## 4 Analysis of Test Results
### Analysis of Internal Forces of Anchors  
Figure 10 shows the axial strain distribution of the five anchors at different depths. From the theory of elasticity, it is known that the axial force and axial strain distribution are the same for the same anchors. Therefore, it is more intuitive to use strain instead of axial force when analyzing the axial force. From Figure 10, the axial force of the anchor tends to be zero for the whole length when it is not tensioned. When the prestressing force is applied, the axial force at each point starts to increase and gradually reaches the peak. After the anchor is tensioned, the frictional resistance at the interface between the anchor solid and the soil starts to play, and the anchor section shares part of the axial force coming from the free section. So, the axial force starts to decrease with the length of the anchor solid and drops to the minimum at the end of the anchor [37]. After the anchor tensioning is completed and the jack is removed, the internal force at each measurement point of the anchor shows a certain decrease. At this time, the relative displacement of the anchor solid and its surrounding soil body no longer increases, and the internal force stabilizes. It can also be seen from the figure that the magnitude of the axial force of the anchor also depends on the magnitude of the applied external force. The greater the applied external force, the greater the axial force of the anchor, so the external force within a reasonable range can give full play to the frictional resistance of the anchor solid and the soil. By connecting with the girders and piles, the anchor reduces the deformation of the supporting pile and the soil behind the pile, improves the force state of the pile, and increases the safety and stability of the supporting structure. Figure 9: Soil pressure test results under different working conditions compared with Rankine soil pressure. Due to the large number of anchors tested in this experiment, only anchor M2-5 was used to analyze the axial force and shear stress distribution of anchors under different excavation conditions. Figure 11 shows the distribution of the axial force of anchor M2-5 under different excavation conditions. From Figure 11, it can be seen that the anchor axial force starts to increase with the application of prestress and continues to reach its peak after the next layer of soil excavation. The reason for this is that the passive earth pressure starts to decrease due to the continuous unloading of the soil in front of the pile. The pile has a tendency to move into the pit under the action of the soil in the active zone, and this tendency is suppressed by the presence of the anchor. In the later excavation conditions,  
Figure 10: Axial force distribution of anchors. (**a**) Axial force distribution of Anchor M1-3; (**b**) Axial force distribution of Anchor M2-3; (**c**) Axial force distribution of Anchor M3-3; (**d**) Axial force distribution of Anchor M4-3; (**e**) Axial force distribution of Anchor M5-3. the anchor shaft force starts to decrease gradually, but it is higher than the initial shaft force after the anchor is tensioned. This indicates that once the anchor is prestressed, its limiting effect on the displacement of the pile and the soil behind the pile will continue to exist, thus ensuring the safety of the support structure. After the anchor is tensioned, the internal force of any section of the anchored section is equal to the sum of the internal force of the reinforcement and the internal force of the anchor, and the quotient of the difference between the internal force of the two sections and the surface area of the anchor is the shear stress of the anchor. Its calculation formula is given by [PERSON] [38].