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 existing mechanical and grouting anchors mostly use the expansion shell method to form a cavity on the borehole wall, and the cement slurry is poured to form multiple enlarged head plates, but the operation is more difficult and the diameter of the formed plate is smaller. In this paper, a new type of large-diameter multi-plate soil anchor and its reaming cavity forming tool are proposed, which can make the operation easier and form a large-diameter enlarged head plate. In order to study the influence of the diameter of anchor plate, the number of anchor plates and the spacing of anchor plates on the vertical uplift capacity of the large-diameter multi-plate soil anchor, 25 sets of comparative models were established for simulation analysis. The finite difference method of FLAC(3D) software is used to simulate the model. It is found that when the length of the anchor is 6 m and the diameter of the anchor rod body is 150 mm, the optimal diameter of the anchor plate of the large diameter multi-plate soil anchor is 590 mm, the optimal number of anchor plates is 6, and the optimal anchor plate spacing is 800 mm, which means the action range of the anchor plate on the lower soil is about 5 times the diameter of the bolt. When the number of anchor plates is too small or the spacing between anchor plates is too large, the structural advantages of large-diameter multi-plate soil anchor cannot be fully utilized, resulting in a decrease in the ultimate uplift capacity. When the number of anchor plates is too large or the spacing between anchor plates is too small, the stress superposition effect occurs in the soil, and the through shear failure occurs, which leads to the decline of the ultimate uplift capacity. Under the condition that the number of anchor plates and the spacing of anchor plates are fixed, the larger the diameter of the anchor plate is, the larger the ultimate pull-out capacity of the large-diameter multi-plate soil anchor is, the smaller the vertical failure displacement of the anchor head is, but the increase of the uplift capacity is gradually reduced. The creep rate of the new large-diameter multi-plate soil anchor bolt is 0.91 mm, and the creep rate of equal-diameter soil anchor bolt is 1.69 mm. It is verified that the new large-diameter multi-plate soil anchor can be effectively applied to various projects.