published_or_final_version / Applied Geosciences / Master / Master of Science

No description available.

No description available.

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering

Includes bibliographical references (p. 249-258).

Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2008. / Includes bibliographical references (p. 221-225).

Accepted as doctoral dissertation by the Technische hochschule, Stuttgart.

Thesis (Ph. D.)--University of Hong Kong, 1988. / Also availalbe in microfilm.

Hong Kong is a small city with a dense population. Due to limited land resources and dense population, skyscrapers are built to meet the commercial and residential needs. To fulfill the functional requirements, the superstructure is usually supported by piles through a thick cap. A bored pile foundation is one of the most common deep foundation systems with a high capacity adopted in Hong Kong. Most of those piles are founded on Grade III or better rock. However, as lack of field experience and high quality database, the behavior of such pile foundation system is still unclear. These bored piles are designed as the end bearing piles. In addition, the load distribution among the piles and the load shared by the pile cap are also not properly addressed in the local design. In order to properly address the above-mentioned issues related to the design of pile foundation, in particular for large diameter bored piles, a comprehensive field study was launched. Furthermore, the numerical simulations were also carried out. A comprehensive field study was carried out on the behavior of a building supported by large diameter bored piles. The building (40-storey public housing) is Y-shaped with three wings (Wing A, Wing B, and Wing C) and a central core (Central Core). The superstructure is resting on a Y-shaped foundation cap (2.3m in thickness) which is supported by 18 bored piles (2.2m in diameter). The piles terminated at Grade III or better rocks. The field test results indicated that the pile group took up most of the applied load, while the cap had an insignificant contribution to the capacity of the foundation system. The axial force in the pile increased from the outer edge to the inner area of the cap. The shaft resistances mobilized in the soil layer and the rock layer were significant. As a result, the axial force reduced to a not significant level at the toe. The finite element model could generally reflect the bored pile deformation and the load distribution along the pile. The numerical simulation results could generally reveal the load distribution among the piles. Based on the numerical analyses, the load distribution among the piles was strongly dependent on the cap stiffness. Moreover, when some pile stiffness reduced, the applied load will redistribute among the piles. More loads will transfer to the nearby stiff piles. The effected region of redistribution in axial force increased with the cap stiffness. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

This thesis presents the result of detailed back-analysis, using three-dimensional finite-element analysis, of the instrumented piled-raft foundation in monitoring site. The piled-raft foundation is a composite foundation structure that consisting of piles, raft and surrounding soils acting as a whole system. To check the reliability of soil taking load under the raft and obtain a reasonable value of load proportion taken by piles for the soil conditions in Hong Kong, a piled-raft foundation was partially instrumented in the monitoring site. The pile head loading, raft-soil contact pressure of specified area and settlement at raft top for selected locations were being monitored. Comparisons of overall settlement, differential settlements and the load carried by the piles show reasonably good agreement. Followed by a 3D finite element modeling of the entire piled-raft foundation of the monitored site, the analysis includes a pile-soil slip interface model. The numerical analysis is performed to give insights to (1) load transfer behavior of the piled-raft foundation (2) effects of pile reduction on pile load ratio. Combined the observation from site monitoring and analysis results from the numerical analysis, the proportion of load shared between piles and raft is revealed as 7:3. The lower limit of pile ratio is proposed as 0.67 for the site after the parametric study by removing piles strategically. In spite of the settlement-reducing purpose of the piles, the design of piled-raft foundation still concentrate on providing adequate axial capacity, with settlement requirement treated as a secondary issue. The significance of the study is that it provides factual evidence of soil taking the load under the raft, and the economical benefits of piled-raft foundation as a reduction of piles will save more than 2 million of the construction budgets. / published_or_final_version / Civil Engineering / Master / Master of Philosophy