To enhance the tensile performance of pile foundations, an inclined anchor-short pile foundation with an anchor plate was proposed for transmission lines in areas with overlying soil and underlying rock layers in mountainous regions. An indoor model test of a reinforced concrete short pile with three inclined anchor foundation joints was conducted to study the mechanical characteristics and failure mechanisms of these joints under multi-directional tension. The results show that the short pile and anchor bar work synergistically. The tensile crack first occurs at the joint of the anchor rod, then the vertical main crack extends to the pile top, leading the overall splitting and failure of the specimen. The cracking load of the specimens is approximately 150 kN, the yield load is approximately 1 611 kN, and the ultimate load is approximately 1 845 kN. Before failure, all the anchor bolts yield, while the longitudinal bar and stirrup inside the pile do not yield, indicating stable anchoring performance of the inclined anchor. When the load on the inclined anchor-short pile foundation is small, the anchoring action between the pile and anchor is mainly borne by the bonding action of the straight anchor of the steel bar. As the load increases, the anchoring effect is mainly borne by the bearing effect of the anchoring plate. The oblique stress between the anchor ribs combines with the corresponding oblique shear stress tau alpha in the short pile, causing the concrete cracks around the anchor bars to deflect and exacerbating the development of concrete cracks to the pile surface. This study provides a reference for the design of composite foundations and the study of deformation characteristics and failure mechanisms.

The bearing and deformation characteristics of embankments with rigid-flexible long-short pile composite foundations (RLPCFs) in thick collapsible loess strata are not yet accurately understood. In this study, a large-scale field experiment was conducted, and screw (long) and compaction (short) piles were employed to reinforce a of the foundation of the Lanzhou-Zhangye high-speed railway in thick collapsible loess. The pile load transfer, foundation settlement, pile-soil stress distribution, and load sharing characteristics were analyzed to reveal the bearing properties of the composite foundation. The results show that negative friction arises along the upper part of the pile, and the neutral points of the short pile and long pile are located at 2/5 and 1/3 down the pile lengths, respectively. The short pile eliminates the collapsibility of the shallow loess and enhances the foundation's bearing capacity. The long pile transfers the load of the shallow foundation and pile top to the deep foundation through lateral friction, which reduces the settlement of the shallow foundation. When the soil arch in the embankment is fully formed, the short pile bears approximately 20% of the load, while the long pile and the soil between piles bear 80%. With the increase in embankment filling height, the load borne by the long pile rises, and the load borne by the soil between piles decreases gradually. The top settlement of the cross- of the composite foundation is distributed in a concave basin shape, and the maximum settlement occurs in the center of the embankment. The parameters of the short pile can be obtained on the basis of the collapsibility grade and bearing capacity of the loess foundation, the length and area replacement rate of the long pile can be obtained based on the settlement control requirements of the superstructure of the composite foundation, and the lateral friction of the long pile can be increased by increasing the roughness of the pile and setting the screw.

Piles are inevitably installed on sloping coastlines or inclined seabeds to support offshore wind turbines, offshore bridges, and other structures. The objective of this paper is to develop an analytical method for investigating the lateral response of short piles near clay slopes. The soil-pile interaction is modelled by a two-spring model which is used to describe the soil resistance around the pile and the horizontal shear force at the pile base. Considering the combined effect of slope angle and near-slope distance, the ultimate soil resistance along the pile is divided into three cases based on the nearby soil flow mechanism. The soil-pile-slope surface deformation mechanism is established according to the rotational deformation characteristics of short piles. In contrast to the modification of the initial stiffness, the p-y curve around the pile is constructed by considering the deformation mechanism. The accuracy of the analytical method is verified by comparing its results with two piles on level ground and five piles near slopes. Considering the soil-pile-slope deformation mechanism, the secant stiffness of the p-y curve is automatically adjusted and reduced without the need for additional numerical simulations or pile tests to determine the reduction factor of the initial stiffness.