Interface Shear Behavior Research Articles

Development of a Cone Penetration Testing Apparatus with a Textured Shaft

The anisotropy of shear resistance depending on friction direction can be selectively utilized in geotechnical structures. For instance, deep foundations and soil nailing, which are subject to axial loads, benefit from increased load transfer due to greater shear resistance. In contrast, minimal shear resistance is desirable in applications such as pile driving and soil sampling. Previous studies explored the shear resistance by interface between soil and surface asperities of a plate inspired by the geometry of snake scales. In this study, the interface friction anisotropy based on the load direction of cones with surface asperities is evaluated. First, a laboratory model chamber and a small-scale cone system are developed to quantitatively assess shear resistance under two load directions (penetration ⟶ pull-out). A preliminary test is conducted to analyze the boundary effects for the size of the model chamber and the distance between cones by confirming similar penetration resistance values at four cone penetration points. The interface shear behavior between the cone surface and the surrounding sand is quantitatively analyzed using cones with various asperity geometries under constant vertical stress. The results show that penetration resistance and pull-out resistance are increased with a higher height, shorter length of asperity and shearing direction with a decreasing height of surface asperity.

Study on monotonic direct shear characteristics of geosynthetics–calcareous sand interface

The investigation of shear behavior at the geosynthetics–calcareous sand interface is crucial for the internal stability design of reinforced revetment structures. A series of large-scale monotonic direct shear tests was conducted to examine the interface shear characteristics of geotextile–calcareous sand (GT–CS), geogrid–calcareous sand (GG–CS), and unreinforced calcareous sand (URCS). The interface shear behavior was investigated by considering the effects of interface types, including URCS, GT–CS, and GG–CS interfaces, and normal stresses ranging from 25 to 100 kPa. The interface interaction mechanism for different interface types is disclosed. The results indicate that embedding geotextiles and geogrids into calcareous sand filler alters the interface dilatancy behaviour of calcareous sand, which is significantly affected by normal stress. The dilatancy curves of GT–CS and GG–CS interfaces predominantly exhibit contraction–dilation and contraction, whereas the dilatancy curves of the URCS interface primarily display contraction–dilation–contraction and contraction. The shear softening behavior of GT–CS and GG–CS interfaces is primarily influenced by interface interaction mechanisms at the hardening stage and post-peak softening stage. The use of geogrid/geotextile has a reinforcing effect on calcareous sand fillers, leading to an increase of 1.22–1.44 times in interface peak cohesion. This increase falls within the range observed for geosynthetics–siliceous sand and geosynthetics–soil.

Experimental study on shear transfer across interfaces with post-installed shear reinforcement

To address the fit-up issues arising from reinforcement congestion and limited seating area over precast beams, an improved joint detail characterized by post-installed interface shear reinforcement has been developed. The incorporation of post-installed narrower looped bars as an alternative to conventional protruding stirrups significantly expedites the erection of precast flooring systems. Moreover, direct shear tests are performed on 30 Z-shaped specimens to investigate the influence of joint details, surface roughness, looped bar ratio, and embedment length of post-installed bars on the interface shear behavior. Experimental results indicate that employing post-installed narrower looped bars not only ensures adequate seating length for precast flooring systems, but also prevents the splitting failure of concrete cover which can induce the degradation of dowel action. Sufficient anchorage is the prerequisite for post-installed looped bars to impose clamping stress on concrete interface, and a shallow embedment length may trigger the occurrence of pull-out failure. Surface roughness is another factor determining the interface shear resistance and stiffness. Untreated surfaces, in contrast to intentionally roughened surfaces, are susceptible to the cohesion fracture and may hinder the development of shear-friction action. Furthermore, a linear correlation exists between looped bar ratio and the shear resistance of concrete interface. Based on the experimental results, design recommendations, including the minimum required anchorage length for post-installed looped bars, are proposed for the novel joint detail.

Multiscale evaluation of sand-geomaterial interface shear response in terms of material geometry effects

This study evaluates the effects of particle and surface geometric features on the interface shear behavior of sand-geomaterial. Particle shape and size were adjusted for the sand, and surface roughness form and height were set for the geomaterial part. 3D printing technology was used to produce geomaterials in the desired form. A custom-made transparent interface shear box was developed to perform digital image processing. For macroscale response, peak and residual strengths and dilation angle were measured. Sliding percentage and shear band thickness were determined from digital image correlation analyses for the mesoscale response. The experimental results showed that the macroscale response parameters increased as the overall regularity of the sand particles decreased. The increase in mean particle size and roughness height led to an increase in macroscale parameters. Digital image correlation analyses showed that the sliding percentage had an inverse correlation with the shear band thickness in terms of the particle shape and the roughness height effects. The roughness form controlled the trend of mean particle size effects on the sliding percentage. Overall, the mesoscale parameters revealed the traces of interlocking response, particle kinematics, and the failure mechanism in the interface region. Thus, a bridge was established between meso- and macro-scale responses.

Interfacial shear behavior of salt freeze-thaw pre-damaged NC with ECC: Experimental and theoretical investigations

This study aims to clarify the interfacial shear behavior of salt freeze-thaw pre-damaged normal concrete (NC) with engineered cementitious composite (ECC). A comprehensive analysis was conducted to study the effects of the cycle number, interfacial roughness, and ECC curing age on the interfacial shear performance. The results showed that, as the cycle number increased, the interfacial shear strength decreased to varying degrees. The optimal interfacial roughness was 5.5mm, and further increasing roughness would decrease the interfacial shear stiffness. When the ECC curing age was 7 days, it had already reached 85% of the interfacial shear strength of specimens cured for 28 days. Additionally, considering the effects of cycle number and interfacial roughness, an interfacial shear strength calculation model and a shear-slip curve prediction model were established, providing a valuable reference for the engineering application of ECC repair for salt freeze-thaw damaged NC.

Investigating the interfacial vertical shear behavior of BFPMPC mortar and cement concrete with pothole repair

Magnesium phosphate cement (MPC) has both traditional cement properties and ceramic properties with fast setting and hardening characteristics. To rapidly reopen traffic and extend its service life, MPC has been widely used in the rapid repair of highway and airport cement concrete pavement. This study utilizes basalt fiber-reinforced polymer-modified magnesium phosphate cement (BFPMPC) developed in previous research to rapid repair the typical potholes on cement concrete pavement, aims to reveal the interface properties between BFPMPC mortar and cement concrete and further investigate the underlying mechanisms for such properties. Firstly, the optimal mixture ratio was determined by orthogonal test design. Then, the shear strength of the repair interface was measured by composite BFPMPC mortar and cement concrete specimens. The mechanical characteristics of the repair interface and the microscopic mechanism were characterized by nano-indentation technology and SEM/EDS. Finally, the interface constitutive model was established by DIGIMAT and finite element model was developed to simulate the interface failure. Results showed that the no new hydration products were produced by the addition of polymer in BFPMPC. BFPMPC matrix became denser with the increase of age, resulting in the better bonding between fiber and paste. The interface vertical shear strength at 6 h and 3 d were 3.1 MPa and 3.9 MPa, respectively. SEM/EDS results showed that polymer has a certain self-healing ability to decrease the crack width with increase of curing age, and a variety of inclusions in the repair interface were observed. The elastic modulus of each inclusion phase can be effectively analyzed by nanoindentation. The simulation results showed that the pressure on upper surface of BFPMPC mortar transfers to the bottom through the repair interface. As the tensile stress on the bottom over the maximum interface tensile stress, the cracks were extend from the bottom to upper, then the structure was failed. Interface vertical shear strength of numerical simulation was, respectively, 3.149 MPa and 3.957 MPa. It is close to the plain shear strength experimental value, validating the proposed interface constitutive relationship.

Influences of the normal loading condition and surface texture on interface shear behavior between sand and suction caisson wall

The mechanical behavior of the interface between soil and the suction caisson wall determines the installation behavior and bearing capacity. A series of interfacial shear tests are conducted to study the effects of the normal loading condition and the interface texture on the sand-suction caisson interface shear characteristics. The relative density of the sand used in the test is 0.9. It is found that with the increase of shear displacement, the shear stress-displacement curve under a constant normal load condition (CNL) has an obvious strain-softening trend. On the contrary, the shear stress increases linearly with increasing the shear displacement under a variable normal load condition (VNL). The stress ratio between shear and normal stress, the broken zone thickness, and the shear deformation zone thickness for a convex suction caisson wall-sand interface are significantly larger than those of the grooved interface. However, when the roughness increases to a certain value, the stress ratio between shear and normal stress would decrease. Under large displacement shearing, the degree of sand particle breakage becomes significantly higher than that under small displacement shearing. These results help understand the shear characteristics of the sand-suction caisson wall and invent the new type of the suction caisson.

The experimental and numerical simulation of interface shear behavior between ECC and coal gangue concrete

Composite concrete structures are designed to integrate various concrete types at different levels, thereby improving their shear properties. In this paper, the effects of the interfacial keyway, reinforcement ratio, and pouring sequence on the shear strength of concrete-coal gangue concrete interface are studied by experiments and analyses. A total of 10 specimens were made, and the push-off test was carried out. Nonlinear finite element simulation was carried out using ABAQUS, and the influence of keyway angle on crack development was studied based on the extended finite element method (XFEM). It is found that the remarkable tensile and crack stability of engineered cementitious composites (ECC) has a positive effect on the shear strength of the ECC-coal gangue concrete interface. The ultimate shear strength of the interface and the ductility of the interface under shear load are significantly improved by interfacial shear reinforcement. The introduction of an interfacial keyway improves the shear strength of the concrete interface, and the number of keyways has the most significant effect on the interfacial shear strength. The angle between the crack propagation direction and interface will increase with the increase of keyway angle, the simulation results are in good agreement with the experiments.

Microstructural Analysis on Shear Behavior of New-fill and Silt Interface in Check Dam

Microstructural Analysis on Shear Behavior of New-fill and Silt Interface in Check Dam

Dynamic shear behavior of CFRP-concrete interface: Test and 3D mesoscale numerical simulation

The study on dynamic shear behavior of fiber reinforced polymer (FRP)-concrete interface is of great significance for the performance evaluation and design of FRP externally strengthened concrete structures. Firstly, the quasi-static and dynamic single shear test on the interfacial shear behavior between carbon fiber reinforced polymer (CFRP) sheet and concrete substrate was carried out. The corresponding failure modes of CFRP-concrete interface, CFRP strain-time histories, load-displacement curves, and interfacial shear stress-slip relationships under loading rates of 8.33 × 10−6–10 m·s−1 were obtained. It was indicated that the dynamic interfacial shear behaviors, i.e., interfacial failure mode, debonding load, interfacial shear stress, etc., were sensitive to loading rates. Then, a 3D mesoscale modeling approach of concrete with random shaped, sized, and spatially distributed convex polyhedron aggregates was proposed, in which the volume fraction of aggregates was adjustable within the range of 0–50 % through gravitational drop and size scaling of aggregates. Furthermore, based on the established 3D mesoscale concrete model and the zero-thickness cohesive elements for adhesive layer, numerical simulations for FPR-concrete interfacial shear behavior were conducted and validated by comparing with the present and existing quasit-static and dynamic single shear tests. The experimental phenomenon of the failure location transferring from concrete substrate to adhesive layer at high loading rates was numerically reproduced. Finally, the influences of strain rate enhancing effects of aggregates and mortar on the interfacial failure modes were discussed. It was revealed that the failure location transferring from the concrete substrate to the adhesive layer was significantly affected by the strength enhancement of mortar and aggregates with the loading rate increasing.

Influence of Apparatus Scale on Geogrid Monotonic and Cyclic/Post-Cyclic Pullout Behavior in Cohesive Soils

Geosynthetics have increasingly been applied to geotechnical engineering works due to their numerous advantages, including cost-effectiveness and their significant role in sustainable development. When geosynthetics are used as reinforcement in earth structures, such as embankments, retaining walls and bridge abutments, soil–geosynthetic interface shear behavior is a critical parameter involved in the design. This paper presents a series of monotonic and cyclic/post-cyclic pullout tests carried out to examine the apparatus scale effect on the pullout response of a geogrid embedded in two different soils. To assess the small-scale equipment feasibility, comparisons were made between pullout test parameters derived from small- and large-scale equipment. The test results indicate that, under a low confining stress of 25 kPa, using a smaller-sized apparatus results in lower values of geogrid pullout resistance and maximum mobilized shear stress, but higher values of confined tensile stiffness at low strains. On the other hand, as the confining stress increases (i.e., 50 kPa and 100 kPa), the difference between the results becomes less significant and similar trends are observed regardless of the equipment type. Adopting small-scale equipment enables obtaining soil–reinforcement interaction parameters using test procedures that are less time-consuming than those associated with large-scale pullout tests. However, proper scale effect correction factors may be considered for more consistent estimates of the interface strength parameters under low normal stress values.

Experimental and data-driven prediction for the impact of free/bond lengths of element specimen on interface characterization of ground anchors

The performance of ground anchor often employed in retaining the stability of onshore structures depends largely on its interface shear behavior. Interface characterization using pullout tests on element specimens of ground anchor is a versatile approach for determining its interface shear behavior. This research combines laboratory experiments and data-driven modeling to investigate the effect of free/bond lengths as a critical configuration condition of element specimen on the interface characterization results of ground anchors. Machine Learning models such as back propagation neural network (BPNN), random forest (RF), and support vector regression (SVR) were employed. Moreover, the particle swarm optimization (PSO) algorithm was used to improve the process. The results indicate that variations in free/bond lengths have a negligible effect on the trends of interface bond curves when bond lengths reach 90–100 mm. Moreover, when the bond and free lengths are set to 80 mm and 20 mm, respectively, the configuration conditions of the element specimen have a limited effect on the average interface shear strength. The PSO-BPNN model provided the most accurate predictions, which closely followed the experimental results compared to RF and SVR models. Compared to the other models, it reached a greater correlation coefficient (0.9975) and a lower root-mean-square error (14.89 kPa). Moreover, Partial dependence plot (PDP) is introduced to visualize the established machine learning model.

Direct shear behaviors of excavated clay reinforced with geocomposite drainage layer encapsulated in thin sand layers.

The objective of this study is to assess the effectiveness of a novel structure comprising a geocomposite drainage layer and a thin sand layer (GDL + sand) in mitigating the rapid dumping of excavated clay and its associated issues, such as landslides. Two sets of direct shear tests were conducted to investigate the influence of sand layer thickness and compaction degree on the interface shear behavior of the GDL + sand structure. As the sand layer thickness increased, both the interface shear strength and friction angle gradually increased, first more sharply and then at a slower rate toward stability, while the interface cohesion decreased gradually. The optimal sand layer thickness for achieving the most effective reinforcement in stabilizing the clay was identified as 10 mm. A higher sand layer compaction degree was found to result in increased interface shear strength, interface friction angle, and interface cohesion. Building on these findings, the reinforcing efficiency of the GDL + sand structure was investigated through mechanism analysis in comparison to that of a geogrid + sand structure and GDL structure as per the interface friction coefficient. The ranking of interface friction coefficients among the three structures emerged as: geogrid + sand > GDL + sand > GDL. These results suggests that the GDL + sand structure exhibits superior reinforcement efficiency compared to the GDL structure and offers better drainage efficiency than the geogrid + sand structure.

Analysis of the Sand-Concrete Interface Shear Behaviors Considering the Soil Unloading and Interface Roughness Effects

Analysis of the Sand-Concrete Interface Shear Behaviors Considering the Soil Unloading and Interface Roughness Effects

Effects of freeze-thaw cycles on the tensile properties of geogrids and shear behavior of geogrid-soil interface

The tensile strength of geogrids and the shear strength of the reinforced soil interface are critical technical indicators for designing reinforced soil structures. This study developed a temperature-controlled apparatus to examine the tensile properties of geogrids subjected to freeze-thaw cycles within the soil, and the effect of interface temperature and freeze-thaw cycles on the shear behavior of the geogrid-soil interface. Eight and four groups of direct shear and tensile tests were conducted on the geogrid-soil interface and geogrids, respectively, under varying conditions. The peak tensile strength of geogrids remained similar to that of non-freeze-thaw samples after experiencing freeze–thaw cycles within the soil. tensile properties of geogrids were independent of the number of freeze–thaw cycles. At constant water content (w=6%), the peak shear stress at the geogrid-soil interface decreased by 24% (7 freeze-thaw cycles) compared to the non-freeze-thaw group. The cohesion and friction angle of the geogrid-soil interface decreased with increasing freeze-thaw cycles but tended to stabilize after 4 freeze-thaw cycles. The reinforcement provided by the geogrid enhanced with decrease in the interface temperature. The shear stress was higher at interface temperature under 0 °C, whereas in a non-frozen state, the interface exhibited lower shear stress with a consistent stable value.

Utjecaj tipova tla i geomembrana na ponašanje sučelja i posmičnu čvrstoću

The interface shear behaviour between the geomembranes and soils was studied. Sand/bentonite (80/20), crushed sand, river sand, crushed gravel, and river gravel were used in this study. Polyvinyl chlorides were cured in the 0.5 molar saltwater and high-density polyethylene was cured in municipal solid waste leachate for eight months. Direct shear experiments were performed using cured GMs. This study recommends the use of crushed gravel in projects that use polyvinyl chloride and high-density polyethylene. The interface friction angles, which were exposed to the effects of saltwater and municipal solid waste leachate, decreased even after eight months, and this reduction effect should be considered in future projects. When designing projects involving GMs exposed to MSW leachate, particularly in landfills, potential damage over time should be considered, and appropriate design parameters should be selected. Failure to do so can lead to disasters that cause the loss of life and property.

Numerical Analysis for Shear Behavior of Binary Interfaces under Different Bonded Conditions

The shear performance of the binary interface formed by mortar and rock cementation is a key factor influencing the stability and safety of basic engineering projects related to livelihood and economy since concrete has become one of the most widely used materials in engineering. Therefore, it is an urgent practical problem to further explore and clarify the shear failure mechanism of the mortar–rock binary interface. In response to the current research objective focused on fully bonded interfaces, this paper constructed binary interface models with different bonded conditions to perform direct shear experiments using numerical simulation methods, and the effect of bonded conditions on the shear behavior of the mortar–rock binary interface was analyzed. The results indicate that the bonded conditions have a significant influence on the shear mechanical behavior of the mortar–rock binary interface, which is mainly reflected in the stress-displacement curve characteristics, the shear strength, the fracture development and the stress distribution state. The research findings are of great theoretical significance for the further study of shear mechanics at the mortar–rock binary interface and of great practical significance for safe construction, resource conservation and disaster warning.

To Study the Behaviour of Single Pile Foundation Under Vertical Loading using Geo 5’’

The objective of the project is to analyze a pile foundation and determine it’s load bearing capacity by static method and a software and compare the results. This project includes the analysis of pile formed on black cotton soil at site of the “Galaxy Sky Residency” Miraj.. The calculations were carried out using the commercial software GEO5 from FINE Inc. This software computes the load-displacement curve on the pile head and the distribution of normal and shear forces along the shaft. The shear behavior of the pile-soil interface is de-scribed according to a modified Mohr- Coulomb’s theory. This paper also focuses on the de-termination of parameters of strength (angle friction and cohesion) and settlement (Young modulus) for deep foundation. The use of GEO4 for foundation design is explained in details herein.

Macro and mesoscopic shear behavior of interface between sand and concrete with different JRC under cyclic load

Macro and mesoscopic shear behavior of interface between sand and concrete with different JRC under cyclic load

Interfacial Shear Behavior of Composite Concrete Substrate to High-Performance Concrete Overly After Exposure to Elevated Temperature

Basically, the interface shear strength between two concrete layers of varying ages must be sufficient to withstand the applied actions on the structure, specifically fire attack, which may cause the complete collapse of the composite structure. Thus, interfacial shear behavior was investigated and analyzed in this paper under the influence of a set of parameters, including temperature (25, 200, 400, and 600 °C), time exposure (30, 60, 90, 120, and 180 min), concrete type, and fibers type (polypropylene fiber (PPF), steel fiber (SF), and hybrid fiber) by employing a Z-shape push-off test. The test consists of two parts with different ages: normal strength concrete (NCS) and high-performance concrete (HPC). HPC includes high-strength concrete (HSC) and fly ash concrete (FAC). Initially, twenty-five Z-shaped push-off tests were made, four of which were cast as one unit (NSC/or concrete with hybrid (FSP)), and the rest were composite specimens. Furthermore, a 3D finite element model of a composite push-off specimen was developed to simulate and analyze the impact of various time and temperature exposures on the interfacial shear strength of composite specimen N-FSP. The results indicated that temperature degree and exposure time adversely affected the interfacial shear strength. Also, interfacial shear strength is significantly influenced by fiber types. Including combined fiber (SF + PPF) improved the interfacial shear strength by 114% compared to the composite specimen NSC-NSC after exposure to a temperature of 600 °C. In contrast, using PPF negatively affected the interfacial shear strength, recording only 84% of the composite specimen NSC-NSC. In addition, the inclusion of supplementary cementitious material enhanced the interfacial shear strength by 60.5% in the NSC-FAC composite specimen with 30% FA, compared to the NSC-NSC specimen. Finally, a finite element (FE) model was proposed with a satisfactory level of accuracy (0.95 to 1.03) in predicting the maximum shear strength. Additionally, the difference between the FE and experimental stiffness was between 0.92 and 1.07.