Dimitrios Zekkos

University of California, Berkeley | UCB · Department of Civil and Environmental Engineering

Knowledge of landslide volumes is needed to connect landslide trigger, geometry, and mechanism with the mechanical characteristics of the displaced soil and rock masses. While landslide volume inventories of widespread events are scarce, increasing availability of high-resolution imagery time-series presents new opportunities for developing volume...

In 2021, a catastrophic flood occurred in the Melamchi Valley of Nepal, causing widely distributed erosion in Himalayan headwaters and mobilizing a large sediment volume. As the flood progressed downstream, it induced an erosional cascade, producing 100 m deep incisions into high-elevation valley fills, generating new landslides and burying the low...

Waste settlement characteristics vary depending on waste composition, physical properties, waste management operations, and time. In this study, the post-closure waste settlement behavior was analyzed using field data measured at two closed municipal solid waste landfills in Korea, for 23 and 5 years after landfill closure. The long-term waste sett...

Retaining walls are important structural systems used in the construction of highways. With asset management methods for retaining wall inventories lagging those developed for highway bridges, there is a need to develop risk management methods for these critical structural systems. A major challenge is the vast inventories of retaining walls that a...

The seismic behavior of earth retaining structures continues to remain a critical consideration in engineering design and lessons learned from the full-scale performance of retaining walls during earthquakes are invaluable. The observed performance of several retaining walls in the area affected by the 2014 Cephalonia, Greece, earthquakes is presen...

The predominant management approach for municipal solid waste (MSW) remains disposal, given significant increases in generation and disposal rates of MSW in recent decades. In addition to the well-documented carbon emissions from disposal sites, these sites accumulate numerous elements, the masses of which are substantial globally yet inadequately...

Landside detection and mapping can be performed semi-automatically with image classification to efficiently identify landslides and assist in developing landslide inventories. Object-based image analysis (OBIA) groups pixels into objects to simulate visual perception. Previous studies have implemented machine learning and deep learning algorithms t...

On August 14, 2021, a Mw 7.2 earthquake struck the Tiburon Peninsula of western Haiti triggering thousands of landslides. Three days after the earthquake on August 17, 2021, Tropical Storm Grace crossed shallow waters offshore of southern Haiti triggering more landslides worsening the situation. In the aftermath of these events, several organizatio...

Developing empirical correlations between the shear-wave velocity (V s) and the standard penetration test (SPT) blow count has been a long-term practice for sandy, silty, and clayey soils. However, the existing correlations are not suitable for gravelly soils because the SPT is not particularly reliable for gravelly soils due to the interference of...

Mining operations can generate a large amount of waste material, usually disposed of in tailings dams. Historical as well as recent tailings dam failures have shown that these facilities remain vulnerable and are prone to catastrophic failures. Remote sensing data can be utilized to regularly and remotely monitor the condition of operational and ab...

Large, sediment-laden floods in mountainous terrain can have disastrous consequences and play important roles in landscape evolution. These events often unfold as a series of interconnected processes, but understanding of such “hazard cascades” has been hampered by lack of quantitative data on sediment movement. Here, we use a time series of high-r...

Ground improvement (GI) techniques have shown promise in effective liquefaction mitigation, but the physical mechanisms governing their three-dimensional (3D) response during dynamic loading are not yet fully understood. To evaluate the 3D performance of one GI technique, the rammed aggregate pier (RAP), in-situ site characterization, full-scale fi...

Excess pore pressure generation of uniform gravel and gravel-sand mixtures was evaluated in this study. Comparisons were made with existing relationships for pore pressure generation of sands and show that gravel and gravel-sand mixtures can exhibit different pore pressure responses. The influence of liquefaction definition, gravel particle angular...

Medicanes, a type of strong hurricanes/cyclones occurring in the Mediterranean, can be the source of major geohazard events in Mediterranean coastal and inland areas. Medicane Ianos that hit Greece during 17–19 September 2020 caused widespread damage, with numerous landsides and floods being the most prominent. Following the landfall of Medicane Ia...

Small Island Developing States (SIDS) are acknowledged as particularly vulnerable to extreme climate events; however, the realities for transport infrastructure and bridges are still poorly studied. Assessing bridges in this context can be challenging due to data scarcity, a lack of local standards, and uncertainty due to climate change. While brid...

Strong earthquakes can trigger thousands of landslides in mountainous areas, and accurate prediction of landslide occurrence can reduce the risk of infrastructure and communities to earthquake-induced regional landslides. However, current methods for regional landslide prediction are still in their infancy and prediction of landslide occurrence rem...

Evaluating the liquefaction potential of gravelly soils using in-situ testing remains a challenge in geotechnical engineering practice. The Chinese Dynamic Cone Penetration (DPT) test provides an alternative for in-situ testing in gravelly soils to Becker Penetration Test (BPT) and the Standard Penetration test (SPT). The Chinese DPT was recently c...

During the Mw 6.5 earthquake (2015) in Lefkada Ιsland, Greece, nearly 700 co-seismic landslides occurred along the western coastline of the island, where carbonate fault rocks, primarily fractured limestones and fault breccias, are encountered on steep slopes. The main objective of the present study is the investigation of a selected number of thes...

Strong winds and heavy rainfall hit western and central Greece on 17–18 September 2020 as the Mediterranean Hurricane (Medicane) “Ianos” made its catastrophic passage through the country. Widespread flooding caused landslides and debris flows, while the erosive forces of water washed away foundation supports and earthworks along swelling rivers, im...

Liquefaction assessment has primarily been performed using in situ penetration testing, but this practice has become problematic for gravelly soils. For example, standard penetration test (SPT)- or cone penetration test (CPT)-based correlations can become unreliable owing to interference with large gravel particles, while the Becker Penetration Tes...

Unmanned aerial vehicles (UAVs) equipped with onboard sensors empower end‐users to collect data within a wide range of civil engineering applications such as structural condition assessment. While UAVs have been used primarily as mobile sensing platforms to obtain imagery or other data, their mobility can also be used to deploy sensor networks. In...

Shallow bedrock strength controls both landslide hazard and the rate and form of erosion, yet regional patterns in near‐surface mechanical properties are rarely known quantitatively due to the challenge in collecting in situ measurements. Here we present seismic and geomechanical characterizations of the shallow subsurface across the central Himala...

Flash floods are common manifestations of extreme weather events and one of the most severe natural hazards. In Europe, they have been responsible for 359 fatalities and an economic loss totalling 67 million USD in the past decade (EM-DAT), while their increasing severity is linked to climate change. Nevertheless, flash floods remain a poorly docum...

On May 19, 2020, after several days of heavy precipitation, two earth dams failed (Edenville and Sanford) and two other dams were damaged (Secord and Smallwood), north of the town of Midland, MI. The failures resulted in about $100M in damages and the evacuation of about 11,000 people during the COVID-19 pandemic. In response to this destructive ev...

Modern regulated landfills are designed to protect the environment by containing and isolating municipal solid waste (MSW) from the environment. Instead of treating MSW as a hazard to be contained, next generation landfills, here termed Sustainable Energy Reactor Facilities (SERFs) are envisioned to be designed and operated with a main focus on ene...

Following the Cephalonia, Greece, 2014 earthquake sequence (Mw=6.1 and Mw=6.0), liquefaction of gravelly earthfill materials at the ports of Lixouri and Argostoli resulted in the manifestation of ground cracking and coarse-grained soil ejecta, while the quay walls in these ports exhibited lateral ground displacements ranging from 0.1 m to 1.5 m. To...

To evaluate ground deformation resulting from large (~10 m) coseismic strike-slip displacements, we focus on deformation of the Kekerengu fault during the November 2016 Mw 7.8 Kaikōura earthquake in New Zealand. Combining post-earthquake field observations with analysis of high-resolution aerial photography and topographic models, we describe the s...

Regional three-dimensional (3D) forward modeling stability analyses are presented for the Egkremnoi coastline of Lefkada Island in Greece. The pre-earthquake 5-m resolution DEM of the region was used as input for the regional 3D model and the modeling results were evaluated for five large landslides that occurred in the area during a Mw 6.5 earthqu...

Rock mass strength is recognized as an important control on landscape morphology and evolution. However, the controls on rock strength in mountainous topography remain poorly characterized, in part because strength remains challenging to quantify at spatial scales relevant to geomorphology. Here we quantify the mechanical properties of rock masses...

Three landfill gas generation models following two established kinetic pathways – first-order decay (Landfill Gas Emissions Model and Intergovernmental Panel on Climate Change) and sigmoidal growth (modified Gompertz) – are considered and fitted against a range of methane generation data generated from large-scale degradation experiments of seven w...

On September 17-20 2020 Medicane Ianos impacted Greece. The Medicane was associated with significant wind speeds, and precipitation. The amount of precipitation during a duration of about ~48 hrs was among the highest recorded in certain areas and exceeded in certain areas the mean annual precipitation. The extent of the affected area was very larg...

Estimation of landslide erosion rates and hazard prediction require a firm understanding of the physical controls on landslide size. In this study we seek to understand how the characteristics of different landscapes and forcing events influence the distribution of landslide size at a regional scale. We explore the parameter space of a mechanically...

In 2017, hurricane Maria caused unprecedented damage and fatalities on the Caribbean island of Dominica. In order to ‘build back better’ and to learn from the processes causing the damage, it is important to quickly document, evaluate and map changes, both in Dominica and in other high-risk countries. This paper presents an innovative and relativel...

Available also at: https://www.michigan.gov/mdot/0,4616,7-151-9622_11045_24249-533554--,00.html

In situ assessment of waste settlements is a critical consideration for the operation, closure, and post-closure development of municipal solid waste (MSW) landfills. Settlement evolution is influenced by the biodegradation processes underway in the waste mass. Presently, the measurement of such settlements involves instrumentation at specific loca...

A case history is presented of lateral spreading in two reclaimed port areas of the Cephalonia island, Greece, in the 2014 earthquake doublet (M w 6.1 & 6). Lateral ground displacements along 24 transects perpendicular to the quay walls in the two port areas were directly measured by ground surveys. Liquefaction of gravel-size fills was observed th...

A fully autonomous flux chamber was designed, built, validated in the laboratory, and deployed at an MSW landfill in the state of Michigan. The self-powered chamber is capable of continuous methane emission data collection, analysis, and transmission. The chamber is controlled by the Urbano low-power microcontroller sensing platform and is equipped...

The Corinth Canal crosses the Isthmus of Corinth and is of great importance for Mediterranean navigation as well as for railroad and highway connectivity between southern and central Greece. Since its operation, in 1893, the slopes have shown stability problems due to their steepness, the mechanical behavior of the Corinth Canal marl and the strong...

Social media activity following the occurrence of an earthquake has the potential to provide valuable data on infrastructure condition and for disaster response and reconnaissance purposes. The challenge however is that the data with valuable content (i.e., the signal) is small compared to the earthquake-related social media activity overall (i.e.,...

On November 17 th 2015, a Mw 6.5 earthquake struck the island of Lefkada in Greece. The shaking caused landslides and rockfalls particularly in the western part of the island. The stability of a major landslide that occurred in Egremnoi beach, was investigated with the objective to back-calculate the shear strength of the failed ground, which is ge...

Constant volume direct simple shear testing is one of the most common tests used to characterize the cyclic response of earth materials. It is especially used to assess liquefaction susceptibility of a soil. Constant volume conditions are typically considered equivalent to undrained conditions, but are dependent on minimal volumetric strain during...

The sequence of two major earthquakes with moment magnitudes of 6.0 and 6.1 that hit the island of Cephalonia in Greece in 2014, resulted in significant liquefaction of gravelly soils. Two of the island's main ports, Lixouri and Argostoli, were impacted by lique-faction of gravel-size fills and experienced significant lateral displacements (up to 1...

Highways consist of many large structures requiring vigilant inspection and maintenance. While significant research attention has been focused on the health management of bridges, comparatively less attention has been paid to other highway structures, including retaining walls. In the United States, there has been a recent emphasis on extending the...

Due to their mobility and autonomy, unmanned aerial vehicles (UAVs) provide an unprecedented opportunity to perform data gathering in a wide array of civil engineering applications such as visual inspection of infrastructure. Given their versatility, the role of UAVs can be expanded by leveraging their autonomous operations to deploy wireless sensi...

Unmanned aerial vehicles (UAV), or drones, have become popular tools for practitioners and researchers alike. Recent years have seen a significant increase in UAV uses for many applications in the fields of science and engineering. A broad array of research development in UAVs has been reported in the literature. This paper provides a summary revie...

Landfill gas (LFG) is a product of the biodegradation of municipal solid waste (MSW) under anaerobic conditions. LFG primarily consists of methane (CH4) (40–60%) and carbon dioxide (CO2) (40–60%), both greenhouse gases. Methane has high energy potential that remains largely untapped as a national energy source. In order to recover LFG for energy ge...

For municipal solid waste (MSW) landfills that are situated in seismically active regions, the response of MSW under dynamic loading is critical to landfill design. In this study, a large-size simple shear device is utilized to perform cyclic testing on MSW under constant load (CL) and constant volume (CV) conditions which are considered equivalent...

Understanding the factors that affect the monotonic and cyclic response of gravelly soils during earthquake events is critical to infrastructure design. In this study a large-size Cyclic Simple Shear (CSS) device was utilized to perform monotonic and cyclic shear tests on mixtures of either subrounded 9 mm Pea Gravel or angular 8 mm Crushed Limesto...

The application of the Structure-from-Motion (SfM) methodology, as enabled by the growth of Unmanned Aerial Vehicle (UAV) technology, is expected to have significant impact in geotechnical engineering research and practice. SfM outputs are presented using selected geotechnical projects as examples, and include orthophotos, 3D point clouds, and thre...

Municipal solid waste (MSW) is biodegradable in landfills under anaerobic conditions. The evolution of the hydrobiochemical-mechanical (HBM) processes during degradation is investigated first through experiments and subsequently through modelling. Three well-characterised MSW specimens from US landfill sites with significantly different waste compo...

The ability to quickly, efficiently and reliably characterize changes in the landscape following an earthquake has remained a challenge for the earthquake engineering profession. The 2016 Mw7.8 Kaikoura earthquake provided a unique opportunity to document changes in topography following an earthquake on a regional scale using satellite derived high...

Following the November 14 2016 Mw7.8 Kaikoura earthquake, field expeditions were undertaken using Unmanned Aerial Vehicles (UAVs) to map 25 sites of scientific interest with a plan area of 7.2 km2. A total of 23,172 images collected by the UAVs were used as input in Structure-from-Motion (SfM) to create 3D models of the target areas with a focus on...

Multichannel analysis of surface waves (MASW) is an established method for measuring the in situ shear wave velocity (Vs) of geomaterials. Depending on the site conditions, a sledgehammer may be incapable of generating a signal within the desired frequency band or the site may be difficult to access. In this study, the sledgehammer was replaced by...