Natural and Artificial Unsaturated Soil Slopes

A special issue of Geosciences (ISSN 2076-3263). This special issue belongs to the section "Natural Hazards".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 19506

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Guest Editor
School of Engineering, University of Basilicata, 85100 Potenza, Italy
Interests: slope stability; unsaturated soils; laboratory testing; ground monitoring; remote sensing; large slow-moving landslides; numerical modeling of landslide processes; chemo-mechanical interaction in clayey soils; soil-structure interaction; soil dynamics

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Guest Editor
Department of Engineering, University of Campania “Luigi Vanvitelli”, 81031 Aversa, Italy
Interests: slope stability; landslide risk mitigation measures; unsaturated soils; fine-grained soils; soil-atmosphere interaction; laboratory testing; site monitoring; large slow-moving landslides; debris flows; numerical modeling of landslide mechanics

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Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Str. dell\'Università, 12, 43121 Parma, PR, Italy
Interests: slope stability; unsaturated soils; soil-atmosphere interaction; field monitoring; rainfall-induced landslides; physical modeling; numerical modeling; early warning systems; regional-scale landslide hazard; hydrological modeling
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Recently, there has been extensive literature on engineering problems involving soils whose mechanical and hydraulic properties are strongly influenced by the degree of saturation. Earthen embankments, soil–vegetation–atmosphere interaction, geoenvironmental applications, risk mitigation, are just a few examples of the constant interest of the scientific community to the subject. The presence of a sloping ground surface is common to many of these problems. In slightly inclined natural slopes, susceptible to deep landslides, the unsaturated condition of shallow soil horizons affects deep pore water pressure distribution and, as a consequence, the stability of the entire slope. The stability of steep mountain areas covered by shallow deposits is often guaranteed by a shear strength contribution related to the unsaturated nature of the soil. In this case, the degree of saturation plays a key role in determining which rainfall events can act as landslide triggers, consequently controlling the post-failure evolution. Partial saturation is the basic characteristic of soils adopted as construction materials of geo-structures like levees, dikes, and dams. This condition governs the structure behavior during construction phases, in serviceability, and in extreme scenarios. Hoping to provide a bridge between theoretical research and practical applications, this Special Issue aims to collect quality contributions related to natural and artificial slopes under unsaturated conditions and focusing on several aspects such as the following: water retention and transport properties, mechanical behavior, advances in experimental methods, laboratory and in situ characterization, soil improvement, field monitoring, small-scale models, geotechnical and geophysical field tests, landslide investigation and prevention, design and maintenance of engineered slopes, analysis at different spatial scales, constitutive and numerical modeling of the chemo-hydro-mechanical behavior.

Prof. Roberto Vassallo
Prof. Luca Comegna
Prof. Roberto Valentino
Guest Editors

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Keywords

  • slope stability
  • unsaturated soils
  • pore water pressures
  • water retention
  • landslides
  • triggering factors
  • earthen embankments
  • geoenvironmental applications
  • soil–vegetation–atmosphere interaction
  • laboratory and site characterization
  • geophysical investigation
  • soil improvement
  • monitoring
  • physical, constitutive and numerical modeling
  • chemo-hydro-mechanical behavior
  • risk mitigation

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Published Papers (7 papers)

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Editorial

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2 pages, 147 KiB  
Editorial
Editorial of Special Issue “Natural and Artificial Unsaturated Soil Slopes”
by Roberto Vassallo, Luca Comegna and Roberto Valentino
Geosciences 2021, 11(8), 334; https://doi.org/10.3390/geosciences11080334 - 7 Aug 2021
Viewed by 1646
Abstract
Natural and artificial slopes are frequently constituted, at least in part, by soils in unsaturated conditions [...] Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)

Research

Jump to: Editorial

11 pages, 7314 KiB  
Article
Determination of Water Retention Properties of Silty Sands by Means of Combined Commercial Techniques
by Elisa Ponzoni, Alessandra Nocilla and Cristina Jommi
Geosciences 2021, 11(8), 315; https://doi.org/10.3390/geosciences11080315 - 27 Jul 2021
Cited by 3 | Viewed by 2104
Abstract
A recent increase in frequency and severity of exceptional climatic events is of concern for the stability of natural and artificial slopes. These undergo continuous evaporation and infiltration cycles, which change the suction distribution and trigger shrinkage, swelling, cracking, and surficial erosion, overall [...] Read more.
A recent increase in frequency and severity of exceptional climatic events is of concern for the stability of natural and artificial slopes. These undergo continuous evaporation and infiltration cycles, which change the suction distribution and trigger shrinkage, swelling, cracking, and surficial erosion, overall decreasing the soil strength. To assess the impact of these climatic stresses, the determination of water retention properties is a priority. Although advanced techniques have been proposed in the last few decades to this end, simpler commercially available techniques allow collecting data for a larger number of samples in a shorter time, thus enabling a basic description of the water retention properties for a larger database of soils. Data on two silty sands, coming from very different climatic environments in Europe, were collected with a combination of two simple commercial devices, and the results were modelled with a van Genuchten’s law. The fitted parameters were found to correlate well with the amount of fines, irrespective of the different origin and composition of the two soils. Eventually, the limitation of the approach is discussed based on the results of cyclic drying–wetting tests. Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)
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14 pages, 5327 KiB  
Article
Capillary Barriers during Rainfall Events in Pyroclastic Deposits of the Vesuvian Area
by Ciro Sepe, Domenico Calcaterra, Manuela Cecconi, Diego Di Martire, Lucia Pappalardo, Riccardo Scarfone, Enza Vitale and Giacomo Russo
Geosciences 2021, 11(7), 274; https://doi.org/10.3390/geosciences11070274 - 29 Jun 2021
Cited by 4 | Viewed by 2237
Abstract
In the present paper, the capillary barrier formation at the interface between soil layers, which is characterized by textural discontinuities, has been analyzed. This mechanism has been investigated by means of a finite element model of a two-layer soil stratification. The two considered [...] Read more.
In the present paper, the capillary barrier formation at the interface between soil layers, which is characterized by textural discontinuities, has been analyzed. This mechanism has been investigated by means of a finite element model of a two-layer soil stratification. The two considered formations, belonging to the pyroclastic succession of the “Pomici di Base” Plinian eruption (22 ka, Santacroce et al., 2008) of the Somma–Vesuvius volcano, are affected by shallow instability phenomena likely caused by progressive saturation during the rainfall events. This mechanism could be compatible with the formation of capillary barriers at the interface between layers of different grain size distributions during infiltration. One-dimensional infiltration into the stratified soil was parametrically simulated considering rainfall events of increasing intensity and duration. The variations in the suction and degree of saturation over time allowed for the evaluation of stability variations in the layers, which were assumed as part of stratified unsaturated infinite slopes. Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)
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22 pages, 5683 KiB  
Article
Experimental and Numerical Investigations of a River Embankment Model under Transient Seepage Conditions
by Roberta Ventini, Elena Dodaro, Carmine Gerardo Gragnano, Daniela Giretti and Marianna Pirone
Geosciences 2021, 11(5), 192; https://doi.org/10.3390/geosciences11050192 - 29 Apr 2021
Cited by 6 | Viewed by 3191
Abstract
The evaluation of riverbank stability often represents an underrated problem in engineering practice, but is also a topical geotechnical research issue. In fact, it is certainly true that soil water content and pore water pressure distributions in the riverbank materials vary with time, [...] Read more.
The evaluation of riverbank stability often represents an underrated problem in engineering practice, but is also a topical geotechnical research issue. In fact, it is certainly true that soil water content and pore water pressure distributions in the riverbank materials vary with time, due to the changeable effects of hydrometric and climatic boundary conditions, strongly influencing the bank stability conditions. Nonetheless, the assessment of hydraulic and mechanical behavior of embankments are currently performed under the simplified hypothesis of steady-state seepage, generally neglecting the unsaturated soil related issues. In this paper, a comprehensive procedure for properly defining the key aspects of the problem is presented and, in particular, the soil characterization in partially saturated conditions of a suitably compacted mixture of sand and finer material, typical of flood embankments of the main river Po tributaries (Italy), is reported. The laboratory results have then been considered for modelling the embankment performance under transient seepage and following a set of possible hydrometric peaks. The outcome of the present contribution may provide meaningful geotechnical insights, for practitioners and researchers, in the flood risk assessment of river embankments. Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)
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15 pages, 7386 KiB  
Article
The Hydromechanical Interplay in the Simplified Three-Dimensional Limit Equilibrium Analyses of Unsaturated Slope Stability
by Panagiotis Sitarenios and Francesca Casini
Geosciences 2021, 11(2), 73; https://doi.org/10.3390/geosciences11020073 - 8 Feb 2021
Cited by 3 | Viewed by 2174
Abstract
This paper presents a three-dimensional slope stability limit equilibrium solution for translational planar failure modes. The proposed solution uses Bishop’s average skeleton stress combined with the Mohr–Coulomb failure criterion to describe soil strength evolution under unsaturated conditions while its formulation ensures a natural [...] Read more.
This paper presents a three-dimensional slope stability limit equilibrium solution for translational planar failure modes. The proposed solution uses Bishop’s average skeleton stress combined with the Mohr–Coulomb failure criterion to describe soil strength evolution under unsaturated conditions while its formulation ensures a natural and smooth transition from the unsaturated to the saturated regime and vice versa. The proposed analytical solution is evaluated by comparing its predictions with the results of the Ruedlingen slope failure experiment. The comparison suggests that, despite its relative simplicity, the analytical solution can capture the experimentally observed behaviour well and highlights the importance of considering lateral resistance together with a realistic interplay between mechanical parameters (cohesion) and hydraulic (pore water pressure) conditions. Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)
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20 pages, 10866 KiB  
Article
Evaluation of Unsaturated Soil Properties for a Debris-Flow Simulation
by Francesco Castelli, Valentina Lentini and Alessandra Di Venti
Geosciences 2021, 11(2), 64; https://doi.org/10.3390/geosciences11020064 - 31 Jan 2021
Cited by 4 | Viewed by 2944
Abstract
Fast-moving landslides (i.e., debris/earth flows) are often caused by heavy rainfall occurring in small areas, and are not predictable. On the other hand, innovative methods for geomechanical characterization, numerical analysis, and modeling are required to attempt to reproduce a given debris/earth flow event. [...] Read more.
Fast-moving landslides (i.e., debris/earth flows) are often caused by heavy rainfall occurring in small areas, and are not predictable. On the other hand, innovative methods for geomechanical characterization, numerical analysis, and modeling are required to attempt to reproduce a given debris/earth flow event. As our capability to reproduce very complex phenomena increases, we can improve our prevention approaches. In this paper, a debris flow event that occurred in the Enna area (Sicily) is described. Starting from the study of the geological framework and the historical background, this research focused on the causes that triggered the landslide. In situ and laboratory tests, including geophysical investigations and triaxial tests in unsaturated conditions, were carried out to investigate the factors affecting the dynamics of the event. This study gives us better knowledge of the mechanical and hydraulic properties that can be used to model these events, to assess the most appropriate strategies for the prevention and mitigation of related risks. Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)
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26 pages, 16284 KiB  
Article
Field Measurements of Soil Water Content at Shallow Depths for Landslide Monitoring
by Rossella Bovolenta, Alessandro Iacopino, Roberto Passalacqua and Bianca Federici
Geosciences 2020, 10(10), 409; https://doi.org/10.3390/geosciences10100409 - 13 Oct 2020
Cited by 11 | Viewed by 3745
Abstract
Monitoring changes in soil saturation is important for slope stability analyses. Soil moisture capacitive sensors have recently been developed; their response time is extremely fast, they require little maintenance, and they are relatively inexpensive. The use of low-cost sensors in landslide areas can [...] Read more.
Monitoring changes in soil saturation is important for slope stability analyses. Soil moisture capacitive sensors have recently been developed; their response time is extremely fast, they require little maintenance, and they are relatively inexpensive. The use of low-cost sensors in landslide areas can allow the monitoring of large territories, but appropriate calibration is required. Installation in the field and the setting up of the monitoring network also require attention. In the ALCOTRA AD-VITAM project, the University of Genoa is involved in the development of a system, called LAMP, for the monitoring, analysis and forecasting of slides triggered by rainfalls. Multiple installations (along vertical alignments) of WaterScout sensors are placed in the nodes of the monitoring network. They provide real-time water content profiles in the shallow layers (typically in the upper meter) of a slope. With particular reference to these measurements, the present paper describes the reliability analysis of the instruments, the operations related to the sensor calibration and the installation phases for the monitoring networks. Finally, some of the data coming from a node, belonging to one of the five monitoring networks, are reported. Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)
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