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22 pages, 23991 KiB

Open AccessArticle

Conceptual and Applied Aspects of Water Retention Tests on Tailings Using Columns

by Fernando A. M. Marinho, Yuri Corrêa, Rosiane Soares, Inácio Diniz Carvalho and João Paulo de Sousa Silva

Geosciences 2024, 14(10), 273; https://doi.org/10.3390/geosciences14100273 - 16 Oct 2024

Viewed by 467

Abstract

The water retention capacity of porous materials is crucial in various geotechnical and environmental engineering applications such as slope stability analysis, landfill management, and mining operations. Filtered tailings stacks are considered an alternative to traditional tailings dams. Nevertheless, the mechanical behaviour and stability [...] Read more.

The water retention capacity of porous materials is crucial in various geotechnical and environmental engineering applications such as slope stability analysis, landfill management, and mining operations. Filtered tailings stacks are considered an alternative to traditional tailings dams. Nevertheless, the mechanical behaviour and stability of the material under different water content conditions are of concern because these stacks can reach considerable heights. The water behaviour in these structures is poorly understood, particularly the effects of the water content on the stability and potential for liquefaction of the stacks. This study aims to investigate the water retention and flow characteristics of compacted iron ore tailings in high columns to better understand their hydromechanical behaviour. The research used 5 m high columns filled with iron ore tailings from the Quadrilátero Ferrífero region in Minas Gerais, Brazil. The columns were prepared in layers, compacted, and instrumented with moisture content sensors and suction sensors to monitor the water movement during various stages of saturation, drainage, infiltration, and evaporation. The sensors provided consistent data and revealed that the tailings exhibited high drainage capacity. The moisture content and suction profiles were effectively established over time and revealed the dynamic water retention behaviour. The comparison of the data with the theoretical soil water retention curve (SWRC) demonstrated a good correlation which indicates that there was no hysteresis in the material response. The study concludes that the column setup effectively captures the water retention and flow characteristics of compacted tailings and provides valuable insights for the hydromechanical analysis of filtered tailings stacks. These findings can significantly help improve numerical models, calibrate material parameters, and contribute to the safer and more efficient management of tailings storage facilities. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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18 pages, 9959 KiB

Open AccessArticle

Seismic Response of Pile Foundations in Clayey Soil Deposits Considering Soil Suction Changes Caused by Soil–Atmospheric Interactions

by Ali Shojaeian, Tommy Bounds, Kanthasamy K. Muraleetharan and Gerald Miller

Geosciences 2024, 14(9), 234; https://doi.org/10.3390/geosciences14090234 - 29 Aug 2024

Viewed by 589

Abstract

Extreme variations in weather patterns have become increasingly common across the Southern Great Plains of the United States. The soil layer in the active zone above the groundwater table is often subjected to moisture variations due to seasonal weather changes that will influence [...] Read more.

Extreme variations in weather patterns have become increasingly common across the Southern Great Plains of the United States. The soil layer in the active zone above the groundwater table is often subjected to moisture variations due to seasonal weather changes that will influence the behavior of soils, including their strength and stiffness parameters. Designing a pile foundation in seismic-prone areas without considering the moisture changes in soil interacting with piles may adversely impact the seismic performance of the piles. The main aim of this study is to investigate the role of soil moisture conditions and suction caused by soil–atmospheric interactions on the dynamic behavior of the pile foundations interacting with clayey soils. This study uses a stand-alone finite element computer code called DYPAC (Dynamic Piles Analysis Code) developed using the Beams on Nonlinear Winkler Foundation (BNWF) approach. The influence of soil suction is incorporated into the p-y curves and free-field soil displacements using site response analyses by employing the concept of apparent cohesion. To perform nonlinear site response analyses, DEEPSOIL software V6.1 is utilized. The variation in soil suction with depth along the pile is considered using unsaturated seepage analysis performed by employing the commercial software PLAXIS LE Groundwater for three different clayey soils with plasticity ranging from low to medium to high. The analyses were performed using actual past daily recorded weather data for a testbed that experienced significant back-to-back flash droughts in 2022. This study found that extreme weather events like flash droughts can significantly affect the soil suction and seismic performance of the piles interacting with the unsaturated clayey soils. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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18 pages, 5530 KiB

Open AccessArticle

Stress-Based Model for Interpreting Shear Wave Velocity from Seismic Cone Penetration Tests in Unsaturated Soil

by Tareq Abuawad, Gerald A. Miller and Kanthasamy K. Muraleetharan

Geosciences 2024, 14(9), 227; https://doi.org/10.3390/geosciences14090227 - 24 Aug 2024

Viewed by 580

Abstract

Shear wave velocity is an important parameter for estimating soil properties used in analyzing the dynamic response of soil to seismic loading. This paper focuses on developing a model for predicting shear wave velocity in unsaturated soils. The model was developed primarily for [...] Read more.

Shear wave velocity is an important parameter for estimating soil properties used in analyzing the dynamic response of soil to seismic loading. This paper focuses on developing a model for predicting shear wave velocity in unsaturated soils. The model was developed primarily for the interpretation of seismic cone penetration tests (SCPTs) in unsaturated soil to account for seasonal variations in moisture conditions. In practice, SCPTs typically occur over a period of days without the option of choosing a wet or dry period. The question becomes, if tests are conducted during a dry period, how can shear wave velocity corresponding to a wetter period be predicted, or vice versa? Answering this question was the primary motivation of this work. The work involved field testing with the seismic cone penetrometer during wet and dry periods and a focused study at three sites involving comparison between field and laboratory testing for shear wave velocity. The model presented in this paper is built upon the significant work of many other researchers with reference to new experimental data obtained by the authors. It is demonstrated that a stress-based model incorporating matric suction can provide reasonable predictions of shear wave velocity and provides a method to interpret the impact of changing moisture content on shear wave velocities determined with SCPTs. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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22 pages, 9040 KiB

Open AccessArticle

Thermally Induced Moisture Flow in a Silty Sand under a 1-D Thermal Gradient

by Nice Kaneza, Aashish Pokhrel, Laureano R. Hoyos and Xinbao Yu

Geosciences 2024, 14(8), 207; https://doi.org/10.3390/geosciences14080207 - 2 Aug 2024

Viewed by 703

Abstract

Thermally induced moisture flow in unsaturated soils involves complex coupled thermal–hydro processes with the moisture flow in both the vapor and liquid phases. The accurate measurement of the moisture flow in unsaturated sands remains a challenging task due to low moisture migration, the [...] Read more.

Thermally induced moisture flow in unsaturated soils involves complex coupled thermal–hydro processes with the moisture flow in both the vapor and liquid phases. The accurate measurement of the moisture flow in unsaturated sands remains a challenging task due to low moisture migration, the temperature effect on moisture sensors, and the gravity effect on moisture flow. This study aims to accurately measure transient moisture flow, heat transfer, and thermal conductivity in a silty sand with 35% non-plastic fines in a closed heat cell with a controlled 1-D temperature gradient. The heat cell consists of two temperature-controlled heat exchanger plates, heat flux sensors, moisture sensors, thermocouples, and thermal conductivity sensors. The soil moisture sensors were calibrated in the test soil at room temperature and then at elevated incremental temperatures. Soil samples compacted at various initial moisture contents were tested under a constant 1-D temperature gradient of 4 °C/cm. Soil moisture redistribution, temperature, and thermal conductivity profiles were determined from the test results. Transient temperature responses indicated that a lower initial moisture content led to a higher temperature drop after reaching the peak, or a more concaved temperature profile in a steady state due to enhanced moisture migration driven by the temperature gradients. Dry soils exhibited uniform thermal properties, while moist soils showed varying thermal conductivity profiles. A critical moisture content was identified when the maximum moisture migration occurred. Thermal conductivity in soils increased with the distance from the heat source due to thermally induced moisture migration. These findings provide valuable insights into coupled moisture–heat flow dynamics in unsaturated sands. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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25 pages, 5625 KiB

Open AccessArticle

A Hyperelastic Bounding Surface Plasticity Model for Unsaturated Granular Soils

by Mehdi Kadivar, Kalehiwot Nega Manahiloh and Victor N. Kaliakin

Geosciences 2024, 14(6), 148; https://doi.org/10.3390/geosciences14060148 - 30 May 2024

Viewed by 718

Abstract

In this paper, a state-dependent, bounding surface plasticity model that simulates the behavior of unsaturated granular soils is presented. An unsaturated, soil mechanics-compatible elastoplastic response is adopted in which no part of the response occurs in a purely elastic fashion. To create an [...] Read more.

In this paper, a state-dependent, bounding surface plasticity model that simulates the behavior of unsaturated granular soils is presented. An unsaturated, soil mechanics-compatible elastoplastic response is adopted in which no part of the response occurs in a purely elastic fashion. To create an appropriate hydro-mechanical coupling, a newer generation stress framework, consisting of the Bishop-type effective stress and a second stress variable, is used in conjunction with a soil-water characteristic curve function. Details regarding the model development, parameter estimation, and assessment of the model’s predictive capabilities are outlined. With a single set of parameter values, the model realistically simulates the main features that characterize the shear and volumetric behavior of unsaturated granular soils over a wide range of matric suction, density, and net confining pressure. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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12 pages, 4068 KiB

Open AccessArticle

Impact of Vetiver Plantation on Unsaturated Soil Behavior and Stability of Highway Slope

by Fariha Rahman, Avipriyo Chakraborty, Sadik Khan and Rakesh Salunke

Geosciences 2024, 14(5), 123; https://doi.org/10.3390/geosciences14050123 - 1 May 2024

Cited by 2 | Viewed by 1390

Abstract

Due to cyclic wetting and drying, the hydro-mechanical behavior of unsaturated soil is impacted significantly. In order to assess the soil strength parameters, knowing the unsaturated behavior is important. Soil moisture content is an important parameter that can define the shear strength of [...] Read more.

Due to cyclic wetting and drying, the hydro-mechanical behavior of unsaturated soil is impacted significantly. In order to assess the soil strength parameters, knowing the unsaturated behavior is important. Soil moisture content is an important parameter that can define the shear strength of the soil. Most of the highway slopes of Mississippi are built on highly expansive clay. During summer, the evaporation of moisture in the soil leads to shrinkage and the formation of desiccation cracks, while during rainfall, the soil swells due to the infiltration of water. In addition to this, the rainwater gets trapped in these cracks and creates perched conditions, leading to the increased moisture content and reduced shear strength of slope soil. The increased precipitation due to climate change is causing failure conditions on many highway slopes of Mississippi. Vetiver, a perennial grass, can be a transformative solution to reduce the highway slope failure challenges of highly plastic clay. The grass has deep and fibrous roots, which provide additional shear strength to the soil. The root can uptake a significant amount of water from the soil, keeping the moisture balance of the slope. The objective of the current study is to assess the changes in moisture contents of a highway slope in Mississippi after the Vetiver plantation. Monitoring equipment, such as rain gauges and moisture sensors, were installed to monitor the rainfall of the area and the moisture content of the soil. The data showed that the moisture content conditions were improved with the aging of the grass. The light detection and ranging (LiDAR) analysis was performed to validate the field data obtained from different sensors, and it was found that there was no significant slope movement after the Vetiver plantation. The study proves the performance of the Vetiver grass in improving the unsaturated soil behavior and stability of highway slopes built on highly expansive clay. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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34 pages, 19182 KiB

Open AccessArticle

Shear Banding and Cracking in Unsaturated Porous Media through a Nonlocal THM Meshfree Paradigm

by Hossein Pashazad and Xiaoyu Song

Geosciences 2024, 14(4), 103; https://doi.org/10.3390/geosciences14040103 - 9 Apr 2024

Viewed by 1202

Abstract

The mechanical behavior of unsaturated porous media under non-isothermal conditions plays a vital role in geo-hazards and geo-energy engineering (e.g., landslides triggered by fire and geothermal energy harvest and foundations). Temperature increase can trigger localized failure and cracking in unsaturated porous media. This [...] Read more.

The mechanical behavior of unsaturated porous media under non-isothermal conditions plays a vital role in geo-hazards and geo-energy engineering (e.g., landslides triggered by fire and geothermal energy harvest and foundations). Temperature increase can trigger localized failure and cracking in unsaturated porous media. This article investigates the shear banding and cracking in unsaturated porous media under non-isothermal conditions through a thermo–hydro–mechanical (THM) periporomechanics (PPM) paradigm. PPM is a nonlocal formulation of classical poromechanics using integral equations, which is robust in simulating continuous and discontinuous deformation in porous media. As a new contribution, we formulate a nonlocal THM constitutive model for unsaturated porous media in the PPM paradigm in this study. The THM meshfree paradigm is implemented through an explicit Lagrangian meshfree algorithm. The return mapping algorithm is used to implement the nonlocal THM constitutive model numerically. Numerical examples are presented to assess the capability of the proposed THM mesh-free paradigm for modeling shear banding and cracking in unsaturated porous media under non-isothermal conditions. The numerical results are examined to study the effect of temperature variations on the formation of shear banding and cracking in unsaturated porous media. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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12 pages, 4884 KiB

Open AccessArticle

Effect of Freeze–Thaw and Wetting–Drying Cycles on the Hydraulic Conductivity of Modified Tailings

by Longlong Meng, Liangxiong Xia, Min Xia, Shaokai Nie, Jiakai Chen, Wenyuan Wang, Aifang Du, Haowen Guo and Bate Bate

Geosciences 2024, 14(4), 93; https://doi.org/10.3390/geosciences14040093 - 25 Mar 2024

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Abstract

Mine tailings have shown viability as the fine–grained layer in a capillary barrier structure for controlling acid mine drainage in a circular economy. Their saturated hydraulic conductivities (k_sat) under wetting–drying cycles and freeze–thaw cycles remain unexplored. In this study, modified [...] Read more.

Mine tailings have shown viability as the fine–grained layer in a capillary barrier structure for controlling acid mine drainage in a circular economy. Their saturated hydraulic conductivities (k_sat) under wetting–drying cycles and freeze–thaw cycles remain unexplored. In this study, modified tailings with a weight ratio of 95:5 (tailings/hydrodesulfurization (HDS) clay from waste–water treatment) and an initial water content of 12% were used. The k_sat of specimens was measured after up to 15 wetting–drying cycles, each lasting 24 h, with a drying temperature of 105 °C. The k_sat for wetting–drying cycles decreased from 3.9 × 10⁻⁶ m/s to 9.5 × 10⁻⁷ m/s in the first three cycles and then stabilized in the subsequent wetting–drying cycles (i.e., 5.7 × 10⁻⁷ m/s–6.3 × 10⁻⁷ m/s). Increased fine particles due to particle breakage are the primary mechanism for the k_sat trend. In addition, the migration of fines and their preferential deposition near the pore throat area may also promote this decreasing trend through the shrinking and potentially clogging–up of pore throats. This could be explained by the movement of the meniscus, increased salinity, and, subsequently, the shrinkage of the electrical diffuse layer during the drying cycle. Similar specimens were tested to measure k_sat under up to 15 freeze–thaw cycles with temperatures circling between −20 °C and 20 °C at 12 h intervals. Compared to the untreated specimen (i.e., 3.8 × 10⁻⁶ m/s), the k_sat after three freeze–thaw cycles decreased by 77.6% (i.e., 8.5 × 10⁻⁷ m/s) and then remained almost unchanged (i.e., 5.6 × 10⁻⁷ m/s–8.9 × 10⁻⁷ m/s) in subsequent freeze–thaw cycles. The increased fine grain content (i.e., 3.1%) can be used to explain the decreased k_sat trend. Moreover, the migration of fines toward the pore throat area, driven by the advancing and receding of ice lens fronts and subsequent deposition at the pore throat, may also contribute to this trend. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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20 pages, 4993 KiB

Open AccessArticle

Models for Considering the Thermo-Hydro-Mechanical-Chemo Effects on Soil–Water Characteristic Curves

by Yao Li, Roberto Alves, Sai Vanapalli and Gilson Gitirana, Jr.

Geosciences 2024, 14(2), 38; https://doi.org/10.3390/geosciences14020038 - 31 Jan 2024

Viewed by 1504

Abstract

The soil–water characteristic curve (SWCC) is widely used as a tool in geotechnical, geo-environmental, hydrology, and soil science fields for predicting and interpreting hydro-mechanical behaviors of unsaturated soils. Several previous studies focused on investigating the influence of initial water content, stress history, temperature, [...] Read more.

The soil–water characteristic curve (SWCC) is widely used as a tool in geotechnical, geo-environmental, hydrology, and soil science fields for predicting and interpreting hydro-mechanical behaviors of unsaturated soils. Several previous studies focused on investigating the influence of initial water content, stress history, temperature, and salt content on the SWCC behavior. However, there is still limited understanding to be gained from the literature on how we can systematically incorporate the influence of complex thermo-hydro-mechanical-chemo (THMC) effects into interpreting and predicting the behavior of unsaturated soils. To address that knowledge gap, in this study, the coupled influence of temperature, initial stress state, initial density, soil structure, and chemical solution effects was modeled using established SWCC equations from the literature. The methodology for incorporating the coupled effects of these influential factors is presented herein. Furthermore, we evaluated the SWCC models proposed in this study, enabling us to provide a comprehensive discussion of their strengths and limitations, using the published SWCC data from the literature. The developments outlined in this paper contribute toward facilitating a rigorous approach for analyzing the THMC behaviors of unsaturated soils. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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16 pages, 3895 KiB

Open AccessArticle

Exploring the Influence of Climate Change on Earthen Embankments with Expansive Soil

by Debayan Ghosh, Aritra Banerjee, Anand J. Puppala and Prince Kumar

Geosciences 2024, 14(2), 37; https://doi.org/10.3390/geosciences14020037 - 30 Jan 2024

Viewed by 2535

Abstract

Climate change is known to cause alterations in weather patterns and disturb the natural equilibrium. Changes in climatic conditions lead to increased environmental stress on embankments, which can result in slope failures. Due to wetting–drying cycles, expansive clayey soil often swells and shrinks, [...] Read more.

Climate change is known to cause alterations in weather patterns and disturb the natural equilibrium. Changes in climatic conditions lead to increased environmental stress on embankments, which can result in slope failures. Due to wetting–drying cycles, expansive clayey soil often swells and shrinks, and matric suction is a major factor that controls the behavior. Increased temperature accelerates soil evaporation and drying, which can cause desiccation cracks, while precipitation can rapidly reduce soil shear strength. Desiccated slopes on embankments built with such soils can cause surficial slope failures after intense precipitation. This study used slope stability analysis to quantify how climate-change-induced extreme weather affects embankments. Historic extreme climatic events were used as a baseline to estimate future extremes. CMIP6 provided historical and future climatic data for the study area. An embankment was numerically modeled to evaluate the effect on slope stability due to the precipitation change induced by climate change. Coupled hydro-mechanical finite element analyses used a two-dimensional transient unsaturated seepage model and a limit equilibrium slope stability model. The study found that extreme climatic interactions like precipitation and temperature due to climate change may reduce embankment slope safety. The reduction in the stability of the embankment due to increased precipitation resulting from different greenhouse gas emission scenarios was investigated. The use of unsaturated soil strength and variation of permeability with suction, along with the phase transition of these earthen embankments from near-dry to near-saturated, shows how unsaturated soil mechanics and the hydro-mechanical model can identify climate change issues on critical geotechnical infrastructure. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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16 pages, 5727 KiB

Open AccessArticle

A Multiphysics Simulation of the Effects of Wicking Geotextile on Mitigating Frost Heave under Cold Region Pavement

by Yusheng Jiang, Zaid Alajlan, Claudia Zapata and Xiong Yu

Geosciences 2024, 14(2), 34; https://doi.org/10.3390/geosciences14020034 - 28 Jan 2024

Viewed by 1781

Abstract

Geotextile offers numerous benefits in improving pavement performance, including drainage, barrier functionality, filtration, and reinforcement. Wicking geotextile, a novel variant in this category, possesses the intrinsic ability to drain water autonomously from soils. This paper details the development and application of a comprehensive [...] Read more.

Geotextile offers numerous benefits in improving pavement performance, including drainage, barrier functionality, filtration, and reinforcement. Wicking geotextile, a novel variant in this category, possesses the intrinsic ability to drain water autonomously from soils. This paper details the development and application of a comprehensive multiphysics model that simulates the performance of wicking geotextile within a pavement system under freezing climates. The model considers the inputs of various environmental dynamics, including the impact of meteorological factors, groundwater levels, ground heat, and drainage on the pavement system. The model was firstly validated using field data from a long-term pavement performance (LTPP) road section in the cold region. It was subsequently applied to assess the impacts of wicking geotextile if it was installed on the road section. The model simulated the coupled temporal and spatial variations in soil moisture content and temperature. The simulation results demonstrated that wicking geotextile would create a suction zone around its installation location to draw water from surrounding soils, therefore reducing the overall unfrozen water content in the pavement. The results also showed that the installation of wicking geotextile would delay the initiation of frost heave and reduce its magnitude in cold region pavement. Full article

(This article belongs to the Special Issue Advances in Thermo-Hydro-Mechanical Characterization and Modelling of Unsaturated Soils)

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