Experimental identification of the dominant fabric in widely graded soils

Jentsch, H. and Winkler, P. and Salehi Sadaghiani, M. and Witt, K. (2016) Experimental identification of the dominant fabric in widely graded soils. In: ICSE 2016 (8th International Conference on Scour and Erosion), 12-15 September 2016, Oxford, UK.

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Abstract

To estimate the vulnerability of widely graded soils to internal erosion, the soil structure has to be analysed. Based on the theory of the bimodal fabric, each particle size distribution (PSD) has a unique diameter that divides the PSD into particles of the soil skeleton and finer mobile particles. The particle diameter, which divides the PSD into these two fractions, is defined as the separation point (dT) and part of the soil skeleton. In this study the Sequential Fill Test (SFT) is used to identify the mobility of particle fractions and the soil matrix. This study is an extension of a series of descriptions of this particular test method. The paper is focused on a widely graded PSD, which is prone to internal erosion. This study demonstrates the change of the soil matrix by variation of the amount of the fine particles. The soil matrix of the investigated PSD does not change until the pore volume is completely filled with mobile particles. If the mobile particles filled completely the pore volume of the coarse soil skeleton, they become also part of the soil skeleton. This matrix is called dual matrix. With further increase of the amount of fine particles, the coarse skeleton is replaced by a new skeleton, where all particles belong to the soil skeleton. For the assessment of a selected PSD, which is prone to internal erosion, it is important to identify the amount of fine fractions, which can stabilize an internally instable dominant fine matrix (i.e. building a dual matrix).

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