Axial Stress Research Articles

Improving the prediction of turbulent kinetic energy for drag reduction in turbulent viscoelastic pipe flow

Reducing turbulence in pipe flows using polymer additives is crucial for industrial applications like crude oil, water, and sewage transportation. While previous research has accurately predicted friction factor and velocity profiles, none has fully understood turbulent kinetic energy (TKE) behavior in such fluids. Authors are now focusing on exploring turbulence models to better understand the TKE behavior. In this research, we have introduced a model to improve the behavior of TKE in a modified generalized Newtonian fluid (GNF). The developed model aims to simulate the viscoelastic effects of fluids that result in drag reduction in turbulent pipe flow. The work is noteworthy as it integrates turbulence and viscoelastic components, offering a comprehensive understanding of the phenomenon. By incorporating the rheological properties of viscoelastic fluids and replacing the damping function with a non-Newtonian alternative proposed by Cruz and Pinho, the Launder–Sharma k–ε turbulence model is now suitable for simulating dilute non-Newtonian viscoelastic fluids. The viscoelastic aspect of the model employs the modified GNF model. The developed model has been subjected to simulations using the computational fluid dynamics software. The results obtained for fluid TKE demonstrate a significant improvement in comparison to our previous research and the findings of other researchers. Furthermore, the model's prediction for the Darcy friction factor has been enhanced, resulting in an average error of only 3.71% in this section. It is noteworthy that the model consistently maintains a high level of accuracy in predicting other essential flow parameters such as mean axial velocity and Reynolds stresses. The provided model advances our understanding of viscoelastic fluid behavior in turbulent pipe flow by applying the modified GNF model.

Promoting Regeneration in Degenerative Disc Disease.

The degenerative disc disease has a multifactorial etiology and mechanical stress is one of the most important etiological factor. The purpose of this study was to evaluate the intervertebral disc (IVD) after axial stress diminution from the point of view of its proteoglycan (PG) content, with preoteoglicans (PGs) being very important in the normal function but also in the degenerative or regenerative processes. This is a single-center, prospective, non-randomized study of 38 degenerated intervertebral discs treated with monosegmental or polisegmental posterior lumbar spinal fixation in 27 patients. During surgery, a posterior intervertebral distraction at operated levels was applied. Patients' mean age was 50.77 years and the mean follow-up 28.74 months. Both clinical (visual analog pain scale, Oswestry disability index) and radiological (lumbar spine lordosis, disc thickness) analyses were made before and after surgery. A new method of cartilage analysis, which was also validated for the IVD, delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) was used to determine the PG content before and after surgery for both the intervertebral degenerative disc and control level L1-L2 disc. The clinical features improved significantly. The thickness of the operated discs increased by an average of 1.71 mm postoperatively and remained unchanged in the control group. The lumbar lordosis did not change significantly. In dGEMRIC studies, the discs accumulated in average 410.08 units /cm2 of gadolinium before surgery and 272.45 units/cm2 after surgery, without significant changes in the control group. Our study shows an improvement of PG quantity in degenerated IVD due to a decrease in gadolinium binding seen in dGEMRIC study. Thus, we can ameliorate IVD homeostasis by eliminating mechanical stress, which could be a step towards the process of disc regeneration.

Considerations for the structural design of wind turbine towers: A practical application

AbstractAiming to achieve efficient structural performance, this article presents a methodology for the design of the shell structure and dimensioning of the connections of an S355J2 tubular steel tower with a height of 80 m, compatible with a SWT‐2.3‐93 wind turbine. The tower is made up of three segments, interconnected by flanged connections made of high‐strength steel. The analysis considers various load cases, taking into account stress and resistance in different directions, as well as designing connections using Petersen's theory, according to maximum strength and fatigue criteria. The results indicate that the circumferential stresses are nearly negligible compared with the resistant stresses, while the shear stress is significantly higher at the base due to the torsional moment. Meridional stress determines the stability of the structure, requiring consideration of internal pressure for safety. Maximum stress values range from 135.00 to 168.47 MPa, depending on the location along the tower height. Flanged connections meet the strength and fatigue criteria, with the first flange enduring 63.0% of the fatigue effect and the second, 39.7%. Therefore, the results provide reliable information and methodologies for tower design, contributing to the practical and efficient development of these structures.

Molecular dynamics study on nanodust removal strategies from nanotrench structures

The process of removing nanodust adhering to nanostructured surfaces is important for improving yield and sustainability in manufacturing fields that utilize the structural characteristics of patterns. In this study, we computationally proposed a method to remove nanodust from a trench-shaped Si substrate using an atomic force microscopy tip. A molecular system is thus constructed in which a Si substrate with a trench structure, a cylindrical C tip, and a spherical Cu nanoparticle coexist. By moving the C tip in a specific direction and pushing it into direct contact with the Cu nanoparticle, the interaction force between the Cu and the sidewall of the Si substrate can be substantially reduced. In particular, moving the C tip in a direction parallel to the pattern can effectively push nanodust away while minimizing damage to the Si substrate. The damage experienced by the substrate during the process was comprehensively evaluated using the von Mises stress, adhesion energy, contact area, and strain energy density developed by the axial stress components. The suitability of this method was systematically evaluated based on the diameter of the Cu nanoparticle and its position relative to the C tip. For each case, the maximum strain energy experienced at the edge of the trench structure was quantified, which suggests appropriate nanoparticle removal process conditions from a structural perspective. The strategy can be potentially used as a repair method for semiconductor production components, such as pellicles and hard masks.

Unified failure criteria for freeze-thaw damaged concrete under multiaxial stress state: An innovative uniaxial strength-dependent prediction method

When concrete is subjected to freeze-thaw (FT) cycles, its mechanical properties under multiaxial stress states will deteriorate. In order to establish corresponding failure criteria, it is common practice to conduct FT and multiaxial tests. However, due to the multiple FT factors, extensive multiaxial tests are required, resulting in low applicability of the existing failure criteria for FT damaged concrete. In this paper, according to the collected multiaxial test data, a rule has been revealed that the normalized failure surface of FT damaged concrete is related to the relative uniaxial compressive strength (fcD/fc), regardless of the types of FT factors. This correlation is related to the degree of confined state. On this basis, a uniaxial strength-dependent method has been proposed to predict the multiaxial ultimate stress state of FT damaged concrete. Through the proposed method, to facilitate various applications, three models including two types of failure criteria for concrete and a peak axial stress model for confined concrete after FT cycles have been established with broad applicability and good accuracy. The proposed method and models might be extended to other damaged concrete with the same mechanism of developing internal cracking.

Peridynamic differential operator for stress analysis of imperfect functionally graded porous sandwich beams based on refined zigzag theory

This study focuses on the stress analysis of imperfect functionally graded porous (FGP) sandwich beams using the Peridynamic Differential Operator (PDDO) and Refined Zigzag Theory (RZT). Functionally graded materials (FGMs) can be found in diverse engineering applications since they offer smooth transitions in the mechanical properties of distinct materials, unlike traditional composite materials. Micro-voids and porosities may appear inside the FGMs due to technical challenges during the manufacturing process of such materials. Therefore, understanding the stress variations of the FG sandwich beams with porosities/micro-voids, which are called imperfect FGMs, under loads is of vital importance. In order to achieve the porous configuration in the FG structures, the modified rule of mixtures is applied to calculate the effective material properties of FGMs. The RZT is very suitable for stress analysis of laminated composites, especially for thick and moderately thick beams. It contains only four kinematic variables and eliminates the use of the shear correction factors. In this study, the equilibrium equations of the RZT are solved by means of the PDDO for the stress analysis of imperfect FG sandwich beams having uniform and non-uniform porosity distributions. The PDDO transforms the differential equations into their nonlocal form, namely integral form, providing highly accurate approximations of the derivatives. A comprehensive PDDO analysis is performed for the investigation of the influence of the material variation, and even and uneven porosity distributions on the stress variations of the imperfect FG sandwich beams. It is noted that when the FG core exhibits soft material distributions, the effect of porosity is evident. The even type porosity distribution pattern is more influential on the axial displacement and stress variations in comparison with those of the uneven type porosity distribution pattern.

An integrated three-dimensional aeromechanical analysis for the prediction of stresses on modern coaxial rotors

This paper presents the first application of an Integrated Three-Dimensional aeromechanical analysis—defined as the coupled solution of three-dimensional finite element-based structural dynamics with a three-dimensional Reynolds-Averaged Navier-Stokes-based fluid dynamics—to predict the stresses on a modern coaxial rotor. The coupling was carried out with the University of Maryland’s structural dynamic solver X3D and the U.S. Army’s CREATETM–AV Helios suite of fluid dynamic solvers. A modern four-bladed hingeless coaxial rotor model—inspired by the gross dimensions of the Sikorsky S-97 Raider but generic and open source otherwise—is developed as a demonstration test case. The new structural solver is driven by parallel and scalable solvers and advanced high performance computing. It is enabled by high-order three-dimensional brick finite elements unified with multibody dynamics, integrated aerodynamics, and a special 3D-to-1D fluid-structure interfaces refines the power of delta-coupling procedure while retaining the advantages of existing CFD mesh motion schemes. The analysis predicts the three-dimensional stresses on the rotor blades and hub, together with the deformations, airloads, and wake, in an integrated manner. Two flight conditions are studied: a low-speed flight at 37 knots and a high-speed flight at 150 knots. Interesting three-dimensional unsteady stress patterns are revealed all across the blade but particularly inboard of 50% rotor radius—patterns that change from flight to flight and have remained invisible until now—since they could neither be predicted nor measured in flight. The maximum axial stresses exhibited 3/rev variation at low speed, and 2/rev variation at high speed flight. The lower rotor carried higher oscillatory stress burden at low speed, whereas both the rotors shared the same stress burden at high speed flight. The key conclusion is that such analysis is now indeed possible, and the stress patterns they reveal provide deeper insights into the dynamics of advanced rotors, and these might provide a path toward mitigating them in the future.

#2570 Non-invasive blood pressure monitoring in dialysis patients using pulse wave velocity

Abstract Background and Aims Dialysis patients are at high risk of circulatory dysregulation and hypotension during treatment. Intradialytic hypotension (IDH) is a potentially life-threatening complication. The main causes are high ultrafiltration volumes and high ultrafiltration rates when patients tend to gain a lot of weight between dialysis treatments. A lack of patient compliance with regard to drinking volumes and a lack of residual diuresis are risk factors for this. Close circulatory monitoring and therapy settings to avoid absolute or relatively high UF rates to prevent IDH are frequently used. These are primarily the frequent non-invasive measurement of blood pressure using cuffs, the measurement of relative blood volume and the adjustment of ultrafiltration rates to these values. Prophylactically, the dialysis time can be extended, ultrafiltration profiles or ultrafiltration breaks can be planned, the dialysate temperature can be lowered and the composition of the dialysate can be adjusted. Despite all attempts, however, the incidence of IDH in everyday clinical practice is too high. The non-invasive measurements with cuffs are not carried out frequently enough, the measurement of the relative blood volume only covers a partial range, sudden changes in vascular tension or cardiac output are not recorded. Method The pulse wave velocity (PWV) is a well-known parameter for describing the propagation of the pressure wave after ejection of the heart beat volume in the arteries. The PWV is dependent on blood pressure, vessel wall tension and cardiac output. Changes in blood pressure can therefore be recognised by measuring the PWV. With the help of a measuring device (PESAS) for the ECG signal and peripheral pulse plethysmography, PWV can be measured non-invasively, continuously, for every heartbeat and, above all, hardly noticed by the patient. The PESAS allows the time-synchronised measurement of ECG and peripheral plethysmography curves and thus the determination of PWV. It is an experimental device. We would like to present a study showing the use of a measuring device (PESAS) in 15 prevalent dialysis patients for the detection of IDH. All study participants were examined during 3 dialysis treatments. Results The measurement of PWV in chronic dialysis patients during treatment is technically feasible. The measurement is tolerated by the patients. Changes in PWV could be detected in the patients during the course of dialysis; these were also dependent on the ultrafiltration rates. Individual patient reactions to volume withdrawal varied, with both increases and decreases in PWV being demonstrated. An acute change in PWV was usually associated with a drop in blood pressure. Continuous measurement allowed IDH events to be detected earlier than intermittent blood pressure measurement with cuffs. Sudden drops in blood pressure could be detected better and earlier with the PESAS system than by measuring the relative blood volume. Conclusion The PESAS system is suitable for monitoring dialysis patients to prevent IDH. Further adjustments and optimisation of the evaluation algorithms are necessary.

Effect of axial stress-induced coal particle breakage on the evolution laws of coal spontaneous combustion characteristics and limit parameters of loose broken coal

Coal particles are broken to varying degrees under the axial stress, thereby affecting the particle size distribution, which has an essential impact on coal spontaneous combustion (CSC). This work investigated the evolution behavior of the characteristic parameters and limit parameters of the coal oxidation process under different breakage degrees. Results showed that as the axial stress increased, the breakage degrees of coal gradually increased, while the permeability gradually declined. The increase in the breakage degree of particle induced by axial stress would promote the CSC process and increase the risk of CSC. The promotion effect reached the most prominent at 12 MPa and began to decrease at 15 MPa. Particle breakage and increasing specific surface area caused by stress were responsible for the change in CSC characteristic parameters. The reduction in permeability caused by stress dominated the changes in CSC limit parameters.

Full‐scale experimental and theoretical investigation on wall stress for underground ecological group tanks with four‐circle tangential connections

SummaryThe storage safety of edible oil is critical for global and Chinese food security. In this study, a practical underground four‐circle tangential group tank with the steel‐plate and concrete structure based on a grain storage warehouse was firstly introduced, and the measured hoop reinforcement stress of the outer tank wall is discussed. Secondly, a numerical model consistent with the practical underground group tank is established from the measured data. The distribution of the hoop reinforcement stress of the outer tank wall under earth pressure is extracted and analyzed thoroughly. Finally, formulas reflecting the properties of the hoop reinforcement stress distribution are presented based on the theoretical analysis, and their accuracy is verified by comparison with the measured data. It could be conducted from the experimental results and theoretical formulas that the outer tank wall is under compressive pressure station generally, and the compressive stress increases with the increasing of the ring angle until reaching a steady state. Moreover, the hoop stress curve follows a disproportional function approximately. The moment at 180° hoop with 1‐m plate belt follows the arc‐tangent function while the moment has a sudden‐change point at 120°, which has minor effect on the reinforcement of this tank wall. Consequently, additional attention should be paid to the effects of this sudden‐change phenomenon on the associated structures in in the process of designing of underground storage tanks.

In-situ studies on environmental degradation in Al 7075 in saltwater environment under tensile loading

Abstract We report the crack growth on peak aged Al 7075 under tensile loading in a saltwater environment to investigate whether hydrogen plays a role in the initiation and the subsequent growth of the crack. As the hydrostatic stress is at a maximum ahead of the notch, it has been speculated that hydrogen would diffuse to region of maximum hydrostatic stress and initiate the crack. An elastic-plastic finite element (FE) model is developed to determine the stress distribution around the circular notch at the edge of the plate. The crack growth was monitored using a camera attached with an optical microscope, and various regimes corresponding to hydrogen evolution, pit formation and growth, crack nucleation and initial growth and rapid crack growth leading to failure have been identified. We observe the crack was nucleated in a region associated with the highest hoop stress instead of the maximum hydrostatic stress from the base of a pit at the circular notch. We demonstrated the crack growth rate in a salt water environment is governed mostly by the dissolution of grain boundary MgZn2 precipitate, rather than the hydrogen induced decohesion mechanism.

Fatigue life and experimental study of high-temperature bellows based on the improved Manson-Coffin equation

Based on the high-temperature fatigue failure mechanism, this study proposes the use of the maximum shear strain range of crystal slip systems as the fatigue damage parameter and improves the Manson-Coffin equation accordingly. An Inconel-625 bellows model is constructed using the ANSYS Workbench platform for thermo-mechanical coupled analysis (temperature of 650 °C, displacement load of 7 mm, internal pressure of 0.3 MPa). Stress tests, including circumferential and axial stress, are conducted on the bellows to verify the accuracy of the finite element model. The six strain components in the model are extracted, and the improved Manson-Coffin equation is applied to calculate the fatigue life of the high-temperature bellows, resulting in a value of 12,318 cycles. Additionally, high-temperature fatigue life tests are performed on the Inconel-625 bellows under the conditions of 650 °C, 7 mm displacement load, and 0.3 MPa internal pressure, yielding a measured fatigue life of 9163 cycles. By comparing the experimental results of this study with those from relevant literature and plotting error band charts, it is demonstrated that the results obtained using the improved Manson-Coffin equation fall within a two-fold error band, validating the applicability of the improved Manson-Coffin equation for calculating the high-temperature fatigue life of bellows with different temperatures and models.

Hydride orientation near pressure tube-end fitting rolled joints

The connection between Zr–2.5%Nb pressure tubes and modified martensitic stainless steel-403 end fittings in Pressurized Heavy Water Reactors (PHWRs) at the rolled joint is a critical site marked by enhanced hydrogen diffusion and elevated tensile residual stresses. The application of circumferential stress above a threshold leads to the formation of radial hydrides. Formation of radial hydride leads to a drastic reduction in fracture toughness and increase in Delayed Hydride Cracking (DHC) velocity. A comprehensive understanding of residual stress, hydride orientation and radial hydride fraction in this region is essential for the assessment of pressure tube structural integrity. In this study, we employ 3D nonlinear finite element analysis to estimate the residual stresses near rolled joints for both 220 MWe and 700 MWe pressure tubes. Additionally, we pioneer an experimental investigation into hydride orientation near roll joints through internal pressurization of hydrided pressure tube and end fitting assemblies. The study delves into the influence of residual stresses due to rolling process on hydride orientation and radial hydride fraction, providing crucial insights for the evaluation of the structural integrity of pressure tubes.

Linear and nonlinear axial behaviour of internal replacement pipe systems for pipeline rehabilitation

Internal replacement pipe (IRP) is an innovative trenchless technology for the rehabilitation of legacy steel and cast-iron pipelines. This advanced IRP system must be properly designed so that it can safely and effectively restore the service of damaged pipelines. This paper studies the axial behaviour of IRP systems for repairing pipelines with circumferential host-pipe discontinuities under seasonal and extreme levels of temperature change. Analytical solutions along with a total of 270 linear and nonlinear finite element (FE) simulations, validated against experimental results and available closed-form solutions, were used for a parametric study on the effects of geometrical and material properties on axial stresses and deformations of IRP systems subjected to temperature change. Effects of the internal pressure, material and geometric nonlinearities, and different modes of IRP-host pipe unbonding were also investigated. An analytical model was developed for the prediction of temperature change induced loading and response of the IRP system. Using the results obtained from a comprehensive FE-based parametric study, three modification factors were extracted for the application to the developed analytical model in order to accurately predict the maximum axial stress of IRP and the opening of a circumferential host-pipe discontinuity subjected to various levels of temperature change.

Role of Vasoactive Hormone-Induced Signal Transduction in Cardiac Hypertrophy and Heart Failure.

Heart failure is the common concluding pathway for a majority of cardiovascular diseases and is associated with cardiac dysfunction. Since heart failure is invariably preceded by adaptive or maladaptive cardiac hypertrophy, several biochemical mechanisms have been proposed to explain the development of cardiac hypertrophy and progression to heart failure. One of these includes the activation of different neuroendocrine systems for elevating the circulating levels of different vasoactive hormones such as catecholamines, angiotensin II, vasopressin, serotonin and endothelins. All these hormones are released in the circulation and stimulate different signal transduction systems by acting on their respective receptors on the cell membrane to promote protein synthesis in cardiomyocytes and induce cardiac hypertrophy. The elevated levels of these vasoactive hormones induce hemodynamic overload, increase ventricular wall tension, increase protein synthesis and the occurrence of cardiac remodeling. In addition, there occurs an increase in proinflammatory cytokines and collagen synthesis for the induction of myocardial fibrosis and the transition of adaptive to maladaptive hypertrophy. The prolonged exposure of the hypertrophied heart to these vasoactive hormones has been reported to result in the oxidation of catecholamines and serotonin via monoamine oxidase as well as the activation of NADPH oxidase via angiotensin II and endothelins to promote oxidative stress. The development of oxidative stress produces subcellular defects, Ca2+-handling abnormalities, mitochondrial Ca2+-overload and cardiac dysfunction by activating different proteases and depressing cardiac gene expression, in addition to destabilizing the extracellular matrix upon activating some metalloproteinases. These observations support the view that elevated levels of various vasoactive hormones, by producing hemodynamic overload and activating their respective receptor-mediated signal transduction mechanisms, induce cardiac hypertrophy. Furthermore, the occurrence of oxidative stress due to the prolonged exposure of the hypertrophied heart to these hormones plays a critical role in the progression of heart failure.

TRIPTANS: HOPE FOR THE BEST, PREPARE FOR THE WORST

Abstract The estimated prevalence of headaches in the population is 66%. According to recent guidelines, basic analgesics, nonsteroidal anti–inflammatory drugs (NSAIDs), or acetaminophen are frequently used as first–line treatment for mild migraine attacks. A triptan is added when analgesic–resistant attacks occur. So these drugs are used as a second–line medication for mild migraines and a first–line medication for moderate to severe headaches. A correlation between spontaneous coronary artery dissection (SCAD) and triptans has already been reported in the literature. If myocardial infarction is more common in patients with cardiovascular risk factors, SCAD seems more frequent in young and smoker females. What is interesting is the speculation of the pathophysiological mechanisms of SCAD after triptans use. A possible option may consist in the fact that the dissection of the anterior descending artery is due to circumferential shear stress caused by these drugs, combined with smoking habits and estrogen deprivation. These latters influence the immune system and the circulating progenitor cells, which are reduced and less active to replace senescent endothelial cells. That is why an intimal flap is formed so that the blood would enter the media and the dissection would be perpetuated. The suspension of the drug is necessary to prevent the vasoconstriction of the vessel from exacerbating the wall stress caused by smoke and sexual hormones deficiency.

SCARY ECG IN TAKOTSUBO CARDIOMYOPATHY

Abstract Takotsubo cardiomyopathy (TTC) is characterized by a transient ventricular wall motion abnormality and shares common features with acute coronary syndrome (ACS) with a wide spectrum of triggers, such as both emotional or physical, activating common toxic catecholamines–mediated pathways. TTC might be associated with severe clinical complications. We report a case of a 74–year female patient with circulatory shock with mixed phenotype, distributive due to sepsis and cardiogenic due to TTC. The patient presented to the emergency department with severe hypotension, pathological qSOFA score and clinical and laboratory findings consistent with severe sepsis. ECG showed diffuse lambda ST–segment elevation, also called “shark fin”(fig.1). According to hemodynamically unstable scenario and ECG pattern, emergency coronary angiography was performed, showing absence of coronary artery disease(fig. 2). Echocardiography revealed severe LV systolic disfunction (EF 20–25%) with apical ballooning and severe systolic anterior motion (SAM) of the anterior mitral leaflet eliciting dynamic LVOTO with peak gradient greater than 90 mmHg; fig. 3) and severe MR. Patient was treated with cautious fluid administration, hemotrasfusion and empiric large spectrum antibiotic therapy. According to TTC working diagnosis, even if septic state was thought to contribute to cardiogenic shock, norepinephrine was not administered due to concerns for LVOTO and SAM. After overcoming of dramatic first phase and after hemodynamic steadiness was achieved, beta blockade and ACEi were progressively administered. Seriate transthoracic echocardiogram revealed progressive improvement of LV systolic function, regression of apical ballooning, SAM and LVOTO. ECG monitoring showed regression of ischemic ST elevation. ST elevation has been described in about 56% of TTC cases, however with amplitude tipically lower than in STEMI. Lambda–wave ST elevation has been rarely reported. Vasospasm, local intermittent microvascular constriction, catecholamine–induced metabolic toxicity, transmural systolic wall tension and its the mechano–electric feedback can explain scaring ECG–pattern. Despite its rare prevalence in TTC “shark fin” pattern appears to relate to adverse outcome and it should be used as an early marker of potential further clinical deterioration, suggesting more intensive monitoring to avoid delays in possible therapy escalation.

Bearing Capacity Characteristic Analysis of Anti-floating Bolts in Unsaturated Soil Based on Mindlin Solution

AbstractBased on Mindlin solution and the theory of unsaturated soil mechanics, the theoretical solutions of shear stress and axial force distribution in the elastic stage of full-length binding-type anti-floating bolts were derived, and the bearing capacity characteristics of such bolts and the influencing factors were analyzed. In this paper, the design parameters of anti-floating anchor in a negative two-floor basement of a commercial square are substituted into the formula derived in this paper. The results show that, in unsaturated soil, the shear stress and axial force of the full-length bonded anti-floating anchor are distributed along the total length of the anchor, but neutral points appear in both of them, which is mainly due to the reduction of the axial force and shear stress of the anti-floating anchor caused by the matric suction. The formula derived in this paper is used to analyze the factors affecting the bearing capacity of anti-floating anchor bolt in unsaturated soil. The results show that: the greater the elastic modulus of soil mass, the greater the peak value of shear stress curve, the closer the peak value is to the head of anchor bolt, and the greater the axial force decline rate. With the increase of anchor solid diameter D, the peak value of shear stress decreases, the peak value moves backward, the neutral point moves forward, the negative shear stress value increases, the decline rate of axial force distribution curve decreases, but the negative axial force increases. With the increase of the additional shear stress τ0, the peak value of the shear stress curve decreases, the peak value moves to the hole of the anchor rod, the neutral point moves to the hole, the negative shear stress increases, the decline rate of the axial force distribution curve increases, and the negative axial force increases.

Co-exploitation of coal and geothermal energy through water-conducting structures: Improving extraction efficiency of geothermal well

Co-exploitation of coal and geothermal energy through water-conducting structures is one of the most promising methods for harnessing renewable energy in some coal mines. A rock compression-erosion coupling test system is built to investigate the extraction efficiency of geothermal wells in the co-exploitation scheme. Compression-erosion tests are carried out to analyze the evolution of mechanics and hydraulic characteristics of broken rocks. The testing results show that the hydrothermal flow erodes the fine rock particles, and compressive deformation can be observed during the erosion process. The erosion effect in broken rocks intensifies with the decrease of axial stress and the increase of fractal dimension, water pressure, and inner radius. Meanwhile, the rock sample shows more significant deformation. Two permeability forecasting models are adopted to forecast permeability evolution during geothermal extraction. The forecasting results indicate that the Brinkman model is better than the Hazen model, and the accuracy of the Brinkman model is lower for the samples with stronger compression-erosion effects. In addition, strategies to improve the extraction efficiency are proposed, i.e., reinforcing the broken rocks above the geothermal well, locating geothermal wells in rocks with higher fragmentation, increasing pumping pressure, and expanding the geothermal well size.

Numerical modeling of RC column reinforced by new strategy using fiberglass tape and cloth

This paper presents the results of finite element analysis (FE) to study the axial compression behavior of reinforced concrete columns wrapped with tapes and fiberglass cloths according to different techniques using ABAQUS software. In the beginning, columns are modeled as 3D solid elements with a concrete damage plasticity model (CDPM), as the columns in this study are considered to be low compressive strength reinforced concrete and the rebar as 3D mesh elements. And once assembled, the specimen is wrapped with tape and cloth in the form of three-dimensional shell elements. Then, in order to analyze the behavior of the ultimate loads, the deformation of the confinement material, and the distribution of deformations in the concrete, the controlled displacement method used to apply the uniaxial compression loads to the specimen. Finally, a new mixed confinement model between partial confinement and complete has been proposed using a database of the results of a numerical simulation for confined concrete by fiberglass tapes and cloths. And it was found that the confinement strategy proposed in this study is very effective for the behavior of the reinforced concrete column, as the stress decreases significantly with the expansion and widening of the confinement stiffness of concrete in the plastic phase which improves the axial stress resistance.