# 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 Coarse Material
#### (a)  
_Less than 5% fine content_  
Gravel or sand were described as clean if fine percentages were less than 5%. Therefore, the presence of fine content did not affect the symbol name of the soil classification. EN ISO 14688-2:2018 uses C\({}_{\rm u}\) and C\({}_{\rm c}\) to define group names and group symbols for coarse particles. The definitions of C\({}_{\rm u}\) and C\({}_{\rm c}\) were used for the particles that include less than 5% fine content. C\({}_{\rm u}\) and C\({}_{\rm c}\) were divided into five subgroups (Table 2) according to EN ISO 14688-2:2018. The definitions of subgroups in EN ISO 14688-2:2018 provide a means  
Figure 4: Flow chart of coarse particles (**a**) flow chart for gravel and sand, (**b**) flow chart for gravel, (**c**) flow chart for sand. for more precise categorization, although the accompanying explanations do not include group symbols. Hence, the initial capital letters of grading shape terms were employed as secondary letters of symbolization in the present study. For this purpose, \"U\" was used for \"Uniformly\" graded, \"P\" was used for \"Poorly\" graded, \"M\" was used for a \"Medium\" graded, \"W\" was used for a \"Well\" graded, and \"G\" was used for \"Gap\" graded (e.g., GrU: Uniformly Graded Gravel). In cases where grain size was absent, the gap-graded term was employed according to EN ISO 14688-2 (e.g., GrG: Gap Graded Gravel). The grading system outlined in ASTM D2487-17e1 is categorized into the following two distinct subgroups: well and poorly. In contrast, the definition of grading shape provided by EN ISO 14688-2:2018 is more comprehensive when compared to that of ASTM D2487-17e1. _(b)_ _Between 5-12% fine content_  
If the fine percentages in coarse material were between 5-12%, the material was marked with the dual symbol, as can be seen in Figure 4. In this section, the definitions of C\({}_{\rm u}\) and C\({}_{\rm c}\) were considered for the identification of particles. Also, it is necessary to utilize a plasticity chart in order to define fine materials such as clay, silt, or silty clay. The plasticity chart requires LL % and PI % parameters for fine material (Figure 1). LL% and PL% laboratory tests were carried out according to ISO 17892-12 [38]. Plasticity was not considered for coarse particles, and thus only the initial two letters of the plasticity symbol were utilized. 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 and so both symbols were used together. Therefore, the symbolization is longer than that of other group symbols, but only at this identification (e.g., SaW-SaClSi). 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 primary group symbol defined the dominant coarse particle and the shape of the grading curve. The secondary group symbol, denoting the presence of fine material within coarse particles was defined according to the plasticity chart (e.g., GrP-GrCl). _(c)_ _More than 12% of fine content_  
If fine percentages in the coarse material were greater than 12%, the group name and group symbol were identified according to the plasticity chart. The plasticity chart was employed to define fine materials such as clay, silt, or silty clay. PI < 7, 4 \(\leq\) PI \(\leq\) 7, and PI > 7 were determined based on the definition and marking symbols. The initial two letters (the first letter is capitalized) defined primary coarse material and the secondary capital letter defined fine fractions in coarse material (e.g., SaSi, GrCl). If the location of LL versus PI fell to 4 \(\leq\) PI \(\leq\) 7 and plots on or above the A line, the particle was defined as CIL-SiL. In this situation, the group symbol was marked as \"GrCl-GrSi\" and \"SaCl-SaSi\". _(d)_ _Secondary coarse content_  
The final assessment of coarse material is for secondary coarse grain.