Mechanical sensitivity to hydrochemical processes of Monastero Bormida clay

Abstract

[1] The paper presents the results of an experimental study on the mechanical behavior of a marly clay, motivated by the recurrent episodes of slope failure induced by intense rainfall events over the area of Langhe (NW Italy). The sensitivity of the material to environmental actions has been systematically explored by reproducing on laboratory samples hydrological and chemical processes similar to those expected to arise on site. Chemomechanical effects due to pore fluid dilution and decalcification have been investigated by testing both reconstituted and intact samples with different degrees of weathering. Pore water salinity was found to have minor consequences on the mechanical behavior of the material at its intact state and at the original calcite content. Decalcification enhanced the chemical sensitivity of the clay minerals constituting the soil matrix, not only by affecting the residual shear strength and the stiffness, but also by magnifying the tendency to swell under chemical loads, inducing a chemical sensitivity over swelling on saturation and enhancing water retention properties. Field observations also support the hypothesis that decalcification followed by interstitial pore water dilution are key factors to take into account to understand the degradation of the mechanical properties and that these phenomena can enhance the instability onset.

Design Strategies to Mitigate Slope Instabilities in Structurally Complex Formations

“…Physio-chemical modification of soil properties along the discontinuities, due to the groundwater flow along the joints, producing processes of alteration of ionic composition of pore water, dissolution of carbonates, and swelling (Hawkins and McDonald 1992 [11]; Di Maio and Fenelli 1994 [12]; Di Maio 1996 [13]; Forlati et al 1998 [14]; Musso et al 2008 [29]).…”

Shear Resistance Variations in Experimentally Sheared Mudstone Granules: A Possible Shear‐Thinning and Thixotropic Mechanism

“…The sliding zone exposed in an exploratory tunnel (Tang et al, ) in the Sanmashan landslide is shown in Figure S4e. The shiny zones in the image correspond to smooth, slickensided areas resulting from large landslide displacements, which are a common feature in shear zones in clay‐bearing soils (e.g., Moore & Lockner, ; Musso et al, ; Skempton, ; Wang et al, ). Evidence of mudstone granules surrounded by muddy matrix also can be seen.…”

Microbiological induced carbonate (CaCO3) precipitation using clay phyllites to replace chemical stabilizers (cement or lime)

“…The results obtained to assess the water retention properties (hygroscopicity and water storage capacity) are presented below. Water retention is essential for understanding the swelling capacity of the tested clay materials and soils (Musso et al, 2008). Figure 15 show the water retention curves (WRC) obtained, for the different materials during drying branch in function of the sample water content.…”