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[Truncated abstract] The axial performance of piles in sand remains an area of great uncertainty in geotechnical engineering. Over the years, database studies have shown that the existing method for offshore piles (e.g. API 2000) is unreliable. There is therefore a clear need for an improved predictive method, which incorporates the state-ofthe- art understanding of the underlying controlling mechanisms. This Thesis is dedicated to address the factors influencing the end bearing performance of displacement piles in siliceous sand with a view to proposing and justifying an improved design formulation. Firstly, a database of displacement pile load tests in sand with CPT data was compiled in collaboration with James Schneider (Schneider 2007). It features the widest database with also the latest available pile load test data (e.g. Euripides, Ras Tanajib, Drammen etc) in electronic form. Evaluation of the three new CPTbased methods (Fugro-05, ICP-05 & NGI-05) against this database has revealed a broadly similar predictive performance despite their end bearing formulations being remarkably different. This anomaly promoted the author to extend the database to include additional tests with base capacity measurements to form new base capacity databases for driven and jacked piles, which resulted in the UWA- 05 method for end bearing of displacement piles in sand. This method accounts for the pile effective area ratio, differentiates between driven and jacked piles, and employs a rational qc averaging technique. ... Field tests were performed in Shenton Park, Perth to supplement the database study and, in particular, to examine the effect of the incremental filling ratio (IFR). 10 open-ended and 2 closed-ended piles were tested in compression followed by tension. The test results provide strong support for the UWA-05 method for base capacity evaluation employing the CPT qc values and the effective area ratio. A series of jacked pile tests was carried out on the UWA beam centrifuge, to further explore the factors affecting pile base response. In total, four uniform and four layered centrifuge samples were prepared and tested at various stress levels and relative densities using three separate pile diameters. The resistance ratio (qb0.1/qc,avg) is found to be independent of the absolute pile diameter, effective stress and soil relative density. The tests in layered soil enabled quantification of the reduction in penetration resistance when a pile/cone approaches a weak layer and revealed the significant influence on base stiffness of underlying soft clay layers. The stiffness decay curves (G/GIN vs. w/D, where GIN is initial operational shear stiffness) measured in static load tests were found to vary with ratios of GIN/qc, while there was a unique relationship between G/GIN and qb/qc. A detailed parametric study was carried out (using the FE code PLAXIS) by idealising pile penetration using a spherical cavity expansion analogue in layered soil. The numerical predictions compare well with the centrifuge results and their generalization enabled guidelines to be established for end bearing in layered soil.
This book results from the 7th ICPMG meeting in Zurich 2010 and covers a broad range of aspects of physical modelling in geotechnics, linking across to other modelling techniques to consider the entire spectrum required in providing innovative geotechnical engineering solutions. Topics presented at the conference: Soil – Structure – Interaction; Natural Hazards; Earthquake Engineering: Soft Soil Engineering; New Geotechnical Physical; Modelling Facilities; Advanced Experimental Techniques; Comparisons between Physical and Numerical Modelling Specific Topics: Offshore Engineering; Ground Improvement and Foundations; Tunnelling, Excavations and Retaining Structures; Dams and slopes; Process Modelling; Goenvironmental Modelling; Education
This dissertation, "Analysis and Prediction of the Axial Capacity and Settlement of Displacement Piles in Sandy Soil" by Feng, Mu, 牟峰, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: ABSTRACT Piles are often used as foundations for tall buildings and critical structures. The performance of displacement piles in sand is recognized as being the area of greatest uncertainty in foundation design. Until recently, design methods throughout the world were almost entirely empirical. The failure to fully understand the underlying mechanisms is due mainly to the complexity of the interaction between the pile and surrounding soil. This thesis describes an investigation into the behavior of displacement piles in sandy soil and proposes a novel approach for the analysis and prediction of both the capacity and settlement of displacement piles under axial load. The estimation of ultimate base resistance is implemented in the framework of spherical cavity expansion theory by taking into account the properties of sandy soils, in terms of nonlinear shear stiffness and state-dependent shear strength. The ultimate local shaft friction is estimated based on a careful investigation of the 'friction fatigue' along the pile shaft during pile installation. Three phases of the load-settlement response are identified according to the mobilization of base and shaft resistances, and thereafter estimates are made in terms of the individual contributions of the base and shaft resistances to the total head settlement in each phase. A database of high-quality pile load tests is compiled for purposes of validating the proposed approach. A reasonably good agreement is shown between the measurements and predictions in both capacity and settlement. To facilitate the practical application, further effort has been made to develop a user-friendly software in the Windows platform that incorporates this novel approach. ii DOI: 10.5353/th_b3955898 Subjects: Piling (Civil engineering) Soil mechanics
A Comprehensive Database of Tests on Axially Loaded Driven Piles in Sands reviews the critical need to develop better load-test databases for piles driven in sands. The key quality parameters, population of current entries and reporting formats are described before offering preliminary results obtained from comparisons between axial capacities calculated by various predictive approaches and site measurements. This book also shows that the "simplified" and "offshore" ICP and UWA variants proposed by some practitioners are over-conservative and that their use could be discontinued. The new pile capacity and stiffness database offers a broad scope for evaluating potential prediction biases relating to a wide range of soil and pile parameters. Submission of further high quality tests for inclusion in regularly updated versions is encouraged. Presents a comprehensive and updated database for piles driven in predominantly silica sands Features reviews of the design procedures for driven piles in sand Assesses the performance of various mainstreams design procedures applied for piles driven in sand Provides comprehensive information of case histories of pile load tests
One of the major difficulties in predicting the capacity of pipe piles in sand has resulted from a lack of understanding of the physical processes that control the behavior of piles during installation and loading. This monograph presents a detailed blue print for developing experimental facilities necessary to identify these processes. These facilities include a unique instrumented double-walled pipe-pile that is used to delineate the frictional stresses acting against the external and internal surfaces of the pile. The pile is fitted with miniature pore-pressure transducers to monitor the generation of pore water pressure during installation and loading. A fast automatic laboratory pile hammer capable of representing the phenomena that occur during pile driving was also developed and used.
Model Uncertainties in Foundation Design is unique in the compilation of the largest and the most diverse load test databases to date, covering many foundation types (shallow foundations, spudcans, driven piles, drilled shafts, rock sockets and helical piles) and a wide range of ground conditions (soil to soft rock). All databases with names prefixed by NUS are available upon request. This book presents a comprehensive evaluation of the model factor mean (bias) and coefficient of variation (COV) for ultimate and serviceability limit state based on these databases. These statistics can be used directly for AASHTO LRFD calibration. Besides load test databases, performance databases for other geo-structures and their model factor statistics are provided. Based on this extensive literature survey, a practical three-tier scheme for classifying the model uncertainty of geo-structures according to the model factor mean and COV is proposed. This empirically grounded scheme can underpin the calibration of resistance factors as a function of the degree of understanding – a concept already adopted in the Canadian Highway Bridge Design Code and being considered for the new draft for Eurocode 7 Part 1 (EN 1997-1:202x). The helical pile research in Chapter 7 was recognised by the 2020 ASCE Norman Medal.
Civil Engineering has recently seen enormous progress in the core field of the construction of deep foundations. This book is the result of the International Workshop on Recent Advances in Deep Foundations (IWDPF07), which was held in Yokosuka, Japan from the 1st to the 2nd of February, 2007. Topics under discussion in this book include recent rese
The book presents a compilation of studies regarding applied geomechanics, mining, and excavation analysis and simulation. The material is suitable for presentation to senior undergraduate and post-graduate students in both mining and geological engineering. It should also be of interest to students of other aspects of Geomechanics and, notably, engineering geologists interested in mining and underground excavation design. Practising mining engineers and rock mechanics engineers involved in mine design may use the book profitably to obtain an appreciation of the current state of engineering knowledge in their area of specialisation. Papers were selected from the 5th GeoChina International Conference on Civil Infrastructures Confronting Severe Weathers and Climate Changes: From Failure to Sustainability, held in July 23-25, 2018 in Hang Zhou, China.