Shear Displacement Research Articles

ASSESSMENT OF CRITICALLY STRESSED FRACTURES DUE TO WATER INJECTION — A CASE STUDY FROM THE DEVONIAN CLASTIC RESERVOIR OF THE BERKAOUI FIELD, ALGERIA

A well-constrained geomechanical model of the Devonian clastic is presented to assess the fracture slip potential due to water injection in the Berkaoui field, Algeria. The studied interval indicates a strike-slip tectonic regime with a mean maximum horizontal stress azimuth of 98°N. A total of 131 natural fractures were interpreted from the acoustic image logs. These fractures have dominantly E-W strike, with true dips ranging between 51°-80° towards north and south. Critically stressed fracture analysis exhibits the onset of shear displacement of optimally oriented steeply dipping fractures occurring at 2.7 MPa of injection-induced pressure build-up. The practical injection threshold was inferred as 7 MPa based on caprock integrity assessment. A total of 10 out of 131 fractures (with dips = 70°) can experience injection-caused slip within the maximum allowable injection limit. The E-W oriented fractures, subparallel to the maximum horizontal stress azimuth, have a higher likelihood of being critically stressed during injection and therefore can contribute to permeability enhancement.

Numerical investigation of bolted rock joints under varying normal stress and joint roughness coefficient conditions

Rock masses are formed through long-term, complex geological processes, and the presence of joints significantly reduces their strength and increases their deformation. Rock bolts effectively enhance the strength and stability of rock masses and are extensively utilized for reinforcement. According to field investigations, a significant portion of the damage to bolted rock masses stems from shear deformation at joint surfaces. Moreover, roughness affects friction and surface contact, thus influencing the shear behavior between rock and rock bolts. This study considers two crucial factors affecting the shear characteristics of bolted rock joints: joint surface roughness and normal stress. Using the Particle Flow Code discrete element numerical method, the Barton standard joint profile lines were input to establish numerical models of both unbolted and bolted rock joints for direct shear tests. Results reveal that the peak shear stress and stiffness of both unbolted and bolted rock joints increase with rising normal stress and joint roughness coefficient. The peak shear stress and stiffness of bolted rock joints are notably higher than those of unbolted ones, with a maximum increase of 17.5%. Crack development in bolted rock joints occurs in stages of rapid, slow, and stable development, whereas no distinct slow development stage is observed in unbolted rock joints. Additionally, micro cracks in both unbolted and bolted rock joints are primarily tensile cracks, originating around the joint surface and extending outward with increasing shear displacement. These findings offer valuable insights into the microscopic shear mechanics of bolted rock joints and provide practical references for engineering design and applications in rock reinforcement projects.

Shear Failure Assessment of a G+3 RC Framed Building via Nonlinear Static Pushover Analysis using SAP2000

Accurately modelling shear behaviour in reinforced concrete (RC) structures is essential for seismic evaluation, as shear failure can lead to catastrophic outcomes. Current industry practices often emphasize nonlinear flexural analysis while underestimating the critical role of shear behaviour. This study aims to develop a nonlinear force-deformation model specifically for shear in RC sections to bridge the gap in existing literature. Standards like IS-456:2000 and ACI-318:2008 provide ultimate strength estimates but may inadequately consider the contribution of concrete under seismic loads. Insights from models by Priestley et al. (1996) and Park and Pauley (1975) are integrated to improve the calculation of shear hinge properties. A comparative nonlinear static (pushover) analysis of an RC framed building, with and without shear hinges, demonstrates the impact of shear modelling. Results show that neglecting shear hinges overestimates base shear and roof displacement capacity, masking non-ductile failure modes. Incorporating shear hinges provides a more realistic assessment of structural strength and ductility, emphasizing their necessity in seismic analysis and design. Keywords: Shear behaviour, Reinforced concrete (RC) structures, Seismic evaluation, Shear failure, Nonlinear analysis, Force-deformation model, Shear hinge.

Mechanical behavior of en-echelon joints under cyclic shear loading conditions: Roles of joint persistence and loading conditions

Studying the mechanical response of en-echelon joints under cyclic shear loading conditions can provide novel insights into the instability of jointed rock masses under seismic conditions. To investigate the effects of joint persistence, normal stress, cyclic distance, and shear velocity on the cyclic shear behavior of en-echelon joints, a series of cyclic shear tests in the laboratory was performed. Findings revealed that the failure morphography of en-echelon joints manifested through brecciated shear zones and abraded rupture surfaces, resulting in notable reductions in shear strength and significant compressibility. The degradation factor of shear strength ranged from 0.363 to 0.708 after ten cycles. The shear strength degradation factor showed an inverse relationship with joint persistence and normal stress while exhibiting a direct correlation with cyclic distance over ten cycles. En-echelon joints characterized by moderate joint persistence, high normal stress, small cyclic distance, and low shear velocity demonstrated increased cyclic friction strength. Moreover, normal stress and joint persistence exerted a more significant influence on shear strength compared to cyclic distance and shear velocity. For en-echelon joints, shear stiffness increased during small shear displacements with cycle number while decreased during large shear displacements; shear stiffness was inversely proportional to the cyclic distance and joint persistence, and directly proportional to the normal stress. Compressibility of en-echelon joints correlated directly with joint persistence, normal stress, cyclic distance, and shear velocity. Compared to normal stress and cyclic distance, joint persistence and shear velocity exhibited less influence on compressibility

Evolution of mechanical behavior in granular soil during fine particle loss simulated by salt dissolution: Insights from ring shear tests

Fine particle loss in soil is one of the main causes of slope instability and geotechnical structure failure. Loss of fines can cause instability in granular assembles by changing the fabric and microstructure of the sample. However, real-time monitoring of the evolution of mechanical behavior in granular soils during the particle loss process is still poorly explored. This study presents a novel approach by simulating fine particle loss through salt dissolution in ring-shear tests, offering real-time insights into the mechanical evolution of granular soils under realistic stress conditions. Meanwhile, the shear resistance, shear displacement, vertical displacement, salt content, and acoustic emissions were simultaneously recorded. The test results showed that the instability of the sample was triggered by the loss of fine particles. With a gradual loss of fine particles, both the vertical and shear deformations and the void ratio increased. The evolution of shear resistance in the sample can be divided into three stages: stress weakening, then strengthening, and finally recovery to the initial value. We infer that the evolution of shear resistance originated from the collapse and rearrangement of its granular fabric and microstructure. Additional evidence for this hypothesis was provided by high-frequency acoustic emissions (approximately 150 kHz), suggesting buckling of the force chains accompanying the particle loss process. Furthermore, the sample experienced greater shear deformations and stress weakening that developed under a larger initial fine content or a higher normal stress. This finding may provide valuable insights into the mechanical behavior of granular soil during the fine particle loss process.

A machine learning-based method for predicting the shear behaviors of rock joints

In this study, machine learning prediction models (MLPMs), including artificial neural network (ANN), support vector regression (SVR), K-nearest neighbors (KNN), and random forest (RF) algorithms, were developed to predict the peak shear stress values and shear stress-displacement curves of rock joints. The database used contained 693 records of peak shear stress and 162 original shear stress-displacement curves derived from direct shear tests. The results demonstrated that the MLPMs provided reliable predictions for shear stress, with the mean squared errors (MSEs) between their predicted and measured shear stress varying from 0.003 to 0.069 and the coefficients of determination (R2 values) varying from 0.964 to 0.998. The feature importance values indicate that the joint surface roughness coefficient (JRC) is the most important influential factor in determining the peak shear stress, followed by the joint wall compressive strength (JCS), basic friction angle (φb), and shear surface area (As). Similarly, for the shear stress-displacement curve, the JRC is the dominant factor, followed by As, φb, and JCS. Additional direct shear tests were conducted for model validation. The validation shows that the MLPM predictions demonstrate improved consistency with the experimental results in relation to both the peak shear stress and peak shear displacement.

45° helical plates are a valid alternative to straight plates for treatment of proximal humeral shaft fractures.

Helical plates used for proximal humeral shaft fracture fixation avoid the radial nerve distally as compared to straight plates. To investigate in a human cadaveric model the biomechanical competence of straight lateral plates versus 45° helical plates used for fixation of proximal comminuted humeral shaft fractures, eight pairs of human cadaveric humeri were instrumented using either a long straight PHILOS plate (Group 1) or a 45° helical plate (Group 2) for treatment of an unstable proximal humeral shaft fracture. All specimens were tested under non-destructive quasi-static loading in axial compression, internal and external rotation, and bending in four directions. Subsequently, progressively increasing cyclic loading in internal rotation was applied until failure and interfragmentary movements were monitored by motion tracking. Axial displacement (mm) was 3.13 ± 0.31 in Group 1 and 2.60 ± 0.42 in Group 2, p = 0.015. Flexion/extension deformation (°) in Group 1 and Group 2 was 0.56 ± 0.42 and 0.43 ± 0.23, p = 0.551. Varus/valgus deformation (°) was 6.39 ± 0.44 in Group 1 and 5.13 ± 0.87 in Group 2, p = 0.012. Shear (mm) and torsional (°) displacement were 5.36 ± 0.76 and 17.75 ± 1.06 in Group 1, and 5.03 ± 0.46 and 16.79 ± 1.36 in Group 2, p ≥ 0.090. Cycles to catastrophic failure were 10000 ± 1401 in Group 1 and 9082 ± 1933 in Group 2, p = 0.708. From a biomechanical perspective, 45° helical plating is associated with lower axial and varus/valgus displacement under axial loading and demonstrates comparable resistance to failure versus straight plating. Therefore, 45° helical plates can be considered as a valid alternative to straight plates for treatment of proximal humeral shaft fractures.

Modelling unstable crack propagation in concrete by finite element method with continuous nodal stress

Cracks in concrete will propagate unstably due to excessive shear stress, interactions at the rock-concrete interface, or sudden energy release, significantly compromising structural bearing capacity. To investigate this phenomenon, a nonlinear numerical method for modelling mixed-mode I-II crack propagation has been developed. This approach integrates dynamic equilibrium with a fictitious crack model and an initiation fracture toughness criterion. Key innovations include the incorporation of a finite element method with continuous nodal stress to enhance calculation accuracy, the utilization of kinetic energy to compensate for abrupt losses of strain energy during crack propagation, and the consideration of the deformation of the distributive beam and its interactions with specimens and supports. It was validated by modelling classic benchmarks for the dynamic initiation and propagation of brittle materials under mode I and mixed-mode I-II loading, and applied to analyse unstable crack propagation in concrete for four-point shear (FPS) beam specimens under various ratios of mode I and II stress intensity factors (KI/KII = 0 to 5.32) and loading rates (2 × 10-7 m/s to 2 × 10-3 m/s). Results indicated that the method effectively captures unstable crack propagation, with load-crack mouth shear displacement (CMSD) curves and crack propagation trajectories closely matching the experimental data. Furthermore, it was observed that when the elastic strain energy within the concrete beam exceeds the residual energy stored in the extended cracks, the crack transitions from stability to instability; conversely, if the elastic strain energy is less than or approximately equal to the residual energy, the crack decelerates and returns to stability. Additionally, parametric analyses reveal that lower distributive beam stiffness, shorter preset crack lengths, reduced concrete fracture energy, and a less robust cohesive force–displacement curve increase the likelihood of unstable crack propagation in concrete.

Effect of Particle Shape on Cyclic Shear Behavior of Granular Mixtures–Geogrid Interface

The cyclic shear stiffness and damping ratio of angular and round particle geogrid interfaces is of much concern in reinforcement structure seismic analysis. In this study, various component percentages of crushed limestone and spherical granular medium mixtures were used to investigate the role of particle regularity in static and cyclic direct shear tests. The test results revealed that an increase in the proportion of round particles decreased cyclic shear strength and volume change. The phenomenon of shear softening was observed with a high amplitude of shear displacement when the proportion of round particles was increased in the mixture. As the percentage of round particles increased, the maximum interface shear stiffness decreased significantly from, 39.69 to 28.28 MPa/m, but a reverse trend in the maximum damping ratio was observed, from 0.308 to 0.37. The effect of cyclic shear history and proportion of round particles on interface strength parameters was also analyzed. A linear regression model was fitted to the data for quantifying the relationship between the proportion of round particles and friction angle. The results suggest that different percentages of round and angular particles can produce varying degrees of particle interlock between aggregate and geogrid, influencing the macro-mechanical behavior of the reinforced soil interface.

Mechanical study and equations for gravity flow pipe liners stretching across ring fractures or joints under shear action

Cured-in-place-pipe (CIPP) liners have been widely used in rehabilitation of gravity flow pipelines. However, the host pipe rehabilitated by the CIPP liner may be subject to shear force and shear displacement at the joint. In this study, a finite element model of a rigid host pipe with liner under shear action is established and used to study the resulting behaviour. Controlling factors such as the gap spanned by the liner between host pipes across the joint, diameter, the liner thickness, the elastic modulus of the liner, and the coefficient of friction between host pipe and liner are studied. The liner stress, displacement, and shear force are reported. Shear stiffness and stress equations are then fitted based on 286 data points. The results show that the maximum stress on the inner surface of the liner occurs at the shoulder and haunch, and the maximum stress on the outer surface occurs at the springline. The inner surface stresses at the crown and invert decrease with increases in liner-host pipe friction, but increase at the shoulder and haunch. Coefficient of Friction has almost no effect on the stresses that develop on the outside surface of the liner.

Angle-based residual strength estimation between geotextile/textured geomembrane interface

Geotextile and geomembrane are widely used in landfill liner systems, but the relationship between geomembrane roughness and geotextile/geomembrane interface residual shear strength remains to be studied. In this paper, by using a large-scale ring shear apparatus, a series of ring shear tests between geotextile/geomembrane was conducted, and the profile inclined angle distribution of the textured geomembrane surface was obtained by a profilometer. The experiment results showed that the geotextile/geomembrane interface has reached the residual status after a shear displacement of 3 m, and the average inclined angle of textured geomembrane was close to zero. With the increase of geomembrane asperity height, the interface residual strength increases. Through force analysis and statistical analysis, quantitative relationships between residual shear strength between geotextile/co-extruded geomembrane and geotextile/cone-shape structured geomembrane interfaces and inclined angle distribution were established. The model was validated by test results and case analysis. This study helps understand the mechanism that how the textured geomembrane surface caused high interface residual strength, and choose geomembrane with appropriate roughness to provide adequate residual strength in engineering applications.

Experimental and Numerical Study on Nonlinear Shear Behavior and Constitutive Model of Deep Shale Laminae Planes

The direct shear tests showed that the degradation of unevenness and waviness of the laminae plane is the primary reason for the dynamic decrease in shear strength. A shear constitutive model was proposed which considers the scale effect and the asperity geometry of the unevenness and waviness of the laminar plane. The evolution of the shear strength and stiffness with a normal stress and scale effect during the shearing of shale laminae planes was explored. The results show that high normal stress aggravates the stiffness hardening of laminae planes and forms larger peak shear stress and peak shear displacement. At the lab scale, the increase in the unevenness wavelength has a hardening effect on the shear stiffness and strength. The small-scale unevenness contributes most to the shear strength of shale laminae planes at the lab scale. At the field scale, the increase in the waviness wavelength has a softening effect on the shear stiffness and strength.

Nonlinear incompressible shear wave models in hyperelasticity and viscoelasticity frameworks, with applications to Love waves

General equations describing shear displacements in incompressible hyperelastic materials, holding for an arbitrary form of strain energy density function, are presented and applied to the description of nonlinear Love-type waves propagating on an interface between materials with different mechanical properties. The model is valid for a broad class of hyper-viscoelastic materials. For the Murnaghan constitutive model, shear wave equations contain cubic and quintic differential polynomial terms, including viscoelasticity contributions in terms of dispersion terms that include mixed derivatives uxxt of the material displacement. Full (2+1)-dimensional numerical simulations of waves propagating in the bulk of a two-layered solid are undertaken and analysed with respect to the source position and mechanical properties of the layers. Interfacial nonlinear Love waves and free upper surface shear waves are tracked; it is demonstrated that in the fully nonlinear case, the variable wave speed of interface and surface waves generally satisfies the linear Love wave existence condition c1<v<c2, while tending to the larger material wave speed c1 or c2 for large times.

Comparative Analysis of Seismic Design Standards for Structures and Safety Standards for High-rise Concrete Building Structures

The core of this study is the comparative analysis of I S. 1893 (Part One): 2016 Edition (Code for Seismic Design of Structures) and I S. 16700:2017 (Code for Safety of High rise Concrete Building Structures). In addition, the study aims to uncover the key factors that contribute to poor performance of buildings in earthquakes, with the aim of improving the safety performance of structures in earthquakes in the future. As a research case, we selected a specific reinforced concrete moment shelving frame (SMRF) building at Jabalpur Airport. The building structure was modeled and analyzed using SAPpro V20i software. According to software calculations, we obtained the time history analysis results of the structure in two directions and ensured that they comply with the two Indian standards mentioned above. Subsequently, by comparing the structural responses under the two standards, we evaluated the significant differences in foundation shear force, displacement, and mass participation. The research results indicate that compared to I S. 1893 (Part One): 2016, following I S. The performance of the 16700:2017 structure in earthquakes is relatively poor.

Analysis of the strength of an infinite matrix with a single-periodic array of healed cracks under torsion load

A boundary-integral approach for the study of the stress-strain state of an infinite body-matrix with single-periodic array of cracks healed by a ductile material and under static torsion loaded is proposed. The ptoblem is reduced to solving a system of 2-d boundary integral equation with respect to an unnown jump functions of shear displacements of defect surfaces.

Experimental Investigation of the Lubricant Effect of Thixotropic Slurry on Pipe–Soil Interfacial Friction Characteristics

Based on the technical issues encountered during underground pipe jacking construction in the Jining area, a series of ring shear tests were conducted on silty clay below the groundwater level to investigate the interfacial friction characteristics under the lubrication of thixotropic slurry during construction. Seven different slurry formulations were prepared, and ring shear tests were conducted under varying normal stresses, shear rates, and shear displacements. The friction characteristics during the shearing process were analyzed, and the corresponding friction coefficients were determined. The experimental results indicate that shear stress increases with increasing normal stress, but it is not affected by shear rate and shear displacement. As normal stress increases, the friction coefficient also exhibits a slight rise, which may be due to the uneven distribution of the slurry under pressure. Among the seven formulations, Slurry 1 exhibited the best lubricating effect, which reduced the friction coefficient by 64.5%, while Slurry 0 had the poorest effect with a reduction of 42.6% in friction coefficient. Additionally, the excessive addition of bentonite in the slurry reduces its lubricating effect, and the content of fiber has a significant effect on the friction reduction degree by thixotropic slurry.

Global and Local Shear Behavior of the Frozen Soil–Concrete Interface: Effects of Temperature, Water Content, Normal Stress, and Shear Rate

The interface between soil and concrete in cold climates has a significant effect on the structural integrity of embedded structures, including piles, liners, and others. In this study, a novel temperature control system was employed to conduct direct shear tests on this interface. The test conditions included normal stress (25 to 100 kPa), temperature (ranging from 20 to −6 °C), water content (from 10 to 19%), and shear rates (0.1 to 1.2 mm/min). Simultaneously, the deformation process of the interface was continuously photographed using a modified visual shear box, and the non-uniform deformation mechanism of the interface was analyzed by combining digital image correlation (DIC) technology with the photographic data. The findings revealed that the shear stress–shear displacement curves did not exhibit a discernible peak strength at elevated temperatures, indicating deformation behavior characterized by strain hardening. In the frozen state, however, the deformation softened, and the interfacial ice bonding strength exhibited a positive correlation with decreasing temperature. When the initial water content was 16% and the normal stress was 100 kPa, the peak shear strength increased significantly from 99.9 kPa to 182.9 kPa as the test temperature dropped from 20 °C to −6 °C. Both shear rate and temperature were found to have a marked effect on the peak shear strength, with interface cohesion being the principal factor contributing to this phenomenon. At a shear rate of 0.1 mm/min, the curve showed hardening characteristics, but at other shear rates, the curves exhibited strain-softening behavior, with the softening becoming more pronounced as shear rates increased and temperatures decreased. Due to the refreezing of interfacial ice, the residual shear strength increased in proportion to the reduction in shear rate. On a mesoscopic level, it was evident that the displacement of soil particles near the interface exhibited more pronounced changes. At lower shear rates, the phenomenon of interfacial refreezing became apparent, as evidenced by the periodic changes in interfacial granular displacement at the interface.

Analysis of wrinkles and corrugations in the electrode calendering process

ABSTRACT Calendering is a crucial process in manufacturing of lithium-ion batteries electrodes. Wrinkles and corrugations are the main manufacturing defects in the calendering process. This study aims at studying the formation mechanism of wrinkles and corrugations. Corrugations and wrinkles of the electrodes were revealed to be more dependent on the difference between the front and back tensions. The tortuosity of corrugations was reduced by 34.2% when the tension difference decreased from 20 to 5 N. The increase in the tension difference led to a linear increase of the shear displacement δ, causing severe wrinkles in the uncoated area of the electrodes. The analytical prediction model for wrinkles during calendering was established based on the shearing of a rectangular membrane. The optimal web tension conditions, at a tension difference of 17 N, was achieved to obtain the optimal calendered electrodes.

Parametric study for shear failure of bearing pads due to hurricane-induced wave loadings

The increasing frequency of extreme weather events, such as hurricanes and rising sea levels due to climate change, presents significant challenges to coastal infrastructure. With 42% of bridges in the United States exceeding 50 years of age, which surpasses their intended service life, there is a pressing need to assess their structural integrity, especially in coastal regions. This study focuses on evaluating the structural performance of bearing pads in coastal bridges under hurricane-induced wave loadings. Utilizing a combination of physics-based models (PBM), nonlinear modal time history analysis, and numerical validation, the research examines the hysteresis response of eight distinct bearing pad configurations. The findings indicate that reinforced circular bearing pads exhibit significantly greater shear displacements compared to plain elastomeric pads, underscoring the critical influence of shape factors on shear response. Fragility functions developed in the study illustrate the probability of shear failure, with reinforced circular pads showing a 28% higher likelihood of exceedance compared to rectangular plain pads. These results highlight the necessity for advanced design methodologies specifically for bearing pads to enhance the resilience of coastal infrastructure against severe hydrodynamic forces induced by hurricanes.

Numerical modelling of large displacement shear in soil-structure interaction

Numerical modelling of large displacement shear in soil-structure interaction