Abstract

In this paper, the serviceability limit state and bearing capacity of tension screw displacement piles were analyzed using the results of static pile load tests, carried out on the test plot near the Elbląg city, and field, and laboratory tests. The paper presents the methodology of determining the pile load-settlement curve using different types of t-z transfer functions. The new method of constructing the pile load-settlement curves using the trilinear transfer curves, analogous to the functions developed by Frank and Zhao (1982) based on pressuremeter test, is proposed taking into consideration the results of flat dilatometer test. The analogy between pile shaft friction mobilization and direct shearing of the concrete-soil interface was used. The proposed method was derived from 44 shear-displacement curves of cohesionless, cohesive and organic soils in tests performed in a direct shear apparatus on rough or smooth concrete interfaces. The maximum shear stresses on interface were determined, and the slope of skin friction mobilization was expressed as a function of constrained modulus from DMT. Separate friction mobilization functions were proposed for coarse-grained soils (sands), fine-grained (cohesive), and organic soils. The proposed transfer curves takes into account the installation effects, i.e. the applied pile technology. The soil parameters and stress state before and after pile installation were evaluated using the results of CPTU and DMT soundings. The proposed method was validated using the results of eight static load pull-out tests on screw displacement piles performed on the trial test plot. The study is also focused on the determination of soil parameters before and after pile installation using the results of CPT and DMT soundings. The results of uplift static pile load tests were analyzed and the influence of pile length and the after their construction (set-up) on bearing capacity was studied. Currently used CPT-based methods (direct methods) for pile bearing capacity were discussed in this thesis. They were applied then to estimate the bearing capacities of three piles of different lengths. The results were compared with the bearing capacities obtained from the method elaborated by the author. In conclusion, the possibilities for future research to expand the proposed method were presented and its limitations were discussed.

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