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Spherical glass beads weaken the influences of particle morphology, surface properties, and microscopic fabric on shear strength, which is significant for revealing the relationship between macroscopic particle friction mechanisms and the particle size distribution of sand. This paper explores the shear mechanical properties of glass beads with different particle size ratios under different confining pressures. It obtains the particle size ratio and fractal dimension D through an optimal mechanical response. Simultaneously, we explore the range of the fractal dimension D under well-graded conditions. The test results show that the strain-softening degree of Rs is more obvious under a highly effective confining pressure, and the strain-softening degree of Rs can reach 0.669 when the average particle size d ¯ is 0.5 mm. The changes in the normalized modulus ratio Eu/Eu50 indicate that the particle ratio and arrangement are the fundamental reasons for the different macroscopic shear behaviors of particles. The range of the peak effective internal friction angle φ is 23 °~35 °, and it first increases and then decreases with the increase in the effective confining pressure. As the average particle size increases, the peak stress ratio MFL and the peak effective internal friction angle φ first increase and then decrease, and both can be expressed using the Gaussian function. The range of the fractal dimension D for well-graded particles is 1.873 to 2.612, and the corresponding average particle size d ¯ ranges from 0.433 to 0.598. Under the optimal mechanical properties of glass beads, the particle size ratio of 0.25 mm to 0.75 mm is 23:27, and the fractal dimension D is 2.368. The study results provide a reference for exploring friction mechanics mechanisms and the optimal particle size distributions of isotropic sand. [ABSTRACT FROM AUTHOR]

AbstractThe traction force of the tracked miner is primarily determined by the shear characteristics of deep-sea sediments. The influence of different parameters on the shear characteristics of deep-sea sediments and the particles change law of the soil–track interface are discussed. By constructing the relationship between the particles horizontal displacement and residual shear strength, a novel shear rheological damage model of deep-sea sediments considering the influence of grounding pressure is proposed, and the microscopic mechanism of shear displacement of deep-sea sediments is explained. The results show that the peak shear strength and residual shear strength increase significantly with the increase of grounding pressure, track length, grouser height and shear speed. Moreover, the particles within the soil–track interface move along the lower right of the vehicle operating direction during the shearing process under different working conditions, the change of particle spacing shows a non-linear trend, and a quantitative equation for the horizontal deformation of soil–track interface under the experimental conditions is constructed. Additionally, the new shear model has a high level of accuracy in fitting with the experimental data, the internal particle migration changes on the soil–track interface can be divided into four characteristics: compaction, failure, deformation and translation. [ABSTRACT FROM AUTHOR]

Rapid dynamic loads, such as those caused by earthquakes or traffic, induce medium strain rates in expansive soil, impacting its mechanical properties, which are vital for geotechnical engineering design. This study aims to deepen understanding of the rate effect on expansive clay under plane strain conditions. It conducts various isotropic triaxial and plane strain shearing tests at different medium strain rates. Post-testing, the microstructures of the clay, affected by varying shearing rates, are examined using scanning electron microscope and nuclear magnetic resonance. The experimental findings revealed that the strength at higher strain rates surpasses that at lower ones. In addition, the strength under plane strain at the same consolidation stress level exceeds that under triaxial loading. The strain rate effect is more pronounced in the clay studied under low consolidation pressure, which is more significant in the triaxial state than under plane strain. Excess pore water pressure initially peaks at low strain rates before decreasing but increases at higher strain rates. The specimen’s intermediate principal stress coefficient (b) rises with the increase in consolidation pressure and strain rate. In addition, the expansion of fissures and changes in internal structure account for the strain rate effect in undisturbed expansive soil under specific loading rates. These new insights aid in better understanding the behavior of expansive clay under medium strain rates, enabling engineers to establish appropriate design parameters and criteria. This ensures the safety and stability of structures under dynamic loading. [ABSTRACT FROM AUTHOR]

Sandy soil in the north of Hebei region of China is widely distributed, the temperature difference between day and night is large, the phenomenon of freezing and thawing is obvious, and the soil body before and after the freezing and thawing cycle of sandy soil slopes is affected by the changes. This paper takes the stability of a sandy soil anchorage interface under a freeze-thaw cycle as the research background and, based on the self-developed anchor-soil interface shear device, analyses the influence of changing sand rate, confining pressure, and the number of freeze-thaw cycles on the shear characteristics of an anchor-soil interface in anchorage specimens. The research findings indicate that, at 50–60% sand contents, the shear strength increases with a higher sand content and is positively correlated with confining pressure within a higher range. A higher sand content stabilises the anchoring body, but an excessively high sand content can lead to failure. Increasing the sand content, confining pressure, and freeze-thaw cycle number all result in a reduction in the shear displacement at the peak strength. After 11 freeze-thaw cycles, the shear strength of the anchoring body stabilises, with a reduction in strength of approximately 32%, and a higher sand content effectively reduces the reduction in strength. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The shear strength parameter of an anchoring interface is one of the key parameters affecting the design of bolt support. To better realize the design of bolt support, the pullout model of fully grouted bolts was established by FLAC3D numerical software. The commonly used tri-linear bond-slip model of the anchoring interface was selected. The variable controlling method was used to investigate the effects of the shear strength parameters of the anchoring interface on the bearing performance of fully grouted bolts. The results show that, with the increase in the displacement at the peak shear stress, the bearing capacity and the energy absorption of fully grouted bolts decrease and the ability of the fully grouted anchoring system to resist external loads weakens. Meanwhile, the deformation capacity of fully grouted bolts increases, and the durability of the fully grouted anchoring system is enhanced. With the increase in the residual shear stress and the displacement at the residual shear stress, the bearing capacity and deformation capacity of fully grouted bolts both increase, and the energy absorption also increases. Increasing the post-peak bearing properties of the anchoring interface can help improve the bearing performance of fully grouted bolts and enhance the ability of the fully grouted bolts to resist failure. The results may provide guidance for support design and performance enhancement of fully grouted bolts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Spherical glass beads weaken the influences of particle morphology, surface properties, and microscopic fabric on shear strength, which is significant for revealing the relationship between macroscopic particle friction mechanisms and the particle size distribution of sand. This paper explores the shear mechanical properties of glass beads with different particle size ratios under different confining pressures. It obtains the particle size ratio and fractal dimension D through an optimal mechanical response. Simultaneously, we explore the range of the fractal dimension D under well-graded conditions. The test results show that the strain-softening degree of Rs is more obvious under a highly effective confining pressure, and the strain-softening degree of Rs can reach 0.669 when the average particle size d¯ is 0.5 mm. The changes in the normalized modulus ratio Eu/Eu50 indicate that the particle ratio and arrangement are the fundamental reasons for the different macroscopic shear behaviors of particles. The range of the peak effective internal friction angle φ is 23 °~35 °, and it first increases and then decreases with the increase in the effective confining pressure. As the average particle size increases, the peak stress ratio MFL and the peak effective internal friction angle φ first increase and then decrease, and both can be expressed using the Gaussian function. The range of the fractal dimension D for well-graded particles is 1.873 to 2.612, and the corresponding average particle size d¯ ranges from 0.433 to 0.598. Under the optimal mechanical properties of glass beads, the particle size ratio of 0.25 mm to 0.75 mm is 23:27, and the fractal dimension D is 2.368. The study results provide a reference for exploring friction mechanics mechanisms and the optimal particle size distributions of isotropic sand.

Red soil is one of the typical soil types in China, which is widely distributed in 17 provinces with a total area of 569,000 km², accounting for about 1/5 of the total land area in China. It is a widely distributed soil type in Yunnan Province. Compared with other natural soils, red soil has high viscosity, high water content, low shear strength, serious loss of organic matter and nutrients, and changes in soil structure and quality, which leads to low root characteristic parameters of root-soil complex and cannot meet the needs of engineering practice. However, the roots of herbaceous plants are mostly dense and fine roots, which have a good reinforcement effect on shallow soil, consolidate soil and prevent erosion, and their root characteristic parameters can better reflect the contribution of roots to soil shear strength. It is of certain significance to study the mechanical properties of root-soil complex of herbs through root characteristic parameters. In order to find out the influence mechanism of root characteristics on the shear characteristics of herb root-soil complex under different mass fractions (0, 0.5%, 2.5% and 5.0%) of wood fiber reconstruction red soil, the shear strength of root-soil complex of white clover and ryegrass was measured by direct shear test, and four root characteristic parameters, such as root surface area index, root volume ratio, root length and underground biomass, were measured by WinRHIZO root analysis system, and their resistance was further revealed. The results showed that proper wood fiber addition was beneficial to the growth of fibrous root herbs. When the wood fiber content is high, the root length of Lolium perenne and white clover are 456.27 and 438.35 cm respectively, and the underground biomass are 0.410 and 0.150 mg respectively. With the increase of root characteristic parameters, the shear strength of ryegrass root-soil composite is greater than that of white clover root-soil composite, and the shear strength of both is better than that of single wood fiber composite soil or root soil, with the increase ranges of 26.55% - 47.20% and 26.21% - 35.07% respectively, but there is a certain change threshold. The Mohr-Coulomb model is used to simulate the shear characteristic parameters of the root-soil complex. When the characteristic parameters of root system reach the change threshold, the change of cohesion is obviously and plays a leading role, but has little influence on internal friction angle. The shear strength of root-soil complex increases first and then decreases. When the root parameter value exceeds the threshold, the shear strength of wood fiber rootsoil composite decreases, showing a trend of increasing first and then decreasing. This study has important theoretical and engineering practice value for further study of slope protection, vegetation restoration and land consolidation in red soil region. [ABSTRACT FROM AUTHOR]

Sandy soil in the north of Hebei region of China is widely distributed, the temperature difference between day and night is large, the phenomenon of freezing and thawing is obvious, and the soil body before and after the freezing and thawing cycle of sandy soil slopes is affected by the changes. This paper takes the stability of a sandy soil anchorage interface under a freeze-thaw cycle as the research background and, based on the self-developed anchor-soil interface shear device, analyses the influence of changing sand rate, confining pressure, and the number of freeze-thaw cycles on the shear characteristics of an anchor-soil interface in anchorage specimens. The research findings indicate that, at 50–60% sand contents, the shear strength increases with a higher sand content and is positively correlated with confining pressure within a higher range. A higher sand content stabilises the anchoring body, but an excessively high sand content can lead to failure. Increasing the sand content, confining pressure, and freeze-thaw cycle number all result in a reduction in the shear displacement at the peak strength. After 11 freeze-thaw cycles, the shear strength of the anchoring body stabilises, with a reduction in strength of approximately 32%, and a higher sand content effectively reduces the reduction in strength.

The shear strength parameter of an anchoring interface is one of the key parameters affecting the design of bolt support. To better realize the design of bolt support, the pullout model of fully grouted bolts was established by FLAC3D numerical software. The commonly used tri-linear bond-slip model of the anchoring interface was selected. The variable controlling method was used to investigate the effects of the shear strength parameters of the anchoring interface on the bearing performance of fully grouted bolts. The results show that, with the increase in the displacement at the peak shear stress, the bearing capacity and the energy absorption of fully grouted bolts decrease and the ability of the fully grouted anchoring system to resist external loads weakens. Meanwhile, the deformation capacity of fully grouted bolts increases, and the durability of the fully grouted anchoring system is enhanced. With the increase in the residual shear stress and the displacement at the residual shear stress, the bearing capacity and deformation capacity of fully grouted bolts both increase, and the energy absorption also increases. Increasing the post-peak bearing properties of the anchoring interface can help improve the bearing performance of fully grouted bolts and enhance the ability of the fully grouted bolts to resist failure. The results may provide guidance for support design and performance enhancement of fully grouted bolts.

Granite binary structure slopes and residual soil slopes containing spheroidal boulders formed by differential weathering are widely distributed along the southeast coast of China. Field studies demonstrate that the failure of differentially weathered granite slopes mainly occurs at soil–rock interfaces. Only few studies have been conducted on the shear characteristics of the interfaces between rocks and granite residual soil. Moreover, mechanics models describing the engineering properties of the interfaces have not been developed. In this study, the ring shear tests are conducted on a granite residual soil–rock interface using the orthogonal design method and considering factors such as the roughness of granite, water content and initial dry density, shear rate, and number of drying–wetting cycles. A mechanics model that can precisely demonstrate the shear characteristics of the interface is also developed, and its validity is verified using test results. The findings indicate that the roughness of granite and the water content of the residual soil are the main factors affecting the interface shear stress. As the increase of granite roughness, the peak internal friction angle, residual internal friction angles, and peak cohesion of soil–rock interface increase. The residual cohesion of the interface, however, decreases as the roughness of granite increases. As the water content of the soil increases, both the interface shear stress and internal friction angle initially start to increase and then decrease. With the increase of the number of drying–wetting cycles, the internal friction angle and peak cohesion of the interface decrease. [ABSTRACT FROM AUTHOR]

Abstract In principle, the mechanical properties of soil particles are irreversibly changed after particles are subjected to heating. Accordingly, this study performed ring-shear tests on calcareous sand samples subjected to high temperatures to qualitatively investigate the influence exerted by the degradation of the calcareous sand, caused by the thermal effect, on the large displacement shear characteristics of the samples. The effects of the shear velocity and normal stress on the quasi-static shear behavior of the calcareous sand samples were analyzed. The influence of the thermal effect on the quasi-static shear flow behavior of the samples is primarily reflected in the change in the particle mineral composition, particle hardness, and sample density. These variations result in changes in the shear strength, residual shear stress, macroscopic friction coefficient, and other shear characteristics of the calcareous sand samples. Both the shear velocity and the high temperature affect the fluctuation amplitude of the residual shear stress. The results have great theoretical and practical significance in terms of explaining the instability mechanism of a slope. Moreover, a feasible and effective technique is proposed to investigate the large-displacement shear behavior of soil subjected to the thermal effect exerted by a long-runout landslide.

In this study, the thermally induced changes in the shear characteristics of unbound granular materials (UGMs) were investigated. A series of drained shear tests were conducted using a large-scale triaxial apparatus under controlled temperatures. The thermal dependence of the peak strength, critical strength, internal friction angle, and dilatancy of UGMs were investigated under different temperatures, initial mean effective stresses, and relative compaction. Dense UGMs tended to expand during heating and slightly contract during cooling. In the heating and cooling process, a nonlinear relationship was observed between thermal deformation and temperature. Thermal deformation was attributed to the deformation, movement, and rotation of soil particles and closely related to the initial mean effective stress and relative compaction. A thermal softening effect was observed during the shear test, and the peak strength decreased with increasing temperature. However, negligible thermal effects were observed relative to residual strength. The effect of temperature on the shear characteristics of UGMs was primarily related to the thermal expansion of pores in the soil skeleton. The relationship between peak strength and initial thermal volumetric strain was found to be exponential. Considering the thermal effect, a normalized semi-empirical model of the parabolic Hvorslev envelope for dense UGMs was proposed to supply guidelines for road base design. [ABSTRACT FROM AUTHOR]

Anisotropic discontinuity exists widely in rock masses of mines, tunnels, slopes, water conservancy and hydropower projects. The shear characteristics of bolted anisotropic rock joints are extremely important for the stability design of engineering rock mass. However, few scholars have studied the bolted anisotropic rock joint. The different rock properties on both sides of the rock joint, especially the different rock strengths, will greatly affect the deformation characteristics and failure mode of the rock mass. Based on this, a series of shear tests were carried out on the bolted anisotropic rock joint under different normal stresses, and the characteristics of shear stress–shear displacement curve, shear strength, failure characteristics of the rock joint and deformation characteristics of the bolt are discussed. λ is defined as the strength ratio of upper and lower rock on the structural surface. The results show that the effect of λ on the shear stress–shear displacement curve is not obvious at the pre-fracture stage. The shear stress–shear displacement curve at the pre-breaking stage of the bolt presents a softening stage when the normal stress is equal to 0.5 MPa, tends to be horizontal when the normal stress is equal to 1 MPa and presents a hardening stage when the normal stress is greater than 1 MPa. After the bolt is broken, the shear stress–shear displacement curve presents a stepped-down descent. With the increase in λ, the breaking shear stress of the bolt increases. Elliptic failure occurs on the surface of the bolted anisotropic rock joint, and the length of the major axis of the ellipse decreases with the increase in λ value and normal stress. The bolts with different λ values of anisotropic rock joint show "Z-shaped" tensile bending deformation characteristics after shear fracture, and the horizontal and vertical components of the bolt deformation decrease with the increase in λ value and normal stress. The fracture shear displacement of the bolt increases with the increase in normal stress and decreases with the increase in λ value. The research results are helpful to further understand the shear mechanical characteristics and differences of bolted rock joints and provide a reference for solving the engineering problems of the composite layered rock mass. [ABSTRACT FROM AUTHOR]

Two-order morphology of rock joints named as waviness and unevenness can be separated by morphology classification method, which plays a decisive role in the evolution of shear stress during the shear test. The joint morphology is obtained by using 3D printing and 3D laser scanning techniques and the joint model samples in two-order morphology are produced by cement mortar. Then, shear tests are performed under different normal loads. Results shows that the waviness is dominant in the total morphology during the shear test, and the shear contribution of unevenness mainly occurs in the climbing phase of shearing process. Comparing the failure modes of two-order morphology, waviness mainly embodies shear dilation characteristics and unevenness mainly shows shear wear characteristics. Based on this, a quantitative parameter is proposed to represent the ratio of the peak shear strength of the two-order morphology to that of total morphology. The functional relationship between the peak shear strength of total and two-order morphologies is determined, providing a theoretical method for further in-depth study on the shear strength of the interaction with two-order morphology of rock joints. [ABSTRACT FROM AUTHOR]

To better study the shear characteristics of infilled joints with soil having different moisture contents, the influence of the moisture content on the shear characteristics of the infilled joint was explored in this paper, and a revised shear strength model of infilled joint surface is proposed. The results show that the shear dilatation modes of joints can be divided into four types: pure shear dilatation, pure shear compression, shear dilation-shear compression and shear compression-shear dilation. As the joint roughness coefficient (JRC) value increases, the normal displacement of the joint surface gradually increases during the shearing process and the normal stress has an inhibitory effect on dilatation. The infill material will weaken the peak shear stress of the joint surface. When the JRC value of joint surface is small, the weakening effect of soil with moisture content of 30% on peak shear stress is obvious. The revised joint roughness coefficient-joint wall compressive strength (JRC-JCS) model of infilled joint is proposed and the maximum shear stress value calculated by the model has a good linear relationship with the test value.

In principle, the mechanical properties of soil particles are irreversibly changed after particles are subjected to heating. Accordingly, this study performed ring-shear tests on calcareous sand samples subjected to high temperatures to qualitatively investigate the influence exerted by the degradation of the calcareous sand, caused by the thermal effect, on the large displacement shear characteristics of the samples. The effects of the shear velocity and normal stress on the quasi-static shear behavior of the calcareous sand samples were analyzed. The influence of the thermal effect on the quasi-static shear flow behavior of the samples is primarily reflected in the change in the particle mineral composition, particle hardness, and sample density. These variations result in changes in the shear strength, residual shear stress, macroscopic friction coefficient, and other shear characteristics of the calcareous sand samples. Both the shear velocity and the high temperature affect the fluctuation amplitude of the residual shear stress. The results have great theoretical and practical significance in terms of explaining the instability mechanism of a slope. Moreover, a feasible and effective technique is proposed to investigate the large-displacement shear behavior of soil subjected to the thermal effect exerted by a long-runout landslide. [ABSTRACT FROM AUTHOR]

In the present study, the shear characteristics of cementitious mortar reinforced with steel and nylon fibres were experimentally investigated through direct shear tests. The primary test parameters of the present study were fibre volume fractions of 0.15, 0.25, and 0.33% for nylon fibres; 0.5, 0.75, and 1.0% for steel fibre; and hybrid fibres comprised of different amounts of steel and nylon fibres. The test specimens were made with a singly rectangular notch at the centre to predefine the shear failure plane. Direct shear test was carried out following the guidelines specified in the Fédération Internationale de la Précontrainte (FIP) standard. The results showed that the cementitious mortar reinforced with fibres exhibited more ductility than plain mortar matrix. It was determined that the use of higher amounts of steel and nylon fibres could significantly improve the peak shear stress. Finally, a shear stress-crack slip model was constructed to idealise shear stress-crack slip curves of cementitious mortar reinforced with steel and nylon fibres, and the prediction results were consistent with the experimental results. [ABSTRACT FROM AUTHOR]

We have investigated the evolution of the shear characteristics of quartz sand subjected to high temperatures present in long-runout landslides. Quartz sand samples were subjected to quantitative heat treatment at a range of peak temperatures. Based on the principle of the irreversibility of mechanical characteristics of soil materials after heating, dynamic ring-shear experiments were subsequently performed and the sample density and X-ray powder diffraction patterns were analyzed. The shear behavior, shear strength, residual shear stress, density of samples, particle size variation, and mineral composition variation were analyzed and the main conclusions are as follows: (1) quartz sand that has been exposed to high temperatures is more easily broken and its density changes; (2) particle size has a substantial influence on the residual shear stress and the amplitude of shear stress fluctuation; (3) copper-gold-iron was found in the samples after heat treatment. We interpret this to mean that a small quantity of metallic elements in the quartz can have adverse effects on the shear properties of the sand with exposure to high temperature. [ABSTRACT FROM AUTHOR]

With the increasing scale and depth of underground engineering, the geological environment that engineering is faced with is becoming more complex. As the weak position of rock mass, the structural surface has a particularly great influence on the mechanical characteristics of the rock mass. In order to obtain the shear strength characteristic of the structural plane and analyze the influence of morphological parameters such as the undulating angle and bulge degree on shearing, taking medium-low permeability tight sandstone as the research object, four kinds of structural plane samples with different undulating angles (10, 20, 30 and 40°) were prepared with a Python and high-precision engraving machine. Direct shear tests under different normal stresses (2, 4, 6 and 8 MPa) and shear rates (0.6, 1.2 and 2.4 mm/min) were performed, and the shear mechanical properties were analyzed. The structural surfaces before and after shearing were scanned using a high-precision three-dimensional scanner, so as to evaluate the roughness of the structural surface and determine the influence from various factors on the shear characteristics. The test results showed that for the structural plane with the same undulating angle, the peak shear stress increased approximately linearly with an increase in normal stress at a 0.6 mm/min shear rate and an increment speed of approximately 0.82, while the peak shear stress negatively correlated with the shear rate at a value of 4 MPa for normal stress. The larger the undulating angle was, the greater the influence of the shear rate (the shear stress decreased by 2.31 MPa at a 40° angle). When the normal stress and the shear rate were fixed, the peak shear stress corresponding to the structural surface gradually increased with the increase in the undulating angle, and the maximum increment was 5.04 MPa at 4 MPa normal stress and a 0.6 mm/min shear rate. An analysis of the morphological characteristics of the structural plane showed that when the undulating angle (40°) and the normal stress (6 and 8 MPa) were larger, the damage of the structural plane became more obvious, the shear point was closer to the tooth valley position, and the mechanical bite force and friction force of the structural plane were better utilized. When the shear rate was lower (0.6 mm/min), the friction characteristics of the shear surface were more visible, the shear was increasingly sufficient, and the corresponding shear strength was also greater. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) can be used as a road material binder, and its mechanical properties, durability, temperature stability, and other road performance metrics are good. However, the interlayer bonding between PU mixtures and asphalt mixtures is poor. The influence of the pavement structure, interlayer treatment scheme, load, and environmental factors on the interlayer shear characteristics of PU mixture composite pavement is analysed. Further, dynamic modulus, Hamburg rutting, accelerated loading, and inclined shear tests were conducted, and the typical PU mixture pavement shear stress was calculated. The interlaminar shear stress of double layer PU mixture pavement, polyurethane–asphalt composite pavement, and typical asphalt pavement were calculated. The results showed that the PU mixture has a low rutting deformation rate, stable mechanical properties, and strong resistance to the coupled action of temperature, water, and loading. The double-layer PU mixture structure has good water-temperature stability and fatigue resistance; however, freeze–thaw and accelerated loading cause great damage to the double-layer PU mixture structure. The residual shear strength ratio after freeze–thaw cycles and accelerated loading is only 50.3% and 35.6%, respectively, while the influence on the double-layer asphalt mixture structure is less. The theoretical calculation results of different pavement structures show that when the temperature increases from 10 °C to 50 °C, the interlaminar shear stress of polyurethane–asphalt composite pavement increases by about 20%. Additionally, the shear stress of pavement PU mixture pavement and typical asphalt pavement is mainly affected by load, and the temperature changes have an obvious effect on the interlayer shear stress of polyurethane–asphalt composite pavement. The calculated maximum shear stress of the three pavement structures with different working conditions is less than the interlaminar shear strength measured by the inclined shear test, indicating that the interlaminar treatment scheme of composite specimens can meet the shear resistance requirements of the three typical pavement structure types. [ABSTRACT FROM AUTHOR]

The shear characteristics of the interfaces between soil and concrete structures are essential for the safety of the structures. In this study, a large-scale direct shear test apparatus was developed to measure the mechanical parameters of soil–concrete interfaces under conditions with different soil types, soil moisture contents, and interfacial filling materials. The results showed that the shear stress of the soil–concrete interface increased initially and then became stable with the increase in the shear displacement. The shear displacement of the sandy soil when the shear stress became stable was smaller than that of the clayey soil. The silty sand–concrete interface had a smaller friction angle than the interface with the medium-coarse sand. Moreover, with the increase in the soil moisture content, the friction angle of the clayey soil–concrete interface decreased rapidly, whereas the cohesion first increased and then decreased, and the peak cohesion was near the plastic limit of the soil. Under the same moisture content, the friction angle and cohesion of the clay–concrete interface was reduced by filling the interface with a thin layer of sandy soil, while filling the silty sand–concrete interface with a thin layer of silt reduced the friction angle and increased the interfacial cohesion. Nonetheless, the filling had little impact on the overall shear strength of the interface. [ABSTRACT FROM AUTHOR]

Knowledge of the shear behavior of landslide soil is very important for understanding landslide dynamics. This study investigated the shear behavior of base soil particle materials using ring shear tests with glass beads. Samples with varying particle sizes and distributions were examined to explore how particle size affects shear behavior at different shear velocities. Analysis of the samples included assessment of shear stress, displacement-shear stress fluctuations, and changes in the shear stress standard deviation. Results showed that with increasing shear displacement, shear stress fluctuations stabilize. Rather large difference particle size differences lead to more uniform particle mixing and a lower shear stress standard deviation. Conversely, when smaller particles predominate, particle mixing is less uniform, resulting in a higher shear stress standard deviation. Additionally, this study discussed the shear dilation and compaction mechanisms of samples under large displacement shear. [Display omitted] • TThe difference of particle size distribution in the upper and lower regions of glass microbeads was studied. • The changes of test parameters under different particle size distributions are analyzed. • The corresponding mechanism is proposed to explain the movement and parameter change of the sample. • The motion patterns of glass beads with different particle sizes were recorded by high-definition cameras. • Piv method was used to track the particle trajectory and demonstrate the velocity displacement. [ABSTRACT FROM AUTHOR]

In recent years, China has established many large water conservancy projects in the western mountainous areas. However, dam foundation excavation produces a huge amount of waste rock mixture. A soil-rock mixture with unique structural characteristics can easily cause geological disasters, such as collapse, landslide, and debris flow following an earthquake, rainfall, and engineering disturbance. Therefore, research on the strength and shear characteristics of the soil-rock mixture is beneficial to avoiding soil-rock mixture disasters. In this study, the soil-rock mixture in the slag dump site of Jinping Hydropower station is taken as the research object. The influence of different fillers on the gravel soil shear characteristics is investigated through a large-scale triaxial test of coarse-grained soil. The slope stability of the slag dump site is analyzed using Midas GTS. Then, the most unfavorable sliding surface of the slag dump site is discovered and the slope stability coefficient under the most unfavorable conditions is calculated. The results lay a scientific foundation for the design and construction of a slag dump slope.

Anisotropic discontinuity exists widely in rock masses of mines, tunnels, slopes, water conservancy and hydropower projects. The shear characteristics of bolted anisotropic rock joints are extremely important for the stability design of engineering rock mass. However, few scholars have studied the bolted anisotropic rock joint. The different rock properties on both sides of the rock joint, especially the different rock strengths, will greatly affect the deformation characteristics and failure mode of the rock mass. Based on this, a series of shear tests were carried out on the bolted anisotropic rock joint under different normal stresses, and the characteristics of shear stress–shear displacement curve, shear strength, failure characteristics of the rock joint and deformation characteristics of the bolt are discussed. λ is defined as the strength ratio of upper and lower rock on the structural surface. The results show that the effect of λ on the shear stress–shear displacement curve is not obvious at the pre-fracture stage. The shear stress–shear displacement curve at the pre-breaking stage of the bolt presents a softening stage when the normal stress is equal to 0.5 MPa, tends to be horizontal when the normal stress is equal to 1 MPa and presents a hardening stage when the normal stress is greater than 1 MPa. After the bolt is broken, the shear stress–shear displacement curve presents a stepped-down descent. With the increase in λ, the breaking shear stress of the bolt increases. Elliptic failure occurs on the surface of the bolted anisotropic rock joint, and the length of the major axis of the ellipse decreases with the increase in λ value and normal stress. The bolts with different λ values of anisotropic rock joint show “Z-shaped” tensile bending deformation characteristics after shear fracture, and the horizontal and vertical components of the bolt deformation decrease with the increase in λ value and normal stress. The fracture shear displacement of the bolt increases with the increase in normal stress and decreases with the increase in λ value. The research results are helpful to further understand the shear mechanical characteristics and differences of bolted rock joints and provide a reference for solving the engineering problems of the composite layered rock mass.

The shear properties of unreinforced masonry are key parameters used in order to understand the behaviour of these structures under horizontal actions. These characteristics are usually determined using Destructive Testing (DT) methods. However, this typology of tests is not always suitable due to both their high impact and cost. The present work aims to design, analyze and apply an innovative Minor Destructive Testing (MDT) technique for the determination of the shear mechanical properties. To limit the impact on the structure, the Flat Jack (FJ) technique was adopted. The geometrical configuration, chosen among six different layouts, was studied in order to comprehend the roleplayed by different parameters and to have then a mathematical model representative of the stresses inside of the sample. Finally, four in situ tests were executed and are analyzed and discussed. [ABSTRACT FROM AUTHOR]

The experiment studied the shear characteristics of silage corn stalks and provided necessary engineering technical parameters for optimizing the design of the shredding and rubbing device. A three-factor and three-level orthogonal test was designed, and a universal testing machine was used to conduct radial and axial shear tests on corn stalks, and the shear failure force under different levels of shear position, shear speed and cutter angle was measured. Analyze and determine the significance and optimal combination of each factor. The results showed that the radial shear destructive force of corn stalk was 689.45~778.69 N, R value was 11.54~75.20, and F value was 12.53~518.83, P value was 0.002~0.074. The axial shear destructive force of corn stalk was 213.99~297.27 N, and the R value was 13.49~49.67, F value was 16.70~258.09, P value was 0.004~0.057. Under the above condition, the order of the influence of each factor on the test index was shearing position>cutter angle>shearing speed. The experiment indicates that the best combination was section 5, cutter angle 35°, cutting speed 300 mm/min, the shear breaking force required in axial shear was less than the shear breaking force required in radial shear. [ABSTRACT FROM AUTHOR]

With the increasing scale and depth of underground engineering, the geological environment that engineering is faced with is becoming more complex. As the weak position of rock mass, the structural surface has a particularly great influence on the mechanical characteristics of the rock mass. In order to obtain the shear strength characteristic of the structural plane and analyze the influence of morphological parameters such as the undulating angle and bulge degree on shearing, taking medium-low permeability tight sandstone as the research object, four kinds of structural plane samples with different undulating angles (10, 20, 30 and 40°) were prepared with a Python and high-precision engraving machine. Direct shear tests under different normal stresses (2, 4, 6 and 8 MPa) and shear rates (0.6, 1.2 and 2.4 mm/min) were performed, and the shear mechanical properties were analyzed. The structural surfaces before and after shearing were scanned using a high-precision three-dimensional scanner, so as to evaluate the roughness of the structural surface and determine the influence from various factors on the shear characteristics. The test results showed that for the structural plane with the same undulating angle, the peak shear stress increased approximately linearly with an increase in normal stress at a 0.6 mm/min shear rate and an increment speed of approximately 0.82, while the peak shear stress negatively correlated with the shear rate at a value of 4 MPa for normal stress. The larger the undulating angle was, the greater the influence of the shear rate (the shear stress decreased by 2.31 MPa at a 40° angle). When the normal stress and the shear rate were fixed, the peak shear stress corresponding to the structural surface gradually increased with the increase in the undulating angle, and the maximum increment was 5.04 MPa at 4 MPa normal stress and a 0.6 mm/min shear rate. An analysis of the morphological characteristics of the structural plane showed that when the undulating angle (40°) and the normal stress (6 and 8 MPa) were larger, the damage of the structural plane became more obvious, the shear point was closer to the tooth valley position, and the mechanical bite force and friction force of the structural plane were better utilized. When the shear rate was lower (0.6 mm/min), the friction characteristics of the shear surface were more visible, the shear was increasingly sufficient, and the corresponding shear strength was also greater.

The shear characteristics of the interfaces between soil and concrete structures are essential for the safety of the structures. In this study, a large-scale direct shear test apparatus was developed to measure the mechanical parameters of soil–concrete interfaces under conditions with different soil types, soil moisture contents, and interfacial filling materials. The results showed that the shear stress of the soil–concrete interface increased initially and then became stable with the increase in the shear displacement. The shear displacement of the sandy soil when the shear stress became stable was smaller than that of the clayey soil. The silty sand–concrete interface had a smaller friction angle than the interface with the medium-coarse sand. Moreover, with the increase in the soil moisture content, the friction angle of the clayey soil–concrete interface decreased rapidly, whereas the cohesion first increased and then decreased, and the peak cohesion was near the plastic limit of the soil. Under the same moisture content, the friction angle and cohesion of the clay–concrete interface was reduced by filling the interface with a thin layer of sandy soil, while filling the silty sand–concrete interface with a thin layer of silt reduced the friction angle and increased the interfacial cohesion. Nonetheless, the filling had little impact on the overall shear strength of the interface.

Polyurethane (PU) can be used as a road material binder, and its mechanical properties, durability, temperature stability, and other road performance metrics are good. However, the interlayer bonding between PU mixtures and asphalt mixtures is poor. The influence of the pavement structure, interlayer treatment scheme, load, and environmental factors on the interlayer shear characteristics of PU mixture composite pavement is analysed. Further, dynamic modulus, Hamburg rutting, accelerated loading, and inclined shear tests were conducted, and the typical PU mixture pavement shear stress was calculated. The interlaminar shear stress of double layer PU mixture pavement, polyurethane–asphalt composite pavement, and typical asphalt pavement were calculated. The results showed that the PU mixture has a low rutting deformation rate, stable mechanical properties, and strong resistance to the coupled action of temperature, water, and loading. The double-layer PU mixture structure has good water-temperature stability and fatigue resistance; however, freeze–thaw and accelerated loading cause great damage to the double-layer PU mixture structure. The residual shear strength ratio after freeze–thaw cycles and accelerated loading is only 50.3% and 35.6%, respectively, while the influence on the double-layer asphalt mixture structure is less. The theoretical calculation results of different pavement structures show that when the temperature increases from 10 °C to 50 °C, the interlaminar shear stress of polyurethane–asphalt composite pavement increases by about 20%. Additionally, the shear stress of pavement PU mixture pavement and typical asphalt pavement is mainly affected by load, and the temperature changes have an obvious effect on the interlayer shear stress of polyurethane–asphalt composite pavement. The calculated maximum shear stress of the three pavement structures with different working conditions is less than the interlaminar shear strength measured by the inclined shear test, indicating that the interlaminar treatment scheme of composite specimens can meet the shear resistance requirements of the three typical pavement structure types.

Soil–rock mixtures (S-RMs) are widely distributed in the shallow surfaces of cold regions that experience frequent freeze–thaw cycles, considerably threatening the stability of the soil–rock slopes on both sides of the road. We examine the S-RM shear strength and deformation characteristics under different freeze–thaw cycles through experiment and simulation. Nuclear magnetic resonance (NMR) was used to analyze the influence of freeze–thaw cycles on the internal pore structure of S-RM and establish the internal relationship between pore structure and shear characteristics under freeze–thaw cycles. Results show that the shear strength parameters of S-RM first decrease, then increase, and finally decrease as the number of freeze–thaw cycles increases; besides, the vertical expansion range of cracks gradually increases during shearing with the number of cycles. Porosity first increases, then decreases, and increases again with the number of freeze–thaw cycles. NMR results showed that S-RM pores had fractal characteristics. According to the fractal dimension, the soil particles inside the sample formed larger aggregates after the first freeze–thaw cycle. After the second–third freeze–thaw cycles, the agglomerated soil particles gradually disintegrate and tend to homogenize. The soil particles cover the surface of the gravel under the skeleton deformation to form an inclusion structure. The subsequent increase in the number of freeze–thaw cycles causes the soil particles attached to the gravels to gradually peel off. [ABSTRACT FROM AUTHOR]

Taking the concrete as an example, this paper studies the shear characteristics of the cohesive soil and rigid base. A series of shear tests are conducted by the refitted DSJ-2 electric four-joint equal stress direct shear apparatus. The results in the shear tests are contrastively analyzed. The results show that under the condition of simple shear tests, the constitutive relation of structural interface between the clay and concrete is rigid, and the residual strength is obvious. Under the condition of direct shear tests, the shear stress-displacement curves present hyperbolic connection. There is obvious strain hardening phenomenon, no obvious peak strength and residual strength. Under the two experimental conditions, the peak shear strength of the interface increases with an increase in the normal stress. With increasing moisture content, the peak shear strength of the interface decreases. The internal friction angle and cohesion of the structural interface decrease with increasing moisture content, and the relationship between internal friction angle, cohesion of the structural interface and moisture content are nonlinear. The peak shear strength of the direct shear tests is greater than that of the simple shear tests. [ABSTRACT FROM AUTHOR]

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Resource utilization of iron tailings powder is an effective measure to reduce the dam-break risk of an iron tailings reservoir. Adding polypropylene fiber to iron tailings powder can improve its shear performance. Direct shear tests were carried out on reinforced iron tailings powder with polypropylene fiber with dosages of 0%, 0.25%, 0.5%, 0.75%, and 1%, respectively. The normal stresses during the tests were 100, 200, 300, and 400 kPa, respectively. The test results show that with the increase of polypropylene fiber dosage, the cohesive force of iron tailings powder firstly increases and then decreases gradually, and the internal friction angle firstly decreases and then increases. The back propagation (BP)neural network was used to fit the shear force (F) and shear displacement (s) of the test to obtain the F-s function relationship that satisfies the accuracy. Based on the energy dissipation theory, the direct shear energy dissipation of polypropylene-fiber-reinforced iron tailings powder was calculated. The mathematical model of energy dissipation of fiber interfacial failure was derived by the fiber distribution model. The interfacial strength parameters of polypropylene fiber were calculated based on the direct shear test data and the mathematical model of fiber interfacial energy dissipation. The test results show that the addition of polypropylene fiber from the perspective of energy dissipation can improve the shear properties of iron tailings powder. [ABSTRACT FROM AUTHOR]

In order to deeply explore the shear characteristics and the meso-structure deformation mechanism of silt lightweight soil, this study combined the indoor uniaxial compression test, the triaxial shear test and ABAQUS finite element numerical simulation. Through the comparison and analysis of meso-simulation monitoring and experimental results, the effects of different cement incorporation ratios, confining pressure, different EPS content ratios and EPS particle size on shear strength characteristics and the meso-structure deformation characteristics of silt lightweight soil were systematically explored. The main results include that a)the content of EPS particles has a significant effect on the failure strain and the yield strength peak of silt lightweight soils. When the difference in EPS content is 1.5%, the failure strain of silt lightweight soil is differs by about 1.8%. b)The high cement content also has a significant effect on the strength characteristics and structural deformation of silt lightweight soil. However, the failure strain is not affected remarkably by the high cement content. The maximum difference of the failure strain in the test results is only about 0.5%. c)The numerical simulation result of the fixed-point monitoring of EPS particles is that,under the same conditions,the deformation of EPS particles at the upper, middle and lower points and their size of stress and strain are different. The strain value of the upper point is the largest. The average strain value of EPS particles at the lower point is smaller about 1.5% than that of the upper point. Additionally, in a certain pressure range, the displacement of EPS particles in the soil before sample destruction is not obvious, which only less 0.15 mm than the displacement of the soil body. And the difference of the simulated value is 1.5 times under the two working conditions and its rate of change is consistent with the results of indoor tests. [ABSTRACT FROM AUTHOR]

Shear failure is the main failure mode of anchorage bolts in coal mines. To improve ground control, it is crucial to improve the shear strength of roadway anchorage systems. In this study, theoretical analysis, numerical simulation and laboratory experiments were carried out to study the shear characteristics of the cuneiform reaming anchorage. The results show that the cuneiform reaming anchorage can reduce the maximum shear stress on the cross section of the anchorage to improve the shear strength. The stress concentration near the joint planes can be transferred to middle parts of the bolts. Moreover, the cuneiform structure can also prolong the period in which the shear load of the anchorage decreases and shorten the period in which the shear load increases, thus reducing the shear load of the anchorage. This paper provides a new economical and practical method for raising the shear strength of an anchorage system and enhancing roadway stability. [ABSTRACT FROM AUTHOR]

This paper explores the physical and mechanical properties of interface transition zone between loess and paleosol. Four samples were collected from Jingyang in the southeast of the Chinese Loess Plateau, and subjected to site and lab shear tests, aiming to disclose the shear behavior of interface transition zone, which contains landslide hazards. The results show that the strength parameters of loess decreased by nearly 2/3 (a 18.8kPa drop in C value and an 8.7° decrease in f value), and the interfacial transition zone and paleosol decreased by less than 10% from the natural state to the saturated state. This means the interfacial transition zone is a natural slip bed of landslide. [ABSTRACT FROM AUTHOR]

Asphalt pavement interface is considered to provide adhesion between two asphalt mixture courses. However, the relationship between shear characteristics of interface and residual performance of asphalt pavement still requires further research. This study investigated the effect of traffic loading, service time and distress type on the shear characteristics of asphalt pavement interface. Leutner shear test was conducted on the cylindrical specimens drilled from highway field, and the specimens are divided according to locations, service time and distress types. Shear strength, fail displacement and flexibility of interface were employed to characterize shear characteristics respectively. The results indicate that, among the locations, interface of rutting locations show the lowest shear strength, fail displacement and flexibility. Moreover, the shear characteristics decrease along with increase of interface’s service time. Interface of specimens with 4-years-service time showed the similar shear characteristics with interface of rutting locations. It demonstrated that the pavement that had served for 4 years had a risk of distress due to the interface shear characteristics loss, which suggests that the residual performance of this pavement was inadequate. Alternatively, the shear characteristics at rutting location are better than that of upheaval location. This research shows a possible way of evaluating residual performance and distress risk of pavement based on interface shear characteristics, which may contribute to the future pavement evaluation and maintenance. [ABSTRACT FROM AUTHOR]

Naturally deposited clays are generally K 0 consolidated. In some cases such as embankment construction and foundation pit excavation, the loading or unloading will lead to the re-consolidation of clays, which can be simulated by a simplified consolidation stress path with a certain ratio of vertical to horizontal consolidation stresses. In this study, a series of triaxial shear tests was conducted on a reconstituted Wenzhou clay, to investigate the effects of consolidation stress paths on the stress-strain, pore water pressure-strain, and effective stress path behaviors of overconsolidated samples. Based on the test results, the shear strength and pore water pressure coefficient at failure are found to grow and reduce linearly with the increase of the ratio of vertical to horizontal consolidation stresses, respectively. More strain softening and shear dilation are observed for the anisotropically consolidated samples compared to isotropically consolidated ones. The slope of failure line is approximately 1.25 for all specimens tested in this study. [ABSTRACT FROM AUTHOR]

The shear and viscous characteristics of a material are strongly dependent on the material's properties, such as cementation, density and grain size distribution, as well as the testing conditions, such as drainage and shearing speed. More complex shear behaviors can occur when the tested materials have diverse grain sizes. The shear and viscous characteristics of gravels are examined in terms of drainage and shear velocity under the constant normal stress using a ring shear apparatus, in which the materials used can be sheared under a large deformation. In this study, the materials used are commercial aquarium gravels with mean diameter of 6 mm. Test results show that the materials typically exhibited strain-hardening behavior when subjected to low shear velocity (i.e., ≤ 0.01 mm/sec) and strain-softening behavior when subjected to high shear velocity (i.e., > 0.1 mm/sec) in the ring shear torque measuring system. As expected, higher shear velocities correspond to higher shear stresses, regardless of the drainage condition. For a given shear velocity (V) ranging from 0.01 to 1 mm/sec, a gradual decrease in shear stress is observed in the drained condition; however, a relatively constant shear stress is observed in undrained shear stress. It is clearly exhibited that the vertical displacement is large in the drained condition but relatively unchanged in the undrained condition. The grain crushing is significant for both drainage conditions when the materials experienced a large deformation. There are two regions: (a) non-dominant grain crushing and (b) dominant grain crushing (with a large amount of sand and fine contents) as a function of shear velocity. For both drainage conditions, a large shear resistance occurred when the shear velocity reaches 1 mm/sec. Through the contraction-particle rearrangement-grain crushing process during shear, when V ≥ 1 mm/sec, it appears that the shear stress is easily reached to the residual state of shear. The amounts of fine contents from grain crushing are much larger in the drained condition than in the undrained condition. In the extreme case that grains are highly crushed, it may result in a high mobilization of materials in natural hazards. [ABSTRACT FROM AUTHOR]

Under the process of urbanization in China, more and more attention has been paid to the reuse of heavy metal-contaminated sites. The shear characteristics of heavy metal-contaminated soils are investigated by electrical detection in this paper. Three metal ions (Zn, Cd, and Pb) were used, the metal concentrations of which are 50, 166.67, 500, 1666.67, and 5000 mg/kg, respectively. Direct shear tests were used to investigate the influence of heavy metal ions on the shear characters of soil samples. It is found that with the addition of heavy metal ions, the shear strength, cohesion, and friction angle of contaminated soils are higher than the control samples. The higher concentration of heavy metal ions penetrated in soils, the higher these engineering characteristics of contaminated soils observed. In addition, an electrical resistivity detection machine is used to evaluate the shear characteristics of contaminated soils. The electrical resistivity test results show that there is a decreasing tendency of resistivity with the increase of heavy metal ion concentrations in soils. Compared with the electrical resistivity and the shear characteristics of metal-contaminated soils, it is found that, under fixed compactness and saturation, shear strength of metal-contaminated soils decreased with the increase of resistivity. A basic linear relationship between C/log( N + 10) and resistivity can be observed, and there is a basic linear relationship between φ/log( N + 10) and resistivity. Besides, a comparison of the measured and predicted shear characteristics shows a high accuracy, indicating that the resistivity can be used to evaluate the shear characteristics of heavy metal contaminated soils. [ABSTRACT FROM AUTHOR]

Because of its angularity, crushability, and high void ratio, calcareous gravelly soil has peculiar geotechnical properties. A series of large-scale direct laboratory shear tests was conducted on calcareous gravelly soil taken from coral reefs in the South China Sea. This study aimed to investigate the shear characteristics of calcareous gravelly soil under conditions of varying gradation, water content, density, and mineral composition. The experimental results revealed the extremely different mechanical properties of calcareous gravelly soil compared to common non-cohesive soil: calcareous gravelly soil has greater apparent cohesion, larger friction angle, and lower softening value than quartz sand. The friction angle increases with dry density, while the apparent cohesion increases with the median particle size ( D ) of the soil. After shear failure, the apparent cohesion decreases significantly from the peak value, but friction angle decreased slightly. Grouting can be employed to reinforce foundations and enhance slopes consisting of calcareous gravelly soil at the early stage of shear failure. This study intends to provide reference information for engineering constructions on coral reefs and report new findings on coarse-grained soil. [ABSTRACT FROM AUTHOR]

• A design method of asphalt mixture suitable for asphalt plug joints was proposed. • Asphalt mixture with lower void ratio, more fine aggregate, more mineral powder, and more asphalt was recommended to use for asphalt plug joints. • Polyacrylonitrile fibers contribute more to improving shear and tensile properties. Although the Asphalt Plug Joint (APJ) has been developed for half a century to overcome the maintenance issues in traditional bridges, its shortcomings, such as short service life and poor deformation capacity, have not been overcome. There are currently no adequate specifications in place to guide the material design and performance evaluation of APJs. Therefore, this study proposes a suitable design method for asphalt mixtures based on the mechanical characteristics and performance requirements of APJ. According to the proposed mixture type, the influence of gradation type on the bonding strength, shear strength, and tensile strength of the APJ mixture is explored mainly based on direct shear test, direct tensile test, and meso-structure analysis. In addition, the effect of fiber type on improving the performance of mixture and the influence of temperature on the performance of the mixture are discussed. The test results show that it is recommended to use a skeleton-filled asphalt mixture with a lower void ratio, more fine aggregates, more mineral powder, and more asphalt in the APJ. Similarly, modified asphalt with good high and low temperature performance should be selected, and an appropriate amount of reinforcing fibers, such as polyacrylonitrile fiber and basalt fiber, should be added to the asphalt mixture. [ABSTRACT FROM AUTHOR]

Shear characteristics of steel–asphalt interface under the influences of temperature, normal stress level and tack coat material were investigated. The direct shear tests were conducted on composite specimens with epoxy asphalt (EA) and polymer modified asphalt (PMA) tack coat materials at temperatures of 25 and 60 °C and normal stress levels of 0, 0.2, 0.4, and 0.7 MPa for each temperature. Results show that the failure modes include adhesive failure at the primer-tack coat interface and material failure of asphalt concrete. Steel–asphalt interface shows strain softening behavior until it reaches the sliding state. The shear strength and the shear reaction modulus increase with decreasing temperature and increasing normal stress levels. The specimens with EA tack coat provides much higher interface shear strengths than those with PMA tack coat at 25 and 60 °C. In addition, the failure envelopes of the shear strength and residual shear strength were obtained for combinations of tack coat materials and temperature conditions based on the Coulomb failure law. [ABSTRACT FROM AUTHOR]