Indirect and Direct Consideration of Microstructure in a Constitutive Model

Abstract It is important to describe and quantify microstructure when modelling microstructure-related behaviour of soils. There are indirect and direct methods to consider microstructure in modelling. Indirect methods only consider the impact of microstructure on soil behaviour. Whilst direct methods focus on geometric and structural features of microstructure such as pore size distribution (PSD). This paper presents two examples of indirect and direct consideration of microstructure in a constitutive model. The indirect method considers the microstructural impact through effective degree of saturation and the direct method adopts the pore size distribution as microstructure index. The performance of each approach is evaluated based on experimental results and it is found that both have good performance in studying the hydro-mechanical behaviour of soils while the direct method can provide more information of microstructure.