## 8 Conclusions and Suggestion  
To solve the subsidence control of thick, soft ground with a hard layer, the Ministry of Railways adopted the new foundation-treatment technology of the bag grouting pile in the test section of Ningbo-Taizhou-Wenzhou Railway. The technology's feasibility was verified through numerical calculations. The following conclusions were made:  
1. The settlement rate and lateral-displacement-change rate of the bag grouting pile meet the code requirements. After completing the construction, the settlement did not exceed the design standard for the main roadbed. This indicates that the bag grouting pile can be used in the bag-grouting-pile reinforcement of a deep soft-soil foundation with a hard interlayer.
2. As for the depth, the distribution and variation of lateral displacement show that the bag grouting pile had a restrictive effect on the deformation of deep soft soil. The dissipation of excess pore pressure was faster than that of the general foundation through calculation. This helps accelerate the consolidation of soft soil under the hard layer and verifies the function of the drainage channel considering the bag around the pile in the design.
3. Through field tests, the pile body with a pile-soil stress ratio between 1-4 was deemed a flexible pile. The pile's calculated axial force and lateral resistance were 223 kN and 67 kPa, which are far less than the allowable bearing capacity. It was also found that pile spacing had less influence on settlement control than pile length diameter. Therefore, we can choose to increase the distance between bagging piles to reduce the project cost.
4. It is suggested that in future research, the factors affecting the bearing capacity of bagged piles can be analyzed in combination with model tests; the application properties of bagged grouting piles in karst, beach silt and other soft foundations can be strengthened.  
Conceptualization, F.C.; Data curation, S.Z., Q.Z., P.L. and Y.C.; Formal analysis, S.Z. and Q.Z.; Funding acquisition, S.Z., J.L. and F.C.; Investigation, P.L.; Methodology, S.Z. and F.C.; Project administration, Q.Z.; Resources, J.L., P.L. and Y.C.; Software, F.C.; Supervision, Q.Z., P.L. and Y.C.; Validation, J.L. and P.L.; Writing--original draft, S.Z.; Writing--review & editing, J.L. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the key R&D projects in Shandong Province under grant number 2019 GSF111008 and the Natural Science Foundation of Shandong Province (grant number ZR2020 QE260) and the Shandong Provincial Department of Transportation Science and Technology Plan Project under grant number 2021B117, the National Natural Science Foundation of China (grant numbers 52178182 and 52108262).  
Not applicable.  
Figure 18: Subsidence calculation contrast curve.  
Data Availability Statement: The data that support the findings of this study are available from the corresponding author.  
This work is supported by the Found of Shandong Key Technology Research and Development Program (2019 GSF111008), the Funding Supported by the Natural Science Foundation of Shandong Province (grant number ZR2020 QE260), Science and technology plan of Shandong Provincial Department of transportation (2021B117), the National Natural Science Foundation of China (grant numbers 52178182 and 52108262). The authors gratefully acknowledge their financial support.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.