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In this study, the pressure-cast-in-situ pile with spray-expanded frustum (PPSF) was proposed to increase pile bearing capacity, reduce pile settlement, and improve construction speed. The construction process of the PPSF composed of pile body, ribbed plate, and expanded body with double frustum was introduced. To capture the PPSF response, field static load tests on three PPSFs installed with string wire stress gauges were carried out. The ultimate bearing capacity (UBC) of a single PPSF was obtained, and the distribution of axial force, skin friction, and end force were analyzed using the measured results. Following the assumption that the strength of pile–soil interface elements was statistically described by the probability density function of the Rayleigh distribution, the load transfer models of PPSF were established based on the disturbed state concept (DSC) theory. The research results showed that there is a compression effect between the expanded body of the PPSF and the surrounding soil, which can effectively improve the bearing capacity of the PPSF. Considering the concrete consumption per unit volume, the UBC of PPSF is 66% more than that of the cast-in-situ bored pile. According to the results of measured and fitted relationships, the load transfer models of PPSF can be well described using the DSC theory and the Rayleigh distribution. [ABSTRACT FROM AUTHOR]

A large amount of excavation waste soil will be produced during highway construction, which will lead to environmental pollution and construction site occupation. To make full use of the excavation waste soil, hydraulic pile-forming equipment with a maximum pressure of 200 t is developed based on the principle of building clean transportation infrastructure. In addition, a precast pile with modified waste soil (PPMS) is proposed to achieve the large-scale consumption of the excavation waste soil. The PPMS has the advantages of regular shape, reliable quality, and stable bearing capacity. The relevant production standards and construction processes are proposed in this paper. The static pressure test analysis of the PPMS and lime–soil compaction pile was performed to verify the feasibility of the PPMS in reinforcing soft foundations. The test results show that the bearing capacity of a single PPMS could reach 600 kN. Under the upper load of 400 kPa, the settlement of the PPMS-reinforced soft foundation is 30% smaller than that of the lime–soil compaction pile. The PPMS has the advantages of high bearing capacity and economic and environmental protection, which is suitable for reinforcing soft foundations. [ABSTRACT FROM AUTHOR]

A simple analytical approach for nonlinear analysis of the load-displacement response of a single pile is presented. Two models are adopted in the proposed approach. One model uses a softening nonlinear relationship to simulate the degradation behavior between the unit skin friction and the pile-soil relative displacement developed in the pile-soil interface, and the other model adopts a bilinear load-displacement relationship to capture the pile-end response. Based on the two proposed models, a highly effective computer program has been developed for nonlinear analysis of the load- settlement behavior of a single pile. Comparisons are made between the present method, other analytical methods, and a well-documented field experimental pile loading case. The results of the comparisons indicate that the proposed method is generally in good agreement with field-observed behavior and the calculated results derived from other approaches. A parametric study is conducted to assess the influence of the parameters related to the proposed model on the load- displacement response of a single pile. Key words: pile, softening model, bilinear model, ultimate unit skin friction, end resistance, settlement. Cet article presente une approche analytique simple pour l'analyse non lineaire du comportement en charge-deplacement d'un pieu unique. Deux modeles sont adoptes dans l'approche proposee. Un modele utilise une relation d'adoucissement non lineaire pour simuler le comportement en degradation entre la friction superficielle unitaire et le deplacement relatif pieu-sol developpe a l'interface pieu-sol; tandis que l'autre modele adopte une relation bilineaire de charge- deplacement pour illustrer le comportement de l'extremite du pieu. A partir de ces deux modeles proposes, un programme informatique tres efficace a ete developpe pour l'analyse non lineaire du comportement en charge-tassement d'un pieu unique. Des comparaisons sont faites entre la methode presentee, d' autres methodes analytiques et un cas bien documente d'un pieu experimental sur le terrain. Les resultats des comparaisons indiquent que la methode proposee concorde generalement bien avec le comportement observe sur le terrain et avec les resultats calcules avec les autres approches. Une etude parametrique est realisee pour evaluer l'influence de parametres relies au modele propose sur le comportement en charge-deplacement d'un pieu unique. Mots-cles: pieu, modele d'adoucissement, modele bilineaire, friction superficielle unitaire ultime, resistance a l'extremite, tassement. [Traduit par la Redaction], Introduction Much effort has been made to develop theoretical methods to analyze the behavior of single piles and pile groups. Many of these various numerical methods fall into five main [...]

Based on disturbed state concept (DSC) theory, this paper reports an analysis of the progressive failure mechanism of a pile–soil system from a new perspective. Assuming that the strengths of the pile–soil interface elements and the soil elements at the pile end follow an exponential distribution, the load transfer models of skin friction and end resistance based on DSC theory are established, and the significance and value method of the parameters in the models are clarified. The analysis of the relevant parameters shows that the proposed DSC load transfer models can simulate the nonlinear hardening or softening behavior of skin friction and end resistance. Based on the proposed DSC load transfer models, a simple and efficient iterative calculation method for the analysis of the bearing behavior of a single pile is established. It is demonstrated from case studies that, compared with calculated results using other methods, the load–settlement curves at the pile head obtained from the method proposed in this paper are in better agreement with the measured values, and could reflect the skin friction and end resistance softening characteristics of the tested piles in a more realistic manner. Furthermore, a parametric study is carried out to analyze the influence of the relevant model parameters on the response of a single pile. [ABSTRACT FROM AUTHOR]