Shear Failure Surface Research Articles

Disturbance shear fracturing process and failure precursors of intermittent structural planes with different connectivity under true triaxial condition

The mechanisms, processes, and precursors of shear failure in rock structural planes under three-dimensional geostress and excavation disturbances are unclear, which poses challenges for disaster prediction and warning in underground rock engineering. Therefore, this study self-developed a new separation rolling-sliding shear device for rock structural plane under true triaxial condition, and proposed a true triaxial shear testing method to simulate the damage of rock structural plane induced by the three-dimensional geostress redistribution during engineering excavation and subsequent dynamic disturbance further triggering failure. True triaxial disturbance shear tests were conducted on intermittent structural planes with different connectivity. With connectivity increasing, disturbance shear strength and failure surface roughness of structural planes gradually decreases. An improved simplex acoustic emission spatial localization method was proposed to reveal disturbance shear fracturing evolution. During disturbance shear fracturing process, micro-tensile cracks dominate, and the proportion of micro-shear cracks continues to increase, showing a mixed tensile-shear fracture mechanism. Approaching to disturbance shear failure, the acoustic emission fractal dimension decreases rapidly then increases to the maximum value, the b-value decreases rapidly to less than 1, the rapid increase in LgN/b exceeds 3, and the low-frequency and high-amplitude dense fracture signal appears abundantly, which can be used as disturbance failure precursors of intermittent structural planes.

Numerical simulation of mechanical properties and damage process of carbon nanotube concrete under triaxial compression and splitting conditions

To investigate the mechanical properties and failure processes of carbon nanotube concrete, a three-dimensional meso-scale finite element model of concrete was constructed. Using ABAQUS software, numerical simulations were conducted on concrete samples with different carbon nanotube concentrations under triaxial compression and splitting conditions. The results indicate that under splitting conditions, the failure of the specimens initially occurs along the loading direction from both ends, with few cracks and slow propagation. Subsequently, the cracks rapidly expand, penetrating the entire specimen, leading to the formation of a macro-fracture surface with a crack aligned with the loading direction. This failure mode manifests as a straight crack. At the same loading rate, the tensile strength of the specimens with different carbon nanotube concentrations increases to varying degrees during splitting failure, with a maximum increase of 45.10% to 4.15 MPa. nder triaxial compression conditions, the main failure mode of the specimens exhibits shear failure characteristics. As the confining pressure gradually increases, the failure angle of the specimens enlarges. Under low confining pressure, there are fewer wing-shaped tensile cracks at the shear failure surface of the specimens. As the confining pressure increases, irregular shear failures and multiple shear planes appear in the specimens, resulting in more complex failure modes. For specimens with the same carbon nanotube concentration, the triaxial compressive strength of carbon nanotube concrete specimens increases with increasing confining pressure. The triaxial compressive strengths of the specimens under confining pressures of 5 MPa, 10 MPa, 15 MPa, and 20 MPa are 90.48 MPa, 122.72 MPa, 137.22 MPa, and 172.65 MPa, with strength increases of 35.63%, 51.66%, and 90.81%, respectively.

Critical state uniqueness of dense granular materials using discrete element method in conjunction with flexible membrane boundary

An explanation of the meso-mechanism of sand granular materials for the uniqueness of critical state is presented by means of the discrete element method (DEM) under flexible boundary loading conditions. A series triaxial drainage shear test (DEM simulations), in conjunction with the flexible boundary technique, of were performed for sand samples subjected to various physical states and with different particle size distributions. After carefully investigating the critical status of the results of the numerical calculation, the macroscopic failure modes and shear band evolution of sand, as well as the velocity vector field due to different initial states, were explored and classified. Furthermore, the evaluation rules and discrepancies between overall void ratios of the specimen and local void ratios within the shear band under the critical state were recorded and analyzed. The results proved that a sample with a small void tends to form a shear band, and the rotation of the particles in the non-shear zone is negligible. Conversely, sandy soil with large initial void ratios exhibited limited development of significant shear bands, and the change in void ratios within the shear region and the non-shear area are not significant. Interestingly, the particle-size distribution exerts minimal influence on the evolution rule which the void ratio converges within the shear band and diverges outside the shear region for both multi-stage and single-stage specimens. The void ratio within the shear band and deviator stress ratio tend to exhibit consistently for the same specimen with different initial physical states, thereby distinguishing the critical state. There is a significantly higher change in void ratio within the shear band compared to outside of it, yet it remains stable within a relatively similar range. Additionally, the invariant of the fabric tensor used to describe the critical state characteristics also demonstrates a high degree of consistency within the shear band. These findings strongly indicate that the critical state exists within the shear failure surface and is highly likely to be unique.

True triaxial shear creep behaviors of sandstone under constant normal load and constant normal stiffness conditions

The long-term stability of rocks is crucial for ensuring safety in deep engineering, where the prolonged influence of shear loading is a key factor in delayed engineering disasters. Despite its significance, research on time-dependent shear failures under true triaxial stress to reflect in situ stress conditions remains limited. This study presents laboratory shear creep measurements on intact sandstone samples under constant normal load (CNL) and constant normal stiffness (CNS) conditions, which are typical of shallow and deep engineering cases, respectively. Our investigation focuses on the effects of various lateral stresses and boundary conditions on the mechanical behaviors and failure modes of the rock samples. Results indicate that lateral stress significantly reduces shear creep deformation and decreases creep rates. Without lateral stress constraints, the samples are prone to lateral tensile fractures leading to macroscopic spalling, likely due to "shear-induced tensile" stress. This failure behavior is mitigated under lateral stress constraints. Additionally, compared to CNL condition, samples under CNS condition demonstrate enhanced long-term shear resistance, reduced shear creep rates, and rougher shear failure surfaces. These findings suggest the need to improve our understanding of rock mass stability and to develop effective disaster prevention and mitigation strategies in engineering applications.

Mechanical responses and fracturing behaviors of coal under complex normal and shear stresses, Part I: Experimental results

This work presents experimental tests based on coal collected from a coal mine based underground water reservoir (CMUWR). The mechanical responses of dry and water-soaked coal samples under the complex normal and shear stresses under multi-amplitude and variable frequency is investigated. The experimental results reveal the effects of stress path, water soaking and frequency on deformation, energy dissipation, secant modulus and shear failure surface roughness. The experimental results show that when normal and shear stresses are applied simultaneously, there is a significant competitive relationship between them. On the dominant side, the strain rate will be significantly increased. The sample under a loading frequency of 0.2 Hz exhibits a longer fatigue life. During the cyclic shear test, the shear strain of the water-soaked sample is higher than that of the dry samples. The average roughness coefficient of failure surface exhibits an increasing pattern with increase in shear strength, the elevated roughness of a shear surface is advantageous in constraining shear displacements of specimens, thereby lowering the energy dissipation. This study can provide theoretical and practical implications for a long-term safety evaluation of CMUWR.

Fracture behaviors of sustainable recycled aggregate concrete under compression-shear loading: Laboratory test, numerical simulation, and environmental safety analysis

A series of compression-shear tests were carried out to investigate the shear failure of sustainable recycled aggregate concrete, and shear failure surfaces were scanned by a 3D laser scanner. The effect of recycled coarse aggregate (RCA) replacement rates and normal stresses on the shear strength, failure mode, and fracture morphology were analyzed. Meanwhile, discrete element method was used to study shear behaviors at a mesoscale. Finally, the carbon emission was calculated to evaluate the effect of RCA on the environment. The result shows that the shear strength, cohesion c, and internal friction angle φ all decrease as the RCA replacement rate increases. The shear damage of RAC can be aggravated by increasing the RCA replacement rate. Fractal dimension and joint roughness coefficient of shear failure surface tend to increase with increasing RCA replacement rate and normal stress. In addition, more microcracks can be found in coarse aggregate with the increase in RCA replacement rate, and the increasing normal stress can cause more microcracks. Given the nonlinear development of stress-displacement, a modified nonlinear constitutive model is proposed. Finally, the total carbon emissions of recycled aggregate concrete are calculated considering production, transportation, and construction, the carbon emission of 100% sustainable recycled aggregate concrete is 10.2% less than that of 100% natural aggregate concrete.

Shear failure analysis of slip zone soil with different coarse particle shapes: Visualized shear test and PIV technology

Coarse particle shape in slip zone soil influences the mesoscopic structure of the soil, which in turn affects soil shear strength and failure behavior. In order to investigate the effect of particle shape on the shear characteristics of coarse–fine-grained mixed slip zone soil, three types of coarse particles (spheroidal, rounded, and angular) were selected for mixing and matching, and a total of 10 sets of medium-scale shear tests were designed for this paper. To quantify the shear deformation and failure process of slip zone soils, particle image velocimetry (PIV) technology and the hanging hammer method were used to obtain mesoscopic data of the soil (displacement vector data of soil particles and elevation data of the shear failure surface), which were used to calculate shear band thickness, shear dilatation, and roughness coefficient of the shear failure surface. The results indicate that coarse particle shape can considerably affect the macroscopic mechanical properties (internal friction angle and shear strength) and mesoscopic deformation characteristics (shear band thickness, shear dilatation, and shear surface morphology) of soils. Angular coarse particles have higher interlocking strength than spheroidal and rounded coarse particles, allowing angular coarse-grained slip zone soils to develop large shear band thickness and rough shear failure surfaces. In addition, mesoscopic damage analysis suggests that the damage rate of slip zone soils decreases with increasing coarse particle shape complexity. These findings enhance comprehension of the failure characteristics of soil-rock mixture slopes and serve as a good reference for the stability analysis of similar slopes.

Finite element analyses of failure of fiber reinforced polymer-concrete interface considering the concrete tension–compression softening effect

The concrete near the shear failure surface of the FRP (fiber reinforced polymer)-concrete interface is subjected to both tensile and compressive biaxial stress. However, existing finite element methods of the interfacial failure behavior of FRP-concrete interface to describe the tension–compression softening effect of concrete failure are not sufficiently accurate, and some detailed results may not be reflected. To address these issues, a finite element analysis method is proposed that accurately considers the tension–compression softening effect on concrete failure. The effectiveness of the method is demonstrated through analysis of literature data from experiments on plain concrete failure, FRP-concrete interface shear, and three-point bending. The method accurately reflects the generation of interfacial discontinuous micro-cracks, the oscillation singularity of stress field near the interfacial crack tip, the phenomenon of interface mismatch, the dispersion observed in the bond-slip curves, and the phenomenon of interfacial shear stress reversal. Moreover, this finite element analysis method is applied to the double shear experiments of the fully-bonded FRP-concrete interface under different boundary conditions, and the reasons for the different failure modes observed in the specimens are explained. The results indicate that considering the biaxial effect on concrete failure strength in numerical analysis can more accurately and comprehensively describe the shear failure behavior of the FRP-concrete interface.

Study on the Influence of Matrix on Mechanical and Failure Characteristics of Miscellaneous Fill

Abstract The matrix has a great influence on the mechanical and failure characteristics of the miscellaneous fill. Based on the laboratory medium-sized triaxial test, the confining pressure tests of 100, 200, and 400 kPa were carried out on the miscellaneous fill under three kinds of matrix with block stone content of 30 %, and the influence of the matrix on the mechanical properties of miscellaneous fill was analyzed. A biaxial test with a confining pressure of 200 kPa was carried out on three kinds of matrix miscellaneous fill samples using the particle flow method, and the influence of miscellaneous fill on the failure characteristics was studied. The test results show that the relation curve of the miscellaneous fill (σ1–σ3)∼εa can be considered as a hyperbola. The miscellaneous fill whose matrix is clay and silty soil always shows shear shrinkage. When the confining pressure is 100 kPa, the miscellaneous fill in the sandy soil matrix shows the property of shrinkage first and then dilatancy. When the confining pressure is 200 kPa and 400 kPa, it shows shear shrinkage. Through numerical simulation, it is found that when the matrix is clay, the shear zone is obvious and the shear failure surface is stable. When the matrix is silty soil, the contact cracks become thinner and the shear bands increase. When the matrix is sandy soil, compared with clay matrix, the overall crack is finer and the shear fracture surface is irregularly distributed.

Experimental study on mechanical behavior deterioration of undisturbed loess considering freeze-thaw action

To solve the problem that the mechanical behavior of undisturbed loess in seasonally frozen soil area is affected by freeze-thaw action, triaxial shear tests of undisturbed loess under freeze-thaw condition were carried out. The results show that the mechanical properties of undisturbed loess are greatly affected by factors including freeze-thaw process, water content, natural density and confining pressure. Freeze-thaw action has a certain impact on the failure surface shape and stress-strain curve. Before and after freeze-thaw, the shape of the shear failure surface is complex, including single oblique failure surface, double oblique failure surface, vertical failure surface, X-shaped failure surface, bulging failure, etc. And under the conditions of low water content, low confining pressure and high dry density, the stress-strain curve tends to be softened. Conversely, the curve tends to harden. Freeze-thaw action can make the stress-strain curve transition from softening to hardening. In addition, the freeze-thaw action significantly weakens the failure strength, shear strength, cohesion, initial tangent modulus and failure ratio of undisturbed soil, but does not change the internal friction angle obviously. Also, the heterogeneity of natural soil is also an important factor affecting the mechanical parameters, failure surface shape and stress-strain curve of undisturbed loess.

Experimental study on the deformation of sandy soil around multi-helical anchor piles under horizontal load

The deformation characteristics of sandy soil around multi-helical anchor piles have an important influence on their bearing capacity under horizontal loading. To explore the interaction mechanism between anchor pile and soil, this study combines a model test system with particle imaging velocimetry to study the deformation and bearing characteristics of the soil around multi-helical anchor piles under horizontal loading. The results show the following. (1) The sand density and anchor sheet buried depth have a significant effect on the range of the influence of the soil displacement around the helical anchor pile, and on the distribution of the active and passive zones. (2) With increasing density, the influence area of the active zone rearward of the pile decreases, whereas the opposite is true for the passive zone in front of the pile. Under shallow buried conditions, the area of influence of the passive zone rearward of the pile extends to the sand surface; whereas under deep buried conditions, the area of influence of the transition zone decreases. (3) The buried depth is the main factor in the formation of the transition zone and the rotating damage zone. As the buried depth increases, the angle between the shear failure surface of the passive zone rearward of the pile and the vertical direction gradually decreases; the development direction of the shear failure surface of the disturbance zone in front of the pile is lower right-vertical downward-lower left. (4) The volume expansion zone on the left side of the helical anchor pile gradually transitions from extending to the surface of the sand to the lower left side of the bottom anchor. Regardless of the buried depth, the maximum value of the volume strain in the soil always occurs in the upper part of the top anchor, and the soil between the two anchor plates is always in the volume contraction zone.

Investigation of shear behavior of notched bedding rock containing welded interface between hard and soft layers; an acoustic emission-based approach

The present work investigates the impacts of layer number, ratios of layer, brittleness of layer, layer angle, and length of notch on the shear failure of bedding rock with a welded interface, using experimental punch test and numerical modeling. The study also analyzed the acoustic emission (AE) events throughout the entire process, from initial shear stress applied to the notched bedding layer to final rock bridge failure. Rectangular samples with varying numbers of soft and hard layers were prepared. The ratio of soft gypsum thickness to total sample thickness in the one soft layered model, one hard layered model, two-layered model, three-layered model with soft interlayer, and four-layered model was 1, 0, 0.5, 0.33, and 0.5, respectively. Each model consisted of two vertical non-persistent edge notches in one direction, with notch lengths of 20, 40, and 60 mm. All layers had a horizontal configuration in the experimental test (layer angle 90°), while angle of bedding layers varied from 0° to 90° with increments of 15°. The considered models were investigated using punch shear tests. The results indicate that a tensile crack was initiated at the tip of the notch, propagating parallel to the shear loading axis until coalescence with the model boundary. Both peak shear strength and shear stiffness decreased as layer angles increased in models consisting of two and four layers. The mechanical properties of the three-layered model improved with increasing layer angles due to the increased presence of the hard gypsum layer in the shear failure surface. Increasing the number of layers resulted in an increased number of major AE hits, while increasing the notch length led to a drop in the number of observed AE hits. Moreover, the number of major AE hits was higher in hard ductile gypsum than in soft brittle gypsum. The failure mechanism was consistent between numerical simulation and experimental testing.

Punching shear failure behavior of fine-grained ZK60 Mg alloy processed by a novel forward shear normal extrusion process at room and elevated temperatures

The shear punch test (SPT) of ZK60 Mg alloy hot deformed by a novel sever plastic deformation technique called the forward shear normal extrusion (FSNE) was carried out at room and elevated temperatures, and the influence of FSNE process temperature on shear deformation behavior was clarified. FSNE of Mg alloy was carried out at temperatures of 200 °C, 250 °C, 300 °C and 350 °C and then SPT behavior of deformed samples was studied at temperature range of 25–250 °C. The results demonstrated that the deformation behavior and mechanical properties during SPT were significantly affected by the initial microstructure owning to different temperatures of the FSNE process. The microstructures in 200 °C, 250 °C and 300 °C FSNE processed specimens were composed of coarse deformed grains and ultra-fine DRXed grains with a near fully DRXed structure in the highest temperature (350 °C). Basal plane intensity was the maximum value in the 200 °C FSNE processed specimen, whiles with increasing FSNE process temperature, the random crystallography orientation was gradually dominated. Mechanical properties results showed that the 350 °C processed specimen presented the superior RT shear properties with the ultimate shear strength (USS) of ∼ 159 MPa and peak shear strain (PSS) of 81% as well as the highest thermal stability. Shear failure surface was mainly composed of rollover, burnished, fractured and burr areas. The percentage of burnished area in punching-out specimens was affected by initial microstructure and strength and for the specimens having high strength, the percentage of this area was low. In each SPT process temperature, higher peak strain postponed rapture and resulted in higher burr area.

Ultrasonic welding of fiber reinforced vitrimer composites

In this investigation, we present an exciting discovery that glass and carbon fiber-reinforced vitrimer composites (vGFRC and vCFRC) can be ultrasonically welded. The study shows that applying mechanical vibrational energy can facilitate dynamic bond exchange reactions in transesterification vitrimer composites, resulting in good weldability and mechanical properties. The results show that ultrasonic welding is potentially a practical and cost-effective option for assembling complex or large parts compared to oven curing, as it requires significantly less energy and time. Moreover, the healing properties of vitrimers make them a promising material for repeated processing and welding at the same spot. The study provides insight into the mechanisms of ultrasonic welding of vitrimers comprising bond exchange reactions and polymer chain diffusion at the surfaces. The composites with carbon fiber show better performance properties during welding compared to glass fiber-embedded composites. Lap shear failure surfaces show mostly cohesive failure. Additionally, the weld strength is also influenced by the catalyst concentration in the vitrimer composites. This investigation opens new avenues for vitrimer composites in industrial applications requiring rapid and energy-efficient welding.

Study on microscopic failure mechanism and numerical simulation of sandstone under different saturated pressure

X-ray diffraction and SEM scanning are conducted to examine the alterations in sandstone under different saturation conditions to reveal the water-rock softening effect on sandstone from the Qilicun tunnels in China under varying saturation pressures. The mechanisms underpinning the strength softening of sandstone are analyzed using uniaxial compression tests. The experimental results demonstrated that after immersion in water, the internal cementing material within the sandstone dissolves, and the mineral particles fragment or disintegrate, increasing porosity. In the presence of water, the macroscopic compressive strength of sandstone exhibits a declining trend. Concurrently, as the saturation pressure escalates, the compressive strength diminishes by approximately 10%, the elastic modulus decreases by about 30%, and Poisson's ratio incrementally falls by about 25%. The sandstone's failure is characterized by both axial multiple splitting surface failure and shear failure surface. Finally, a strain-softening numerical model is employed to simulate the failure behaviors of sandstone under various saturation pressures. The findings indicated that the sandstone sample exhibits plastic failure characteristics under high saturation pressure.

Steel fiber reinforced concrete beams with predetermined failure surface and no stirrups

This paper treats an experimental study of shear problems in steel fiber reinforced concrete beams without shear reinforcement, where a specific groove in the shear span is used to specify the location of diagonal cracks, aiming to reduce the arch effect, controlling the critical crack inclination at 30°, and evaluating the assertiveness of the normative shear strength predictions. The experimental program includes four (4) beams, varying the steel fiber ratio. The results showed that the mechanism was satisfactorily induced shear failure, as expected. Also, it was observed that the ratio av/d did not influence the proposed model significantly, such behavior was expected because the shear cracks observed in the beams were more pronounced after distance av/4, making the arching action and dowel action less effective in the ultimate shear strength value. The proposed model excelled in the accuracy of the normative predictions, with a coefficient of variability between 4 and 8 %, probably to eliminate any arch effect for the ratio av/d = 1.86. However, a simplified calculation model based on the fiber residual stress distribution along the considered inclined section was proposed, and it was noted that the proposal presented better results, with an average value of 1.0 and a coefficient of variation (CoV) of only 3 %. It also showed a mean of 1.02 and a CoV of 8 % compared to the experimental results from the literature. Thus, the proposed predetermined shear failure surface and the calculation model are viable alternatives to evaluate estimates for shear resistance even with shear reinforcement or steel fibers.

Fracturing evolution and strain characteristics of layered rock-like materials with rough interfaces

Layered rock-like samples containing saw-tooth interfaces of various joint roughness coefficients (JRC) and included angles were conducted uniaxial compression with the loading rate of 0.005 mm/s. The peak stress declines from 38.36–39.90 MPa to 17.35–30.67 MPa for included angle = 15°–60°, and then increases to 24.30–33.83 MPa for 60°–75°, but the peak strain decreases by 22.39%–41.30%. For JRC = 0–19.55, mechanical properties of samples are enhanced, while the anisotropy weakens. When the included angle is small (15°, 30°), the layered samples show a typical tensile splitting failure crossing the weak interlayers. For a large included angle of 45°–75°, failure modes are featured by shear sliding along weak interlayers combined with tensile splitting. As JRC increases, fracturing mechanism transition from shear sliding to mixed tension shear failure then to tensile splitting can be identified. With an increase in JRC or included angles, the global lateral strain of samples in plastic deformation stages changes from “sudden increase” to “progressive increase” to “jump increase”. For included angle = 15°, the layered sample produces dramatic lateral local strain at the weak interlayers due to tensile splitting failure. For included angle = 45°, both axial and lateral local strains at the weak interlayers show an obvious increase at the main shear failure surface. For a large included angle of 75°, the lateral local strain remarkably increases at the weak interlayers along with tensile failure of samples.

Mechanical properties and acoustic emission characteristics of deep hard coal after segmented high-temperature treatment

Based on engineering background that local heating of coal seam is uneven due to underground coal gasification, coal-bed gas exploitation via heat injection, spontaneous combustion of coal seam, etc., segmented heating coal sample was used to simulate coal seam under uneven heating condition, and experimental study on mechanical behaviors of coal sample after segmented heat treatment at high temperatures was conducted. Test results show that temperature at 100 °C ~ 400 °C did not reach ignition temperature of deep hard coal for the experiment and was not enough to change main ingredients of coal sample, which less affected compression strength, elastic modulus, acoustic emission behavior of coal sample. Although compaction stage-elastic stage-plastic stage-broken stage appeared in compression stress–strain curve of coal sample, height increase led to decrease of compression strength, elastic modulus of coal sample, cumulative amplitude and ringing count for acoustic emission in the form of power function. Meanwhile, it is found that final failure modes of coal sample after segmented heat were mainly shear failure and separation failure and friction mixed failure was secondary. In addition, influence of heating temperature at 100 °C ~ 400 °C on failure modes of coal sample was small. However, height increase in the heating section of coal sample made shear failure surface gradually move to the heating section and separation failure surface moved with the change of contact surface position between heating section and non-heating section. Furthermore, the integral failure degree of coal sample was more serious. Finally, based on variation behaviors of acoustic emission parameter for coal sample after segmented heating, inversion formula on acoustic emission parameter for strength of coal sample was discussed and verified via experimental result of coal sample with different segmented heat height after heating treatment at 200 °C.

Bond Degradation Mechanism and Constitutive Relationship of Ribbed Steel Bars Embedded in Engineered Cementitious Composites under Cyclic Loading

In order to investigate the bond degradation mechanism and constitutive relationship of ribbed steel bars in engineered cementitious composites (ECCs) under cyclic loading, 12 groups of specimens were tested in this paper. The design parameters included ECC compressive strength, ECC flexural toughness, cover thickness, and anchorage length. The results indicated that the degradation of the bond behavior of the ribbed steel bars in the ECCs under cyclic loading was mainly caused by the degradation of the properties of the ECC material itself, concentrating on the development of cracks in the ECC, the extrusion and shear failure of the ECC between the steel bar ribs, and the continuous grinding of the ECC particles on the shear failure surface. The degradation of the bond stress-slip curves under cyclic loading was mainly reflected by the degradation in the ultimate bond strength and unloading stiffness. According to the monotonic loading test results, a monotonic bond stress-slip relationship model was proposed. On this basis, through building the hysteretic rules of the bond stress-slip curves under cyclic loading, a calculation model was proposed to predict the bond stress-slip constitutive relationship between the ribbed steel bars embedded in the ECCs under cyclic loading. Finally, the validity of the proposed model was verified by a comparison between the model curves and the tested curves.

Experimental study on shear characteristics of the silty clay soil-ice interface

During the spring thawing, the decrease of soil-ice interface strength by temperature may lead to slope instability. For this reason, some researchers have explored the relationship between temperature and soil-ice interface strength. However, previous studies have not systematically explored the change law of strength at the soil-ice interface from negative temperature to 0 °C. Therefore, direct shear tests were conducted at different shear temperatures and different moisture contents. The effects of temperature and moisture content on strength, cohesion, and internal friction angle are analyzed, while the shear failure mechanism of specimens at different temperatures is discussed according to the location of the shear failure surface. The results show that: Shear properties of soil ice specimens are related to the unfrozen moisture content. The strength of the sample decreases with increasing temperature, and the change in strength is most significant from − 2 to − 0 °C. The strength reduction in this range is from 21.8 to 74.8%, and the higher the moisture content the more obvious this phenomenon is. The shear index tends to decrease with the increase of unfrozen water content, and the greater the increase of unfrozen water, the faster the decrease of both, especially in stage 2. When the temperature is higher than − 5℃, the failure surface is located above the soil-ice interface, and the strength of the specimen is similar to that of the frozen soil. When the temperature is − 10℃, the shear damage surface appears at the soil-ice interface, and the strength of the specimen is determined by the strength of the soil-ice interface.