An empirical relationship of permeability coefficient for soil with wide range in particle size.

Purpose: Permeability is one of the primary concerns in geotechnical engineering research. The permeability coefficient, the most significant parameter defining permeability, has a significant impact on the mechanical and physical properties of the soil by virtue of its value. Because soil is a bulk material and its internal seepage channels are intricate, it is challenging to accurately describe those using straightforward physical parameters. As a result, the models currently in use for calculating the coefficient of permeability of soils are mostly skewed towards empirical statistics and have issues with uneven magnitude and ambiguous physical significance. Thus, one of the key scientific issues in the field of geotechnical engineering is the development of a permeability coefficient estimate model that can characterize the seepage channel. Methods: Based on the idea of hydraulic radius in circular pipe flow, this paper establishes the calculation method of the equivalent hydraulic diameter by analyzing the microstructure of the soil body and proposes the idea of equivalent hydraulic force inside the soil body, taking into account factors such as granular gradation, dry density, and specific gravity of solid particle. Furthermore, a theoretical model based on the equivalent hydraulic diameter has been constructed for the permeability coefficient of the soil body, by introducing the coefficient of fluid dynamic viscous and the water gravity. In order to assess the accuracy and validity of the equivalent hydraulic diameter and the model of soil permeability coefficient estimation, permeability tests were designed and the results of undisturbed loess, single particle size quartz sand, and multi-grain-size quartz sand combinations were obtained. The results of the estimated model, the traditional estimated model, and the permeability coefficient of the tests were compared and analyzed. Results and conclusions: The findings indicate a square relationship between the permeability coefficient and the equivalent hydraulic diameter and a correlation coefficient of more than 97% between the equivalent hydraulic diameter calculation results and the measured permeability coefficient results; the error analysis results demonstrate that the equivalent hydraulic diameter calculation results can meet the permeability test error range. This paper presents an estimation model for the soil permeability coefficient that is universally applicable to a wide range of particle sizes (0.002 to 2 mm). It is compared with experimental test results, Terzaghi formula, Hazen formula, and Amer formula. The results demonstrate that the model developed in this paper has a higher degree of agreement with the experimental results. [ABSTRACT FROM AUTHOR]