Proceedings of the
8th International Symposium on Geotechnical Safety and Risk (ISGSR)
14 – 16 December 2022, Newcastle, Australia
Editors: Jinsong Huang, D.V. Griffiths, Shui-Hua Jiang, Anna Giacomini, Richard Kelly
doi:10.3850/978-981-18-5182-7_11-018-cd
Influence of the Evapo-Transpiration Contribution by Long-Stem Planting on the Stability Assessment of a Back-Filled Slope
1DICAM Department, University of Bologna, viale del Risorgimento 2, Bologna, Italy
2Priority Research Centre for Geotechnical Science and Engineering, The University of Newcastle, Callaghan Campus, NSW 2308, Australia.
ABSTRACT
Evapotranspiration is a crucial phenomenon for the hydrological balance of the vadose zone; its evaluation is useful for those geotechnical problems in which climatic actions are impactful, as in the case of slope stability assessment. Yet, conventional engineering approaches ignore its impact on geotechnical design and assessment, due to the intrinsic complexity of the analysis required to achieve a rigorous solution to soil-vegetation-atmosphere interaction problems. An attempt in bridging the gap among researchers and practitioners in this field can be referred to a back-filled slope close to the traffic artery Inner City Bypass in Newcastle (Australia) that experienced in 2017 shallow landslides most likely due to heavy rains. To stabilise the slope, the use of drains at the toe of the slope together with long-stem planting have been proposed by Transport New South Wales (formerly Road and Maritime Services), the governmental agency responsible for building and maintaining road infrastructure. A native Australian plant, the Melaleuca Styphelioides, has been chosen for this purpose. A laboratory scale experiment has been carried out to evaluate the influence of a two years Melaleuca Styphelioides plant on the pore water pressure distribution in the site-specific soil when subjected to different hydraulic boundary conditions. The commercial Finite Element (FE) software Hydrus 2D by Pc-Progress has been used to reproduce the laboratory experiments and calibrate the root water uptake spatial distribution against experimental data. Subsequently, numerical models of the bank slope vegetated with an increasing number of plants (from 1 to 4) have been elaborated through the calibrated RWU model on a 50 days simulation period. Stability analyses, performed by means of the Limit Equilibrium method, were then performed on the different surface soil conditions and compared to a non-vegetated slope to highlight the influence of the soil-vegetation-atmosphere interaction on the stability assessment of the slope.
Keywords: Evapo-transpiration contribution, Slope stability, Long stem planting, Root water uptake.
