Case Studies and Benchmark Examples for the Use of Grading Entropy in Geotechnics

Abstract

Abstract:The grading entropy concept can be adapted to the field of geotechnics, to establish criteria for phenomena such as particle packing, particle migration and filtering, through a quantified expression of the order/disorder in the grain size distribution, in terms of two entropy-based parameters. In this paper, the grading entropy theory is applied in some geotechnical case studies, which serve as benchmark examples to illustrate its application to the characterisation of piping, softening and dispersive soils, and to filtering problems in the context of a leachate collection system for a landfill site. Further, since unstable cohesive (dispersive) soils are generally improved by lime, the effect of lime addition is also considered, on the basis of some measurements and a further application of the grading entropy concept, which allows evolutions in the entropy of a soil to be considered as its grading is modified. The examples described support the hypothesis that the potential for soil erosion and particle migration can be reliably identified using grading entropy parameters derived from grading curve data, and applied through an established soil structure OPEN ACCESSEntropy 2012, 14 1080 stability criteria and a filtering rule. It is shown that lime modification is not necessarily helpful in stabilizing against particle migration.

Some Comments on the Entropy-Based Criteria for Piping

“…This observation was described and validated in the previous work [12] by demonstrating that the cover layer was erodible, according to the criterion of Lőrincz [13]. This previous validation is reiterated for two typical piping sites in the next section, and then further validated by the consideration of some new data on soils that have been washed out during piping events, in the section that follows.…”

“…This technical note is an extension of a previous work [12] to provide some clarification regarding the failure mechanism in cases of piping. It combines a short description of an entropy based internal stability criterion (see further details in [13]) and the description of the piping failure mechanism in Hungarian dikes, with some additional research.…”

“…The above data is augmented by more recent data for the washed-out soil materials, sampled from sites of piping events at Bölcske on the Danube river, and at Tiszasas and the Tisza right bank on the Tisza river [12]. Typical grading curves for these soils are shown in Figures 12 and 13.…”

“…In previous work [12], it was proposed that the soils washed-out from beneath the dikes originate from the cover layer, on the basis of only four samples. In this paper, the idea is tested further using measured data for 20 additional washed-out soil samples.…”

The Grading Entropy-based Criteria for Structural Stability of Granular Materials and Filters

“…The engineering performance of these soils in their different applications depends upon achieving a stable internal granular structure in their compacted condition (see e.g., [1][2][3][4][5][6][7][8][9][10]). Internal instability may result in various types of particle migrations like erosion, piping and suffosion in the case of flowing water (see e.g., [10][11][12][13][14][15]).…”