Deterioration of an infrastructure cutting subjected to climate change

Abstract

Observations show that many soils in linear geotechnical infrastructure including embankments and cuttings undergo seasonal volume changes, and different studies confirm that this is due to cycles in climatic and hydrological conditions. These cycles can give rise to progressive failure of the soil mass, which in turn may lead to deterioration of performance and ultimately slope failure. It is expected that the magnitude of the seasonal cycles of pore pressure will be increased by more extreme and more frequent events of wet and dry periods predicted by future climate scenarios. In this paper, numerical modelling has been undertaken to simulate a continuous time series pore water pressure within a representative cutting in London Clay. The approach uses synthetic control and future climate scenarios from a weather generator to investigate the potential impacts of climate change on cutting stability. Surface pore water pressures are obtained by a hydrological model, which are then applied to a coupled fluid-mechanical model. These models are able to capture the significant soil–vegetation–atmospheric interaction processes allowing the induced unsaturated hydro-mechanical response to be investigated. The chosen hydraulic conductivity variables in the model are shown to affect the total magnitude of pore pressure fluctuation and hence the rate of progressive failure. The results demonstrate for the first time that higher total magnitude of annual variation in pore pressures caused by future climate scenarios can have a significant effect on deformations in cuttings. This in turn leads to increased rates of deterioration and reduces time to failure.

Strength parameter selection framework for evaluating the design life of clay cut slopes

“…To address this, later work allowed additional strain-softening beyond the average field failure strength towards a residual value (characterised by c ′ = 0 and reduction in ϕ ′ : Rouainia et al, 2020;. This decision was informed by the discussion in Leroueil (2001) regarding the progressive failure mechanism with localised softening to residual, and other sections remaining closer to peak which produces an average mobilised strength close to the back-analysed value.…”

“…Annual wet/dry cycles, and resultant effective stress changes drive shrink-swell behaviour and the accumulation of plastic deformations causing strain-softening, stress redistribution and progressive failure (Take and Bolton, 2011;Postill et al, 2020;Rouainia et al, 2020). For a single slope model, Figure 4a shows target annual pore pressure cycles at the mid-slope surface where one year is characterised by a cycle from 0 kPa (winter) to −40 kPa (summer) and then back to 0 kPa.…”

“…It is suggested that slope design using limit equilibrium analysis to examine stability related to seasonal ratcheting should include a conservative nearsurface water table. In addition, recent work has demonstrated the importance of changing climate and long duration wet periods increasing deterioration rates (Rouainia et al, 2020; and so the effects of realistic weather patterns and how these may change over time should be considered.…”

Emulating computer experiments of transport infrastructure slope stability using Gaussian processes and Bayesian inference

“…This subsection is a summary of the key mechanisms and properties that influence the slope deterioration behavior in the GM used in our simulator. For more detail, see Rouainia et al (2020) and Postill et al (2021).…”

Centrifuge modelling of rainfall-induced slope failure in variably saturated soil

“…Thus, we still lack well-instrumented and documented physical models to confirm the mechanisms involved. On the other hand, rainfall infiltration in unsaturated soil deposits has been the object of several theoretical and numerical studies [1,6,24,36]. Those models rely on comprehensive experimental data obtained from element tests and physical model tests.…”