Coupled hydro-mechanical modelling of soil–vegetation–atmosphere interaction in natural clay slopes

Abstract

Soil-vegetation-atmosphere interaction is long known to induce significant pore pressure variations at shallow depths and associated superficial slope movements. Recent findings suggest that the effect of this interaction may also extend to large depths in natural clay slopes. Multiple examples of weather-induced deep landslide mechanisms can be found in the Southern Apennines (Italy), where slopes are often formed of fissured clays. The relationship between the activity of these landslides and the hydro-mechanical processes due to soil-vegetation-atmosphere interaction was investigated herein by means of a two-dimensional coupled hydro-mechanical finite element analysis. A constitutive model capable of simulating the behaviour of highly overconsolidated clays, in both saturated and unsaturated states, was adopted in the analysis, in conjunction with a boundary condition capable of reproducing the combined effects of rainfall infiltration, evapo-transpiration and run-off. The results of the analysis corroborate the connection between weather conditions, pore pressure variations and slope movements in natural clay slopes. The importance of reproducing adequately the geological history of a natural slope in order to define its current state is also demonstrated.

Two-Scale Investigation of the Retention Behavior of a Well-Graded Mixed Soil

“…This is an ideal behavior that is intermediate between that of swelling soils recovering full saturation at negative pore pressures [18] and that of soils needing positive pore pressures to be fully saturated, for which suction disappears at relatively low saturation degrees, i.e., right, and left of the intermediate behavior ([19]; Figure 2; Table 1). This last behavior, due to air entrapment upon wetting, is typical of coarse-grained soils [20][21][22] but it has also been observed for fissured natural clays [23]. In the following, the retention behavior of the mixed soil under study will also be discussed in light of the frameworks presented in both Figures 1 and 2.…”

“…Geosciences 2021, 11, 431 3 of 21 left of the intermediate behavior ([19]; Figure 2; Table 1). This last behavior, due to air entrapment upon wetting, is typical of coarse-grained soils [20][21][22] but it has also been observed for fissured natural clays [23]. In the following, the retention behavior of the mixed soil under study will also be discussed in light of the frameworks presented in both Figures 1 and 2.…”

The importance of permeability in modelling soil-atmosphere interaction

“…Mechanical soil properties, such as stiffness and strength, have traditionally monopolised the interest of practicing geotechnical engineers and researchers. The effect of pore water pressures (pwp) and of their variation on the stability and serviceability of geotechnical structures [1][2][3] and natural slopes [4,5], and on the coefficient of earth pressure at rest [6], has also long been recognised. Although, by association, the influence of hydraulic parameters, such as permeability and soil-water retention, is widely accepted in theory [7,8], in practice it is rare that complete and comprehensive laboratory and field data are dedicated to determining hydraulic parameters with accuracy and confidence, perhaps owing to the difficulty of the task.…”

The Use of Soil Moisture and Pore-Water Pressure Sensors for the Interpretation of Landslide Behavior in Small-Scale Physical Models

“…Despite considerable efforts and advancements in understanding of the physical processes and mechanisms responsible for landslide initiation due to rainfall infiltration [ 6 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ], the issue remains a major concern for the landslide scientific community. At the same time, many researchers are emphasizing the need for faster implementation of new knowledge into engineering practices, as the gap between the state of the art and the state of the practice continues to widen.…”

“…Various approaches have been successfully applied to investigate the hydraulic and mechanical response of slopes exposed to different rainfall conditions and the mechanisms leading to the initiation of rainfall-induced landslides. For example, numerical modelling has been successfully used to investigate how different factors affect the stability of both shallow (e.g., [ 1 , 7 , 8 , 10 , 16 , 17 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]) and deep-seated landslides under different rainfall conditions (e.g., [ 19 , 43 , 44 , 45 , 46 , 47 , 48 ]). Field monitoring has been successfully used to observe the hydraulic and mechanical performance of slopes in different geological and climatic contexts (e.g., [ 7 , 17 , 21 , 22 , 31 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ...…”