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Many instances of severe damage to pile foundations and pile-supported infrastructures have been caused by liquefaction-induced lateral spreading during major earthquakes, particularly in coastal areas. The current study conducted a series of shaking table experiments to determine the differences between the responses of a free- and a fixed-head group pile under lateral spreading in the presence of finned and circular protection piles. The results indicated that the maximum bending moment tolerated by nonprotected free-head piles was more than that by fixed-head piles. Also, reductions in bending moments were more significant in free-head piles in the presence of protection piles than in fixed-head piles. The bending moments of front and rear piles under restricted pile head conditions were reduced by about 31% and 21%, respectively, when finned piles were used as protection piles, while they were 34% and 42%, respectively, under free-head conditions. Furthermore, modification factors of recommended lateral pressure distribution along a pile per the current design code were determined for the protected and nonprotected free- and fixed-head pile groups of the current study and it was observed that this modification factor (CL) was highly dependent on the location of piles in a group, pile head conditions, and the presence of protection piles in the lateral spreading analysis. [ABSTRACT FROM AUTHOR]

This summary discusses the article "Installation Effects and Behavior of a Driven Prestressed High-Strength Concrete Nodular Pile in Deep Saturated Soft Clay" by Jian-lin Yu, Jia-jin Zhou, Ri-hong Zhang, and Xiao-nan Gong. The authors conducted a full-scale experimental study to investigate the behavioral characteristics of a driven prestressed high-strength concrete (PHC) nodular pile in deep-saturated soft clay. They compared the installation effects and shaft frictional resistance of the nodular pile to a similar nonnodular pile. The study found that nodular piles had higher load-bearing capacity and improved shaft resistance compared to nonnodular piles. The authors also discussed the influence of pile installation on the surrounding soil and provided information on pile spacing and pore-water pressure. [Extracted from the article]

In this study, the uplift load-carrying capacity of micropiles was investigated, focusing on the effect of various installation conditions including installation angle (θ), spacing (S), and group configuration. For this purpose, a series of uplift model load tests was conducted using single micropiles (SMP) and group micropiles (GMP). The uplift load capacity of both SMP and GMP increased with θ up to 30° but decreased for a higher installation angle of θ = 45°. Micropile spacing had less effect on the uplift load capacity for GMP. The uplift loadcarrying mechanism of inclined micropiles is proposed based on decomposed axial and lateral loads and resistance components. Based on the proposed load-carrying mechanism, axial and lateral load capacity ratios were proposed and adopted to formulate the uplift load-capacity equation for inclined micropiles. For GMP, the group-effect factor was proposed based on the reduction effect of group micropiles on the overall uplift load capacity. Full-scale uplift load tests were conducted to check the validity of the proposed method. Both SMP and GMP were constructed and tested. It was observed that the estimated results using the proposed method were in good agreement with the measured results. [ABSTRACT FROM AUTHOR]

The combined pile-raft foundation (CPRF) has been widely recognized as economic and rational foundation for high-rise buildings when subjected to vertical loading because of its effectiveness in load sharing by both raft and pile components. This results in smaller total and differential settlements with a reduced number of piles as compared with group piles. Until recently, the behavior of CPRF when subjected to lateral and real earthquake loading conditions in addition to vertical loads has not been well understood as a result of the complexities involved in the interaction of the pile, soil, and raft under such loading considerations. In the present study, an attempt has been made to investigate the behavior of CPRF with the use of centrifuge testing and a numerical model under pseudostatic and dynamic loading conditions carried out with finite-element software. After successful validation of the present CPRF model with both centrifuge and numerical model results, the same model was used for further study under El-Centro 1979, Loma Prieta 1989, Bhuj 2001 and Sikkim 2011 real earthquake pseudostatic loading and real acceleration-time history. The maximum displacement and bending moment were observed at the pile head, which is attributable to the rigid fixity of the piles with the raft. The crossover point in the bending moment profile was observed at shallow depths for all cases of loading. The occurrence of the resonance condition that yielded maximum horizontal displacement of the CPRF as a result of one of the input motions is also highlighted in the present study. The difference in the response of soil just below the raft of the CPRF and at the far field indicated that near-field and far-field ground motions were not in tandem. A case study on an existing CPRF of Messeturm Tower, Frankfurt am Main, Germany, is also presented. The existing CPRF of Messeturm Tower was modeled and analyzed under static and pseudostatic loading conditions. Obtained results show good correlation with the static field-measured results. Results in terms of bending moment in piles, total settlements, and normalized lateral displacement (u/D) are reported. The present findings are useful because they provide broader understanding of the response of the CPRF under pseudostatic and dynamic loading conditions. [ABSTRACT FROM AUTHOR]

The present research intends to study the effects of the seismic soil-pile-structure interaction (SSPSI) on the dynamic response of buildings with various heights by conducting a series of shaking table tests on 5-, 10-story, and 15-story model structures. Two types of foundations for each case are investigated, including (1) a fixed-base structure, representing the situation excluding the soil-structure interaction; and (2) a structure supported by an end-bearing pile foundation in soft soil. An advanced laminar soil container has been designed that uses three-dimensional numerical modeling to minimize the boundary effects and to simulate free-field motion during the shaking table tests. Four real earthquake events, including Kobe 1995, Northridge 1994, El Centro 1940, and Hachinohe 1968, are imposed to each model. According to the experimental measurements, it is observed that the SSPSI amplifies the maximum lateral deflections and in turn interstory drifts of the structures supported by end-bearing pile foundations in comparison with the fixed-base structures. The rocking component plays an important role in increasing the lateral deflection of the superstructures, which can shift the performance level of the structures to near collapse or even collapse levels and as a result should be assessed precisely in the seismic design of buildings resting on soft soils. [ABSTRACT FROM AUTHOR]

A review of the article "Shielding Piles from Downdrag in Consolidating Ground," by S.Y. Lam, C.W.W. Ng, and H.G. Poulos, which appeared in the periodical Journal of Geotechnical and Geoenvironmental Engineering on June 2013, is presented.

A fully instrumented experiment was conducted to investigate the soil-structure interaction of single short, stiff laterally loaded piles. A hollow steel pipe pile with a diameter of 102 mm, a thickness of 6.4 mm, and a length of 1.524 m was installed in well-graded sand and subjected to increasing lateral load. The pile and surrounding soil were fully instrumented using advanced sensors, including flexible shape acceleration arrays, thin tactile pressure sheets, and in-soil null pressure sensors. The sensors attached to the pile were used to develop the compressive soil-pile interaction pressures and the lateral displacement along the pile length. The tactile pressure sheet sensors provided the soil-pile interaction compressive pressures on the circumference of the pile at a specific depth and along the length of the pile. The measured soil-pile interaction compressive pressures combined with the measured lateral displacement along the pile length were used to develop the soil-pile interaction force-displacement relationships ( curves) using direct measurements. In addition, the in-soil null pressure sensor measurements were used to develop the distribution of horizontal stress changes around the pile as the lateral pile displacement increased. When appropriate, the measured results were compared with data and methods available in the literature. [ABSTRACT FROM AUTHOR]

The article discusses the response of researchers to a review of their study on implications of shielding effects to negative skin friction (NSF) published in the June 2013 issue of the periodical "Journal of Geotechnical and Geoenvironmental Engineering." Topics covered include the relationship between the drag load and piles, various ways of evaluating NSF and the relevance of the research to bearing capacity.

The author discusses the paper "Shaft Resistance of Drilled Shafts in Clay" by Tanusree Chakraborty, Rodrigo Salgado, Prasenjit Basu and Mônica Prezzi. He commends the paper for examining the influence of the method of pile installation on the alpha factor used in determining the unit shaft resistance. He also describes the process of removal and reinsertion of the auger during the installation.