# 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)
Therefore, the approach presented here facilitates the description of the materials in detail. In geotechnical applications, providing a comprehensive account of soils contributes to the process of decision-making. EN ISO 14688-2:2018 designates symbols for particles such as Cl for clay, Si for silt, Sa for sand, and Gr for gravel. These same symbols were used as the initial two letters of identification in this study but were insufficient to mark the soil mixtures properly. Soil particles were classified and marked with group symbols properly using EN ISO 14688-2:2018 and ASTM D2487-17e1 together, the idea being to develop an approach where EN ISO 14688-2:2018 can be used in practice. The study is based on EN ISO 14688-2:2018. In accordance with this line of reasoning, the utilization of EN ISO 14688-2:2018 was employed to establish precise delineations and definitions of grain particle boundaries. However, in cases where EN ISO 14688-2:2018 fails to adequately define soil grains or where the division of grains is not feasible, ASTM D2487-17e1 was employed. This is because the current state of EN ISO 14688-2:2018 does not allow for the detailed classification of grains. According to EN ISO 14688-2:2018, a group symbol (CIL, SiM, etc.) can be assigned to fine-grained soils from the plasticity chart. Nevertheless, this standard does not include any specific details regarding the required percentages of fine grains that a sample must contain to be classified as fine-grained. According to Table 1 of the EN ISO 14688-1 standard, which is also utilized by the EN ISO 14688-2:2018 standard, the group symbols Gr and Sa are designated for Gravel and Sand, respectively. However, the specific percentages of coarse grains necessary for soil to be classified as coarse-grained are not specified. Furthermore, while classifying the mixed materials, the percentage of the secondary fraction is not specified. Hence, it is not feasible to conduct a comprehensive classification using this particular standard. Hence, a novel approach was required to define the soil in detail and thus PSNA was developed. According to EN ISO 14688-2:2018, the classification of very coarse material should be performed on that material alone. Additionally, it is asserted that coarse and fine material should be classified together. Therefore, coarse and fine materials were classified together in this study. According to PSNA, the soil was divided into coarse, fine, and organic particles. In this study, the proposed method was used to explain coarse, fine, and organic materials in three sections. The first section includes the identification and final marking of coarse material (gravel and sand), the second section includes the identification and final marking of fine material (silt and clay), and the third section includes organic material. The determination of particle size boundaries for PSNA was conducted using the data provided in Table 1.  
Initially, a determination was made regarding the granular composition of the soil material, which was classified as either coarse or fine. According to EN ISO 14688-2:2018, there is a 0.063 mm (No. 230 sieve) boundary size between coarse and fine material. Nevertheless, the standard EN ISO 14688-2:2018 lacks a comprehensive explanation regarding the inclusion of percentage ratios and the specific criteria used to delineate the boundaries between coarse and fine materials. The application of the ASTM D2487-17e1 methodology involved the utilization of logical reasoning to initially separate the coarse and fine materials. For this purpose, if more than 50% of total soil particles were retained on 0.063 mm, a material was defined as coarse. Alternatively, if 50% and more than 50% of the total soil particles passed through a sieve opening of 0.063 mm (No. 230 sieve), the material was defined as fine. The boundary between coarse and fine materials, defined by EN ISO 14688-2:2018 at a size of 0.063 mm, was utilized in this study. This standard differs from the classification specified in ASTM D2487-17e1 which employs a No.