Effect Of Stress History Research Articles

Effects of early social isolation and adolescent single prolonged stress on anxiety-like behaviors and voluntary ethanol consumption in female Long Evans rats.

Exposure to stress during childhood and adolescence is a risk factor for alcohol use disorder (AUD) and comorbid conditions, including posttraumatic stress disorder (PTSD). We previously established an adolescent social isolation (SI) model that leads to the emergence of a wide range of behavioral risk factors for AUD, including increased anxiety-like behavior, locomotor activity, and ethanol consumption in male and female rats. Here, we sought to test the hypothesis that SI may increase vulnerability to single prolonged stress (SPS), a rodent model of PTSD. Female Long Evans rats (n = 8/group) were either single-housed or group-housed (GH) (4/cage) on postnatal day 21. One week later, rats underwent testing in the open field test (OFT), elevated plus-maze (EPM), and successive alleys test (SAT). Following initial behavioral testing, a subset of SI/GH rats were exposed to SPS. All rats were then tested on the novelty-suppressed feeding test (NSFT) followed by fear conditioning and home cage two-bottle choice to assess ethanol consumption. SI significantly increased activity in the OFT and anxiety-like behavior on the SAT, but not the EPM. While SI and SPS alone had no effect on the NSFT, exposure to both stressors significantly increased approach latency. Complex effects of stress history were observed across a 3-day fear conditioning paradigm and no group differences were observed with home cage ethanol consumption, regardless of prior ethanol exposure. The results from this study provide novel evidence that SI interacts with SPS in female rats to influence behavior in assays of unconditioned anxiety-like behavior (NSFT) and conditioned fear. Surprisingly, stress exposure had no effect on home cage ethanol consumption. Ultimately, these models provide useful avenues to examine the interaction between stressful experiences, alcohol exposure, biological sex, and the neurobiological adaptations underlying potential risk factors for psychiatric conditions.

Experimental evaluation of stress history effect on compressibility characteristics of lime-stabilized expansive soils

ABSTRACT Lime stabilization has long been identified as an effective method for reducing the swelling potential of expansive soils. Despite numerous studies evaluating the volumetric behaviour of lime-stabilized expansive soils, the influence of stress history variations on deformation characteristics of these soils has not been adequately explored. This study specifically evaluates the impact of stress history conditions on compressibility characteristics of lime-stabilized expansive soils, with special attention to the rebound index at different loading stages. In this regard, one-dimensional consolidation-swell tests were conducted on samples containing different lime percentages (3% to 12%) under various stress history conditions. To include different stress history conditions, overconsolidation ratio (OCR), seating pressure, and loading step were varied during the induction of stress history in the samples. Results showed that OCR and seating pressure significantly influenced both the rebound (increased up to 118%) and compression indices (decreased up to 53%), while the loading step had a negligible impact on the compressibility properties of stabilized soils. Additionally, when comparing the relative importance of investigated parameters, it was revealed that, OCR had the highest influence on the rebound index (up to 118.0% increase), while the compression index was most significantly affected by lime percentage (up to 61.4% decrease).

Constitutive modeling of anisotropic small-strain stiffness behavior of Shanghai soft clay

Small strain stiffness plays an important role in determining the deformation of geotechnical engineering in soft soils. To model the anisotropic small strain stiffness behavior of soft clay, an enhancement to the bounding surface plasticity model is proposed. This enhancement involves incorporating the anisotropy in soil stiffness at very small strains and its non-linear degradation. Small strains are considered via cross-anisotropy elasticity, while the concept of intergranular strain is used to reflect the non-linear degradation of stiffness with strains and the effect of recent stress history. Using the proposed model, the triaxial test results on K0 consolidated Shanghai clay specimens are simulated to investigate the model’s performance. In the simulation, three typical shear stress paths are adopted. The comparison of the model simulations against experimental evidence is discussed, where the effects of anisotropy in initial soil stiffness and stress-induced anisotropy on the variation of small-strain stiffness, pore pressure, and shear-volume coupling response are highlighted.

An improved hypoplastic model incorporating intergranular strain for overconsolidated clay

Hypoplastic constitutive models are able to describe overconsolidated behaviors of clay with a single nonlinear tensor function using a set of parameters. For instance, an advanced hypoplastic model by Wang and Wu (2020) has successfully reproduced overconsolidated history by incorporating a structure tensor. To simulate the recent stress history effects and the stiffness variations at small strains of clay, the intergranular strain tensor is introduced by Niemunis and Herle (1997) to reproduce stress-path dependent stiffness of clay. The improved hypoplastic model is examined against experiments on overconsolidated Chicago clay. It is evidently concluded that the improved model is capable of replicating stress-path dependency on the small-strain behavior of overconsolidated clay.

Effects of stress history on compressibility characteristics of undisturbed landfill waste material

An extensive set of experiments were conducted in this study to evaluate the impacts of different levels of loading and unloading on compressibility characteristics of landfill waste materials. To achieve this purpose, a large undisturbed waste sample with a diameter of 250 mm was collected from a landfill site, in Sydney. The collected sample was composed of mainly construction waste, decayed organic material, wood, metal, plastic, glass, paper, and cardboard. A large diameter Rowe cell setup was utilised to saturate the undisturbed sample followed by multi-stage unloading and reloading consolidation and creep tests, lasting approximately 330 days. The testing data on the landfill waste were used to determine the compression and recompression indices, as well as the coefficient of consolidation and creep index. These experimental results demonstrate that the compressibility parameters of the collected landfill material significantly depend on the loading history, and in particular, the over consolidation ratio. The findings revealed that the stress history of the waste material has a significant effect on the primary settlement and its rate as well as the long-term creep rate. Thus, it is inferred that the application of the preloading method can improve the compressibility parameters and significantly reduce the post-construction consolidation and creep settlement of landfills.

Comparative Study of Stress History Effects on Shear-Deformation Relations of Sands from the Mediterranean Region Integrating Specimen Preparation Techniques

Comparative Study of Stress History Effects on Shear-Deformation Relations of Sands from the Mediterranean Region Integrating Specimen Preparation Techniques

Influence of overconsolidation ratio on hydromechanical behaviour of unsaturated silty soil under various shearing rates

Due to the limited land resources in major cities, reclamation becomes an optimal option to solve this issue, unsaturated soil is often involved in these projects, and the hydro-mechanical behaviour of this type of soil significantly are affected by the stress history and time effect. In this study, the overconsolidation ratio (OCR) effect of unsaturated silt under different shearing rates was studied through a series of constant water content tests. The specimens were under an effective confining pressure of 400 kPa. The samples were unloaded to 100 kPa, and 50 kPa to achieve different values of OCRs (4 and 8). The samples with different OCRs were then dried from saturated state to initial suction = 100, 200, and 300 kPa via axis-translation, and then sheared at three different rates. The results show that higher strain rates led to a higher degree of saturation during shearing under different OCRs. The shear strength increased with increasing shearing rates while the maximum deviator stress decreased when OCR decreased. Higher OCRs resulted in larger volume change during shearing; similar behaviour was observed for increasing rates.

A thermal state‐dependent bounding surface model for volume change of clay

AbstractThermally induced volumetric strain of clay is crucial for geotechnical applications involving thermal loading. The volumetric response of clay shows a ratcheting pattern during thermal cycles until reaching a thermal stabilized state. It is also affected by the stress history of soil, including over‐consolidation ratio (OCR) and recent stress history (RSH). This paper introduces a new bounding surface model to capture effects of OCR and RSH on thermo‐mechanical behaviour of soil. A thermal state parameter is proposed to characterize the effects of stress history and thermal history. Based on the new thermal state parameter, the commonly recognised thermal softening mechanism is modified and incorporated with a bounding surface. The newly proposed model, with only 10 parameters, can provide an elegant approach to predict the volumetric response under thermal cycles coupled with different stress histories well.

Creep subsidence prediction algorithm considering the effect of stress history for subgrades

Creep subsidence prediction algorithm considering the effect of stress history for subgrades

Time-dependent creep analysis of ultra-high-temperature functionally graded rotating disks of variable thickness

Functionally graded materials (FGMs) are high temperature-resistant materials that can simultaneously maintain metallic tenacity and anti-corrosive properties. Nevertheless, using FGMs during a multi-year service life at ultrahigh temperatures is crucial. Hence, the time-dependent creep response of variable-thickness rotating disks made of FGM is investigated. Four different disk profiles of linear, concave, convex, and uniform are considered. The material's creep properties are defined by the Bailey-Norton creep law. Loading is a rotation-based mechanical body force and a uniform temperature throughout the disk. Simultaneous solution of equilibrium, stress-strain, and strain-displacement equations yields a non-homogenous differential equation containing variable and time-dependent coefficients. In an attempt to optimize the computation cost, Bat and Fish algorithms were used to optimize the initial strain presumptions. Semi-analytical solution of this differential equation gives radial and circumferential stress histories and displacement histories. To confirm the solution method, initial thermo-elastic radial stress, and the effective stress history are validated with the existing literature; there is a good agreement between the results. In addition, the finite element software ABAQUS was used to model the FGM disk thermo-elastic behavior, and the result was compared with the semi-analytical solution results. This study emphasizes the significance of accounting for creep effects in the design of FGM rotating disks, as remarkable changes in their displacements and stresses occur over time. This study emphasizes the significance of accounting for creep effects in the design of FGM rotating disks, as notable changes in their displacements and stresses occur over time.

Relationship closeness as a protective factor against the sensitizing effect of adversity history

Exposure to adversity has been shown to amplify individuals’ sensitivity to stress, increasing the risk of developing mental health problems in adulthood. Romantic relationships can serve as a broad resource in mitigating the negative impacts of adversity and stress on mental health; however, less is known about how everyday moments of closeness with one’s romantic partner impact experiences of daily stress for people exposed to adversity. The present study uses ecological momentary assessment to examine moment-to-moment relationship closeness as a protective buffer against the effects of stress and adversity history (AH) on mood. Using a mobile app, 109 emerging adult couples ( M age = 23.1) reported hourly feelings of stress, relationship closeness, and mood (i.e., happy, sad, nervous, angry) for one day. Results showed AH and relationship closeness each moderated the association between stress and negative mood. Specifically, greater AH was associated with increased same-hour links between stress and heightened nervousness and anger. Greater relationship closeness was associated with decreased drops in happiness and decreased rises in sadness and anger when stressed. A 3-way interaction between stress, AH, and relationship closeness indicated higher relationship closeness was a buffer against the impact of stress on happiness and anger. Specifically, high relationship closeness mitigated drops in happiness when stressed, especially for those with high AH; relationship closeness also mitigated rises in anger, but this effect was heightened for those with low AH. Exploratory gender moderation analyses showed complex links between stress, AH, closeness, and mood, with evidence indicating enhanced emotional intensity in women when stressed and enhanced protective benefits of relationship closeness in men, although this pattern was inconsistent. The discussion focuses on how experiences of AH can carry forward to shape emotional responses in adults and how relationship closeness may serve as a protective factor against the sensitizing effects of AH.

Deviatoric Creep Effect of Unsaturated Soil during Shearing under Different Suctions and Stress Histories

In this research, creep behavior during shearing (deviatoric creep) was studied through a series of constant water content triaxial tests for unsaturated soil under different stress histories. The test samples were first compressed to a net confining pressure of 400 kPa and three different overconsolidation ratios (OCRs = 1, 2, 4) were obtained by unloading the confining pressure from 400 to 200 and 100 kPa, respectively. The samples were then dried with different sections (0, 150, 300, and 500 kPa) by the axis-translation technique. After that, the unsaturated samples were sheared until the deviatoric stress ratio reached around 1.2, and the axial stress was maintained during shearing until failure or reaching 200 h. The responses of samples, including the time, volumetric strain, axial strain, degree of saturation, and suction, were monitored during the triaxial testing. The test results are presented and thoroughly discussed in this paper, including the relationships between the deviatoric creep effect and stress history effect under different suctions.

Mechanical Performance of Puzzle-Shaped Shear Connectors Subjected to Fully Reversed Cyclic Stress

Recent innovations in composite dowels have led to the realization that robust hybrid systems can provide excellent strength and stiffness. In this contemporary era, puzzle-shaped and modified clothoid-shaped shear connectors are attracting interest, particularly in Europe. Their popularity stems from their outstanding shear capacities and their ease of manufacturing by virtue of having a single cutting line. Moreover, earlier studies based on pushout tests have proven this fact. Composite beams in buildings experience fully reversed cyclic stress between compression and tension during seismic events. When the concrete slab starts to crack under tensile stress, the shear capacity of the composite dowel can deteriorate considerably. Nevertheless, the influence of this cyclically applied stress on mechanical performance remains unclear. This study specifically examined puzzle-shaped shear connectors, with cyclic loading tests conducted using a component model of the composite beam, which can carry the various stress histories to the concrete slab. In all, findings obtained from 14 specimens with several influential factors clarified the cyclic behaviors and stress transfer mechanisms of puzzle-shaped shear connectors. Based on the experimentally obtained results, the applicability of existing evaluation equations was investigated with respect to the ultimate shear strength and shear force–slip displacement relation. Results indicate that those formulas overestimate the mechanical capacities of composite dowels under fully reversed cyclic stress. For that reason, this study has led to an evaluation formulation of mechanical performance that reflects the stress history effects. Ultimately, this study has proven that the proposed equations can assess the ultimate shear strength and shear force–slip displacement accurately while embracing simplicity.

Pre- and Post-Liquefaction Behaviors of Manufactured Sand Considering the Particle Shape and Stress History Effects

As the substitution of natural quartz sand (QS), manufactured sand (MS) is highly demanded in the filling and reclamation of foundations in geotechnical engineering, which may be subjected to cyclic shear stresses induced by wave, seismic, and traffic loadings. One of the noticeable distinctions between MS and QS is their particle shape, which has a significant effect on their shear and liquefaction behaviors under the monotonic and cyclic shear stresses, and needs to be further investigated. In this study, the particle shapes of MS and QS were quantitatively characterized by metallurgical microscope tests and digital image processing. Their pre- and post-liquefaction behaviors were evaluated by a series of direct shear tests, cyclic simple shear tests (CSS), and post-liquefaction monotonic shear tests (PMS). The results show that in the CSS test, samples with irregular particles showed stronger liquefaction and shear resistances, indicating that MS was more stable under cyclic shear loadings. In the PMS tests, it was found that the liquefaction and shear resistances of the samples not only increased with the increasing particle irregularity but also with the increasing shear amplitude in the pre-liquefaction stage. Furthermore, quantitative relationships between the particle shape, shear history, and indexes of shear and liquefaction behaviors of the samples were proposed by regression analysis. The research findings could guide the application of MS in offshore and foundation engineering and provide a reference for the selection of MS and its foundation design.

Modelling the Structure and Anisotropy of London Clay Using the SA_BRICK Model

Several constitutive models had been developed by other researchers to cover the main features of mechanical behaviour of natural overconsolidated clays, such as the nonlinear stress–strain response at small and large strains, and the recent stress history effect. Kinematic hardening models include these features to facilitate realistic predictions of soil–structure interaction. This paper presents the further development of a kinematic hardening model BRICK that includes anisotropy and the influence of soil structure on the mechanical behaviour of a natural clay. High quality laboratory tests were used to calibrate the input parameters of the model in a single element configuration, and a documented boundary value problem of tunnel excavation was used to validate the model in finite element calculations. A comprehensive comparative study between the predictions of different kinematic hardening models, using two different software packages, was carried out. It was observed that the SA_BRICK model is in fair agreement with the observed data and gives improved predictions in comparison to other kinematic hardening models, particularly in terms of narrowness of the settlement trough above the tunnel. Advanced predictions of ground deformations caused by tunnel excavations can be effectively used to mitigate possible damage of existing structures affected by tunnelling in an urban environment.

Low volumes of quartz cement in deeply buried Fulmar Formation sandstones explained by a low effective stress burial history

Upper Jurassic Fulmar Formation sandstones from the Fulmar Field in the Central North Sea are buried to 3.2 km and 128 °C but contain only 3.7 ± 1.7% (1σ) quartz cement, substantially less than volumes predicted by models based on temperature-related quartz precipitation kinetics. Oxygen isotope microanalysis of quartz overgrowths suggests that only limited cementation occurred at temperatures above 110 °C. We suggest that the anomalously low volumes of quartz cement are most readily explained by the effective stress history of the Fulmar Formation. Regional pore pressure analysis strongly suggests that pore fluid pressures in the Fulmar Formation decreased substantially in the last <0.5 Ma as a result of lateral seal failure, increasing effective stress from ca. 10 MPa to the current 31 MPa. A recent increase in effective stress is supported by the common occurrence of grains that are both fractured and unhealed by quartz cement. Intergranular pressure dissolution can account for around one third of the observed quartz cement, with the remainder from deep burial feldspar dissolution. We argue that the continuous history of low effective stress, until the very recent geological past, limited the rate of silica supply by intergranular pressure dissolution, and thus the rate of quartz cementation. Effective stress histories should be incorporated into predictive models of quartz cementation of sandstones.

Oxytocin Reduces Sensitized Stress–Induced Alcohol Relapse in a Model of Posttraumatic Stress Disorder and Alcohol Use Disorder Comorbidity

BackgroundThere is high comorbidity of posttraumatic stress disorder (PTSD) and alcohol use disorder with few effective treatment options. Animal models of PTSD have shown increases in alcohol drinking, but effects of stress history on subsequent vulnerability to alcohol relapse have not been examined. Here we present a mouse model of PTSD involving chronic multimodal stress exposure that resulted in long-lasting sensitization to stress-induced alcohol relapse, and this sensitized stress response was blocked by oxytocin (OT) administration. MethodsMale and female mice trained to self-administer alcohol were exposed to predator odor (TMT) + yohimbine over 5 consecutive days or left undisturbed. After reestablishing stable alcohol responding/intake, mice were tested under extinction conditions, and then all mice were exposed to TMT or context cues previously associated with TMT before a reinstatement test session. Separate studies examined messenger RNA expression of Oxt and Oxtr in hypothalamus following chronic stress exposure. A final study examined the effects of systemic administration of OT on stress-induced alcohol relapse in mice with and without a history of chronic stress experience. ResultsChronic stress exposure produced long-lasting sensitization to subsequent stress-induced alcohol relapse that also generalized to stress-related context cues and transcriptional changes in hypothalamic OT system. OT injected before the reinstatement test session completely blocked the sensitized stress–induced alcohol relapse effect. ConclusionsCollectively, these results provide support for the therapeutic potential of OT, along with highlighting the value of utilizing this model in evaluating other pharmacological interventions for treatment of PTSD/alcohol use disorder comorbidity.

The effect of stress history on fluctuation of bedload transport rate and bed topography in gravel-bed streams

Mountainous gravel-bed stream characterized by large-scale roughness generally goes through the seasonal flow, including flood and interevent periods. Recent studies suggest the effect of the interevent period (termed “stress history”) is significant for the bedload incipient motion and bed topography evolution. However, the research on bedload transport fluctuation and protruding microtopography (a fundamental element in the riverbed) under the effect of stress history is limited, especially for quantitative description. As such, this study evaluated experimentally the effect of stress history on bedload transport and bed topography in gravel-bed streams. The long-duration interevent period restrains the variation of bedload transport fluctuation by decreasing the microtopography spatial density, while the large-magnitude interevent period enhances the variation of bedload transport fluctuation through the increasing spatial density. Meanwhile, the grain distribution of transported bedload is significantly affected by the magnitude of the interevent period, rather than the duration. Bed topography becomes smoother through an intermittent adjustment of structure-scale bed topography in the interevent period. Moreover, the decreasing bedload cumulative transport rate and lower variation coefficient of bedload transport fluctuation after short-duration and small-magnitude interevent period are attributed to the stable riverbed with the decreasing microtopography spatial density of less flow drag. An assumption of the larger rate and higher fluctuation after the long-duration and middle/large-magnitude interevent period is proved that the magnitude of the interevent period can promote the microtopography spatial density to generate large flow drag and carry coarse particles of microtopography to randomly hit the bed to generate abundant sediment ejection and transport. Additionally, the relations among microtopography spatial density, characteristic grain sizes, and statistical parameters of bed topography at the different scales are further explored, indicating bed topography at the grain-scale has more relation with bed topography.

Conversion of Triaxial Compression Strain–Time Curves from Stepwise Loading to Respective Loading

Numerous researchers of soil creep behavior adopt stepwise loading (SL) rather than respective loading (RL) to perform the triaxial creep tests. However, a complete continuous strain–time curve of SL needs to be converted into assumed curve clusters supposing obtained under RL before the deformation data are used to develop creep constitutive models. Classical methods realize the conversion mainly by focusing on the creep deformation parts and classifying them into linear and nonlinear compositions. Mostly, the linear parts are simply superposed while the nonlinear parts are complex to consider and so are neglected. Moreover, classical methods are not sufficiently valid to eliminate the stress history effect on the conversion. Here, a new method is proposed to achieve the conversion without neglecting the stress history effect. The method rebuilds the triaxial creep test mathematically and physically, adhering to the revising of energy. The method treats the tested deformation in its entirety, instead of distinguishing it into elastic, visco-elastic, plastic and creep (linear and nonlinear) deformation to convert respectively. The comparison among actual measured SL and RL strain–time curves and the curves converted by the new method proves the stress history effect should not be neglected. The higher the vertical load level, the larger the discrepancy between the RL and SL strain–time curve, and the disparity becomes larger with time. The new method highlights the necessity of considering the stress history effect in analysis and design for higher accuracy. The comparisons illustrate the conversion method at least produces more satisfactory results for clayey soil. Primarily examined, at the later stages of loading, the disparity in strain between the converted RL and measured RL decreases by 52.5%~53.5% compared with strain between the measured SL and measured RL.

Modelling the permanent deformation of unbound granular materials in pavements

ABSTRACT An existing permanent deformation (PD) model for the unbound granular materials (UGMs) in pavements, developed based on multistage (MS) repeated load triaxial (RLT) tests, was modified to better suit to field conditions and software applications. The model was calibrated for a few UGMs with a series of moisture contents (w) using MS (to include the stress-history effect) RLT tests and was validated by predicting the PD under different sets of stress levels and w’s. Generally, it exhibited improved predictions over the Mechanistic-Empirical Pavement Design Guide (MEPDG) model. The model was further applied for field conditions and was implemented in a pavement design software entitled ERAPave PP, using data from accelerated testing of three structures employing a heavy vehicle simulator (HVS). Based on additional MS RLT tests, a guideline for the ranges of the material parameters for different types of UGMs was presented.