# Research on Construction Sequencing and Deformation Control for Foundation Pit Groups
## 4 Discussion
### The Influence of Foundation Pit Spacing on the Deformation of Retaining Structures  
The parametric analysis of pit spacing (B/He) addresses a persistent knowledge gap concerning the quantitative definition of critical spacing thresholds and their governing influence on stress redistribution mechanisms in adjacent pit groups [15; 21]. While prior investigations, such as [PERSON] et al. [11], have established correlations between excavation \begin{table}
\begin{tabular}{l l l l l l} \hline \hline \multirow{2}{*}{**Excavation Sequence**} & \multicolumn{5}{c}{**Maximum Horizontal Displacement of the Wall (mm)**} \\ \cline{3-6}  & & **1\#** & **2\#** & **3\#** & **4\#** \\ \hline \multirow{4}{*}{Excavation Sequence 1} & excavate the small-section deep foundation & \multirow{2}{*}{0.22} & \multirow{2}{*}{\(-\)0.26} & \multirow{2}{*}{\(-\)0.04} & \multirow{2}{*}{\(-\)0.007} \\  & pit first & & & & \\ \cline{1-1} \cline{5-6}  & excavate the large-section shallow & & & & \\ \cline{1-1} \cline{5-6}  & foundation pit afterward & & & & \\ \cline{1-1} \cline{5-6}  & additional displacements & 0.06 & 0.118 & - & - \\ \hline \multirow{4}{*}{Excavation Sequence 2} & excavate the large-section shallow & \multirow{2}{*}{0.003} & \multirow{2}{*}{0.005} & \multirow{2}{*}{0.22} & \multirow{2}{*}{\(-\)0.193} \\  & foundation pit first & & & & \\ \cline{1-1} \cline{5-6}  & excavate the small-section deep foundation & & & & \\ \cline{1-1} \cline{5-6}  & pit afterward & & & & \\ \cline{1-1} \cline{5-6}  & additional displacements & - & & & \\ \hline Excavation Sequence 3 & simultaneous excavation & \multirow{2}{*}{0.325} & \multirow{2}{*}{\(-\)0.258} & \multirow{2}{*}{0.296} & \multirow{2}{*}{\(-\)0.379} \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Maximum horizontal displacements and additional displacements under different excavation sequences. influence zones and depth for adjacent structures, the specific quantification of the B/He ratio as a primary controller of interaction intensity between adjacent excavations remained elusive. Figure 21 shows the relationship between the maximum horizontal displacement of the diaphragm wall and the width-to-depth ratio of the foundation pit. As illustrated in the figure, when the foundation pit spacing is B = 1.0 He and B = 1.4 He, the increase in the curve becomes more gradual. However, within the range of one times the excavation depth (B \(\leq\) 1.0 He), the increase in the curve is more pronounced. This indicates that the horizontal displacement of the retaining structure is significantly influenced by pit spacing within one times the excavation depth. Beyond this range, the influence of spacing on displacement diminishes. These findings exhibit congruence with the theoretical framework of finite-width soil mechanics applied to earth pressure analysis, wherein inter-pit spacing governs the kinematic interaction potential of active Rankine wedges. The experimental data provide empirical validation that at B/He \(<\) 1, pronounced wedge interaction occurs, resulting in synergistic reductions in earth pressure and consequential amplification of retaining wall displacements. Quantitative analysis of earth pressure distributions (Figure 18) further demonstrates that diminished finite soil widths (i.e., lower B/He ratios) induce more substantial earth pressure attenuation at the wall toe--a phenomenon observed despite comparatively smaller incremental displacements per excavation stage. Moreover, the consistent emergence of an inflection point proximal to the excavation face across all B/He cases, coupled with the linearly distributed pressure profile beneath it, conforms to established mechanical principles governing confined soil domains. This section systematically examines the influence of varying pit spacings (B/He = 0.2-1.4) on the stress-deformation response of retaining structures. The analysis elucidates a critical threshold effect inherent to adjacent pit spacing and establishes its underlying engineering control logic.