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In this research programme, a small-scale laboratory test was carried out to investigate the phenomenon of negative skin friction through studying the interaction between a pile and the surrounding soil and to obtain, by means of an instrumented 50mm diameter model pile, an expression for the magnitude and distribution of negative skin friction for an end-bearing pile in soft clay. The programme included measurements of pore water pressures using miniature piezometers, both vertically along the pile shaft and laterally from it, as the pattern of dissipation of this pressure controls the distribution of negative skin friction along pile length at any given time. Two testing programmes were conducted. Each testing programme consisted of applying load increments on the soil up to 90 kPa as surcharge pressures. Pore pressures, settlements and pile loads were monitored until 90% consolidation had been achieved. From test results, expressions relating the surcharge pressure and soil shear strength with the developed negative skin friction have been established. The study has been extended to include predictions of negative skin friction and pore water pressures by the use of Numerical Methods such as the Finite Element Method and the Finite Difference Method. Results obtained by these methods have been compared with those measured.

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Idea of this diploma thesis is comparison of different diameters of piles which are used for bridge foundation. Diameters of piles are 1200 and 1500 mm in this case. Diploma thesis is about technical implementation, financial comparison. In outset you can read about possibilities of bridge foundation on water surface. In the end of this thesis there is described technological process of foundation for bridge across the dam Hričov.

Piles are often used to resist vertical and lateral loads when shallow foundations are inadequate or uneconomical. A critical part in designing pile foundations is the pile-to-cap connection. When a moment resisting connection is desired, reinforcement is typically used between the pile and the cap. A pile-to-cap connection with sufficient pile embedment depth, however, may provide similar results. One model that is currently used to determine the capacity of a pile-to-cap connection was developed by Marcakis and Mitchell for steel members embedded in concrete. This model considers an embedment mechanism that resists rotation at the connection. Recent testing has shown, however, that this model is conservative and that additional mechanisms contribute to the strength of the connection. An experimental study was conducted to investigate pile-to-cap connections for pipe piles without reinforcement. Three pile-to-cap specimens with varying pile embedment depth were loaded laterally to failure. The results from the testing confirm that pile-to-cap connections with shallow pile embedment depth have significant stiffness. An improved model was developed to estimate elastic and ultimate capacities of embedded connections. In addition to the embedment mechanism used by Marcakis and Mitchell, this model includes a bearing mechanism at the end of the pile. For pile-to-cap connections with a large pile bearing area to pile embedment depth ratio, this bearing mechanism provides more strength than the embedment mechanism. For pile-to-cap connections with a small pile bearing area to pile embedment depth ratio, this bearing mechanism has little contribution to the strength of the connection.

Bridges and buildings are often supported on deep foundations. These foundations consist of groups of piles coupled together by concrete pile caps. These pile caps, which are often massive and deeply buried, would be expected to provide significant resistance to lateral loads. However, practical procedures for computing the resistance of pile caps to lateral loads have not been developed, and, for this reason, cap resistance is usually ignored. Neglecting cap resistance results in estimates of pile group deflections and bending moments under load that may exceed the actual deflections and bending moments by 100 % or more. Advances could be realized in the design of economical pile-supported foundations, and their behavior more accurately predicted, if the cap resistance can be accurately assessed. This research provides a means of assessing and quantifying many important aspects of pile group and pile cap behavior under lateral loads. The program of work performed in this study includes developing a full-scale field test facility, conducting approximately 30 lateral load tests on pile groups and pile caps, performing laboratory geotechnical tests on natural soils obtained from the site and on imported backfill materials, and performing analytical studies. A detailed literature review was also conducted to assess the current state of practice in the area of laterally loaded pile groups. A method called the "group-equivalent pile" approach (abbreviated GEP) was developed for creating analytical models of pile groups and pile caps that are compatible with established approaches for analyzing single laterally loaded piles. A method for calculating pile cap resistance-deflection curves (p-y curves) was developed during this study, and has been programmed in the spreadsheet called PYCAP. A practical, rational, and systematic procedure was developed for assessing and quantifying the lateral resistance that pile caps provide to pile groups. Comparisons between measured and calculated load-deflection responses indicate that the analytical approach developed in this study is conservative, reasonably accurate, and suitable for use in design. The results of this research are expected to improve the current state of knowledge and practice regarding pile group and pile cap behavior. / Ph. D.

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