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14 pages, 1130 KiB

Open AccessArticle

An Estimation of Clayey-Oriented Rock Mass Material Properties, Sited in Koropi, Athens, Greece, through Feed-Forward Neural Networks

by Ambrosios-Antonios Savvides, Andreas A. Antoniou, Leonidas Papadopoulos, Anastasia Monia and Kalliopi Kofina

Geotechnics 2023, 3(4), 975-988; https://doi.org/10.3390/geotechnics3040052 - 24 Sep 2023

Cited by 1 | Viewed by 1008

Abstract

Rock mechanics and the estimation of their material properties through field tests are important aspects and challengees in civil and geotechnical engineering. However, this procedure is expensive and difficult to attain, while the machine learning and neural network theory provide a computational tool [...] Read more.

Rock mechanics and the estimation of their material properties through field tests are important aspects and challengees in civil and geotechnical engineering. However, this procedure is expensive and difficult to attain, while the machine learning and neural network theory provide a computational tool for estimating the material properties with limited data. In this work, an estimation of the Young Modulus and the cohesion of a clayey-originated rock through feed-forward neural networks constructed from in situ data measurements is given. The input values come from the Geological Strength Index (GSI) proposed values of the point load index

I_{s 50}

, the uniaxial compression strength

σ_{s}

, as well as the specific gravity

γ

of the rock mass. The convergence analysis revealed that the convergence occurs at approximately 2000 epochs, with the largest

L_{2}

mean square error norm being no greater than

10^{- 5}

. In addition, it is demonstrated that augmenting

γ

results in the estimation of rock that is stiffer and stronger. The aforementioned increase in the specific site may be up to 20% for the stiffness and up to 25% for the cohesion. This model, aside from readability and accuracy, offers the convenience of enriching it with more in situ data, thereby enhancing the flexibility of the proposed numerical tool proposed. However, its applicability is limited to the specific data acquired from the particular site, so a more general estimation requires a substantially larger dataset. Finally, the justification of the proposed model has been carried out based on suggestions from the literature for common values of clayey-oriented rock, which is fairly disintegrated as seen in the field. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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16 pages, 2314 KiB

Open AccessArticle

In Situ Alteration of the Hydro-Mechanical Behaviour of a Compacted Stabilised Expansive Soil

by Nicolas Chabrat, Olivier Cuisinier and Farimah Masrouri

Geotechnics 2023, 3(3), 921-936; https://doi.org/10.3390/geotechnics3030049 - 13 Sep 2023

Viewed by 688

Abstract

This paper assesses the performance of an embankment constructed in 2010 with a stabilised expansive soil. Two types of treatment were employed at construction time: 4% lime and a mix of 2% lime and 3% cement. A sampling campaign was carried out in [...] Read more.

This paper assesses the performance of an embankment constructed in 2010 with a stabilised expansive soil. Two types of treatment were employed at construction time: 4% lime and a mix of 2% lime and 3% cement. A sampling campaign was carried out in 2021 to evaluate the long-term performance of the stabilised soil properties. To assess the compressibility of the soil, oedometer tests were carried out on samples from different parts of the embankment. The results were compared to the compression curve of the untreated soil, also sampled in the same embankment. Complementary shrinkage tests were performed to investigate the effect of the treatment on swelling and shrinkage. The obtained results show that the yield stress of the material from the outer part was inferior to 100 kPa, similarly to the yield stress of the untreated soil, demonstrating a strong alteration in the effect of both treatments over time. This alteration was noticeable to a distance of approximately 2 m from the external surface. Beyond this distance, the performance of the soil was comparable to the behaviour of recently treated soil, with yield stresses close to 1000 kPa. These observations, similar for each treatment dosage, raise questions as to the durability of the treatment on the outer part of the backfill. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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25 pages, 8317 KiB

Open AccessArticle

Stochastic Finite Element Analysis of Root-Reinforcement Effects in Long and Steep Slopes

by Ram Chandra Tiwari and Netra Prakash Bhandary

Geotechnics 2023, 3(3), 829-853; https://doi.org/10.3390/geotechnics3030045 - 23 Aug 2023

Viewed by 944

Abstract

This article introduces a novel numerical scheme within the finite element method (FEM) to study soil heterogeneity, specifically focusing on the root–soil matrix in fracture treatments. Material properties, such as Young’s modulus of elasticity, cohesion, and the friction angle, are considered as randomly [...] Read more.

This article introduces a novel numerical scheme within the finite element method (FEM) to study soil heterogeneity, specifically focusing on the root–soil matrix in fracture treatments. Material properties, such as Young’s modulus of elasticity, cohesion, and the friction angle, are considered as randomly distributed variables. To address the inherent uncertainty associated with these distributions, a Monte Carlo simulation is employed. By incorporating the uncertainties related to material properties, particularly the root component that contributes to soil heterogeneity, this article provides a reliable estimation of the factor of safety, failure surface, and slope deformation, all of which demonstrate a progressive behavior. The probability distribution curve for the factor of safety (FOS) reveals that an increase in the root area ratio (RAR) results in a narrower range and greater certainty in the population mean, indicating reduced material variation. Moreover, as the slope angle increases, the sample mean falls within a wider range of the probability density curve, indicating an enhanced level of material heterogeneity. This heterogeneity amplifies the level of uncertainty when predicting the factor of safety, highlighting the crucial importance of accurate information regarding heterogeneity to enhancing prediction accuracy. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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14 pages, 9904 KiB

Open AccessArticle

An Analytical Study on Soil Water Index (SWI), Landslide Prediction and Other Related Factors Using XRAIN Data during the July 2018 Heavy Rain Disasters in Hiroshima, Japan

by José Maria dos Santos Rodrigues Neto, Netra Prakash Bhandary and Yuichi Fujita

Geotechnics 2023, 3(3), 686-699; https://doi.org/10.3390/geotechnics3030037 - 21 Jul 2023

Viewed by 997

Abstract

The rainfall-induced landslide disasters in July 2018 in Southwestern Japan yet again exemplified the severity of slope failure-related damage and the need for improvement of early warning systems. The Japanese Meteorological Agency (JMA) uses a method based on a threshold value of soil [...] Read more.

The rainfall-induced landslide disasters in July 2018 in Southwestern Japan yet again exemplified the severity of slope failure-related damage and the need for improvement of early warning systems. The Japanese Meteorological Agency (JMA) uses a method based on a threshold value of soil water index (SWI), a conceptual measurement that represents saturation of slope soil. The current SWI early warning system uses 60-min rainfall data on a 5-km² mesh and does not take into consideration other landslide conditioning factors such as slope angle and geology. This study calculates SWI values during the July 2018 disasters in Kure City (Hiroshima Prefecture) using 1-min XRAIN rainfall data in a 250-m mesh to investigate the relationship between SWI and landslide occurrence. It was found that the SWI threshold of 124 mm used in the JMA early warning system for the area was surpassed in all cells. A new SWI threshold calculation method taking slope angle and geology into consideration and produced with machine learning is proposed, comprising power lines for different geological units at a two-dimensional graph where points located above the threshold line represent landslide risk. It is judged that this method would provide a more accurate early warning system for landslide disasters. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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23 pages, 13679 KiB

Open AccessArticle

Electromagnetic Waves’ Impact on Hydraulic Conductivity of Granular Soils

by Arvin Farid, Holly Gunderson, Rakesh Acharya and Jim Browning

Geotechnics 2023, 3(3), 561-583; https://doi.org/10.3390/geotechnics3030031 - 30 Jun 2023

Viewed by 631

Abstract

Electromagnetic (EM) waves, traditionally used for purposes such as geophysical characterization, impact properties to be measured. This paper describes the effects of radio frequency (RF) waves on the hydraulic conductivity of glass beads and natural sand. A series of tests was conducted using [...] Read more.

Electromagnetic (EM) waves, traditionally used for purposes such as geophysical characterization, impact properties to be measured. This paper describes the effects of radio frequency (RF) waves on the hydraulic conductivity of glass beads and natural sand. A series of tests was conducted using a customized, rigid-wall, cylindrical permeameter inside a resonant cavity made of Plexiglas covered with electrically conductive transparent films. Constant-head ASTM-D2434 tests were performed to measure the samples’ hydraulic conductivity. RF stimulation was performed using a magnetically coupled loop antenna at various frequencies and input RF-power levels. The hydraulic conductivity of both natural sand and glass-bead samples increased with RF stimulation. Furthermore, the measurement of the electric field component of RF waves was also performed to illustrate the pattern of the electric field, as well as evaluate RF’s impact on the hydraulic conductivity tests. The electric field was numerically simulated and validated against experimentally measured electric fields. A finite-difference numerical model was developed in MATLAB to analyze the seepage flow, which was then validated against the experimental results. An optimization scheme was then used to develop a governing equation for RF’s impact on hydraulic conductivity. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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13 pages, 36023 KiB

Open AccessArticle

Post-Wildfire Debris Flows in Montecito, California (USA): A Case Study and Empirically Based Debris Volume Estimation

by Diwakar KC and Liangbo Hu

Geotechnics 2023, 3(2), 347-359; https://doi.org/10.3390/geotechnics3020020 - 15 May 2023

Viewed by 1163

Abstract

Wildfires have a strong influence on various geotechnical and hydraulic properties of soils and sediments, which may become more vulnerable to landslides or debris flows. In the present study, a case investigation of the 2018 post-wildfire debris flows in Montecito, California, USA, was [...] Read more.

Wildfires have a strong influence on various geotechnical and hydraulic properties of soils and sediments, which may become more vulnerable to landslides or debris flows. In the present study, a case investigation of the 2018 post-wildfire debris flows in Montecito, California, USA, was conducted, with a focus on the wildfire-affected areas and debris volume estimation. Significant debris were deposited around four major creeks, i.e., Montecito Creek, San Ysidro Creek, Buena Vista Creek, and Romero Creek in January, 2018, one month after the Thomas fire. Satellite images utilizing remote sensing techniques and geographic information system (GIS) data were analyzed to identify areas affected by the wildfire. Relevant data, including the slope, catchment area, and rainfall were used in two empirical models to estimate the debris volumes around the four creeks. As compared with field observation, each debris volume estimated with these empirical models was within the same order of magnitude. The debris volumes were generally underestimated when using the rainfall recorded at the Montecito Weather Station; the estimates considerably improved with the rainfall record from the Doulton Tunnel Station. The results showed that, overall, such empirical approaches are still of benefit for engineering practice, as they are capable of offering first-order approximations. The accuracy and availability of rainfall data are critical factors; the rainfall data in mountainous areas are generally higher than in the low lands, and consequently were more suitable for debris volume estimation in the present study, where the debris flows typically occurred in areas with steep slopes and at higher elevations. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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24 pages, 11825 KiB

Open AccessArticle

Dynamic Properties of a Compacted Residual Soil from the West Indies

by Lila Mouali, Guillaume Veylon, Daniel Dias, Laurent Peyras, Claudio Carvajal, Jérôme Duriez and Eric Antoinet

Geotechnics 2023, 3(2), 254-277; https://doi.org/10.3390/geotechnics3020015 - 28 Apr 2023

Cited by 1 | Viewed by 1484

Abstract

This paper presents a laboratory investigation of the strain-dependent cyclic properties of a compacted tropical residual soil as measured in a resonant column and cyclic triaxial testing program. The mechanical properties were evaluated with respect to cyclic shear strain amplitude, initial void ratio, [...] Read more.

This paper presents a laboratory investigation of the strain-dependent cyclic properties of a compacted tropical residual soil as measured in a resonant column and cyclic triaxial testing program. The mechanical properties were evaluated with respect to cyclic shear strain amplitude, initial void ratio, and confining pressure. It was shown that the existing models for the prediction of shear modulus reduction and damping ratio curves were not pertinent in the case of the compacted residual soil studied. Empirical equations were developed for the small-strain shear modulus and the normalized shear modulus, damping ratio, and pore water pressure ratio curves for void ratios between e = 1.00 and e = 1.50 and mean effective pressures of

p^{'}

= 50−300 kPa. The comparison of the models to the measured values suggest that the uncertainties associated with each of these models are lower than 20% of the predicted values. The results were established as part of a project for the construction of an embankment dam in the West Indies. However, the methodology as well as the model formulation framework presented in the article can be generalized to other residual soils and applied in all fields of geotechnical engineering. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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30 pages, 10100 KiB

Open AccessArticle

Simultaneous Biocementation and Compaction of a Soil to Avoid the Breakage of Cementitious Structures during the Execution of Earthwork Constructions

by Laura Morales Hernández, Eduardo Garzón Garzón, Pedro J. Sánchez-Soto and Enrique Romero Morales

Geotechnics 2023, 3(2), 224-253; https://doi.org/10.3390/geotechnics3020014 - 23 Apr 2023

Cited by 1 | Viewed by 1452

Abstract

This research focuses on the potential for microbial treatment to stabilize compacted soils, which are often utilized in earthwork projects. A silt–clay sand was used to describe a particular kind of soil. The suggested remedy makes use of the soil’s naturally occurring urea [...] Read more.

This research focuses on the potential for microbial treatment to stabilize compacted soils, which are often utilized in earthwork projects. A silt–clay sand was used to describe a particular kind of soil. The suggested remedy makes use of the soil’s naturally occurring urea and Ca²⁺, as well as microorganisms introduced to the compaction water. Two alternative initial water-content types were examined: those on the dry side and those close to the ideal Proctor conditions. Bacillaceae microorganisms were used to induce microbial CaCO₃ precipitation and improve the hydraulic and mechanical properties of the compacted soil. The samples were biotreated and immediately compacted, so that the precipitation of calcium carbonate during the curing process took place in the contact areas between the particles (biocementation) and in the pore space (bioclogging). A set of techniques were used to study the ageing effects, such as the water-retention curve by dew-points psychrometer, mercury porosimetry intrusion, permeability, ultrasonic pulse velocity, resonant column, and unconfined and tensile-compression tests. During the ageing, it was observed that the bacterial activity consumed water for the hydrolysis of urea and other intermediate reactions to precipitate CaCO₃. This process resulted in a retraction of the microstructure and a change in the macrostructure. The bioclogging phenomenon was more evident in the soil microstructure, while the biocementation process was easier to observe in the macrostructure. The suction’s effects on the soil stiffness were studied in detail, and a significant increase was detected. Despite these water-content losses, which caused soil stiffening by increasing the suction, it was still feasible to identify the gradual rise in small-strain stiffness throughout incubation. The unconfined and tensile-compression tests showed a similar progressive increase in terms of peak compressive and peak splitting strength during the incubation. These results are of interest when microbiological treatments are applied in soils to produce cementitious materials, with the present investigation demonstrating a complete study of their geotechnical behaviour. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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18 pages, 4966 KiB

Open AccessArticle

Microstructure and Strength Parameters of Cement-Stabilized Loess

by Mani Axel, Xi’an Li, Feng Wen and Ming-Xiao An

Geotechnics 2023, 3(2), 161-178; https://doi.org/10.3390/geotechnics3020010 - 06 Apr 2023

Cited by 1 | Viewed by 1960

Abstract

In this study, cement was used as a component to provide a stabilizing effect in order to evaluate the hardness and stability of loess soil. To evaluate the strength properties of loess soil reinforced with cement, samples with four distinct cement concentrations (3%, [...] Read more.

In this study, cement was used as a component to provide a stabilizing effect in order to evaluate the hardness and stability of loess soil. To evaluate the strength properties of loess soil reinforced with cement, samples with four distinct cement concentrations (3%, 5%, 7%, and 9%) and three distinct curing durations (7, 14, and 28 days) were generated. During a series of tests, the flexural strength, direct shear strength, indirect tensile strength, and unconfined compressive strength were determined. An appropriate cement dosage was found, in addition to a durability index that could be used to quantify the effect of water absorption investigations on cement-stabilized loess. Both of these discoveries were made simultaneously. Scanning electron microscopy (SEM) and energy dispersive X-ray fluorescence spectrometry (XRF) examinations were carried out so that the fundamental mechanics of the materials could be comprehended. The results show that the cohesion of cement-stabilized loess is much more sensitive to structure than the friction angle of the material. The increase in shear strength after remoulding is due to cohesion. The SEM study showed that the cement interacted with the loess particles to produce a thick cement network that successfully covered the voids and boosted the mixture’s strength parameters. The 28-days UCS for the samples containing 7% cement was the greatest, at 3.5 MPa, while the UCS for those containing 9% cement was 4.78 MPa. The highest flexural tensile strength of 1.98 N/mm² was determined after 28 days. The tensile strength after 7 days in samples containing 3%, 5%, 7%, and 9% cement reached a maximum force of 0.15 MPa, 0.23 MPa, 0.27 MPa, and 0.37 MPa, respectively, and increased with each passing day. To achieve the desired level of strength, it is necessary to adjust the proportion of cement. In addition, as the curing period progressed, we observed an increase in the resistance and stiffness of the cement-stabilized loess due to the interactions that take place between the structure and the mineral composition. It is believed that this event was caused by naturally occurring cementation. As a consequence of this reaction, the production of new cementitious materials takes place. The cation exchange that causes the hydration and pozzolanic reaction that leads to the creation of aggregates and interparticle flocculation is responsible for their production. These findings suggest that cement may be utilised as a simple and effective method of loess stabilization, ultimately resulting in improved performance of the loess. Therefore, this study revealed that cement may considerably enhance the microstructure and strength parameters of loess. This research provides important information on cement-stabilized loess that has ramifications for geotechnical investigation, construction, research, and testing to achieve a successful project. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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18 pages, 9932 KiB

Open AccessArticle

Digital Rock Mechanical Properties by Simulation of True Triaxial Test: Impact of Microscale Factors

by Wenjie Ma, Yongfei Yang, Wendong Yang, Changran Lv, Jiangshan Yang, Wenhui Song, Hai Sun, Lei Zhang, Kai Zhang and Jun Yao

Geotechnics 2023, 3(1), 3-20; https://doi.org/10.3390/geotechnics3010002 - 26 Jan 2023

Cited by 1 | Viewed by 1929

Abstract

Complex fractures and pore structures in the rock strongly influence the mechanical properties, and the process from compression to failure is complicated. Under the action of rock stress, pore structure deformation and fractures close or propagate, easily leading to deterioration in the rock [...] Read more.

Complex fractures and pore structures in the rock strongly influence the mechanical properties, and the process from compression to failure is complicated. Under the action of rock stress, pore structure deformation and fractures close or propagate, easily leading to deterioration in the rock mechanical properties until rock failure. Thus, the effects of microscale factors are critical in mechanical properties such as rock strength, elastic modulus, and stress–strain state under the triaxial stress state. It is difficult for physical and mechanical experiments to obtain the qualitative rules of regular structures, but numerical simulation can make up for this defect. In this work, the accuracy of the model was proven through a comparison with previous experimental results. The true triaxial numerical simulation experiments were conducted on representative rocks and natural pore structures. These simulated results revealed that the pore and throat parameters will change abruptly when the particle model volumetric strain is between 0.0108 and 0.0157. When the fracture angle is between 45° and 75°, the fracture has a great influence on the peak stress. The angle between the natural fracture and the fracturing direction should be less than 45° as much as possible. Clay affects the rock strength by influencing the force chains formed by the rock skeleton. Fracturing is easier when the structural clay content is higher than 25%. It is easier to fracture in a direction parallel to the laminated clay when the clay content is below 27%. This work indicates the effects of rock particles, fractures, and clay on the mechanical parameters, providing key fundamental data for further quantifying the fracturing patterns. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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25 pages, 1882 KiB

Open AccessArticle

A Neural Network Model for Estimation of Failure Stresses and Strains in Cohesive Soils

by Ambrosios-Antonios Savvides and Leonidas Papadopoulos

Geotechnics 2022, 2(4), 1084-1108; https://doi.org/10.3390/geotechnics2040051 - 02 Dec 2022

Cited by 9 | Viewed by 1831

Abstract

In this article, a set of neural networks for the prediction of the stresses and the corresponding strains at failure of cohesive soils when subjected to a load of a shallow foundation are presented. The data are acquired via Monte Carlo analyses for [...] Read more.

In this article, a set of neural networks for the prediction of the stresses and the corresponding strains at failure of cohesive soils when subjected to a load of a shallow foundation are presented. The data are acquired via Monte Carlo analyses for different types of loadings and stochastic input material variabilities, and by adopting the clayey soil domain and modified Cam Clay material yield function. The mathematical functions for the estimation of the failure stresses and strains are computed with the feed forward neural network method (FNN). It is demonstrated that the accuracy of the derived relations is in the order of a maximum relative error of

10^{- 5}

in all monitored output variables. In addition, the number of training epochs required for convergence is relatively low and this means that the computational and data costs for the construction of the FNN are low. The critical input variable for the estimation of the most unfavorable situations is the Karhunen Loeve series expansion for porous analyses, while for non-porous analyses the constant distribution over depth is the one that provides more critical estimations for the monitored output variables of stresses and strains at failure. This set of functions can estimate the aforementioned variables of the footing settlement in clays with high accuracy; consequently, it can be an important tool for geotechnical engineering design, especially in providing the largest stress allowed from the foundation. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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27 pages, 12808 KiB

Open AccessArticle

Finite Element Simulations of Fluids Leakage through the Faulted Reservoir

by Mohammad Nurul Islam

Geotechnics 2022, 2(4), 908-934; https://doi.org/10.3390/geotechnics2040043 - 29 Oct 2022

Viewed by 1099

Abstract

Carbon dioxide (CO₂) capture and storage (CCS) in geological formation as a supercritical fluid is a viable option to reduce anthropogenic greenhouse gas emissions. Due to the density difference between CO₂ and formation fluid, CO₂ shows a buoyant tendency. [...] Read more.

Carbon dioxide (CO₂) capture and storage (CCS) in geological formation as a supercritical fluid is a viable option to reduce anthropogenic greenhouse gas emissions. Due to the density difference between CO₂ and formation fluid, CO₂ shows a buoyant tendency. Thereby, if CO₂ migrates towards the fault in a compromised faulted reservoir, it may escape the storage reservoir. Therefore, it is essential to predict fluids leakage through the faulted reservoir into the aquifer, associated pressure development, and fluids properties over time to assess associated risk and quantification of leakage. We present finite element simulations of miscible fluids flow through the faulted reservoir to elucidate this behavior. There are very few attempts to model multicomponent fluids non-isothermal model during phase change including the Equation of State (EoS) which we addressed by coupling the mass balance equation of fluids, the fractional mass transport, and the energy balance equation. To obtain fluids mixture thermo-physical properties, we used the Peng-Robinson EoS. For validation of the coupled formulation, we compared the simulation results with Ketzin Pilot project field monitoring data, which shows good agreement. A faulted reservoir comprised of five layers is used to investigate fluids leakage through a compromised reservoir. These layers are a CO₂ storage reservoir, overlain by alternating caprocks and aquifers. We also considered three different CO₂ injection rates to study the injection rate effect to assess the pressure buildup during injection process. We present the thermal effect by comparing the isothermal and the non-isothermal conditions. For the latter case, we assumed three different thermal gradients. Additionally, to assess the fault aperture effect, we studied three different apertures. We observed that developed pressure and fluids properties have effects on injection rates, temperature gradient, and fault aperture. Additionally, such responses in the near-field and the far-field from the injection well are critical to assess the risk, which we discussed in this paper. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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35 pages, 12283 KiB

Open AccessArticle

Development of Soil Moisture Content and Soil Matric Suction Model Based on Field Instrumentation and Electrical Resistivity Imaging (ERI) for Highway Slopes Constructed on High Expansive Clay Soil

by Masoud Nobahar, Rakesh Salunke, Mohammad Sadik Khan and Farshad Amini

Geotechnics 2022, 2(3), 671-705; https://doi.org/10.3390/geotechnics2030033 - 17 Aug 2022

Cited by 3 | Viewed by 1753

Abstract

In highway slopes (HWS) constructed on high expansive clay soil (HECS), in situ moisture variation is an environmentally driven variable that can significantly impact the safety of the constructed soil. Electrical resistivity imaging (ERI) is a non-destructive method with a considerable potential for [...] Read more.

In highway slopes (HWS) constructed on high expansive clay soil (HECS), in situ moisture variation is an environmentally driven variable that can significantly impact the safety of the constructed soil. Electrical resistivity imaging (ERI) is a non-destructive method with a considerable potential for subsurface soil moisture mapping, which can be correlated with volumetric soil moisture content (VSMC) and soil matric suction (SMS) of HECS to remarkably enhance the evaluation of the performance of the HWS. However, limited datasets are available to evaluate the accuracy and feasibility of the available correlative field-based models for the HECS under various field conditions. The objective of the current study is to develop a field-based model of VSMC and SMS using real-time field monitoring and ERI data. Six HWS located in the Jackson metro area in Mississippi (MS), USA were considered as reference slopes in this study. Comprehensive field instrumentation was executed at the six HWS to monitor the VSMC, SMS and rainfall intensity. The sensors were installed at the crest, middle and toe of the slope. The 2D ERI test was conducted using a dipole–dipole array with multiple electrodes at 5 ft (1.5 m) spacing. The ERI survey was conducted at the crest and middle of the six HWS to image the continuous soil subsurface profile in terms of moisture variation. The developed models indicated a good agreement between instrumented and ERI data. The developed models will facilitate the estimation of VSMC and SMS variations and aid in performance monitoring of the HWS built on HECS such as Yazoo clay. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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16 pages, 3936 KiB

Open AccessArticle

Large Displacement Finite Element Modelling of the Screw Driving Sounding Test in Sandy Soil Using the Coupled Eulerian-Lagrangian Method

by Seyed Yasin Mirjafari, Rolando P. Orense and Raj Das

Geotechnics 2022, 2(2), 441-456; https://doi.org/10.3390/geotechnics2020021 - 13 Jun 2022

Viewed by 2209

Abstract

The Screw Driving Sounding (SDS) is a recently developed in-situ testing method for soil/site characterisation. To better understand the mechanism of testing, it is essential to create a simulation model for the SDS test to assist in better understanding the response and in [...] Read more.

The Screw Driving Sounding (SDS) is a recently developed in-situ testing method for soil/site characterisation. To better understand the mechanism of testing, it is essential to create a simulation model for the SDS test to assist in better understanding the response and in improving the testing process, not to mention the development of empirical correlations to estimate geotechnical parameters for use in design. Complex problems involving large deformations are usually difficult to solve with the classical finite element (FE) method because large deformations can lead to large mesh distortions and contact problems. In this paper, a computational model using the finite element method is developed to simulate the drilling process involved in SDS tests; the Coupled Eulerian-Lagrangian (CEL) approach is used to deal with large deformation problems. The SDS drilling process in a sandy deposit with defined stress states (i.e., relative density and effective confining pressure) is simulated, and the SDS-derived parameters are monitored. Based on the simulation results, a chart was established to correlate the measured SDS parameter with the internal friction angle for different vertical effective overburden stresses. The derived chart is validated with the results of laboratory tests performed on samples taken from several sites in Christchurch, NZ, adjacent to the locations of the SDS tests. The results show that the CEL FE framework can model complex physical processes encountered during the SDS drilling. Moreover, the developed chart can be used to estimate the friction angle of the sandy soil based on the SDS-measured torque at a given depth. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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10 pages, 1655 KiB

Open AccessArticle

Effect of Water Content on Apparent Cohesion of Soils from Landslide Sites

by Sinnappoo Ravindran and Ivan Gratchev

Geotechnics 2022, 2(2), 385-394; https://doi.org/10.3390/geotechnics2020017 - 29 Apr 2022

Cited by 4 | Viewed by 2886

Abstract

There are many empirical equations published for unsaturated fine-grained soils. However, there is only one empirical equation established for silty sand using the shear-box test and filter-paper-based suction test, but with the suction range of 0 to 200 kPa. It is reported that [...] Read more.

There are many empirical equations published for unsaturated fine-grained soils. However, there is only one empirical equation established for silty sand using the shear-box test and filter-paper-based suction test, but with the suction range of 0 to 200 kPa. It is reported that there is a significant discrepancy between the predicted values and test results of apparent cohesion within the range of 0 to 100 kPa for unsaturated coarse-grained soils. The purpose of this research is to study the effect of water content on apparent cohesion and predict apparent cohesion for coarse-grained soils within the range of 0 to 100 kPa using shear-box test and suction test results without much inconsistency. In this research, soil samples from the rainfall-induced landslide sites were obtained; laboratory tests such as soil-classification tests, shear-box tests and consolidated undrained triaxial tests were carried out. Test results were analyzed, and the findings are presented. When the water content is increased from 0% to 30%, there is a reduction of 89% in apparent cohesion on average. A newly developed prediction model for apparent cohesion based on the low range of matric suction from 0 to 100 kPa for unsaturated coarse-grained soils is introduced in this paper and compared with published models. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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37 pages, 2523 KiB

Open AccessArticle

Uncertainty Quantification of Failure of Shallow Foundation on Clayey Soils with a Modified Cam-Clay Yield Criterion and Stochastic FEM

by Ambrosios-Antonios Savvides and Manolis Papadrakakis

Geotechnics 2022, 2(2), 348-384; https://doi.org/10.3390/geotechnics2020016 - 28 Apr 2022

Cited by 5 | Viewed by 1894

Abstract

In this article, a quantitative numerical study of the random distribution of the soil material parameters to the probability density functions of the failure load and failure displacements of a shallow foundation is presented. A modified Cam-Clay yield function is used for this [...] Read more.

In this article, a quantitative numerical study of the random distribution of the soil material parameters to the probability density functions of the failure load and failure displacements of a shallow foundation is presented. A modified Cam-Clay yield function is used for this scope into a stochastic finite element numerical formulation. Several hypotheses for the random distribution of the compressibility factor

κ

, of the material constitutive relation, the critical state line inclination c of the soil, as well as of the permeability k of the continuum, have been tested and assessed with Monte Carlo simulation accelerated with Latin hypercube sampling. It is validated that both failure load and failure displacements follow Gaussian normal distribution despite the non-linear behaviour of the soil. Furthermore, as the soil depth increases, the mean value of failure load decreases and the failure displacement increases. The failure mechanism of clays can be determined with accuracy using this numerical implementation, without the restrictions imposed by analytical solutions, taking into consideration the eccentricity of the load in combination with non-linear constitutive relations. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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13 pages, 639 KiB

Open AccessArticle

Chemo-Mechanical Couplings at Granular Contact: The Effect of Mineral Dissolution and Precipitation across the Scales

by Hemanta Bista, Sadrish Panthi and Liangbo Hu

Geotechnics 2022, 2(1), 158-170; https://doi.org/10.3390/geotechnics2010007 - 01 Feb 2022

Cited by 1 | Viewed by 2510

Abstract

Strong interactions between mechanical deformation and chemical reactions may play a critical role in the response of geomaterials or geological systems to evolving environmental circumstances that may occur in both natural and engineered processes. The present study focuses on mineral dissolution and precipitation [...] Read more.

Strong interactions between mechanical deformation and chemical reactions may play a critical role in the response of geomaterials or geological systems to evolving environmental circumstances that may occur in both natural and engineered processes. The present study focuses on mineral dissolution and precipitation at the intergranular contact whose consequences are often manifested at the macro-scale where the mechanical and transport properties of the geomaterial may be altered. Discrete element modeling is employed to explore two applications involving such mineral transformations. The first example is primarily focused on the chemo-mechanical coupling mechanisms of intergranular contact in the natural process of pressure solution and secondary compression. The effect of the mineral dissolution on the mechanical response at the grain contact is incorporated into the contact model. Discrete element simulations are performed to examine the overall mechanical response of particle assembles subject to mineral dissolution and the results demonstrate the important role of the kinetic rate characteristics of the dissolution process. The second part of the present study revolves around the effect of mineral precipitation in an engineered process known as microbially induced calcite precipitation for potential soil improvement. The kinetics of involved bio-chemical process is incorporated into on the contact model and the simulation results indicate considerable strengthening effect. Overall, the present study demonstrates the feasibility of discrete element approach as a numerical tool to model coupled chemo-mechanical phenomena across the scales. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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18 pages, 8593 KiB

Open AccessArticle

Seismic Hazard Assessment for a Wind Farm Offshore England

by Brian Carlton, Andy Barwise and Amir M. Kaynia

Geotechnics 2022, 2(1), 14-31; https://doi.org/10.3390/geotechnics2010002 - 06 Jan 2022

Cited by 1 | Viewed by 2684

Abstract

Offshore wind has become a major contributor to reducing global carbon emissions. This paper presents a probabilistic seismic hazard analysis for the Sofia Offshore Wind Farm, which is located about 200 km north-east of England in the southern North Sea and will be [...] Read more.

Offshore wind has become a major contributor to reducing global carbon emissions. This paper presents a probabilistic seismic hazard analysis for the Sofia Offshore Wind Farm, which is located about 200 km north-east of England in the southern North Sea and will be one of the largest offshore wind farms in the world once completed. The seismic source characterization is composed of two areal seismic source models and four seismic source models derived using smoothed gridded seismicity with earthquake catalogue data processed by different techniques. The ground motion characterization contains eight ground motion models selected based on comparisons with regional data. The main findings are (1) the variation in seismic hazard across the site is negligible; (2) the main source controlling the hazard is the source that includes the 1931 Dogger Bank earthquake; (3) earthquake scenarios controlling the hazard are M_w = 5.0–6.3 and R = 110–210 km; and (4) the peak ground accelerations on rock are lower than for previous regional studies. These results could help guide future seismic hazard assessments in the North Sea. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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Review

Jump to: Research

18 pages, 2916 KiB

Open AccessReview

Advances in Coupling Computational Fluid Dynamics and Discrete Element Method in Geotechnical Problems

by Yang Cao, Hoang Bao Khoi Nguyen, Derrick Aikins, Md. Rajibul Karim and Md. Mizanur Rahman

Geotechnics 2023, 3(4), 1162-1179; https://doi.org/10.3390/geotechnics3040063 - 01 Nov 2023

Viewed by 1300

Abstract

In some cases, the water content in granular soil increases to the extent that it becomes saturated, which noticeably alters its responses. For example, the pore water pressure within saturated granular soil would increase rapidly under sudden external loading, which is equivalent to [...] Read more.

In some cases, the water content in granular soil increases to the extent that it becomes saturated, which noticeably alters its responses. For example, the pore water pressure within saturated granular soil would increase rapidly under sudden external loading, which is equivalent to undrained or constant volume conditions. This reduces the effective stress in soil dramatically and may result in catastrophic failure. There have been different numerical approaches to analyse such a failure mechanism of soil to provide a deeper understanding of soil behaviour at the microscopic level. One of the most common numerical tools for such analysis is the discrete element method (DEM) due to its advantage in obtaining microscopic properties (e.g., statistics on particle contacts and fabric), reproducibility and simple feedback control. However, most DEM studies ignore the fluid phase and merely consider the solid particles while the fluid pressure is indirectly calculated by mimicking undrained condition to a constant volume condition. Note that fluid’s influence does not limit to the change of pore water pressure. For example, the external loading would induce the movement of fluid, and the fluid-solid interaction could subsequently drag the solid particles to shift within the system. In addition, the state of soil could change from solid to suspension under an excess hydraulic gradient. Therefore, the study of the fluid-solid mixture is essential as it is a typical scenario in geotechnical practice, and the simulations of saturated sand should be conducted in numerical forms in which both the solid and fluid phases can be modelled. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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35 pages, 11904 KiB

Open AccessReview

The Dynamic Properties of Sand under Torsion: A Literature Review

by Majd Ahmad and Richard Ray

Geotechnics 2023, 3(2), 480-514; https://doi.org/10.3390/geotechnics3020027 - 11 Jun 2023

Cited by 2 | Viewed by 1369

Abstract

Resonant column (RC) and the torsional simple shear (TOSS) tests have shown proven competency in acquiring precise and repeatable measurements regarding the shear modulus and damping ratio of soil. For most dynamic geotechnical problems, the shear modulus represents the stiffness of the soil, [...] Read more.

Resonant column (RC) and the torsional simple shear (TOSS) tests have shown proven competency in acquiring precise and repeatable measurements regarding the shear modulus and damping ratio of soil. For most dynamic geotechnical problems, the shear modulus represents the stiffness of the soil, while the damping ratio describes energy dissipation. Many studies in the last few decades focused on developing the relevant equipment and investigating the effect of different soil properties on the dynamic behavior of soil. Researchers have introduced correlations to approximate this behavior without conducting dynamic torsional testing. Soil models (e.g., Ramberg-Osgood and Hardin-Drnevich) can simulate shear stress-strain curves after finding the curve-fitting parameters. Due to the complexity of dynamic behavior and its dependency on various factors in soils, the RO and HD equations help model the behavior more simply. This paper presents a literature review and evaluation of the studies, correlations, soil models, and parameters affecting the dynamic behavior of dry sand under torsion. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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22 pages, 2895 KiB

Open AccessReview

Review of Geotechnical Properties of Reclaimed Asphalt Pavement for Reuse in Infrastructure

by Catherine H. Dager, Robert H. Morro, Jonathan F. Hubler and Kristin M. Sample-Lord

Geotechnics 2023, 3(1), 21-42; https://doi.org/10.3390/geotechnics3010003 - 15 Feb 2023

Cited by 1 | Viewed by 2516

Abstract

Reclaimed Asphalt Pavement (RAP) has been extensively studied for potential use as a recycled material in infrastructure construction. There is consensus that utilization of RAP provides environmental and economic benefits for most projects. However, impacts to engineering performance are less known, owing to [...] Read more.

Reclaimed Asphalt Pavement (RAP) has been extensively studied for potential use as a recycled material in infrastructure construction. There is consensus that utilization of RAP provides environmental and economic benefits for most projects. However, impacts to engineering performance are less known, owing to the highly variable nature of RAP sources with different asphalt pavement mixtures and milling processes, which has limited the adoption of RAP as fill material in geotechnical infrastructure. This study conducted a comprehensive review of geotechnical properties reported for RAP in the experimental literature. The gradation, specific gravity, density, moisture content, hydraulic conductivity, leaching, shear strength, and creep properties of different RAP sources are summarized and compared. These geotechnical properties, as well as recent investigations into the effects of temperature and aggregate mixing, were used to identify the potential reuse of RAP in highway transportation applications beyond just asphalt mixture design, such as embankments. Additionally, correlations between gradation properties (C_u, D₁₀, D₈₅), asphalt content, and the geotechnical properties of maximum dry density, saturated hydraulic conductivity, and shear strength were identified. Full article

(This article belongs to the Special Issue Recent Advances in Geotechnical Engineering)

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