# Assessment of Spatial Variability in Ground Models Using Mini-Cone Penetration Testing
## 5 Conclusions  
To evaluate spatial variability in uncertain ground conditions, it is challenging to conduct field experiments. Therefore, we investigated the spatial variability in two types of ground models. Using a Mini-Cone Penetration Test apparatus, cone penetration resistances were measured at each location. Based on the measured cone penetration resistances, coefficients of variation, and vertical and horizontal _CLs_ were calculated. The conclusions of this study are as follows:  
1. Below the 50 mm threshold, the coefficient of variation (\(CV\)) was found to be relatively stable. Especially, in the silica sand ground model, the average \(CV\) was measured at 6.76%, indicating minimal variability and suggesting a well-composed homogeneous ground model. In contrast, the weathered soil ground model exhibited a \(CV\) of 13.70%, showing a comparatively higher level of variability than that of the silica sand ground model.
2. The horizontal _CL_ was calculated using the average cone penetration resistance measured at each point. The _CL_ for the silica sand ground in the two-soil layer was calculated to be smaller than that for the silica sand ground in the single soil layer and the weathered soil ground in the two-soil layer. This is believed to be due to the lower penetration depth in the silica sand ground of the two-soil layer, and the impact of having fewer data points (smaller separation distances). This suggests that further research may be needed, such as conducting experiments with more data points or deeper penetration.
3. In the calculation of vertical _CLs_, the \(CV\) for the silica sand layer was observed to be very low, confirming the validity of the _CL_ calculations. In contrast, the \(CV\) for the weathered soil layer was relatively high. This is believed to be a result of the homogeneous particles of the silica sand layer and the various particles of the weathered soil layer, which are considered to be the primary influencing factors on vertical _CLs_.
4. The results of this experiment, conducted under the assumption of a homogeneously built ground model, revealed that the ground model exhibits less variability compared to the average variability observed in the field. The observed variability suggests that evaluating spatial variability through field and laboratory tests requires careful consideration of the non-homogeneity present in field conditions.  
Although it is very important to consider spatial variability for the accurate evaluation of soil behavior, spatial variability in soils in the reduced scaled tests such as the 1 g shaking table test has rarely been considered. The results obtained from this study such as the \(CV\) and _CL_ values can be used for further numerical study considering spatial variability. Obtaining the \(CV\) and _CL_ values for various ground models in the laboratory can enhance the accuracy of the numerical study of spatial variability in soils.  
Writing--original draft preparation, S.J.; project administration, review and editing, Y.L., H.K. and J.P.; review, editing and supervision, D.K. All authors have read and agreed to the published version of the manuscript.  
This study is supported by the Korea Hydro and Nuclear Power Co., Ltd. (KHNP).  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author/s.  
Authors [PERSON], [PERSON] and [PERSON] were employed by the company Korea Hydro and Nuclear Power Co. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.