## 4 Design Methodology of Composite-Anchor Uplift Piles
### The Use of Load-Bearing Capacity Design Formulas in Engineering Examples  
The design steps for determining the bearing capacity of composite-anchor piles are outlined as follows: Firstly, apply the relevant provisions stated in the \"Technical Specification for Building Pile Foundations\" (JGJ 94-2008), specifically in Sections 5.4.5 and 5.4.6. Utilize these provisions to calculate the uplift bearing capacity of a single composite-anchor pile. This calculation will determine the required pile length, pile diameter, and reinforcement specifications for the composite-anchor piles. Secondly, verify the uplift bearing capacity by employing the formulas provided in Sections 4.1 and 4.2. These formulas should be applied to two different scenarios. Next, carry out crack verification based on the guidelines mentioned in Section 4.3. Finally, conduct corrosion resistance verification of the steel pipe in accordance with the instructions given in Section 4.4. The specific application of these steps in an engineering example will be elaborated in the subsequent text. Composite-anchor piles have emerged as a novel form of uplift-resistant piles, specifically designed for combating flotation in construction projects. Leveraging their remarkable load-bearing properties and uniform load transmission advantages, composite-anchor piles have revolutionized the original design approach that relied on anti-floating anchor cables. By incorporating composite-anchor piles, the new design scheme optimizes uplift resistance. These innovative piles not only make efficient use of the frictional resistance at the pile-soil interface, but also yield substantial cost savings and time reduction in construction. Consequently, they offer significant benefits to engineering projects. The construction site of the engineering application case is located in Liangxiang Town, Fangshan District, Beijing. The project covers an area of 10,384 m\({}^{2}\), with a proposed construction area of 42,506 m\({}^{2}\), including 25,960 m\({}^{2}\) aboveground construction area and 16,546 m\({}^{2}\) underground construction area. The proposed building is a commercial building with 6 floors above ground and 3 floors underground, with a building height of 41.82 m. The structure type is frame shear wall, with a foundation buried depth of 14.10 m and a foundation form of raft foundation. The engineering design method is composed of the following steps: Initially, based on the project's geological conditions, structural drawings, and calculation models provided by the design unit, the stress distribution of the raft slab under various load combinations is analyzed. This analysis determines the area requiring anti-floating treatment and the corresponding load parameters for anti-floating measures. Then, considering the owner's requirements, the load magnitude on the structural base plate, the bearing capacity of the base plate, and the crack resistance, the selection of composite-anchor piles with large diameters for uplift resistance is determined. The single-pile uplift bearing capacity is calculated, and the pile length, diameter, and reinforcement requirements are established following the relevant provisions outlined in the Technical Code for Building Pile Foundations (JGJ 94-2008) Sections 5.4.5 and 5.4.6 [24]. Due to the project's tight construction schedule and the proximity of the construction site to residential and office buildings, the construction process for the composite-anchor piles will utilize the long spiral dry drilling technique. This approach aims to accelerate construction, save time, reduce noise disturbances, and minimize the environmental impact caused by mud. (1) The layout plan of anti-floating piles is shown in Figure 8.  
(2) The calculation table of composite-anchor pile is shown in Table 6.