Which method is NOT recognized for soil classification according to standards?

The recognition of classification methods for soil often stems from established engineering practices and testing standards. In this context, expert judgment alone is not a formal method of soil classification. While expert judgment can certainly play a role in interpreting data and making decisions based on experience, it lacks the systematic approach and repeatability that recognized methods provide.

Visual analysis, manual analysis, and established testing methods are all structured ways to classify soil. Visual analysis involves looking at soil characteristics such as color, texture, and structure to make observations. Manual analysis typically includes tactile assessments, such as feeling soil to determine its texture when wet or dry. Established testing methods refer to standardized procedures, like sieve analysis, Atterberg limits, and moisture content tests, which yield quantifiable and reproducible results.

By relying solely on expert judgment, there is a risk of subjective bias, which can lead to inconsistent classification outcomes. Therefore, expert judgment is not considered a reliable or formal method for soil classification according to engineering standards.