## 3 Comparative Analysis of Monitoring Data and Numerical Simulation
### Space-Time Deformation Analysis of Foundation Pit Structure  
#### 3.3.1 Foundation Pit Column  
The omnidirectional displacement meter is used to monitor the structural deformation inside the foundation pit and the surrounding surface settlement. The actual deformation monitoring values and numerical simulation values of columns and ground walls at different positions in the foundation pit during construction are shown in Figures 4-6. It can be seen that the numerical simulation results and monitoring data have a high agreement, indicating that the established finite element simulation model can better reflect the deformation characteristics of the structure in the ultra-large deep foundation pit. From the elevation of 13 m to the top plate of B3, the construction sequence is spatially expressed as earth excavation from top to bottom and from east to west. In the early stage of construction, the excavation of the eastern part of the foundation pit was carried out first. As a result, the vertical deformation amplitude of the No. 3 and No. 5 columns in section 1-1 was larger than that of the columns in the other two sections, and the total uplift deformation reached 20 mm and 23 mm, respectively. The total deformation of the column in sections 7-7 and 11-11 is between 9 mm and 12 mm. Figure 4: 01-01 Profile column monitoring deformation value and numerical simulation value. With the earth excavation in the middle and west of the foundation pit, the total deformation of the column at the position of section 1-1 is 3 mm and 6.7 mm, respectively, and the total deformation of the column in sections 7-7 and 11-11 is between 5.2 mm and 8 mm. The amount of deformation is smaller than that of the previous construction stage, and the deformation rate is 3-4 times lower than that of the previous stage. The main reason is that when earthwork excavation is carried out, B3 roof pouring construction and B2 roof forward construction are carried out in the foundation pit. Deformation constraints are imposed on the bottom of the foundation pit. At the same time, the B2 forward slab and the B3 reverse slab are combined with the column to form the overall structure of the foundation pit, which can effectively restrain the unloading and rebound phenomenon. Figure 5: 07-07 Profile column monitoring deformation value and numerical simulation value. Figure 6: 11-11 Profile column monitoring deformation value and numerical simulation value. of the foundation pit bottom caused by the surrounding earthwork excavation. It can effectively inhibit the uplift and deformation of the column, and the construction time at this stage is twice the construction time of the eastern excavation of the foundation pit; as the construction time is longer, the soil at the bottom of the pit has enough time to release the stress, and the deformation rate of the overall column monitoring point is controlled at about 0.1 mm/d. The excavation was carried out under the roof of layer B3 (elevation 0 m) to 2 m above the foundation plate (elevation \(-\)11 m), and the deformation of the columns of the three monitoring profiles decreased from east to west. By observing the foundation pit plan, it can be seen that the excavation length-width ratio of the foundation pit section gradually decreases from east to west, and the load of earthwork also decreases correspondingly, resulting in low uplift deformation at the bottom of the pit. The actual deformation monitoring values and numerical simulation values of the columns and ground walls at different positions in the foundation pit along with construction are given in Figures 4-6. It can be seen that the numerical simulation results and monitoring data have a high agreement, indicating that the established finite element simulation model can better reflect the deformation characteristics of the structure in the ultra-large deep foundation pit.