# Ground Deformation Associated with Deep Excavations in Beijing, China
## 5 Conclusions  
Based on data from 88 cases, characteristics of surface deformation caused by excavations have been studied. The following provides a summary of the field measurements and our findings:  
1. Long strip pits are susceptible to considerable deformation, which increases with the length-width ratio. The typical range of surface deformations that occur due to deep excavations is between 0 and \(-\)30 mm, accounting for approximately 83.9% of the total. Only 8% of measurement points exhibited settlements with values greater than \(-\)30 mm. Points indicative of upheaval represent 8.1% of the points. Deep excavations can lead to both surface settlement and ground upheaval. Minor upheavals were observed within a range of 5 m from the edge corners, which decreased in accordance with increased excavation levels, and they featured a few final data points.
2. Maximum ground surface settlements are influenced by workmanship, they increase in accordance with the excavation depth, and they decrease as the embedded depth ratio (EDR) increases. The average values for these are 0.089%\(H\) (typically under 30 mm) and 0.36, respectively. Settlements are affected both by ground conditions and support system stiffness, and they reduce in size as stiffness increases. However, an increase of 0.6 \(\pm\) 0.4 mm-2.8 \(\pm\) 0.75 mm occurred during the demolition of 1-2 struts above the base plate. The additional stress from this demolition was the result of substantial soil stress and a smaller internal structure stiffness. Unlike some studies in the literature, the maximum surface settlement was found to not always occur during excavations to the bottom level. It is suggested that temporary reinforcements should be utilized in deep and large excavations as to minimize distortion.
3. The deformation exhibits clear temporal and spatial effects. Each point's settlement rate gradually increases with the progression of the excavation level over time, particularly at the start of drainage consolidation. However, once the internal structure is operating, the deformation tends to stabilize. Each wall tends to exhibit a depression behind it, with maximum deformations occurring in the middle of its long edge. Deformation is comparatively lower along the shorter side, and it reaches its minimum at the corners where stiffness is increased due to the additional constraints of the oil and support structures.
* The \"groove\" patterns of the surface deformations are detected in excavations which have sufficient stiffness in Beijing, which are located at a distance of 0.5\(H\)-0.75\(H\) from the wall. The influence zones generally extend up to a maximum distance of 25-40 m (\(\leq\)2.5-3\(H\)) from the excavation site, with few deformations occurring further than 25 m away the wall.  
S.L.: conceptualization, formal analysis, writing--original draft preparation, review and editing; C.G.: data curation, investigation, writing--review and editing; P.L.: investigation, data curation; M.Y.: conceptualization, review. All authors have read and agreed to the published version of the manuscript.  
The authors gratefully acknowledge the financial support provided by the Natural Science Foundation of China under Grant No. 51978018, the \"14 th five-year plan\" adult continuing education research project of the Chinese Adult Education Association, Grant No. 2021-330Y, the Science and Technology Subsidy Program of China Construction Second Bureau, No. 2021 ZX000001, the Science and Technology Funding Scheme for Three Companies of China, and Construction Bureau II, No. CSCEC2b3c-2021-K-65.  
Not applicable.  
Data Availability Statement: Data are contained within this article.  
The authors declare no conflict of interest.