Adda Athanasopoulos-Zekkos

Dynamic Properties of Municipal Solid Waste

Assistant Professor, Dept. of Civil and Environmental Engineering, University of Michigan, USA; Associate, Geosyntec Consultants, Huntington Beach, California, USA; Assistant Professor, Faculty of Engineering, Cairo University, Cairo, Egypt; Professor, Dept. of Civil Engineering, University of Tokyo, 7-3-1, Bunkyo, Tokyo 113-8656, Japan; Professor, Department of Civil and Environmental Engineering, University of Catania, Italy

Ground Vibration Measurements near Impact Pile Driving

Pile driving is a complex dynamic process where little insight has been garnered in terms of the energy transfer from the driver to the soil and surrounding structures. Ground motion measurements during driving of full scale steel H-piles with diesel hammers are presented. The key feature of this work is the in-depth sensor installation starting very close to the pile (0.2 m), at other radial distances from the pile, and at various depths in the ground. Differences in wave sources from the tip and the shaft of the pile as well as wave attenuation coefficients are revealed from the sensor measurements. Attenuation relationships fitted through the data could be used to predict ground motion that could cause shakedown settlement. A conventional line array of surface mounted geophones was also used and results are presented.

Predictive Equations to Quantify the Impact of Spectral Matching on Ground Motion Characteristics

Spectral matching, the process of modifying a seed acceleration time history in intensity and frequency content until its acceleration response spectrum matches a target spectrum, is used extensively in practice. Predictive equations that quantify the impact of spectral matching on the peak ground velocity, peak ground displacement, Arias intensity, and cumulative absolute velocity of a scaled seed time history have been developed and validated on the basis of thousands of matched motions, three different earthquake scenarios, and numerous target spectra. It is found that spectral mismatch is the most critical factor affecting the changes in ground motion characteristics. The technique used for modification (e.g., time domain or frequency domain) is in many cases not critical. Based on the results, recommendations in order to minimize the impact of matching on the ground motion characteristics are provided.

Impact of Modification on Ground Motion Characteristics and Geotechnical Seismic Analyses for a California Site

The impact of different modification techniques on ground motion characteristics and results of seismic geotechnical analyses is investigated for a site in California. Twenty-eight motions were selected and scaled and also modified using both time domain (TD) and frequency domain (FD) techniques. PGV and PGD of the TD-modified motions are found to be larger than their FD-modified counterparts, but slightly less than the scaled ground motion characteristics. Cyclic stress ratios and amplification factors are similar for all sets of motions. Newmark-type slope displacements caused by the scaled and modified ground motions are similar (within 25%) for a variety of sliding masses.

Monotonic, Cyclic, and Postcyclic Simple Shear Response of Three Uniform Gravels in Constant Volume Conditions

AbstractThis paper presents the results of large-size cyclic simple shear testing on three uniform gravels (Pea Gravel, 8-mm Crushed Limestone, and 5-mm Crushed Limestone), which varied in particle...

Measurement of Ground Motion near Piles during Driving

Two types of vibration damage caused by driving piles have been reported in the literature: direct structural damage and damage due to settlement. Direct damage results from vibratory excitation of structures at amplitude exceeding the structural tolerance. Damage from settlement is a consequence from vibratory densification of loose soils resulting in total or differential settlement of structures. Problems of settlement due to pile driving have been experienced recently by the Michigan Department of Transportation (MDOT) during operations associated with replacement of deteriorating bridges. The work described here represents an attempt to understand the mechanisms of energy transfer from steel H-piles driven with diesel hammers to the surrounding soil and the energy attenuation through the soil by measuring ground motion in the near vicinity of the pile. The main feature of this study consisted of installing motion transducers very close, within 0.5 foot, to piles and measuring the resulting ground motion during pile driving. Selection, fabrication, and installation of the transducers and preliminary measured pile driving vibrations are presented.

U.S. Levee and flood protection engineering in the wake of Hurricane Katrina

After more than half a century of increasing neglect, the nation’s flood defenses are currently rated by the ASCE as having the very lowest levels of adequacy and reliability among all types of critical U.S. infrastructure, receiving a letter grade of straight “F” on the ASCE’s Annual Infrastructure Report Card for the nation. Accordingly, the U.S. now finds itself at a crossroads in the wake of the recent catastrophic flooding of New Orleans by Hurricane Katrina, and the spate of other significant flood events of recent years. There is much to be learned from these recent events, and that learning opportunity has been seized upon at both the national and more local (State and regional) levels; and some promising changes have been initiated. This paper discusses key lessons learned from the Hurricane Katrina experience, and other recent flood disasters, and then presents a discussion of ongoing efforts to implement these lessons in effecting positive changes and improvements in U.S. flood protection practice.

The May 25th 2011 Railroad Embankment Failure in Ann Arbor, Michigan, As a Means for Teaching Geotechnical Engineer

A 30-m long railroad embankment failure that occurred on May 25 2011 in the city of Ann Arbor, Michigan, is presented. Emphasis is given on the field observations of the failure, the characterization of the site conditions and the seepage and slope stability analyses, all of which represent important components of the training and practice of a geotechnical engineer. The failure occurred following a record wet season that resulted in ponding water against the embankment and high enough water pressures and exit gradients that resulted in instability of the railroad embankment. Detailed background material and the methodology for using the case history in geotechnical engineering education are presented.