# Low Carbon Optimization of Deep Foundation Pit Support in Undulating Strata
## 4 Calculation Results Comparison Analysis
### Analysis of Numerical Simulation Optimization
#### 4.2.3 Results of the Internal Force of Structural Element Simulation  
When the foundation pit is not excavated, the force exerted on the supporting pile can be disregarded. Subsequent to the excavation of the foundation pit, the supporting pile constrains the deformation of the foundation pit's sidewall and is subject to lateral soil pressure. The force of the supporting pile is shown in Figure 13. At this time, no internal support is added, and the soil pressure borne by the supporting pile is very uneven. The shear force of the supporting pile is 1.75 \(\times\) 10\({}^{6}\) N, and the maximum shear force of the single pile is 1.341 \(\times\) 10\({}^{6}\) N in design calculation. The simulated shear force obviously exceeds the calculated value, which is unfavorable to the structure.  
Figure 11: Midsettlement of the foundation pit.  
Figure 12: Horizontal displacement of the monitoring points by numerical calculation.  
When the inner support is added, it can be seen that the pile force is not only reduced but also becomes very uniform, and the inner support balances the earth pressure on both sides. The internal support and supporting pile force are shown in Figure 14. It can be seen from the figure that the shear force in the supporting pile is \(1\times 10^{6}\) N, and the maximum shear force in the design value of the supporting pile is \(1.341\times 10^{6}\) N. The shear force is significantly reduced.  
Upon the inclusion of the anchor rod, Figure 15 illustrates the force acting on the supporting structure. Due to the addition of the anchor rod, the maximum shear force of the pile unit is reduced, and the shear force of most piles is 0.25106 N. As a result of implementing the anchor rod, the internal force exerted on the supporting pile decreases and the supporting capacity of the anchor-pile structure increases. Compared with the design value of 1.341106 N, the diameter of the pile can be reduced. According to material quantity estimation, the material can be saved by about 20%. The maximum force of the anchor rod is prestress and appears in the anchor pull section.  
The simulation results of the optimization scheme show that the optimized supporting structure has a good constraint effect on the deformation of the foundation pit. There are 6 anchor rods, and the longest supporting pile is 16.5 m, which is far less than the length  
Figure 14: Internal support and support pile joint force.  
Figure 13: Stress of the supporting pile without internal support.  
Figure 15: Structural unit force.  
of a single pile in the design calculation. The maximum shear force of the supporting pile is \(1.25\times 10^{6}\) N, which is less than the shear force of \(1.341\times 10^{6}\) N calculated by design. The maximum force of the inner support is \(2\times 10^{6}\) N, which is less than the maximum internal force value of \(2.69\times 10^{6}\) N in the design calculation. The maximum force of the bolt is \(0.5\times 10^{6}\) N, which is less than the maximum force of \(0.8\times 10^{6}\) N in the design calculation. All of them meet the requirements for foundation pit support and foundation pit deformation. The optimized design scheme is reasonable and effective.