## 6 Conclusions  
The Saemangeum project is underway for road, railway, and port constructions for internal development. Suitable granular soil for embankment material is difficult to find in the Saemangeum  
Figure 21: The actual model test photos at 50 mm loading plate vertical displacement; (a) Case 1; (b) Case 2; (c) Case 3; and (d) Case 4.  
area. However, silty clay is widely distributed. Thus, this research will maximize the utilization of clayey soil, which will serve as an effective, alternative solution to the limited supply of good quality, granular fill materials in the Saemangeum projects or any applicable locations.  
A series of model bearing capacity tests were carried out as basic research to investigate the feasibility of clayey soil being utilized as embankment material. The main conclusions drawn from the series of model bearing capacity tests are as follows:  
* Clayey soil with NMC exhibited large deformation and low bearing capacity. However, when clayey soil is well-compacted with OMC, it exhibited a higher bearing capacity than dense sand;
* The bearing capacity of loose sand was constant regardless of vertical displacements, and the bearing capacity of dense sand was found to be maximum at the point where vertical displacement is at \(0.08B\). The bearing capacity of dense sand was about 2.5 times larger than that of loose sand;
* When the clayey soil was reinforced with composite geotextiles only, the bearing capacity improvement was small, and its bearing capacity is smaller than that of the combination of clayey soils and crushed gravel;
* The bearing capacity of clayey soil in combination with crushed gravel and composite geotextiles was significantly higher than that of clayey soil and crushed gravel only. Also, its bearing capacity was similar to, or larger than, that of dense sand.  
From the viewpoint of bearing capacity, it is considered that clayey soil can be used as embankment material when the clays, crushed gravel, and composite geotextiles are properly combined.  
Conceptualization, M.-S.W.; Data curation, C.P.L.; Formal analysis, M.-S.W., C.P.L. and Y.-C.G.; Funding acquisition, M.-S.W.; Investigation, C.P.L.; Supervision, M.-S.W.; Writing--original draft, C.P.L.; Writing--review and editing, C.P.L. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the Technology Innovation Development Project of the SME (C0565624, Development of Technology to Utilize High-Strength Clay Soils as Efficient Soil Materials), Brain Korea 21 Plus Project (22A20152713403) funded by the Ministry of Education and National Research Foundation of Korea (NRF), and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (20183010025200).  
This study was carried out as a part of the Technology Innovation Development Project of the SME (C0565624, Development of Technology to Utilize High-Strength Clay Soils as Efficient Soil Materials), Brain Korea 21 Plus Project (22A20152713403) funded by the Ministry of Education and National Research Foundation of Korea (NRF), and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (20183010025200).  
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.