# A Practical Group Symbol and Group Name Approach (PSNA) according to EN ISO 14688-2:2018
## 3 Practical Group Symbol and Group Name Approach (PSNA)
### PSNA for Fine Material  
The plasticity chart specified in the EN ISO 14688-2:2018 [21] standard was utilized to determine the distribution of fine particles within a soil mass. A flow chart was prepared for the categorization of fine materials (Figure 5). The location of fine particles on the PI versus LL plot determined the group symbol for the fine particles. The initial symbol defines the dominant fine particle, such as Cl or Si. The secondary capital letter provides information about the plasticity of fine material. The plasticity symbol was identified according to LL% values. The secondary symbols changed according to plasticity, such as low, medium, high,and very high (Table 3). L, M, H, and V were employed for low, medium, high, and very high [21], respectively in this study.  
Initially, 50% or more than 50% of soil particles that passed sieve No. 230 were divided into four subgroups according to LL percentages and used in proper categorization according to their plasticity. For this purpose, if an LL% value is <35%, the plasticity of fine particle is categorized as \"Low (L)\". If the LL% value is \(\geq\)35% to 50%, the plasticity of the  
Figure 5: Flow chart of fine particles.  
fine particle is categorized as \"Medium (M)\". Similarly, if the LL% value is \(\geq\)50% to 70%, the plasticity of fine particle is categorized as \"High (H)\". Lastly, if an LL% value is \(\geq\)70, the plasticity of the fine particle is categorized as \"Very High (V)\". The other assessment of fine particles is performed using the PI plot and A line. If the location of the PI versus LL plot fell to PI < 4 or below the A line, the soil was identified as \"Si\". If the location of the PI versus LL plot fell to 4 \(\leq\) PI \(\leq\) 7 and on or above the A line, the soil was identified as \"Cl-Si\". Lastly, if the location of the PI versus LL plot fell to PI > 7 and on or above the A line, the soil was identified as \"Cl\".  
The process of symbolization was executed by following these sequential steps. While fine particles can also contain coarse particles, EN ISO 14688-2:2018 does not explain this type of composite soil and so ASTM D2487-17e1 is employed. According to the ASTM D2487-17e1 standard, coarse particles in fine materials are not added to the symbol. However, the group name is determined according to the coarse percentages within them. The same method was used in this proposed approach as in ASTM D2487-17e1 (Figure 5). The classification of soil should consist of both a group name and a group symbol. If only a symbol is used, it can be misleading.  
For the definition of group name, three different percentages were used in this study according to ASTM D2487-17e1:  
1. _If the coarse particle in fine material retained on No. 230 sieve is less than 15%, no expression is not added to the group name (e.g., CIH: High Plasticity Clay)._
2. _If the coarse particle retained on the No. 230 sieve is between \(\geq\)15-30%, the dominant coarse particle name is added at the end of the group name such as \"with gravel \"or \"with sand\" (e.g., CIH: High Plasticity Clay with sand)._
3. _If the coarse particle retained on No. 230 sieve is more than \(\geq\)30%, the initially dominant coarse particle name was added such as \"Gravelly\" or \"Sandy\". Then, secondary coarse material was assessed. If secondary coarse material percentages are less than 15%, secondary coarse material was not considered (e.g., CIH: Gravelly High Plasticity Clay). If this percentage is 15% or more than 15%, additionally \"with gravel \"or \"with sand\" was added to the end of the group name (e.g., CIH: Gravelly High Plasticity Clay with sand)._