查看更多>>摘要：? 2021 Elsevier B.V.The construction of the Three Gorges Reservoir (TGR) has considerably increased landslide hazard due to the 30-m annual fluctuating reservoir water level. In this study, the influence of permeability on the stability of dual-structure landslide with different deposit-bedding interface (DBI) morphology were comprehensively investigated. A landslide database including 560 recorded dual-structure landslides was built for the statistical analysis. The DBI morphology, the slope structure and the permeability were classified and presented. The statistical analysis of the DBI morphological parameters indicates that the armchair type (AT) is the most popular in over-dip landslide, the curved type (CT) is very widespread in anaclinal landslide, the stepped type (ST) is the most common DBI morphology in over-dip landslide, and the linear type (LT) could be found widely at the under-dip landslide. Two conceptual models, downslide-locked model and locked model, were proposed according to the change rules of the dip angle of the DBI. The stability for these two conceptual models were analyzed and modeled as well as verified by specific case studies. The numerical results manifest that the permeability and the DBI morphology could pose significant impacts on the stability of the dual-structure landslide. Deepening our understanding of the effect of the fluctuating reservoir water level on the factor of safety (FOS) of the defined conceptual models, which are of paramount importance to improve the design of mitigation countermeasures and, consequently, to reduce fatalities and property losses in the TGR and many other analogous reservoir areas.
查看更多>>摘要：? 2021 Elsevier B.V.Earthflows are widespread phenomena in the Mediterranean area. These landslides involve fine-grained soils and clay-bearing rocks, and despite their low speed are responsible for significant economic losses in vast areas. The dynamics of these landslides is still relatively obscure thus reducing our ability to forecast and mitigate their effects. In this study, we present a methodological approach for the characterization of active earthflows based on the combination of geophysical surveys, laboratory tests, and empirical formulas. Geophysical surveys consist of periodic measurements of Rayleigh wave velocities repeated over time to evaluate the change of stiffness with time of the landslide material. Laboratory tests combine Atterberg limits, fall cone and oedometric tests and allow to constrain the empirical correlations between geophysical and geotechnical properties. The method is designed to obtain relevant data when direct methods like boreholes or geotechnical soundings are not possible for safety reasons, with the aim of investigating the solid-to-fluid transition that can occur in rapid earthflows. We applied this approach to study the Montevecchio landslide (Northern Apennines of Italy), an active earthflow in young marine clays which was affected by multiple reactivations in the recent years. Results show that after a surge the earthflow material is very soft (shear wave velocity in the order of 50–60 m/s) and characterized by a high water content. However, the exact value of the Liquidity Index remains unknown due to the lack of direct measurements and to the uncertainty dictated by the empirical relationships.
查看更多>>摘要：? 2021This research develops a framework for determining cyclic and transient volume changes in unsaturated expansive clays using suction-based modeling. A governing equation along with a coefficient of swell-shrink was developed with soil suction as the driving state variable. This soil property function was determined from laboratory tests using new sigmoidal formulations for the e-based water retention curve and the S-shaped swell-shrink curve along with the hydraulic conductivity curve. The model comprises of two components (soil-atmosphere and volume change) and couples material properties with climate data. Daily suction values were applied at the top boundary whereas transient swell-shrink, hydraulic conductivity curve, and time-dependent suction difference were used to obtain the velocity of an automatically refined moving mesh. Vertical deformations due to variation in soil suction were obtained from the governing equation using the coefficient of swell-shrink. Results indicated that the model adequately captures seasonal weather variations with respect to time and corroborates well with field monitoring data. This means that the model is useful in estimating total, cyclic, and transient heave and settlement in expansive clays.
查看更多>>摘要：? 2021 Elsevier B.V.Drought-induced soil desiccation cracking has attracted great attention in various disciplines with the advent of global climate change. Accurately obtaining soil crack networks is essential to understand the cracking mechanism. Inspired by recent advances of artificial intelligence (AI) in computer vision, we propose a new automatic soil crack recognition method based a novel network architecture, named Attention Res-UNet. Deep Res-UNet inherits both the advantages from residual learning for training deeper networks and U-Net for semantic segmentation. Moreover, attention mechanism is utilized to alleviate the influences caused by the uneven illumination conditions. Firstly, the soil crack images under different uneven illumination conditions are collected to create a new soil cracking image dataset. Then, traditional method and multiple state-of-the-art deep learning based different semantic segmentation models are tested on our collected dataset. Finally, a professional evaluation standard, which considers both the overall metrics (precision, recall, dice, surface crack ratio) and details (crack total length, average crack width, number of crack segments) of the soil crack features is proposed to evaluate the recognition results of the different models. Extensive experimental results demonstrate the superiority of our proposed Attention Res-UNet approach compared with traditional methods and other deep learning models in recognizing soil cracks under complex environmental conditions. Our method is also suitable for crack recognition of other materials under complex environmental conditions.
查看更多>>摘要：? 2021 Elsevier B.V.The effects on hydromechanical performance due to chemical interactions between pore solution and soil components in lime-treated soil are investigated. Static- and kneading-compacted soils are percolated by demineralized water (DW) and a low-ionic strength solution. Kneading action causes aggregate deformation, thus consequently reducing macropores of diameter 105 ?. This increases the hydraulic tortuosity and lengthens the pore fluid-soil structure contact, which favors the long-term pozzolanic reactions. DW being relatively more aggressive than low-ionic strength solution accelerates the leaching of Calcium, thus negatively impacting the hydromechanical performance. The study shows that the hydromechanical evolution in lime-treated soil is governed by the duration of pore fluid and soil structure contact, depending on the compaction mechanisms implemented. The extent of the effect of pore fluid-soil structure interaction is regulated by the pore solution chemistry and the lime content. Thus, importance should be given to the relevancy of the selected compaction procedure and the permeant solution at the laboratory scale with respect to in-situ compaction mechanism and pore water.
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