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Ground failure in the 2001 Mw 8.4 southern Peru earthquake
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|Title: ||Ground failure in the 2001 Mw 8.4 southern Peru earthquake|
|Authors: ||Rondinel-Oviedo, Efrain Alejandro|
|Keywords: ||Civil engineering|
|Issue Date: ||21-Sep-2010|
|Abstract: ||On June 23rd 2001 a moment magnitude (Mw) 8.4, earthquake shook the southern portion of Peru. This rare large-magnitude event provided a unique opportunity to develop a suite of high quality case histories and also to test and calibrate existing geotechnical earthquake engineering analysis procedures and models against observations from the earthquake. The work presented in this thesis is focused on three topics pertaining to ground failure (i.e., the permanent deformation of the ground resulting from an earthquake) observed during the event: 1) surface ground damage in small basin geometries, 2) seismic compression, and 3) performance of a concrete faced rockfill dam (CFRD) dam.
Surface ground strain damage patterns in small basin geometries has previously been typically studied at the large (i.e., geological) scale, but not at the scale of civil engineering infrastructure. During seismic events basin geometries containing soft material confined by stiffer material trap the seismic waves and generate surface waves that travel on the ground along the soft material. Numerical modeling shows that surface waves are generated at basin edges and travel on the ground creating higher duration, higher response (peak ground acceleration, PGA), higher energy (Arias Intensity) and higher angular distortion, especially in zones close to the edges. The impedance contrast between the stiff material and the soft material, and the dip angle play an important role in basin response.
Seismic compression (i.e., the shaking induced densification of unsaturated soil) was observed in many highway embankments in the region of the earthquake. In many instances, this phenomenon was exasperated by soil-structure interaction with adjacent bridge or culvert structures. Numerical modeling conducted as part of this research showed (i) a significantly different response when the structure (culvert) is considered, (ii) impedance contrast plays a role in the system responses, and (iii) low horizontal stresses are observed when the peak of the shear strain occurs. It is believed that the effect of low confining stresses was responsible for the large amounts of settlement observed, and which was not directly captured by classical seismic compression models.
The third topic of study considered evaluates the performance of a concrete faced rockfill dam (CFRD) dam in the earthquake. Analysis considered the effect of the time, PGA of
rock, and change in amplification ratio with PGA. It appears that the natural frequency of the dam increases with time in the transversal direction and slightly decreases in the
longitudinal direction. It is believed that the increase in the natural frequency might be associated with change in the dam stiffness (i.e. densification) with time. However, reason for the slight decrease in the longitudinal direction is not clear and requires further research.|
|Appears in Collections:||Drexel Theses and Dissertations|
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