Thomas D. O'Rourke

Assessment of Liquefaction-Induced Land Damage for Residential Christchurch

Christchurch, New Zealand, experienced four major earthquakes (Mw 5.9 to 7.1) since 4 September 2010 that triggered localized to widespread liquefaction. Liquefaction caused significant damage to residential foundations due to ground subsidence, ground failure, and lateral spreading. This paper describes the land damage assessment process for Christchurch, including the collection and processing of extensive data and observations related to liquefaction, the characterization of liquefaction effects on land performance, and the quantification of losses for insurance compensation purposes. The paper also examines the effectiveness of several existing liquefaction vulnerability parameters and a new parameter developed through this research, Liquefaction Severity Number (LSN), in explaining the observed liquefaction-induced damage in residential areas of Christchurch using results from 11,500 cone penetration tests (CPTs) as well as a robust regional groundwater model.

Numerical Modeling of Buried HDPE Pipelines Subjected to Normal Faulting: A Case Study

A systematic study is presented herein on the seismic response of buried pipelines subjected to ground fault rupture in the form of normal faulting. In this study, advanced computational simulations are conducted in parallel with physical testing using a geotechnical centrifuge. For the numerical simulations, the pipeline was modeled using isotropic 3-D shell elements and the soil was modeled using either 1-D spring elements or 3-D solid (continuum) elements. The results from continuum finite-element analyses are compared with those from a Winkler-type model (in which the pipe is supported by a series of discrete springs) and with results from centrifuge tests. In addition, via appropriate modeling of the soil-pipe interaction, the q-z relation of the soil medium is elucidated for normal faulting events. The numerical analysis results demonstrate the potential for continuum modeling of events that induce pipe-soil interaction and results in improved understanding of pipe-soil interaction under normal faulting.

Mass wasting triggered by the 5 March 1987 ecuador earthquakes

On 5 March 1987, two earthquakes (Ms = 6.1 and Ms = 6.9) occurred about 25 km north of Reventador Volcano, along the eastern slopes of the Andes Mountains in northeastern Ecuador. Although the shaking damaged structures in towns and villages near the epicentral area, the economic and social losses directly due to earthquake shaking were small compared to the effects of catastrophic earthquake-triggered mass wasting and flooding. About 600 mm of rain fell in the region in the month preceding the earthquakes; thus, the surficial soils had high moisture contents. Slope failures commonly started as thin slides, which rapidly turned into fluid debris avalanches and debris flows. The surficial soils and thick vegetation covering them flowed down the slopes into minor tributaries and then were carried into major rivers. Rock and earth slides, debris avalanches, debris and mud flows, and resulting floods destroyed about 40 km of the Trans-Ecuadorian oil pipeline and the only highway from Quito to Ecuadors northeastern rain forests and oil fields. Estimates of total volume of earthquake-induced mass wastage ranged from 75–110 million m3. Economic losses were about US

Earthquake Faulting Effects on Buried Pipelines – Case History and Centrifuge Study

1 billion. Nearly all of the approximately 1000 deaths from the earthquakes were a consequence of mass wasting and/or flooding.

Numerical Modeling of Buried HDPE Pipelines Subjected to Strike-Slip Faulting

Permanent ground deformation (PGD) is one of the most damaging hazards for continuous buried lifelines. This hazard is especially severe when the PGD results in net compression in the pipe. In that case, buckling of pipe material can occur. If buckling is moderate, deformation of the pipe cross-section can lead to flow restriction and high friction losses, and eventually require line replacement. If buckling is severe, high localized strains can lead to pipe rupture, loss of contents, and possible pollution of surrounding soil. In this article, centrifuge tests of buried pipelines subject to abrupt ground failure in the form of surface faulting are presented. The fault movement results in mostly compression in the pipe. The test results are compared with a case history of pipe failure in the 1999 Izmit, Turkey earthquake and also with the results from the centrifuge tests which result in net tension in the pipe. The experimental setup, procedures, and instrumentation are described in detail. Suggestions for design practice are offered based on the analysis of results from both the 1999 Izmit case history and the centrifuge modeling.

Selected Effects of the 2012 Hurricane Sandy along the U.S. East Coast: A Geotechnical Perspective

A systematic study of buried pipeline response to strike-slip faulting was performed wherein advanced computational simulations were conducted in parallel with a series of physical tests employing split-boxes within the geotechnical centrifuge at Rensselaer Polytechnic Institute and the full-scale testing facility at Cornell University. This article describes the numerical modeling and simulations of the experimental tests. The buried pipeline and the surrounding soil are modeled using nonlinear beam (shell) elements and elasto-plastic springs distributed along the pipeline, respectively. Using the finite element method, reasonable predictions are obtained for the axial and bending strain distributions measured during the tests. It is also shown that finite element analysis using pipe beam elements and a modified soil spring model can accurately predict the pipeline seismic behavior due to strike-slip fault rupture, especially when the pipe is subjected to combined bending and tension. In addition, existing closed-form solutions are evaluated.

GEOTECHNICAL ASPECTS OF THE 22 FEBRUARY 2011 CHRISTCHURCH EARTHQUAKE

Hurricane Sandy was unprecedented in impact on the urban cluster comprised of New York City and the surrounding metro areas, in addition to numerous coastal communities along the New Jersey and New York coasts. The storm caused severe coastal damage and major flooding that disrupted daily life in a number of communities as well as business activities of Lower Manhattan, the financial capital of the world. In addition to damaging winds, Hurricane Sandy had several major consequences of geotechnical engineering interest, including: (i) the storm surge modified the coastal geomorphology of the region with the birth of new inlets , erosion, scour of soil at the shorelines, showing how marshes, dunes, and barrier islands influence soil erosion patterns and the resulting damage; (ii) storm surge damage in coastal communities revealed the vulnerability of residential building foundations not built to modern flood protection standards; and (iii) flood damage to non-structural components took many buried structures and below ground infrastructure out of service. The hurricane initiated discussions among civil infrastructure planners, engineers, architects and environmental scientists on how to create resilient and sustainable future designs. Short-term geotechnical engineering solutions are needed to retrofit or