# Dewatering-Induced Stratified Settlement around Deep Excavation: Physical Model Study
## 6 Conclusions  
In this study, a physical model test was conducted to examine the law of stratified settlement in MAMA. A similar material was developed, which achieved deformation and seepage similar to real conditions. Buildings and a tunnel were added inside the physical model to analyze the impact of environmental conditions on the stratified settlement in MAMA. The following conclusions were obtained:  
* According to whether the overlying aquitard is coupled with groundwater seepage, the process of dewatering-induced stratified settlement in MAMA can be divided as compression in the confined aquifer, coordinated deformation in the overlying strata, and seepage and compression in the overlying strata. The soil shows compression under the drive of seepage within the range of the hydraulic gradient, whereas the soil above it is still affected by the coordinated deformation and shows expansion.
* Stratified settlement around the diaphragm wall is confined and expanded at the top strata (layer 3 + 4 in this test). The maximum ground settlement occurs approximately 45.0 m away from the deep excavation. When the groundwater level is recovered, the deformation of the sandy strata (layers 2 and 3) rebounds quickly. Meanwhile, such a rebound is difficult in the clayey strata (layers 3 + 4 and 3) due to plastic strain, and about 50.0% of the ground settlement is rebound. The large-scale and uninterrupted excavation and dewatering of the underground space are the main reasons for the continuous development of land subsidence.
* The existence of artificial underground structures will limit the deformation and internal expansion of the strata. Affected by the frictional resistance of buildings' pile foundations, the settlement of each stratum within its length range is decreased, and the ground settlement is approximately 80.0% of that in open space. Therefore, dewatering-induced uneven settlement will cause damage to existing foundations and underground structures.
* When a tunnel exists, the ground settlement above it is decreased by about 45.0% because of its structural integrity. The maximum uneven settlement appears in the range of 45.0-90.0 m away from the perpendicular point to the deep excavation, especially when buildings exist around it. Artificial groundwater recharging can reduce the settlement of the tunnel and the surrounding strata. However, meeting the settlement control requirements is difficult because of their scope and amount.  
[PERSON] and [PERSON] carried out the main research task and wrote the manuscript. [PERSON] proposed the original idea and contributed to the revision of the obtained results and the whole manuscript. [PERSON], [PERSON] and [PERSON] performed the physical model test. [PERSON], [PERSON] and [PERSON] performed data analysis. All authors have read and agreed to the published version of the manuscript.  
Figure 11: Conceptual schema of stratified settlement in strata around the tunnel.  
**Funding:** This work is supported by the National Natural Science Foundation of China (grant No. 41907230), Science and Technology Commission of Shanghai Municipality (grant Nos. 18 DZ1201301, 19 DZ1200901), Open Fund of Key Laboratory of Land Subsidence Monitoring and Prevention, Ministry of Natural Resources of China (grant No. KLLSMP202101).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.