Effects of compaction on internal stability of granular soils: An experimental evaluation of particle-based methods

Internal instability occurs when the filtrate under the influence of strong seepage forces accompanies the finer fraction from broadly graded granular soils and induces marked changes in its original particle distributions. The changes in particle size distribution may occasionally render the granular filters ineffective in retaining the protected base soils. A prior assessment of internal instability potential is emphasized through some of the well-accepted constriction and particle size-based criteria. The former criteria are too computationally complex to apply in practice, while the latter require only the particle distribution of a soil and are thus preferred by the practitioners for prompt assessments of internal stability. In this study, gradient-controlled hydraulic tests conducted over a range of variably compacted soils were used to analyze some of the existing criteria, which showed partial success in assessing the current test specimens. Further analysis facilitated a useful revision of a well-accepted criterion, which could then reliably interpret the current test results with enhanced accuracy. Additional experimental data from 15 published filtration studies could further validate the current revision, which incorporates both the particle size distribution and relative density of soils, thus making it more appealing for practitioners. Furthermore, a couple of real-life design examples presented to demonstrate the advantages and implications of the current proposition for practical purposes