Ongoing challenges in Engineering Geology for Tunnelling in Difficult Ground
The growth of infrastructure needs has increased demands for the excavation of tunnels in poor ground or varying geological conditions. This development includes site investigation techniques, analytical design method (notably numerical), risk analysis, techniques of construction, and monitoring. The assessment of ground for design has to be based on a sound understanding of the regional geological rules and the establishment of a geological model where data and conditions are translated into an engineering geology description. Examples of geological models and cases from both mountain and urban tunnels under complex or difficult geological conditions are presented. These include the base tunnels in the Alps in a variety of conditions at great depth, tunnels through heavily folded formations with shear zones and cataclasites, Metro works in heterogeneous and weak ground and the selection of the appropriate TBM, and the project for the Gibraltar strait tunnel.

Tunnel design requires knowledge on the quality of the material in which the tunnel will be constructed. Engineering design requires numbers and the lecture explores and discusses methods that can be used by Engineering Geologists to assess the geological factors that have an impact on the design. Since the attempt of Terzaghi (1946) to describe the characteristics of rock masses, a number of rock mass classifications have been developed and play an important role in tunnel design, providing input data on strength and deformation properties of the ground for numerical models. Together with the rock mass properties, the in situ stresses field has to be estimated or measured and this is one of the most difficult tasks. Although the role of engineering geology has been extended into the area of defining the design parameters, the idealization process, in the form of numerical analysis, should be driven by sound geologic reasoning together with the engineering logic.

The understanding of real behaviour is indeed absolutely necessary before any calculation is attempted. Thus, the engineering geological "I.D" of the geomaterial and the stress environment define this ground behaviour such as:

• Brittle failure of strong massive rock under high stress level.
• Gravitational falling or sliding of blocks or wedges defined by intersecting structural features or "chimney" type failure, or ravelling in disintegrated and heavily broken and loose masses.
• Formation of a "plastic" zone by shear failure under high stress relative to the strength of the rock mass with deformation problems or even squeezing.
• Swelling, in case of appropriate mineralogical constitution.

Comments on the methods for design for each of those cases are discussed and the presentation concludes with a discussion on excavation methods in conventional tunneling construction with special attention to support devices in order to deal with squeezing ground. Examples from a number of tunnels from around the world illustrate the design and construction procedures discussed.

Paul Marinos AEG 2010 Jahns Distinguished Lecturer
Dr. Paul Marinos has been named the 2010 Jahns Distinguished Lecturer. The Association of Environmental & Engineering Geologists (AEG) and the Engineering Geology Division of the Geological Society of America (GSA) jointly established the Richard H. Jahns Distinguished Lectureship in 1988 to commemorate Jahns and to promote student awareness of engineering geology trough a series of lectures offered at various locations around the country. Richard H. Jahns (1915 - 1983) was an engineering geologist who had a diverse and distinguished career in academia, consulting and government.

Dr. Paul Marinos received a Mining Engineering degree from the School of Mines of the National Technical University of Athens, Greece in 1966, a postgraduate degree in Applied Geology from the University of Grenoble, France, and his Doctorate in Engineering Geology from the same University in 1969. He worked for French and Greek design and construction companies until 1977 and then was elected as Professor at Democritus University in Northern Greece. Since 1988 Dr Marinos has been Professor of Engineering Geology in the School of Civil Engineering in the National Technical University of Athens and has served as head of the Geotechnical Section of the School for several years. From 2001 to 2004 and from 2006 to 2008 he was the Director of a Graduate Course in Tunneling and Underground Construction. He was a visiting Professor in the Geology Department of the University of Grenoble (1987) and of the School of Mines in Paris (2003).

Dr Marinos is a member of AEG and GSA and fellow of the Geological Society of London. He is a past President of the International Association of Engineering Geology and the Environment (IAEG), immediate past president of the Geological Society of Greece and honorary member of the International Association of Hydrogeologists (IAH). Dr Paul Marinos has received several awards, including the Hans Cloos medal of IAEG, and the Andre Dumont medal of the Geological Society of Belgium. He was selected for the presentation of named lectures, including the 6th Glossop Lecture in London (2002), the 19th Rocha Lecture in Lisbon (2002), the 33rd Cross Canada Lectures Tour (2005), and the Rock Mechanics annual Lecture in Madrid (2006).

Dr Marinos and his team conduct research on a variety of applications of geology to engineering, mainly rock mass characterization, weak rock properties and behavior, with special emphasis to tunnel design. His work also covers landslides, dam geology, and engineering in karstic terrain. His other significant interest is the protection of historic monuments and archeological sites. Dr Marinos has authored or co-authored over 300 papers in journals or major conference proceedings. He was a key or invited lecturer in more than 40 conferences or special events. He has given lectures to University Courses or Workshops, among them the Federal Technical University (EPFL) in Lausanne, Switzerland, the Polytecnico of Turin, Italy, the University of Durham, U.K., the University of Coimbra, Portugal, the University of Kobe, Japan, the Black Sea University Romania, the Aristotle University of Thessalonica, Greece, and the Griffiths University, Australia. He has edited proceedings published by international publishers. Dr Marinos is a member of the Editorial Board of a number of prominent journals as "Engineering Geology", "Bulletin of the International Association of Geology"," Landslides", "Environmental Geology", "Rock Mechanics" and from 2009 "Environmental and Engineering Geosciences".

Dr Paul Marinos has extensive industrial experience having served as consultant, independent reviewer and member of consulting boards or panel of experts on major civil engineering projects in Greece, France, India, Iran, Jordan, Morocco, Portugal, Saudi Arabia, South East Asia, Spain, Sweden, and Turkey.

The presentation includes geotechnical findings and remedial construction activities for the June 1, 2005 Bluebird Canyon Landslide in Laguna Beach, California. The failure occurred in bedrock terrain, and was initiated by an elevated groundwater level from the 2004-2005 Winter's high rainfall. The resulting risks to the public improvements and the community included downstream flood hazard, headscarp retreat, potential mudflow-debris flow hazards along the landslide margins, and the potential loss of three more public streets. The emergency mitigation and the eventual public infrastructure repair were conducted in two Phases. Phase I consisted of winterization of the slope by removal of the destroyed homes, surface regrading and drainage control, dewatering, removal of slide debris in the Bluebird Canyon drainage, installation of a storm drain, construction of a gravity buttress in the canyon, and stabilization of the headscarp with a temporary tieback /shoring wall. This work was fast-tracked and required constant coordination between the design and contracting teams to respond to difficult field conditions. Phase II included removal of the majority of the landslide mass, construction of two soil-cement shear keys, placement of a subdrain network, and placement of engineered fill to rebuild the slope.

HANNES RICHTER, GE, Chief Geotechnical Engineer, Geofirm/Stoney-Miller Consultants, Inc.
He earned Bachelor of Science in Civil Engineering from California State Polytechnic University, Pomona, and a Master of Science in Geotechnical Engineering from University of California, Berkeley. He has over 30 years of geotechnical experience throughout the United States involving a diverse range of residential, commercial, industrial, and governmental projects, and has consulted to the City of Laguna Beach for over 15 years. Mr. Richter has participated in many comprehensive landslide investigations, monitoring programs and stabilization efforts, both for new construction projects and as a forensic expert.