## 5 Deformation Control Measures
### Comparative Analysis of Deformation Results
#### 5.2.3 Comparative Analysis of Differential Settlement Between Ground Wall and Lattice Column  
The stress release caused by excavation and unloading led to the upward heating of the soil at the bottom of the foundation pit. Concurrently, the finished main structure caused the lattice columns and the diaphragm wall to bear the load transmitted from  
Figure 14: Maximum ground surface settlement at different excavation depths. the structure. This scenario inevitably resulted in differential settlement between the diaphragm wall and the lattice columns. Controlling this uneven settlement is critical to the success of the top-down construction method and involves implementing various measures during construction. Otherwise, uneven settlement could lead to cracks in the poured floor slabs and beam systems, resulting in leakage and potentially jeopardizing the safety of the permanent structure. Currently, the control standards for differential settlement are largely based on empirical construction experiences. For example, [PERSON] et al. [28] stated that the differential settlement between the diaphragm wall and the lattice columns should not exceed 20 mm or 1/400 of the column spacing length through numerical simulation. They concluded that the floor slab should be poured as promptly as possible to minimize the differential settlement. Table 8 summarizes the maximum vertical displacements of the diaphragm wall, the maximum vertical displacements of the lattice columns, and the differential settlement between the two under the three different construction schemes. The maximum vertical displacement of the diaphragm wall gradually decreased as the number of segmented excavations increased. Among the three schemes, the original scheme exhibited the largest settlement, while Plan 3 showed the smallest settlement at only \(-\)2.97 mm. Conversely, the maximum vertical displacement of the lattice columns showed a gradually increasing trend. The original scheme displayed the smallest settlement, while Plan 3 exhibited the largest settlement at \(-\)4.04 mm. This trend can be attributed to the fact that an increase in the number of segments constrained the horizontal displacement of the diaphragm wall, which in turn limited the maximum vertical displacement of the diaphragm wall. However, a smaller horizontal displacement of the diaphragm wall weakened its ability to compress the soil within the foundation pit. Consequently, the heaving of the pit bottom and lattice columns was reduced in comparison to the original excavation scheme. As previously described, the maximum settlement of the lattice column occurred at the top, as illustrated in Figure 8. The pressure transmitted from the main structure and the backfilled soil in the lattice column remained unchanged. Consequently, decreasing the heaving of the lattice column diminished its ability to counteract the vertical displacement of the main structure, resulting in an increase in the settlement at the top of the lattice column. This caused the maximum vertical displacement of the lattice column to increase as the number of segments increased. Further examination of the differential settlement between the diaphragm wall and the lattice column revealed that the differential settlement fluctuated with the increasing number of segments (As shown Table 6). Plan 2 achieved the smallest differential settlement at only 0.55 mm, while Plan 3 recorded the largest differential settlement at 1.07 mm. [PERSON] et al. [28] stated that the differential settlement should not exceed 20 mm. Notably, all three construction schemes met the deformation control requirements. Additionally, as detailed in Section 4.2.1, the horizontal displacements of the diaphragm wall in Plan 3 and Plan 2 were recorded at 0.15% H and 0.17% H, respectively, both of which comply with the regulatory requirement that the maximum horizontal displacement of the diaphragm wall for a first-class foundation pit should not exceed 0.18% H.