In the opening plenary session, Edward Cording presented on the “Assessment of Excavation-Induced Building Damage”. He presented a general procedure to examine ground loss as well as lateral deformation at the wall face to evaluate the response of the soil mass and the structures behind the wall face using numerical analysis. Richard Bathhurst then discussed “Facing Displacements in Geosynthetic Reinforced Soil Walls” where he reviewed practices and tolerances specified in various codes as well as summarizing a review of a database of performance data on wall facing deformations.
Andrew Whittle spoke on “Advances in the prediction of excavation performance” and Allen Marr on “Displacement-based design for deep excavations”. Both presenters emphasized the use of numerical modeling for computing displacements, and Dr. Marr presented procedures for performing the calculations. Helmut Schweiger discussed the “Design of deep excavations with FEM – Influence of constitutive model and comparison of EC7 design approaches.” He discussed some of the issues with load factor design in relation to finite element modeling. In Eurocode 7, there are several design approaches, and he discussed the differences and how Design Approach 3 may be the most promising method when it comes to deep excavations where deformations are most important because the method utilizes partial factors on the parameters of the model as opposed to factoring the final result (such as deformation, bending moment, etc.). Professor Schweiger also had one of the more memorable quotes from the conference, one he indicated he had shared with his students in Austria:
The gamma of water is the only thing we know in soil mechanics.
— Helmut F. Schweiger
At the award luncheon, the keynote speaker was Bob Holtz, for the young geotechs like me, yes, that’s the Holtz in Holtz and Kovacs. He shared his personal reflections on earth retention from 1962-2010. It was a very unique retrospective, and one that not too many people in the world could provide. At the luncheon, Rich Finno was presented with the Harry Schnabel Jr. Award for excellence in the field of earth retaining structures.
There were two concurrent afternoon sessions, one on seismic design of retaining walls, which I wasn’t able to attend. The other session was on various topics in fill walls plus another excavation support case study at the end. James Parkes shared about his project to review some 20-year old RECo MSE walls at BWI Airport in Maryland. The site that of a former rental car facility was being redeveloped, and they wanted to review the condition of the walls. Among other investigations, they dug down to expose the top row of reinforcement (steel strips) at several locations. After 20-years, the galvanization was still pretty much fully intact. In fact, the walls had held up well, they just needed some fairly minor maintenance, and most of the problems being observed seemed to be related to improper drainage of the parking lot above the wall which was remedied.
Ken Fishman discussed corrosion as well, his presentation was entitled “Metal loss for metallic reinforcements and implications for LRFD design of MSE walls”. His work involved using a reliability based calibration of resistance factors for the rupture limit state (tensile breakage) for steel reinforcements based on variable corrosion rates. Robert Gladstone presented “Coherent Gravity: The correct design method for steel-reinforced MSE walls”, reiterating that the steel reinforcement MSE wall folks still prefer the coherent gravity method. The final presentation in the session was by David Cotton on “Recent advances in the top-down construction of a 26.4 m deep soil nail retention system – Bellevue Technology Tower”. Unfortunately I had to leave before the presentation to catch my flight.
I also missed the closing plenary session with presentations by Hubert Deaton and Thomas O’Rourke, both attempting to summarize and wrap up the developments in the field of earth retention and attempt to look into the future of this area of geotechnical practice.
It was an excellent conference, and I was very glad I was able to attend. The technical content, exhibitors and networking was tremendously valuable, and hopefully the coverage I provided was useful to GeoPrac readers who perhaps could not attend in person. I might have another post or two left related to the ER2010 conference, so stay tuned.