The Seismic Geotechnical Modeling Performance And Analysis Of Pile Supported Wharves

This dissertation presents the results of a research effort conducted to better understand the seismic performance and analysis of pile-supported wharves. Given the limited number of well-documented field case histories, the seismic performance of pile-supported wharves has been poorly quantified, and the analysis methods commonly employed in engineering practice have generally not been validated. Field case histories documenting the seismic performance of pile-supported wharves commonly contain only limited information, such as approximations of wharf and embankment deformations and peak ground surface accelerations. In order to supplement the field data, five centrifuge models were dynamically tested, with each model containing close to 100 instruments monitoring pile bending moments, excess pore pressures, displacements, and accelerations. The combined field and model database was used to develop seismic performance relationships between permanent lateral deformations, maximum and residual bending moments and peak ground surface displacements. Key issues such as the seismic performance of batter piles, the development of large moments at depth, and the need to account for permanent lateral deformations for high levels of shaking, even for very stable geometries, are discussed. The field data and model studies were also used to validate two geotechnical seismic performance analysis methods: 1) the limit-equilibrium based rigid, sliding block (Newmark) method, and 2) an advanced finite-difference effective stress based numerical model (FLAC). Favorable predictions were generally obtained for both methods, yet there was a large variability in the results predicted using the rigid, sliding block method. The numerical model predicted the permanent deformations, pore pressure generation, and accelerations fairly well, however, pile bending moments were poorly predicted. The results of this research clearly highlighted the need for analysis validation studies, and note the uncertainty and variability inherent in the seismic performance of complex structures. The lack of adequate validation may lead to an over-confidence and false sense of security in the results of the seismic analysis methods. This dissertation specifically addresses pile-supported wharves, yet the results presented herein are applicable to other pile-supported structures located near, or on, slopes adjacent to the waterfront, such as: bridge abutments, railroad trestles, and pile-supported buildings near open slopes. Performance and analysis issues common to all of these structures are addressed, such as: liquefiable soils, lateral pile response in horizontal and sloping soils, the lateral behavior of piles in rock fill, and global slope stability, as well as the general observed seismic behavior.