Mohammed Sakr

Performance of helical piles in oil sand

The results of a comprehensive pile load-test program and observations from field monitoring of helical piles with either a single helix or double helixes installed in oil sand are presented in this paper. Eleven full-scale pile load tests were carried out including axial compression, uplift, and lateral load tests. The results of the full-scale load tests are used to develop a theoretical design model for helical piles installed in oil sand. Test results confirm that the helical pile is a viable deep foundation option for support of heavily loaded structures. The test results also demonstrated that circular-shaft helical piles can resist considerable lateral loads.

Centrifuge Modeling of Tapered Piles in Sand

An experimental study was performed to investigate the performance of tapered and cylindrical piles driven into loose sand using the geotechnical centrifuge located at C-CORE, Memorial University, Newfoundland. Twelve open-ended model piles with different configurations, instrumented externally along the shaft, were successfully installed and load tested using the facility. The piles were driven at 1 g, and the loading tests were conducted at 10 g. The paper discusses the design of model piles and details of loading equipment and presents the results of axial compression tests. The results obtained showed that modeling tapered and cylindrical piles with different length-to-diameter ratios was successfully achieved. The external instrumentation technique used in this study proved to be efficient. The surface ronghness effect was found to be important and must be considered when interpreting the test results. The raining technique used in this study produced reasonably uniform soil samples. It was found that as the taper angle increased the shaft resistance increased, and the shaft resistance of the tapered pile was up to 185 % larger than that of the equivalent cylindrical pile. It was also found that the values of the combined shaft resistance factor β for cylindrical piles were consistent with Canadian Foundation Engineering Manual (1992) guidelines. In the case of tapered piles, β values were found to be 80 % higher than those for cylindrical piles, whereas the CFEM design guidelines suggest they should be 30 to 50 % higher. The effect of the taper established from experimental results compared well with the results obtained from an analytical solution based on cavity expansion theory.

Toe-Driven Tapered Fiber-Reinforced Polymer Self-Consolidating Concrete Composite Piles: New High-Performance Technology for Deep Foundations

Field experience shows it has often been difficult to assure the structural integrity and uniformity of the cross-sectional area of cast-in-place concrete piles, as cavities and soil pockets tend to form due to the lack of visibility and accessibility during construction. Moreover, corrosion in prestressed concrete, reinforced concrete, and steel shell piles has been very costly, exceeding

Cyclic response of axially loaded tapered piles

2 billion in annual repairs in the United States alone. This paper summarizes the findings of a comprehensive research program that was undertaken to develop novel technology that addresses both construction and durability related problems of piles. A new toe-driving technique was developed to install empty fiber-reinforced polymer (FRP) shells into dense soils. A specially developed cost-effective self-consolidating concrete (SCC), a material that flows under gravity and assures the integrity of piles is subsequently cast into the FRP tubes, which provide corrosion-resistant reinforcement. Driving tests were conducted on large-scale model FRP-SCC and steel piles installed in dense dry sand enclosed in a pressure chamber using the new technique along with conventional hammering at the pile head. FRP-sand interface characteristics were evaluated. The pile specimens were instrumented to investigate their dynamic behavior during driving, and their response to static compressive, uplift, and lateral loading. Both cylindrical and tapered FRP-SCC piles were tested. It is shown that the new toe-driving technique is very suitable for installing FRP and other thin-walled piles in dense soils. Results from dynamic pile driving and static load tests indicate that FRP-SCC composite piles are a very competitive and attractive option for deep foundation applications.

Evaluation of axial performance of tapered piles from centrifuge tests

Instrumented model piles were used to investigate the fundamental behaviour of tapered and cylindrical piles in loose sand due to cyclic loading, using a centrifuge facility. The objectives of this study were to understand and evaluate the cyclic performance of tapered and cylindrical piles and to investigate the degradation in the pile capacity due to cyclic loading. The results of controlled-displacement cyclic loading tests on twelve one tenth-scale model piles with different taper angles in a centrifuge setup were presented and discussed. Six piles were instrumented and six were not. The load-movement curves of tapered and cylindrical piles were measured and compared. The load settlement curves due to axial compressive loading tests before and after cyclic loading tests were compared as well. The comparison showed that cyclic loading led to a change in the load transfer patterns so that a greater portion of the load was carried by toe resistance and a smaller portion by the shaft resistance. The degra...