Investigation on Lateral Bearing Performance of Short Rock-socketed Pile Combined with Inclined Anchor Bolts in Soft Rock Mass

A new composite foundation of electricity transmission lines in mountainous areas has been used in recent years, which is composed of a short rock-socketed pile and three inclined anchor bolts. In this study, the finite element method (FEM) was firstly utilized to establish and verify its FEM calculation model. In addition, the parameters of rock-socketed pile diameter and its embedded depth, inclined anchor length, and the depth of the inclined anchor connection position to the ground surface were considered to design and simulate the lateral bearing capacity of this new type composite foundation. Lateral bearing performances of the composite foundation were simulated, which were also compared to those of rock-socketed short piles without anchor bolts. According to the typical initial linear, curvilinear transition, and final linear regions of the lateral load-displacement curve of each foundation, the corresponding lateral bearing capacity was suggested. The stress distribution characteristics of the rock mass around pile body and that of the concrete section of the pile, as well as the variation of the depth of the inclined anchor connection position to the ground surface against the lateral bearing capacity indicated that the anchoring effect of the inclined anchor can convert the lateral loadings at the top of the foundation into the tension force of the inclined anchor, and can transfer the lateral load to the rock mass around the inclined anchor and below the end of the short pile, thereby effectively improving the lateral bearing capacity of the composite foundation. By optimizing the depth of the inclined anchor connection position to the ground surface, it is possible to reduce the diameter and the embedded depth of a rock-socketed pile and achieve the same lateral capacity of design requirements of transmission tower foundations. As a result, the difficulty of foundation construction can be effectively reduced, thus achieving significant safety and economic benefits.