Modelling weathering effects on the mechanical behaviour of rocks

Abstract

The paper presents an experimental, theoretical and numerical approach in order to describe the effects of rock weathering on bonded geomaterials. The term rock weathering is used to refer to a number of chemical and physical phenomena that continuously transform a rock mass into granular soil. From an engineering point of view, rock weathering can be interpreted as a generalised decay of the mechanical properties of the original material. It acts at a constitutive level essentially by reducing the strength of the bonds joining the grains together. Such a material degradation can occur in a time scale which is comparable to the average life of engineering structures. Weathering can be crucial for what concerns the stability of slopes, cliffs and abandoned underground caves. In the experimental part of the paper micro and macro experimental investigations performed on calcarenite, a natural soft rock, are shown; short-and long-term debonding processes are identified as characterising rock weathering. A large set of hydro-chemo-mechanical data are recovered to properly characterise debonding processes by means of specific weathering tests. In particular, to reproduce long-term rock weathering in laboratory time, the progressive chemical debonding has been induced through the exposition of the rock to a uniform flow of an acid solution. In the theoretical part, it is shown how the progressive deterioration of the intergranular bonds due to weathering has been modelled satisfactorily by extending a strain hardening elastoplastic model by means of multiscale approach coupling hydro-chemo-mechanical processes. Such a model has been corroborated by simulating some tests of the previous part. Finally, in the numerical part of the work, some boundary value problems are presented, in which weathering effects cannot be neglected.

Modelling the risk of deterioration at earthen heritage sites in drylands

“…Dunkerley, 1997; Kerner et al ., 2002; Nield and Baas, 2008a), but vertical‐plane processes, such as the deterioration of wall faces, have rarely been investigated using CAs. This is partly a result of vertical‐plane processes being generally undertaken over scales small enough to apply computationally expensive models, which are able to capture the complex stresses and strains within vertical materials (Ciantia and Castellanza, 2016; Zhang et al ., 2016a; Allen, 2019). However, such computationally expensive solutions cannot be applied to earthen sites, where walls regularly span hundreds of metres.…”

Role of Brittle Behaviour of Soft Calcarenites Under Low Confinement: Laboratory Observations and Numerical Investigation

“…A review of numerical techniques used in rock slope stability analysis, with recent developments in the application of continuum and discontinuum numerical codes, is proposed by Stead et al (2006). With regard to the assessment of stability of underground cavities, Parise and Lollino (2011), Lollino et al (2013), Ferrero et al (2010, Suchowerska et al (2012) and Ciantia and Castellanza (2016), just to mention few examples, apply the elastic-perfectly plastic model, using either the Mohr-Coulomb or the Hoek-Brown failure criterion, to simulate the behaviour of intact rock masses surrounding the cavities examined.…”

Characterization of Weathering Processes of the Giant Copper Deposit of Tizert (Igherm Inlier, Anti-Atlas, Morocco)

“…The structure, the porosity and the permeability of the host rocks and the presence of faults/fractures facilitate the percolation of meteoric waters, and therefore, control the flow of supergene fluids [3,47]. In addition, the nature of the host rocks (e.g., limestone or dolostone) influences neutralization processes of acidic fluids [2,48,49]. The weathering profile can be separated into different zones.…”