Evaluating the shear strength of a natural heterogeneous soil using reconstituted mixtures

Abstract

This work originates from the need to provide the geotechnical characterisation of a natural heterogeneous soil outcropping along a landslide-prone hillside. The soil, geologically identified as highly tectonised phyllite, results from the large tectonic strain deformation of the original weak rock, which produced a melange of grain particles enclosed in a fine matrix. This study investigates the possibility of estimating the shear strength using the framework established for binary mixtures to overcome the difficulties of undisturbed sampling. Two main problems were tackled: the identification of the matrix fraction in well-graded mixtures and the effect of variation in the grading of the granular fraction.

Design Strategies to Mitigate Slope Instabilities in Structurally Complex Formations

“…2015 [31]; Ruggeri et at. 2016 [32]; Ruggeri et al 2020 [33]), in the analysis of tunnels along the road (Paternesi et al 2017 [34]), and with more general studies of structurally complex formations (Scarpelli et al 2003 [35]; Ruggeri et al 2016 [36]; Ferretti et al 2019 [37]), aims at addressing possible design strategies to reduce the risk of inducing slope instabilities, dangerous releases of soil masses, and excessive stresses in the retaining structures. Because of the main structural features of the Blue Clay formation, the most effective design strategies could be found only on the basis of a detailed geological model, on the top of which geotechnical models could be implemented with due consideration of the pattern of existing discontinuities; in most cases, design solutions were sought with the aim of reducing stress release in the zone of influence of excavations.…”

A homogenization‐based state‐dependent model for gap‐graded granular materials with fine‐dominated structure

“…The soil is a typical gap‐graded granular material which is composed of small sand particles and large gravels. The sand particles in gap‐graded soils are typically created due to the degradation of rock blocks during the change of weather factors, for example, seasonal moist change and temperature oscillation 2–5 . The gap‐graded granular soils can also be created during transportation and further deposition process 6–9 .…”

“…Gap‐graded soils are usually treated as inhomogeneous materials, with the fines and voids being matrix and the aggregates being inclusions 10–12 . This type of soils are widely distributed in mountainous regions and are commonly used as construction and building materials 2,13 . The physical and mechanical properties of the gap‐graded soils are affected by the presence of rock aggregates, especially when there are partial contacts between the aggregates.…”

“…It is well recognized that the mechanical behavior of gap‐graded soils is associated with the coarse fraction: the behavior is dominated by fines with a fine fraction beyond the “transitional fine content,” and transients to be controlled by the coarse grain structure at a lower fine fraction 2,14,15 . In weathered residual soils, strong weathering induces fine‐dominated structure where the coarse aggregates are floating in the fine matrix 1,16 .…”

“…It is well reported that the coarse fraction effect is affected by the stress level, the initial density of the fine matrix, and the nature of rock aggregates 2,16,27–29 . To evaluate the coarse fraction effect on the mechanical behavior of gap‐graded granular soils, a new homogenization equation is adopted to correlate the overall tangent stiffness and the tangent stiffness of matrix.…”