Clay Model Research Articles

Aposematism vs. scavenging? camera trapping unveils low and seasonal-dependent consumption of toxic salamander carcasses by wild boars

Abstract Aposematic species rely on primary and secondary antipredator strategies. Yet, some opportunistic and generalist species may consume them, although this has been largely supported by indirect evidence such as dietary analyses or clay model experiments. Here, we studied the role of the wild boar, Sus scrofa, as a consumer and possible predator of an aposematic and toxic salamander, Salamandra salamandra gallaica. We investigated this behaviour using camera traps and salamander carcasses on a small island where both species co-occur. Our results show a very low proportion of salamanders consumed by wild boars (3.8%), which indicates that fire salamanders might not completely rely on their aposematic strategy to avoid being consumed by this generalist species. The number of predation events does not differ between wild boar age classes, but it does between seasons, with a higher consumption in spring, which can be associated with an increase in animal consumption when fruits (e.g., acorns) are no longer available on this island. We also highlight the need for temporal studies targeting predator-prey interactions through behavioural data and complementary approaches to better understand the possible impact of opportunistic and generalist species in the ecosystem. This is particularly important in management plans involving the control of generalist species such as the wild boar, which is considered one of the most invasive species globally and a threat to countless species worldwide.

Novel pseudo-hexagonal montmorillonite model and microsecond MD simulations of hydrate formation in mixed clay sediments with surface defects.

Both CH4 hydrate accumulation and hydrate-based CO2 sequestration involve hydrate formation in mixed clay sediments. The development of realistic clay models and a nanoscale understanding of hydrate formation in mixed clay sediments are crucial for energy recovery and carbon sequestration. Here, we propose a novel molecular model of pseudo-hexagonal montmorillonite nanoparticles. The stress-strain curves of tension, compression, and shear of pseudo-hexagonal montmorillonite nanoparticles exhibit linear characteristics, with tension, compression, and shear moduli of ∼435, 410, and 137GPa, respectively. We perform microsecond molecular dynamics simulations to study CH4 and CH4/CO2 hydrate formation in montmorillonite-illite mixed clay sediments with surface defects. The results indicate that hydrate formation in mixed clay sediments is significantly influenced by the presence of clay defects. CH4 and CH4/CO2 mixed hydrates are challenging to form at the junction between the inside and outside clay defects. CH4 and CH4/CO2 mixed hydrates exhibit a preference for forming outside the clay defects rather than inside the clay defects. Some CH4 and CO2 molecules from the inside clay defect migrate to the outside clay defect, thereby promoting CH4 and CH4/CO2 mixed hydrate formation outside the clay defects. This molecular insight advances the development of clay particle models and expands an understanding of natural gas hydrate accumulation and hydrate-based CO2 sequestration.

Experimental Study: Stress Path Coefficient in Unconsolidated Sands: Effects of Re-Pressurization and Depletion Hysteresis

Accurate estimation of in-situ stresses is a critical parameter for geo-mechanical modelling. In-situ stresses are estimated in the field from logs and frac tests. Laboratory tests are performed with cored material to estimate horizontal stress changes under defined boundary conditions to complement field data. Horizontal stress path coefficient is used to estimate a change in in-situ stresses as the reservoir undergoes depletion or injection. Uniaxial Strain boundary conditions are representative of far field stress state. The laboratory data provides the change in horizontal stress with a change in pore pressure. It is used to complement the field data acquisition of absolute stress values to predict the value of total stresses. This experimental study provides a novel method of simulating geological compaction for fabricating representative samples from unconsolidated sands. It investigates the variability of horizontal stress path coefficient as a function of changing pore pressure (depressurization and re-pressurization) in unconsolidated sandstone reservoirs. Synthetic sandstones samples were made from sand packs by consolidating them under an isostatic stress path at ambient pore pressure. After getting to initial reservoir conditions, a series of pore pressure depletion and injection tests with varying magnitudes (injection and depletion) were performed to study the effects of stress path direction and associated hysteresis. The magnitude of the stress path coefficient under depletion is lower than that under injection for the first load-unload cycle. In subsequent load-unload cycles, the stress path coefficient values remain constant until the sample is depleted to a new level of pore pressure. A Modified Cam Clay model is fit to the data to map the expansion of the yield surface and quantify the model parameters. Application of this research includes accurate prediction of changes in-situ stresses during depletion and injection stress paths for simulating unconsolidated reservoirs behavior under fluid injection or further depletion.

Cracking Sensitivity Analysis of Red Clay With Pre‐Crack Under Three‐Point Bending

ABSTRACTRed clay is highly susceptible to cracking due to its nature, and the reduction in strength caused by cracking can lead to engineering disasters. To investigate the cracking sensitivity of red clay, a homogeneous fracture model of red clay based on the cohesive zone model was established using ABAQUS in this work, the reliability of the model was verified through a three‐point bending test, and then the crack propagation process and sensitivity to test factors of red clay were further analyzed. The results show that the fracture simulation of the cohesive zone model is in good agreement with the test results, confirming by the high reliability. The depth of prefabricated cracks and fulcrum spacing had the significant effects on the crack path, and the decrease of prefabricated crack depth and fulcrum spacing led to the increase of critical load. Meanwhile, the loading rate had little effect on the load–displacement curves.

CASM-U: a unified critical state model for unsaturated clays and sands

CASM-U: a unified critical state model for unsaturated clays and sands

Numerical investigation on rotation accumulation and natural frequency degradation for offshore wind turbine in clays

Prolonged lateral cyclic loading leads to soil stiffness degradation around offshore wind turbine (OWT) foundations, which reduces the system's natural frequency and increases the accumulation of foundation rotation angle. Proper evaluation of natural frequency and rotation angle is crucial for the design of OWT foundations. This study develops a two-stages numerical approach to calculate the fundamental frequency of OWT systems considering the foundation stiffness degradation by integrating a stiffness degradation model of soft clays with a simplified three-spring model. Subsequently, it investigates the evolution of accumulated rotation and natural frequency for three foundation types—monopile, monopod bucket, and hybrid monopile-bucket—throughout their service life. It is observed that the hybrid foundation shows the smallest rotation in the first cycle, attributable to its relatively high initial stiffness compared to the other two foundations with the same steel consumption. However, it also exhibits the highest rate of cumulative rotation growth. At the same load level, the monopod bucket foundation exhibits the largest cumulative rotation angle due to its lower bearing capacity, and the degradation of natural frequency is most pronounced for monopod bucket OWT. For all three foundation configurations, increasing either the pile diameter or the bucket diameter is the most effective approach to reduce the cumulative rotation angle and improve natural frequency degradation, while maintaining the same steel consumption. These findings should be considered in the design of OWT foundations.

Soil Texture Mapping in the Permafrost Region: A Case Study on the Eastern Qinghai–Tibet Plateau

Soil particle distribution is one of the basic parameters for many Earth system models, while the soil texture data are largely not available. This is especially true for complex terrains due to the difficulties in data acquisition. Here, we selected an area, Wenquan area, with rolling mountains and valleys, in the eastern Qinghai–Tibet Plateau (QTP) as the study area. Using the random forest model, we established quantitative models of silt, clay, and sand content, and environmental variables, including elevation, slope, aspect, plane curvature, slope curvature, topographic wetness index, NDVI, EVI, MAT, and MAP at different depths based on the survey data of 58 soil sample points. The results showed that sand content was the highest, accounting for more than 75% of the soil particles. Overall, the average values of clay and silt gradually decreased with increasing soil profile depth, while sand showed the opposite pattern. In terms of spatial distribution, clay and silt are higher in the southeast and lower in the northwest in each standard layer, while sand is just the opposite. The random forest regression model showed that vegetation condition was a controlling factor of soil particle size. These results showed that random forest applies to predicting the spatial distribution of soil particle sizes for areas with complex terrains.

Effect of torsional shear stress on the deformation characteristics of clay under traffic load

The soft clay under the road ground will suffer cyclic torsional shear stress encountered traffic load in addition to axial stress, which will cause further deformation of clay. To investigate the effect of torsional shear stress on the cumulative axial strain of clay, a series of undrained tests under cardioid stress path were performed on K0 consolidated undisturbed samples by using a hollow cylinder apparatus (HCA). The effect of vertical cyclic stress ratio (VCSR) and shear stress ratio (η) on the deformation and degradation characteristics of clay was investigated. The results indicate that there is inconsistency between the strain path and stress path. The increase in η further accelerates the accumulation of axial strain, which resulted from the degradation of clay induced by torsional shear stress. Considering the VCSR and η, a calculation method of degradation index was developed. Furthermore, a cumulative axial strain prediction model of clay under the cardioid stress path was established considering the degradation. This model addresses the limitation of traditional prediction models by considering the impact of torsional shear stress on cumulative axial strain.

A Critical State Constitutive Model for Methane Hydrate‐Bearing Sediments Considering Hydrate Pore‐Filling and Cementing Effects

ABSTRACTTo safely and effectively explore the natural methane hydrate, it is crucial to examine the mechanical behavior of methane hydrate‐bearing sediments (MHBSs). Natural methane hydrate unevenly distributes in pores or bonds with soil particles in MHBS, changing the mechanical behavior of MHBS including stiffness, shear strength, and dilatancy. This paper presents an anisotropic critical state model for MHBS considering hydrate pore‐filling and cementing effects. Based on the unified critical state model for both clay and sand, an equivalent hydrate ratio is defined to address pore‐filling effect. Cohesive strength and its hardening law are introduced to characterize hydrate cementation. To describe the anisotropic behavior, the inherent anisotropy of soil particles and hydrates are modeled separately, and rotation hardening is introduced to describe the stress‐induced anisotropy. Comparisons with existing triaxial tests of both synthetic and natural MHBS demonstrate that the proposed model comprehensively describes the mechanical behavior of MHBS. Detailed predictions indicate that hydrate pore‐filling affects the hydrate‐dependent stiffness and dilatancy of MHBS, which become more pronounced with increasing hydrate saturation. Cementing effect increases the initial stiffness and peak strength of MHBS. The pronounced influence of inherent anisotropic parameters on pre‐peak stress–strain relation of MHBS is noted, and increasing hydrate saturation enhances the effect of hydrate anisotropy. These predictions contribute to a better understanding of the relation between hydrate morphologies and MHBS mechanical properties.

Modeling Realistic Clay Systems with ClayCode.

Clays are a broad class of ubiquitous layered materials. Their specific chemophysical properties are intimately connected to their molecular structure, featuring repeating patterns broken by substitutions. Molecular dynamics simulations can provide insight into the mechanisms leading to the emergent properties of these layered materials; however, up to now, idealized clay structures have been simulated to make the modeling process tractable. We present ClayCode, a software facilitating the modeling of clay systems closely resembling experimentally determined structures. By comparing a realistic model to a commonly used montmorillonite clay model, we demonstrate that idealized models feature noticeably different ionic adsorption patterns. We then present an application of ClayCode to the study the competitive barium and sodium adsorption on Wyoming montmorillonite, Georgia kaolinite, and Montana Illite, of interest in the context of nuclear waste disposal.

APD: An automated parameter determination system based on in-situ tests

In-situ testing has numerous applications in geotechnical engineering. The interpretation of in-situ test results includes soil stratification and determination of soil parameters. This paper presents an automated parameter determination framework that aims to determine constitutive model parameters based on in-situ tests. The ongoing research project relies on a graph-based approach for determining the parameters. The framework has two main attributes: transparency and adaptability. Transparency is achieved by illustrating how a certain parameter was computed. Adaptability is ensured by allowing users to incorporate their expertise into the framework. The system currently determines parameters based on three main workflows that utilize the results of cone penetration tests, dilatometer tests, and shear wave velocity measurements. This study employs the three main workflows to determine soil parameters for one of the Norwegian GeoTest Sites. Additionally, the connection between the parameter determination system and finite element analysis is discussed, where the parameters for the Modified Cam Clay model are evaluated. The framework is valuable in the early stages of projects, providing detailed soil information when soil data is limited. Ongoing research aims to assess the accuracy of the derived soil and constitutive model parameters and to expand the system’s capabilities by including additional in-situ tests.

Integrating Clay Modeling in Implant Fabrication for Craniofacial Defect.

Manufacturing craniofacial implants using 3-dimensional (3D) methods and computed tomography data has become popular. The image object for the defect is produced as the first step, followed by several methods to create the implant. The authors have used a novel method that combines clay modeling with 3D scanning to create implants for craniofacial contour reconstruction. This approach does not require complicated resources. The method allows for high customization and immediate modifications, resulting in implants that achieve an accurate fit and high patient satisfaction. It is particularly beneficial for addressing complex defects and achieving aesthetic improvements. In addition, it reduces the need for cumbersome digital processing and expensive materials, making it a practical and feasible solution for a wide range of craniofacial deformities.

Thermo-elasto-plastic constitutive model of saturated clay considering state-dependent

Thermo-elasto-plastic constitutive model of saturated clay considering state-dependent

한 중년여성의 자아정체성탐색 경험에 대한 예술 기반 내러티브 탐구

In this study, the experience and meaning of a middle-aged woman’s self-identity search were explored in a narrative based on art. The participant of this study, Kim Min-seo (pseudonym), is a woman in her 50s. The researcher and the participant conducted a total of 10 sessions from July 26, 2022, to September 27, 2022, followed by two additional interviews 9 months later. To explore the meaning of the participant’s experiences of self-identity, formed throughout her life, the researcher employed various artistic media and techniques such as clay modeling for emotional expression, drawing family figures, writing poetry, collage-making, and reading fairy tales. Through these sensory, perceptual, cognitive, and symbolic methods, the participant was encouraged to express her life story, and the researcher engaged in discussions with the participant centered around her artistic creations. Based on the verbatim transcripts of all conversations, photographs of the participant’s artistic creations, and the researcher’s journal, a narrative of the participant’s self-identity exploration experience was constructed within a three-dimensional narrative inquiry space. The meaning of the participant’s experiences was then analyzed through this process. As a result, the meaning of the participant’s self-identity exploration experience was constructed as follows: 1. Catharsis through opening up about childhood experiences of abuse. 2. Confession and reflection on guilt related to child abuse. 3. Understanding of interpersonal conflict caused by the lack of nurturing care. 4. Discovery of a new identity for the wounded inner child. Through the relational inquiry space facilitated by her artistic creations, the participant was able to unravel various self-identity narratives embedded in her experiences of both victimhood and perpetration of abuse within the family, as well as her current interpersonal conflicts. In doing so, she discovered the symbol of a “fully bloomed yellow flower,” representing a beautiful and confident version of herself.

Aerodynamic development of the BYD SEAL – Part 2: Overview

BYD SEAL is a new developed A+ class sedan by BYD Auto, based on third generation high-performance and high-safety electric platform for EVs. SEAL gives full play to the advantages of electric vehicles in terms of space, handling, NVH, etc., while striving to reach the same level of fuel vehicles in terms of cost and recharge mileage. Therefore it has been dedicated to minimizing energy consumption from all components since its inception, and an important one is to reduce the aerodynamic drag effectively. However, the “ocean aesthetics” styling design based on the original concept model and platform with short overhangs must be kept on this car, which brings great challenge to aerodynamic development. An adaptable aerodynamic development process is set up and correlation between CFD simulation and wind tunnel test are established. This paper depicts the features of the flow field determined in the aerodynamic development process of the BYD SEAL, and describes the key factors in aerodynamic drag reduction as a full model change in detail. Effective rear roofline angle, tail design, front bumper corners, underbody, wheel, detail management such as sealing loss are studied and optimized by Powerflow and Star-CCM+ simulation softwares, and verified in wind tunnel tests of full-scale clay models and prototype vehicles. Design fusion and development tool/efficiency improvement around the vehicle are established, and the inherent drag reduction mechanism is revealed. These findings are of great significance to the aerodynamic optimization with diverse aesthetic and engineering requirements under the background of EV platformization.

Non-isothermal Fractional Order Two-surface Viscoplastic Model for Stiff Clays

Stiff clay exists widely in the world, but its significant time- and temperature-dependent mechanical features have not been fully modelled. In the context of fractional consistency viscoplasticity and bounding/subloading surface theory, this study proposes a novel non-isothermal fractional order two-surface viscoplastic model for stiff clays. First, with proposing a generalized plastic strain rate, the isotach viscosity is modified and extended to both over-consolidated and non-isothermal conditions that takes into consideration the effects of temperature and OCR on thermal accelerated creep. Then, two strain rate and temperature dependent yield surfaces are proposed with isotropic and progressive hardening rules to consider thermal collapse, strain rate effects, and smooth transition from elastic to viscoplastic behaviors. Next, the stress-fractional operator of the loading surface, according to the principle of the fractional consistency viscoplasticity, is introduced to describe the non-associativity of stiff clays. Finally, the predictive ability of the model is validated through simulating triaxial tests on Boom clay with various stress paths considering the temperature- and time-dependent features of stiff clays.

Investigation of strain-softening behaviours and development of constitutive model of red clays in Guiyang, China

Red clay is widely used in engineering projects; it is characterized by high moisture content, high plasticity, large porosity, high strength and low compressibility. The engineering properties and deformation modelling of red clay in Guiyang differ significantly from those of ordinary soils. Consequently, it is essential to conduct a detailed study of the stress–strain relationship of red clay in order to obtain accurate engineering parameters. Hence, a series of unconsolidated undrained triaxial compression tests (UU) was conducted on red clay in Guiyang under different water contents and confining pressures. The test results show that the stress–strain curve of the clay undergoes three stages: elastic deformation, plastic yielding and stress reduction after failure. After reaching peak deviatoric stress, the deviatoric stress decreases gradually and stabilizes, showing noticeable strain-softening characteristics. The non-linear model from the Nanjing Hydraulic Research Institute (NHRI) was introduced for fitting and obtaining relevant parameters. Then, based on the FLAC 3D platform, numerical simulation was carried out on a standard soil sample. The research results show that the calculated curve from the non-linear model fits the experimental curve quite well, and the numerical test curve also agrees with it. This indicates that the non-linear model from NHRI can effectively reflect the strain-softening behaviour of clay and is highly applicable to Guiyang red clay.

Study of Determination Settlement of Shallow Foundations in Case of sufficient Foundations Load Bearing Capacity in Clay Layers and 2D Modeling by Finite Element Method Case Study: (Ban Donmai Campus, Souphanouvong University)

The purpose of this research study was to study the behavior and Study of determination settlement of shallow foundations in case of sufficient foundations load bearing capacity in clay layer and 2D modeling by Finite Element Method (FEM). The wash boring was performed and the Undisturbed Sample soil was sampled to obtain the basic soil properties in the laboratory according to the 7.5 - 10 m the soil excavation characteristics from the actual construction at the level of excavation from 1 - 1.45 meters, For 1.5 x 1.5 m foundations and 2 x 2 m foundations. In addition, the bearing capacity of the foundation and the soil bearing capacity under the foundation. To analyze the parameters used to evaluate the settlement value and the effect. To analyze the settlement of the various theories and to use the Static Method to analyze the load-bearing capacity of the foundation and to evaluate the Settlement value, The Finite Element Method (FEM) model and the Mohr coulomb soil behavior model was used. The Result for a 1.5 x 1.5 m settlement of shallow foundation with a bearing capacity of 80 Tons. The mean settlement of shallow foundation values ​​for the and Perloff = 6.136 cm. For 2 x 2 m foundations, the bearing capacity of the foundation is 80 Tons. The total settlement values ​​for the Finite Element Method (FEM) = 60 Tons. Perloff's method can receive only 40 Tons of bearing capacity. For a 2 x 2 m foundation, the Bowles, Harr, Christian and Carrier, and Janbu methods = 80 Tons of bearing capacity, while the Perloff method and the FEM method only 40 Tons of bearing capacity.

A novel creep-damage constitutive model of clay–gravel composite considering the effect of water content and saturation-undersaturation cycles and its engineering application

A novel creep-damage constitutive model of clay–gravel composite considering the effect of water content and saturation-undersaturation cycles and its engineering application

Case report on clay sculpting of Platonic solids for anxiety: Exploration of effects and mechanisms of change

Touch is an essential component of the human experience, especially evident in art therapy where activities like clay work serve as powerful tools for sensory expression. While art therapy is often associated with free expression and creativity, structured interventions prove most effective in addressing negative moods. A structured art intervention, used in anthroposophic art therapy, is clay modeling of Platonic solids. The idea is that sculpting these abstract geometric forms helps individuals to regain or strengthen a sense of stability. In this specific case study, the therapeutic effects of Platonic solids were explored concerning anxiety reduction. The patient suffered from anxiety, panic attacks, severe distress and somatization. After three months art therapy, her anxiety and somatization were significantly reduced. It was found that patient’s ability to accept her emotions and responses to distress improved. This case report sheds light on the mechanisms underlying art therapy, particularly the role of tactile engagement in facilitating emotional integration across different levels of consciousness, increasing patient’s self-awareness. This case report contributes to the ongoing exploration of art therapy's transformative potential, emphasizing the significance of tactile experiences and combining a body-oriented approach with a cognitive challenge (Platonic solids) in the therapeutic process.