# Effect of Wetting Conditions on the In Situ Density of Soil Using the Sand-Cone Method
## 3 Results and Discussion  
### Effect of Moist Ground  
Table 4 summarizes the results of the sand-cone method for four different moist ground conditions. It compares the effect of a moist ground for test holes with different shapes and depths. The exact dry unit weight (\(\gamma_{\text{d(exact)}}\)) was calculated with the weight and volume of the vessel, which included the compacted soil before digging the artificial hole. The experiment dry unit weight (\(\gamma_{\text{d(experiment)}}\)) is the result of the sand-cone method. The dry unit weight determined from the sand-cone method (\(\gamma_{\text{d(experiment)}}\)) increased as the water content of compacted soil increased from 2% to 16%, regardless of the shape and depth of the test hole, as shown in Figure 6. In general, the unit weight of soil increased until the moisture content reached the optimum moisture content (OMC). The increase in the unit weight of soil, as shown in Figure 6, also illustrated this trend. The variation in the calculated dry unit weight and its error, depending on the water content of the compacted ground, were compared for the different types of holes (Figure 7). As the base shape of the test hole was changed from flat to sharp, and as the moisture content of the compacted soil increased, the error became increasingly severe. As the hole depth increased from 10 to 15 cm, the error generally decreased, regardless of the test-hole shape and the water content in the ground. In particular, the result for the cylindrical test hole with a flat base and a depth of 15 cm under slightly wet conditions (2%) had the lowest error, 1.04%. By contrast, the value for the conical test hole with a sharp base and a depth  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Hole Type**} & \multirow{2}{*}{ \begin{tabular}{c} **Ground** \\ **Water Content (\%)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Depth** \\ **(cm)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Moist** \\ **Volume** \\ **(cm)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Moisture Content (\%)** \\ **Unit** \\ **(cm)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Moisture Content (\%)** \\ **Unit** \\ **Weight** \\ **Weight** \\ **(kN/m3)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Moisture Content (\%)** \\ **Weight** \\ **(kN/m3)** \\ \end{tabular}  } & \multirow{2}{*}{\ \begin{tabular}{c} **Drop Unit** \\ **Weight** \\ **(kN/m3)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Error** \\ **Weight** \\ **(kN/m3)** \\ \end{tabular}  } \\ \hline C & 2 & & 1815.52 & 12.87 & 2.44 & 2.43 & 12.56 & 12.80 & \(-\)0.24(\(-\)1.88) \\ Y & 7 & & 1695.46 & 14.68 & 7.10 & 7.12 & 13.70 & 13.43 & 0.27(2.01) \\ L & 12 & & 1558.57 & 15.69 &  
of 10 cm under fully wet conditions (16%) showed the highest error, i.e., 22.54%. When the density degree of soil was expressed as loose and dense in previous studies [7; 8; 9], the difference in dry unit weight (density) between loose and dense appeared as 2-3 kN/m\({}^{3}\) (0.20-0.31 g/cm\({}^{3}\)). In this study, the result of the conical test hole, showing the highest dry unit-weight (density) error, showed a difference of 2.31 kN/m\({}^{3}\) (0.24 g/cm\({}^{3}\)), which can cause a very large defect when judging the compaction condition of the soil. On the other hand, the results of the cylindrical test hole with a depth of 15 cm showed a difference of less than 0.491 kN/m\({}^{3}\) (0.05 g/cm\({}^{3}\)). Figure 8 shows several wet, compacted grounds filled with dry colored sand. Similar behavior was observed, regardless of soil types, as shown in Figure 8a-d. Therefore, the field density could be incorrectly evaluated due to the ground wetness. When investigating the dry unit weight with the sand-cone method in the field, the use of a deep hole in a cylindrical shape can minimize the error due to ground wetting. Figure 6: Variation in the calculated dry unit weight of moist ground for different types of holes.