Liquefaction remediation near existing lifeline structures

Organized and systematic studies on the phenomenom of liquefaction began after the 1964 Niigata earthquake. Great progress has been made through research, much of it conducted by researchers in Japan and U.S., to develop a dfundamental understanding of the mechanism of liquefaction. A number of in-situ ground improvement methods have been developed to reduce the vulnerability of ground susceptible to liquefaction. May of these methods were developed empirically, and some are very costly to implement. This paper examines the critical factors that influence the effectiveness of live ground improvement techniques which are most suitable for remedial work near existing lifeline structures. Expected cost of using these methods are given, even though the cost data from cases examined is scarce. Advantages and constraints of each of these methods are presented. Eight case histories of remedial work near existing lifeline structures are reviewed.(AU)

Evaluation of liquefying soil through time using system identification

A new approach to evaluating earthquake strong motion, parametric modeling (System Identification) is introduced. This method avoids many of the problems inherent in Fourier Methods. Both stationary and recursive parametric modeling methods are applied to input-output data sets from the Wildlife Site, CA, which was subjected to two large earthquakes on November 24, 1987. During the second, larger, earthquake (Superstition Hills earthquake) the site soils liquefied. The data set collected is unique since it is the only available record of buried and surface motions publicly available. Existing seismological analyses of the two earthquakes show that the Superstition Hills earthquake actually consisted of three distinct subevents. The strong motion records and pore water pressure records show excellent correlation with the subevents. The results show weakening of the soils system as pore pressure increases, with estimates of natural frequency, damping ratio, and participation factor given.(AU)

The role of postearthquake investigations in the National Earthquake Hazard Reduction Program

Data and basic knowledge gained from postearthquake investigation conducted under the auspices of the National Earthquake Hazard Reduction Program (NEHRP) have advanced the state - of - knowledge and state od practice in earthquake engineering. These advances have led to significant changes in public policy, focused research and accelerated the adoption of improved mitigation, preparedness, emergency response, and recovery measures in communities throughout the United Stated. Many countries throughout the world have benefited from investigations made during the past decade (AU)