Faculty Research Overview

Dr. Abrahamson has been involved in strong motion seismology for over two decades. He has extensive experience in the practical application of seismology to the development of deterministic and probabilistic seismic criteria (response spectra and time histories) for engineering design or analyses. He has been involved in developing design ground motions for hundreds of projects including dams, bridges, nuclear power plants, nuclear waste repositories, water and gas pipelines, rail lines, ports, landfills, hospitals, electric substations, and office buildings. About 3/4 of these projects have been in the Western US and the other 1/4 have been in the Eastern US or outside of the US.

Dr. Abrahamson has published over 100 papers on ground motion and seismic hazard. He has been a leader in the development of empirical ground motion models, including using advanced statistical methods for regression analyses. He was involved in the development of the first ground motion models that included hanging wall effects, directivity effects, and fling effects. His ground motion models have been widely used in practice. He was one of the leaders of the NGA project conducted funded through the Pacific Engineering Research (PEER) Center (http://peer.berkeley.edu/) and was the developer of one of the new NGA ground motion models. He is currently one of the leaders for a NGA-style project for the eastern U.S. and is leading a project to develop new ground motion models for subduction earthquakes.

Dr Abrahamson developed the time-domain spectral matching method (RSPMATCH) that allows the engineer to modify time histories for match the target response spectrum while preserving the key non-stationary character of the time history. This computer program is freely available and is a standard approach that is used in engineering practice. He has also developed models of the spatial variation of ground motion over short distances. These models have been used in for seismic analyses of nuclear power plants and for long-span bridges. 

Dr. Abrahamson served as the technical leader for the PG&E/DOE program on extreme ground motions. This program integrated advanced numerical modeling of ground motions, empirical ground motion models, non-linear site response analyses, and observations of fragile geologic features to constrain the ground motions at very long return periods that are needed for critical facilities such as the proposed nuclear waste repository at Yucca Mountain.  

At PG&E, Dr. Abrahamson is responsible for developing ground for seismic evaluations of PG&E facilities including nuclear power plants, nuclear waste storage, dams, penstocks, electric substations, office buildings, and gas pipelines. He is also responsible for the technical management of the PG&E seismic research program.

As a consultant, Dr. Abrahamson has been involved in the ground motion studies for several major engineering projects in California. Projects include the Caltrans major toll bridge retrofit projects, the CalFed project for the Sacramento Delta levee system, the BART seismic retrofit project, and the SFO expansion. He has been involved in developing ground motion for nuclear plants and dams in the United States and in other countries.

Adda Athanasopoulos-Zekkos is an Associate Professor in the Civil and Environmental Engineering Department at the University of California, Berkeley. Prior to her appointment at Cal, she was an Associate Professor and the Graduate Chair in the Civil and Environmental Engineering Department at the University of Michigan. She holds a joint BS/MSc in Civil Engineering from the University of Patras, Greece (2003), and received her MSc (2004) and PhD (2008) Degrees in Geotechnical Engineering from the University of California, Berkeley. She has received the NSF CAREER award (2013), the 2014 Faculty Excellence Award by the CEE Dept at the Univ. of Michigan, the 2015 ASCE Arthur Casagrande Award and the 2015 ASCE Thomas Middlebrooks Award, and more recently the 2016 Chi Epsilon (XE) Outstanding Teaching Award.

Dr. Athanasopoulos-Zekkos has actively communicated her research results through more than 60 publications, including ~24 archival journal papers and 40+ peer-reviewed conference papers. She has given ~26 invited presentations (for both academia and industry) both in the US and abroad, and was a key contributor to several technical reports produced following disaster reconnaissance efforts supported by GEER. Some notable presentations include the 2017 Berkeley Geoengineering Distinguished Lecture Series, the Annual ACEC NY Geotechnical Symposium, and the Impact Testing for Site Characterization Workshop at SuperPile ’19.

Her research focuses on assessing and mitigating the impact of multi-hazard stressors on geotechnical engineering infrastructure, with particular emphasis on challenges due to age-related deterioration, population growth and densification, natural and human-made hazards, and new demands from climate change. Prof. Athanasopoulos-Zekkos and her research team have improved our understanding of (1) the seismic response of flood protection systems such as levees that are old and rapidly deteriorating as well as threatened by increasing demands due to increasing water levels, (2) the performance of critical systems such as ports during earthquakes by conducting unique testing of challenging materials such as gravels, (3) the effects of man-induced vibrations from pile driving in dense urban environments and near critical infrastructure such as bridges and retaining walls, and (4) the use of new materials, advanced sensing and next-generation laboratory and field testing to inform us on efficient and sustainable mitigation and seismic reinforcement of aging systems.

   Dr. Athanasopoulos-Zekkos research work on investigating the response of levees under extreme load conditions and developing methods for assessing the vulnerability of these systems has had a profound impact on the practice of civil engineering with respect to such infrastructure (e.g. Athanasopoulos-Zekkos and Seed, 2013). Furthermore, her recommendations on ground motion selection for dynamic analyses of earthen levees (both in the context of soil liquefaction triggering and seismic slope stability) are a valuable tool for engineers as they enable them to select a smaller set of ground motions that will provide the average response of the system (e.g. Athanasopoulos-Zekkos and Saadi, 2012, and Athanasopoulos-Zekkos et al., 2013). Her research group is also working on assessing the feasibility of using non-conventional materials, like fiber reinforced concrete mixes (e.g. ECC or bendable concrete) to strengthen levees and dams in terms of their seismic performance and also underseepage.

     Prof. Athanasopoulos-Zekkos is currently working on developing an integrated approach for the liquefaction assessment of gravelly soils, that combines large-scale dynamic physical experiments with high-end discrete element analysis, and refine and calibrate the resulting methodology using field performance data from field case histories from documented seismic events. Specifically she co-developed and have been using a prototype 300-mm diameter cyclic simple shear (CSS) device to evaluate the cyclic (and monotonic) undrained shear response of gravelly soils in the laboratory (Zekkos et al., 2016). She is also working on a next-generation dynamic cone penetration test (DPT) that is equipped with key instrumentation and will be used for field testing along with in-situ shear wave velocity (Vs) measurements (Athanasopoulos-Zekkos et al., 2019). Shear wave velocity measurements on CSS specimens tested in the laboratory will allow for the multi-scale assessment from meso-scale (laboratory) response to the macro scale (field) response.

   Adda’s research work on the effectiveness of EPS Geofoam inclusion as seismic isolation for retaining systems has also provided invaluable insights in the response of such systems by conducting the first ever centrifuge tests of retaining walls with EPS Geofoam inclusions and clearly documenting the observed reduction in seismic earth pressures (Athanasopoulos-Zekkos et al., 2013). This work has been supported by the European Manufacturers of EPS Association, a further testament to the benefit provided by this research and its applicability in engineering practice.

    Finally, Dr. Athanasopoulos-Zekkos’ research work on pile-driving induced vibrations has resulted in a simplified procedure for estimating expected intensity of vibrations (by computing peak particle velocities) at different depths and distances from the driven piles for sandy sites and is currently the standard practice at the Michigan DOT for pile driving monitoring decisions, and has also been used by several other consultants (Grizi et al., 2016). This work was nominated for an AASHTO award by the Geotechnical division of MDOT in 2014.

Jonathan D. Bray, Ph.D., P.E., NAE is the Faculty Chair in Earthquake Engineering Excellence at Berkeley. He earned engineering degrees from West Point, Stanford, and Berkeley. Dr. Bray is a registered professional civil engineer and has served as a consultant on several important engineering projects and peer review panels. He has authored more than 350 research publications on topics that include liquefaction and its effects on structures, seismic performance of earth structures, earthquake ground motions, and earthquake fault rupture propagation. He leads the National Science Foundation (NSF) sponsored Geotechnical Extreme Events Reconnaissance (GEER) Association (geerassociation.org). Dr. Bray is a member of the US National Academy of Engineering and has received several honors, including the Ishihara Lecture, Peck Award, Joyner Lecture, Middlebrooks Award, Huber Research Prize, Packard Foundation Fellowship, and NSF Presidential Young Investigator Award. 

Professor Bray has supervised the research of 32 Ph.D. students. Much of this research was in response to issues raised following major earthquakes. For example, the Bray and Sancio (2006) liquefaction of fine-grained soil criteria followed observations of silt liquefaction in the 1999 Kocaeli, Turkey earthquake (Bray et al. 2004). The simplified seismic slope displacement procedures of Bray and Travasarou (2007, 2009) were calibrated to provide results consistent with post-earthquake field measurements of earth dams and municipal solid waste (MSW) landfills. Damage observed during the 1994 Northridge earthquake motivated studies of the engineering properties of MSW with insights on its shear strength by Bray et al. (2009). The devastating effects of near-fault, pulse ground motions due to forward-directivity led to characterization schemes developed by Bray et al. (2009) and Hayden et al. (2014). Geotechnical mitigation measures proposed in Oettle and Bray (2013) are well-founded by observations of the effects of surface fault rupture following several important earthquakes. Lastly, recent studies documenting and discerning lessons from the effects of soil liquefaction on office buildings in Christchurch, New Zealand (e.g., Bray et al. 2014, 2017) have provided key insights on the important roles of the CPT and cyclic laboratory testing to characterize soil deposits and on the use of dynamic soil-structure-interaction (SSI) effective stress analyses to evaluate shear-induced liquefaction building settlement. A simplified procedure for evaluating liquefaction-induced building settlement is proposed in his 2017 Ishihara Lecture.

Significant research thrusts also utilize advanced geotechnical centrifuge modeling and advanced numerical tools such as discrete element modeling (DEM). The Dashti et al. (2010a,b) centrifuge experiments identified and evaluated the relative importance of key shear-induced and volumetric-induced liquefaction mechanisms. Mason et al. (2013), Trombetta et al. (2014), and Hayden et al. (2015) explored key dynamic SSI responses of structures founded on non-liquefiable and liquefiable ground. O’Sullivan et al. (2002, 2003a,b, 2004) emphasized the need to utilize realistic 3D sphere-cluster particles to capture the response of granular media. Work is continuing with Ph.D. Candidate Garcia who has developed a parallel-computing algorithm for evaluating fault rupture propagation through sand deposits.  

Steven D. Glaser is a professor in the Dept. of Civil and Environmental Engineering, University of California, Berkeley, distinguished affiliate professor at the Technical University of Munich, and a research scientist at the Lawrence Berkeley National Laboratory.  Glaser’s engineering training was at The University of Texas at Austin.  He also has a B.A. in philosophy from Clark University, 1975.  He completed the apprentice program of Local 77 of the International Union of Operating Engineers, following which Glaser worked eight years as a driller, including one year in Iraq.

Glaser has worked on many aspects of rock mechanics and rock physics, most often by applying principles from geophysics. His work in this field has been published in Nature, Journal of Geophysical Research and other significant journals. Glaser currently operates the largest wireless network in the world, monitoring forest hydrology of snow melt and water balance in the Sierra Nevada (arho.org; https://vimeo.com/162487136). 

The Glaser lab has a laboratory earthquake device that is now being used by the third PhD student.  The device can duplicate virtually any fault behavior leading up to gross rupture using lightly loaded PMMA.  We are beginning to use extended fault source models to interpret the nanoseismic signals recoded during tests.  We make use of the absolutely calibrated Glaser-type displacement sensor, which has a noise floor of 0.2 fm.  We have examined asperity mechanics, effects of fault healing time, preslip mechanisms, slow-slip, and the mechanics of foreshock swarms. (https://www.youtube.com/watch?v=AMw490jPDlA&feature=youtu.be)

Glaser is currently working on an experiment looking at injection-induced seismicity from injecting cold water into hot rock.  We are investigating the effects of thermal contraction, and injected water flashing to steam, as proximate causes of fault weakening. In particular we are modeling the Geysers geothermal field in N. California.  The experiments take place in our true-triaxial geothermal reservoir simulator. Integral to this device is a high-pressure boiler that floods 250 mm cubes of rock with 2 MPa steam, duplicating the Geysers. The dynamic junction-level displacement ‘seeds’ that lead to macro-rupture will be studied through nano-seismic imaging using high temperature increased sensitivity Glaser-type sensors.  We have just finished an experiment looking at the efficiency of using supercritical CO2 as the circulating fluid in an enhanced geothermal reservoir.

Robert Kayen teaches Engineering Geology, extreme-event modeling methods, and Engineering Geomatics in the Dept. of Civil and Environmental Engineering, and for nearly three decades has also worked as a research scientist at the United States Geological Survey, Menlo Park, CA.  He serves as an Adjunct Professor in the Department of Civil and Environmental engineering at UCLA, and previously was a Visiting Professor and Visiting Scholar at Kobe University, Japan.  He earned his undergraduate training in civil engineering and geology from Tufts University in Massachusetts, and has Masters degrees in both Geology and Civil Engineering.  His doctoral work at the University of California, Berkeley started a career–long interest in the probabilistic assessment of seismic-soil liquefaction.

Kayen has authored over 350 research publications in the fields of earthquake geotechnical engineering, LIDAR, Structure-From-Motion geomatics, engineering geophysics, marine-geotechnics, and marine methane hydrate stability. He is one of the founders and a long-time steering committee member of the National Science Foundation (NSF) sponsored Geotechnical Extreme Events Reconnaissance (GEER) Association (geerassociation.org).  Dr. Kayen has received honors that include the Middlebrooks Award from ASCE, United States Department of Justice Commendation awarded by the Environmental Division, and the NASA-Ames Honor Award. In 2017, he was an SFGI-U.C. Berkeley Distinguished Lecturer.  He is the current Vice-Chairman of the Marine Engineering Geology Commission of the IAEG.  He was the editor of a multi-volume U.S. Geological Survey Professional Paper Series on ‘Earthquake Hazards of the Pacific Northwest Coastal and Marine Regions’.

Kayen has led a decade-long international research program to acquire field-shear wave velocities at most the world’s well-documents liquefaction case-histories, principally in Japan, China, Taiwan, United States, Chile, and the Mediterranean region of Europe.  These globally-derived data have been useful to synthesize and model the most comprehensive shear wave velocity-based catalog for soil-liquefaction triggering relationships.  The analytical foundation of these probabilistic models are Bayesian inference and System Reliability models. A cornerstone of his research is the use of non-invasive surface wave-dispersion to model the shear wave properties of the ground.  These methods include the multi-channel assessment of surface waves and ambient vibration methods such as spatial autocorrelation.  Collaborations with researchers at UC Berkeley, Middle Eastern Technical University, and Cal Poly have led to parallel assessment methodologies for the Cone Penetration Test and Standard Penetration Test.

Geotechnical engineering methods are validated through comparison with field-data of surface deformations and sub-surface state properties.  Recent advances in non-invasive surface imaging technology allow us to rapidly and inexpensively map spatial aspects of deformations.  Kayen is one of the pioneers in the application of LIDAR laser-technology to geosystem problems.  Recent work is expanding that focus to include photogrammetric computational imaging (Structure-From-Motion, SFM) using unmanned-aerial systems (UAS) to create ultra high-resolution three-dimensional models of surface damage. LIDAR and SFM technologies in earthquake engineering allow for the rapid capture of failure morphologies and their permanent archiving.

Professor Rector has been a member of the Berkeley Faculty since 1992. He is an expert in applied seismology with a focus on both near surface seismology and deep oil and gas reservoir imaging and has been a seminal contributor to seismic while drilling, crosswell seismic, near surface imaging, interferometry, anisotropic imaging, passive seismic, fracture mapping, and machine learning in seismology.  He has supervised over 40 PhD and Masters’ thesis and holds a faculty appointment in the Department of Earth and Planetary Science and the Lawrence Berkeley National Laboratory.  In addition to his work at Berkeley, he founded several successful commercial seismic technology companies, works with many of the major oil companies, and has patented a number of innovative technologies. He has won several major awards in the Society of Exploration Geophysicists, and has served as Editor in Chief of the Journal of Applied Seismology.

Rector’s work in oil and gas is focused on fracking and he has been a keynote speaker recently with his talk entitled “Fact and Fiction in Fracking”. His research has been focused on improving the quality of microseismic data analysis. Compared to conventional event locations, event locations in real world situations have been dramatically improved through the development of Baysian machine learning algorithms and the incorporation of other arrivals such as head waves

He is also applying his expertise in seismic imaging to environmental and near surface geophysics. This work is aimed at understanding the mechanical properties of the soil and rock in the first 100 m of the earth. He developed and patented a new technique that uses tomographic techniques to analyze surface waves which provides a cost-effective 3D extension of conventional 2-D analysis in MASW. This information can be used to characterize near surface soil profiles (for example to design building parameters), to detect voids, and to find near surface objects (bunkers, buried pipes, etc.), and to characterize fluids and flow such as contaminant transport and groundwater.

Michael Riemer is an Adjunct Professor in Civil and Environmental Engineering, as well as the manager of the geotechnical laboratories at UC Berkeley since 1992. He completed his undergraduate studies at Virginia Tech in Civil Engineering, and focused on Geotechnical engineering for his Masters and Doctoral studies at UC Berkeley.  From 2000 through 2003, he also served as Manager of the Lifelines Research Program within the Pacific Earthquake Engineering Research (PEER) Center, coordinating a $1.3 million program of user-directed research ranging from ground motions through soil and structure response, to network risk and emergency response.

His research interests center on static and dynamic property evaluation for a broad range of geomaterials, from naturally occurring silty sands and deep clay deposits through mine tailings, rubble fills and Municipal Solid Waste. 

The testing conditions necessary for such measurements range in scale from conventional lab samples to triaxial testing at 12” diameter; confining pressures range from a few psi to over 60 atm.; and deformations range from a few microns to nearly a foot.  As such, an important part of the research is the development, refinement and upgrading of equipment across multiple scales and the incorporation of newer technologies within existing facilities.

One such example is the implementation of the Elastomer Strain Gauge (Safaqah & Riemer, 2007), a deformable elastic strip containing a metallic-filled capillary that can be attached to conventional latex or other membranes and deployed as a local strain sensor. Depending on the signal conditioning, these are capable of measuring strains as low as 0.001% up through 25%, and have been utilized both in extension and torsional shear.                                                  

In addition to his own research, Prof. Riemer often collaborates with other faculty in the program, training research students in advanced laboratory testing techniques, modifying existing research equipment to enhance particular capabilities for a specific project, or developing specialized procedures for given research goals.

Yoram Rubin received his undergraduate and master degree in civil engineering at the Technion (Israel) and his PhD degree in mechanical engineering at Tel-Aviv University. Following an appointment as a post-doc at Stanford University, he joined the faculty of the Dept. of Civil and Environmental Engineering at UC Berkeley where he has been an active member of both the Geoengineering and Environmental Engineering programs. Rubin is the recipient of the Hydrology Sciences Award of the American Geophysical Union. He is also a Fellow of the American Geophysical Union. In 2016 he was awarded the Darcy Medal by the European Geophysical Union.

Rubin’s research covers hydrogeology and the study of spatial variability and uncertainty (geostatistics).  A major focus of research is Subsurface Characterization and Risk Assessment related to groundwater. Groundwater is one of the major sources of drinking water, and it is widely used in the agricultural and the industrial sector. Understanding how contaminants are transported in the subsurface and evaluating the risks they pose to humans are important environmental issues. For example, an accidental oil spill or the occurrence of leaking hazardous waste storage may severely affect groundwater quality. Thus, characterization of the subsurface is vital in order to maintain the long-term health of subsurface water resources and of water-stressed ecosystems, as well as for controlling subsurface contamination and reducing human health risks. Modeling flow and transport processes in geological media is a significant challenge, given the underlying heterogeneity in the subsurface and the difficulty in characterizing it. Soil properties, such as hydraulic conductivity and porosity, exhibit a high degree of spatial variability at all length scales. Hence, characterizing geological media, which means obtaining 3D images of the important media properties, is a major challenge. The problem of subsurface characterization is simple to define: proving a three-dimensional image of the subsurface, analogous to CT-SCAN for humans, only at a much larger scale. Such imaging is still largely elusive, and environmental remediation efforts have suffered, because of the huge price tag involved. Geological media are defined by complex patterns of spatial variability in geological and hydrogeological parameters. Current methods are failing to reach this goal because of the poor spatial coverage (e.g., depth of penetration) and resolution they offer, and because they rely extensively on invasive drilling, which is in many cases is prohibited, and is almost always prohibitively expensive. Costly overdesign is employed to compensate for uncertainty, leading to huge societal costs associated with environmental remediation. Our goal here is to develop methods for surveying and generating 3D images the subsurface using minimally invasive measurement techniques, and by assimilating multi-type, multi-scale data. 

In recent years he expanded his research to cover issues of risk and environmental impact in large scale geoengineering projects such as large-scale tunnels.  One example is the environmental impact analysis conducted by Rubin’s lab related for the 11km Mingtang Tunnel in China (Anhui province), where the focus has been on eliminating any adverse impact to the pristine ecosystem overlying the tunnel). More recently, Rubin’ s lab started working on the risk associated with the construction of a 13-km tunnel in Yunnan Province (shown in the picture is the entrance to the incline shaft). One of the major challenges here is modeling groundwater flow in a Karst rock formation, where low-Reynolds flow (in soils) is taking place next to high Reynolds numbers (in Karst caves and in faults).  

A new effort is also taking place towards development of instrumentation (see the figure below).

Nicholas Sitar holds the Edward G. Cahill and John R. Cahill Chair in Civil and Environmental Engineering. His undergraduate training is in Geological Engineering at the University of Windsor in Ontario, Canada, and he has completed M.S. in Hydrogeology and Ph.D. in Geotechnical Engineering, both from Stanford University. His research activities encompass a broad range of areas in engineering geology, geological engineering, groundwater hydrology, and risk and reliability, with an overarching interest in natural hazard evaluation, modeling, and mitigation. His research is driven by coupling field observations with experimental and numerical analyses.

His experience with the challenges in field data acquisition in landslide monitoring led to his involvement in the early development of sensor boards and applications for wireless sensor systems, motes, capable of ad-hoc networking, remote data acquisition, and position tracking. Among the prototype demonstrations was an environmental sensor demonstration network for tracking of wildfires in Northern California. The basic sensor boards demonstrated in these experiments and their derivatives are now used by researchers worldwide and are starting to be implemented in engineering practice.

His involvement in geotechnical earthquake engineering started with post-earthquake investigation of seismically induced landslides in Guatemala in 1976. Since then his focus has been the seismic response of underground space, seismic earth pressures on retaining structures, and seismic slope stability. His most recent research with his graduate students (L. Al-Atik, R.G. Mikola, G. Candia and N. Wagner) focused on the seismic response of retaining walls and basements. This effort combined field observations with extensive experimental work using geotechnical centrifuge and numerical modeling to develop new guidance for analysis and design of these structures in high seismicity regions (for more information see: 10.21418/G8WC7H).

The overall focus of his research in rock mechanics has been the influence of kinematics on the response of fractured rock masses. His current research is focusing on the behavior of jointed rock masses under different environmental conditions, including rock fall hazard identification using acoustic emission monitoring, evaluation of conditions leading rock erosion in unlined spillways, and kinematics of large rock slides.  With student M. Gardner he is currently leading an effort to develop a new generation of numerical codes for modeling dynamic response of jointed rock masses and rock fluid interaction. This effort aims to combine 3-D DEM rock mass model with LBM fluid model while taking advantage of new developments in parallel computing in order to make analyses of realistic field-scale problems achievable and suitable for wide application in research and practice.

The overarching element in his research, starting with his Ph.D. dissertation, has been the influence of geologic environment on the properties of sedimentary deposits.  He and his students have performed extensive studies of the influence of depositional fabric on the stability of steep slopes in sands and gravels. He is currently embarking on the exploration of the influence of depositional fabric on the strength characteristics of fluvial sediments from micro- to macro-scale.

http://geomechanics.berkeley.edu/

Kenichi Soga, FREng, FICE, is the Donald H. McLaughlin Chair in Mineral Engineering and a Chancellor’s Professor at the University of California, Berkeley. He is also a faculty scientist at Lawrence Berkeley National Laboratory. He received his B.Eng. and M.Eng. from Kyoto University, Japan, and Ph.D. from the University of California, Berkeley, US. Prior to his move to UC-Berkeley in 2016, he was Professor of Civil Engineering at the University of Cambridge, UK. He is the chair of Technical Committee TC105 "Getechnics from Micro to Macro" of the International Society for Soil Mechanics and Geotechncial Engineering and is an editor-in-chief of ICE Smart Infrastructure and Construction Journal. He is also chair of ASCE Infrastructure Resilience Divison-Emerging Technologies Committee. He is a Bakar Fellow of UC Berkeley, promoting commercialization of smart infrastructure technologies.He is co-author of “Fundamentals of soil behavior, 3rd edition” with Professor James Mitchell. His research interests are fundamental soil behavior, computational geomechanics and infrastructure sensing and modeling.

Professor Soga and his research team have been developing innovative sensor technologies for civil infrastructur systems. The technologies include distributed fiber optics (FO) sensing, wireless sensor network (WSN), low power micro-electro-mechanical sensors, energy harvesting and computer vision. They have been deployed in tunnels, deep excavations, piles and slopes, leading to industry adoption and commercial spin offs. These activities resulted in the establishment of the Cambridge Centre for Smart Infrastructure and Construction (https://www-smartinfrastructure.eng.cam.ac.uk/) at Cambridge. He is co-author of “Distributed Fibre Optic Strain Sensing for Monitoring Civil Infrastructure” and “Wireless Sensor Networks for Civil Infrastructure Monitoring”, which are available from ICE publishing. At Berkeley, he initiated research projects to test these technologies to improve infrastructure resilience. His group also develops high performance computing based infrastuture models for transporation network and pipeline networks. The main goal of these projects is to promote the concept of performance based design, construction and maintenance of our civil engineering structures by actively monitoring and modeling them throughout their lifetime.

His interest in computational geotechnics started when he was working on UC Berkeley’s finite element code FEAP his PhD research 25 years ago. Over the years, his research team has developed new codes for geotechnical engineering applications.  These include: (i) Coupled fluid flow-deformation Material Point Method code for large deformation landslide analysis, (ii) Lattice Boltzmann Method-Discrete Element Method code for particle-scale solid-fluid interaction analysis, (iii) Coupled Lattice Element Method code for hydraulic fracturing simulations, and (iv) Thermo-Hydro-Mechanical code to solve energy geostructures and methane hydrate problems. The research also investigates the role of various constitutive models in understanding the fundamental deformation mechanisms of various geotechnical problems. The current research activities utilize high performance computing facility and techniques to conduct large scale simulations.

The overall arching theme of his research is investigation of fundamental soil behavior in geotechnical engineering using the research tools described above. The current research topics include: (i) thermo-hydro-mechanical interactions for geothermal and deep geomechanics problems, (ii) large deformation for landslides and sand production, (iii) soil fabric and micro-macro relationships for developing models for microbial induced-cementing and soil erosion, and (iv) long term performance of underground structures.

More information about his research group can be found from http://geomechanics.berkeley.edu/.

Dimitrios Zekkos, P.E., is an Associate Professor in the Department who joined UC Berkeley in January 2020. He has previously worked for a major consulting firm in the Bay Area and was a Faculty member at the University of Michigan as an Assistant and then Associate Professor. His research and scientific papers have been recognized by a number of Awards by organizations such as the American Society of Civil Engineers and the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). He is also founder of ARGO-E, an infrastructure informatics firm and a Board Member of Elxis Group, based in Greece, which is the entity behind Geoengineer.org. He serves as Chair of the ASCE Geo-Institute Geoenvironmental Engineering Technical Committee and Chair of the Innovation and Development Committee of the ISSMGE.

Prof. Zekkos' research interests span the fields of geotechnical engineering, geoenvironmental engineering and earthquake engineering. His research approach has commonly involved designing and employing innovative experimental (in the laboratory and the field), and computational approaches that aim to provide new insights and inform improved models of earth material response to static and dynamic loads.

Prof. Zekkos has also been devising and implementing autonomy-enabled approaches for characterization & post-disaster reconnaissance of infrastructure systems. His research team has deployed Unmanned Aerial Vehicles (UAV) to enable the development of large coverage, high resolution, spatially distributed datasets on the performance of infrastructure systems following natural disasters. These UAVs have been used to characterize not only the surface, but also the subsurface conditions  by taking advantage of the capacity of UAVs to analyze the field data mid-flight and make mid-flight decisions autonomously. His research team has been successful in developing a UAV swarm-based approach for subsurface characterization using seismic geophysics, and specifically the Multichannel Analysis of Surface Waves (MASW) technique.

Prof. Zekkos has been conducting research on landslides using the latest technological tools for data acquisition and analysis. Sensor-equipped UAVs and satellites are used to generate high resolution topography for hundreds to thousands of square kilometers. High resolution optical and infrared data can be used to provide an assessment of rockmass characteristics, and moisture conditions using digital image analyses in 3D. The data collected is used in 1D, 2D or 3D landslide models that span many square kilometers.

Prof. Zekkos has been also developing frameworks and objective criteria for the selection and modification of input ground motions that are used as input in seismic design of civil infrastructure. His research team explored the conditions under which time domain or frequency domain modified ground motions can result in “reasonable” input ground motions, using thousands of ground motions.

Prof. Zekkos research thrust on Resiliency of Municipal Solid Waste (MSW) Landfills has been spanning more than 15 years and involved the development of characterization approaches and testing schemes to improve our understanding of the mechanical response of MSW. He has combined field and laboratory testing approaches to provide insights on material behavior. For example, in the laboratory, he co-developed a unique 300-mm diameter cyclic simple shear (CSS) with shear wave velocity measurements, and has conducted 300-mm diameter triaxial testing. In the field, he has used seismic geophysical techniques, such as the Multichannel Analyses of Surface Waves (MASW) and the Microtremor Analysis Methods, self-powered autonomous sensors for long-term deployment, and UAVs.  He also characterized the nonlinear dynamic properties of MSW in-situ using the NHERI @UT large-size mobile vibroseis.  

Prof. Zekkos is promoting energy harvesting in Next-Generation Municipal Solid Waste (MSW) Facilities, by investigating the physico-bio-chemical processes of anaerobic degradation of MSW.  His research group developed large-size degradation simulators to degrade MSW specimens in anaerobic conditions with testing durations up to 1500 days. This testing guided the development of a coupled bio-chemo-physical computational performance model (CPM) and predicts energy output. Self-powered, autonomous, surface and subsurface distributed wireless nodes paired with land-based robots and UAVs provide critical input to this model.

More information about his research directions can be found here.

3D model of complex of landslides caused by 2015 Lefkada earthquake (left) and UAV conducting survey using optical, infrared and methane sensors (right).

Left: Vibroseis to shake intensely soils and solid waste and assess the nonlinear dynamic properties of materials in-situ.

Right: 2D profile of shear wave velocity of solid waste.

Satellite-based mapping vs. modelled landslides for a 4 square kilometer area affected by an earthquake.

SEM imagery of incinerated material