathematics. His research focuses on the mathematical modeling of dredging systems, including cutter suction dredges, hopper dredges, clamshell dredges, backhoe dredges and trenchers. He has published books on cutting sand, clay and rock, and slurry transport.
Dr.ir. Miedema considers shaping the different engineering curricula at DUT as his most significant accomplishment — from 1995 to 2000 for the BSc Mechanical Engineering and Marine Technology programs and from 2004 to 2021 for the MScOffshore & Dredging Engineering program.
Prof. Miedema saw the creation of an outstanding dredging engineering curriculum at TU Delft as his most important achievement. Here he appears in the upper left corner with his students who accompanied him tothe 2001 WODCON 16 in Kuala Lumpur.“In the breaks and during social functions he is always surrounded with students,” CEDA General Manager Anna Csiti said.
When he joined the engineering faculty, the program was “very traditional, mostly reproducing knowledge”, he said. Over five years he changed the curriculum to about 50% course and 50% project- and problem-based learning, adopting the philosophy that knowledge and skills require different teaching styles.
“With this (curriculum) the graduates get a toolbox to develop their problem solving capabilities,” he explained. “So, it’s not about what they think, it’s about how they think and solve complex problems. At the end we need engineers with high problem solving capabilities,” he said.
In 1999 he began participating in development projects in China and Vietnam. In China he established, along with Prof. W.J. Vlasblom, a chair of Dredging Engineering. In Can Tho, Vietnam he was project manager of a 15 million Euro MHO (M. Hoger Onderwijs – a Joint Financing Higher Education Program financed by the Dutch government) project where 10 Dutch universities joined forces to develop one general Vietnamese university that included all disciplines of study, and also construction of all the physical infrastructure. The University’s website is https://en.ctu.edu.vn/
After suffering a heart attack in 2000 at age 45, he stepped down as director of education and continued as associate professor of dredging, still continuing in Vietnam.
Sape’s mentor Prof. Jan de Koning, left, and Prof. Miedema at a photo op in Guangzhou, China. Prof. de Koning hosted educational trips with his students, a practice Prof. Miedema continued, studying the culture of the countries they visited as well as the dredging operations.
International Students in Delft Program
In 1999, ministers of education of 29 European countries agreed on the Bologna process, in which students and graduates can move freely between countries using prior qualifications in one country as acceptable entry requirements for further study in another. In 2003, Prof. Miedema suggested that all groups involved in large scale offshore activities join in one MSc program under the agreement, creating the MSc Offshore & Dredging Engineering program in 2004 at DUT with Prof. Miedema as Director of Education.
Since the program was established, international students have comprised about 25% of the dredging engineering students, or approximately 15 per year, from all over the world.
“From 2015 to 2019 I added the energy transition to the curriculum, and we now have an Offshore Renewables specialization and staff carrying out research in this field. My latest PhD will graduate in December 2022 with a dissertation on wave energy converters,” he said.
Visiting the Saigon Museum in 2019 are Prof. Cees van Rhee, who holds the Chair of Dredging Technology at TU Delft, Prof. Miedema, and his wife Thi Kim Thuy Nguyen.
“Scientifically, I consider my slurry transport book and theory (the Delft Head Loss & Limit Deposit Velocity (DHLLDV) Framework) as an important achievement,” he said, referring to the book “Slurry Transport: Fundamentals, a Historical Overview and the Delft Head Loss & Limit Deposit Velocity (DHLLDV) Framework. 808 pages. Delft University of Technology, June 2016.
He has been consulting for Great Lakes Dredge & Dock Company (GLDD) since a1989 trip to WODCONXIIin Orlando, Florida, where he received the International Association of Dredging Companies (IADC) Best Paper by an author under 35 for his paper “On the Cutting Forces in Saturated Sand of a Seagoing Cutter Suction Dredger”, and also signed a consulting agreement with GLDD, resulting in about 150 visits to the USA since then.
He advises the company on equipment selection and configuration and has created engineered solutions to help the company’s estimators and field people to operate equipment with the highest efficiency.
“His work has heavily influenced the way we approached technical issues. Over the years (Miedema) trained over 100 GLDD estimators, engineers, and field people,” said Robert Ramsdell, who was Director of Production Engineering and R&D at GLDD, and now works as an independent consultant.
“Sape is one of the smartest people I’ve ever known,” he said.
Russ Zimmerman, left, Robert Ramsdell, Thi Kim Thuy Nguyen, and Prof. Miedema at the 2016 WEDA conference in Miami, where Ramsdell and Miedema presented A comparison of different slurry transport models for sands & gravels, and introduced the DHLLDV Framework for comparing transport models.
Simulating Dredging Payloads
Ramsdell worked with Miedema performing clamshell, backhoe, cutter suction and hopper simulations to calculate payloads.
“His PhD dissertation was on cutting sand and clay, and he leveraged that research into calculating full cycle production for different dredges. He worked with Steve Becker, another GLDD engineer, on clamshell cutting theory, and did training and specific advisory services,” Ramsdell explained.
Prof. Miedema said “In 1982 I started research into the interaction of a seagoing cutter dredge with the soil, resulting in the program Dredmo. From 1983 to 1987 my PhD research resulted in a more fundamental model for the cutting of water saturated sand. Because the model also contained terms that made it suitable for other types of soil like clay and rock, I later added ductile failure modes, then brittle failure modes.”
The model distinguishes six possible failure mechanisms for small blade angles, and the “wedge theory” for large blade angles, where a static or dynamic wedge will occur in front of the blade, reducing the cutting forces.
The simulation software allows input for a certain type of material, for instance a certain type of clay. The program simulates the clamshell closing process and estimates quantity of material in the bucket. For a hopper, the software calculates the filling process when pumping a specified type of soil into the hopper, calculates the time it takes for the solids to settle out, and when decanting water to increase hopper capacity, the point at which solid material begins leaving the hopper in the decant water.
Prof. Miedema explained “In the past 15 years my focus has been on the MSc program and on writing scientific papers. About ten years ago the idea emerged to put all the knowledge in books, so the whole world can use it for free,” he said.
His first book described the cutting of sand, clay, and rock, including basic soil mechanics.
Steve Becker, left and Prof. Miedema accepting the Best Paper award along with fellow authors P.S. de Jong and S. Wittekoek for The Closing Process of Clamshell Dredges in Water-Saturated Sand,at WODCON XIII, Mumbai, India, 1992.
Miedema, S.A., The Delft Sand, Clay, and Rock Cutting Model. Book, 574 pages, Delft University of Technology/IOS Press, 2014. Book, second version, first edition. ISBN Book: 978-94-6186-249-5, ISBN eBook: 978-94-6186-252-5.
On the subject of transport of slurry, GLDD had a challenging pumping project and wanted to know how to calculate head loss in a large-diameter pipeline up to 20 miles long. The existing models were based on theories for long line pumping that were not developed at the scale of this project. Miedema acknowledged that the models had holes.
“We started digging into slurry transport and developed a whole new theory of that work,” said Ramsdell. He joined Miedema in analyzing the physics in a big pipeline that were much different than those applied to tests in a small pipe, and also on a range of grain sizes in the materials, including for dredging only oyster shells, which exhibit vastly different behavior in the pipeline. The study involved testing nearly 10 head loss models that are used in different countries. They developed the Delft Head Loss & Limit Deposit Velocity (DHLLDV) Framework and were able to advise GLDD on what the total pump pressure should be to avoid plugging the line; where to locate the booster stations to avoid cavitation at the entrance of each pump; and how particle size distribution affects the behavior of the pumps and the slurry.
“Since there was no good book with an overview of the topic, we decided to write it ourselves and extended it with a new physical model,” Prof. Miedema said.
Miedema, S.A., Slurry Transport: Fundamentals, a Historical Overview, and the Delft Head Loss & Limit Deposit Velocity Framework. Book, 808 pages. Delft University of Technology, June 2016.
Sharing His Findings
Miedema presented A method to compare slurry transport models at the 17th International Conference on Transport & Sedimentation of Solid Particles in September 2015, and Miedema and Ramsdell together presented A comparison of different slurry transport models for sands & gravels and DHLLDV – open source software for slurry transport at WODCON XXI in June 2016 in Miami.
The third book comprises all other subjects and is entitled Dredging Engineering Special Topics.
“The books and the Excel workbooks are free and can be downloaded at TU Delft Open Textbooks, but software developed for a customer is owned by the customer, although I’m always allowed to do consultancy,” he said.
Prof. Miedema, left, at WODCON XXI in Miami, 2016, with Barbara Randall, Ram Mohan, Ankita Mohan, Robert Randall, and David Padman, all colleagues of many years.
Anna Csiti, longtime general manager of the Central Dredging Association (CEDA), has high praise for Prof. Miedema and his contribution to the organization: “Sape has always been a well-known and much appreciated member of the CEDA (Central Dredging Association) community. He has been an important connection for us with the dredging students, many of whom later became active CEDA members themselves.
“No CEDA Dredging Days or WODCON has been imaginable without him, where he would give excellent presentations or chair a session. In the breaks and during social functions he was always surrounded with students. I don’t expect any different at the coming WODCON in Copenhagen either.
“Some years ago, together with Professor Cees van Rhee, they presented a series of successful CEDA webinars on Dredging Equipment and Technology focusing on the cutter suction dredger and the trailing suction hopper dredger. The series started with two foundation-level presentations and continued with fourpractitioner-level presentations tuning in on particular aspects of the two dredgers. These webinars can still be accessed through the CEDA website. Prof. Miedema is planning a new series of webinars to be presented in the fall of 2022.”
Prof. ir. Miedema’s curriculum vitae lists 157 titles of technical papers, journal entries and books, 57 reports and 16 prestigious awards on his research into a universe of dredging and transport methods. At the end of the list is the best paper award with Thomas Combe, for The influence of adhesion on cutting processes in dredging at the WEDA/TAMU Conference in June 2015 in Houston and Modeling the effect of water depth on rock cutting processes with the use of discrete element method with Rudy Helmons, receiving the best paper award at CEDA Dredging Days in Rotterdam, November 2015, and the Excellent Paper Award at the 1st International Water Environment Ecological Construction Development Conference, Wuhan, China in October 2018.
At WODCON XXII in Shanghai, 2019, Prof. Miedema received top billing for his presentations. Here he describes his simulation methods for estimating production volumes using dragheads in trailing suction hopper dredging.
What does retirement hold for Prof. Miedema?
“For the time being, consultancy and teaching for a year. Working on my stamp collection. Walking, biking, staying in Vietnam with (the family of my wife Thi Kim Thuy Nguyen), and maybe in the future study philosophy or something similar. Time will tell,” he said.
Prof. Miedema has two grown children, Esther and Erik, a grandson, two granddaughters, and another granddaughter on the way.
Prof. Miedema’s consulting company is SAM Consult. His CV can be seen on the DUT website: http://www.dredgingengineering.com/
