Inclination Angle Of Interface Research Articles

Study on mechanical behavior of inclined cemented tailings composite backfill (CTCB) under uniaxial compression

The goaf volume in the vacancy method of hard rock mines is significantly larger than the filling capacity, forming layered and inclined planes during the large-scale filling process. This results in unclear mechanical impact mechanisms on the backfill. To investigate the effect of interface inclination angle on the mechanical behavior of backfill, a set of cemented tailings composite backfill (CTCB) samples with interface inclination angles of 15°, 30°, and 45° are prepared. Uniaxial compression tests and digital image correlation techniques are used to investigate the influence of various interface inclination angles on the strength, deformation behavior, and failure mode of the CTCB. The results show that: (1) The uniaxial compressive strength (UCS) of the CTCB weakens with increasing interface inclination angle but consistently shows exponential growth with curing age (CA) regardless of the interface inclination angle. (2) The interface inclination angle controls the behavior and classification characteristics of the stress-strain curve of CTCB samples, and the increase of interface inclination angle weakens the elastic modulus. (3) The interface inclination angle significantly influences the failure mode and classification characteristics of the samples compared to CA and tailing-to-cement ratio (TCR), with shear slip failure induced by the former and axial splitting failure induced by the latter. The research provides a theoretical basis for understanding the mechanical behavior and stability control of inclined CTCB in underground mining.

The effect of interface on the strength characteristics and fracture mechanism of the coral reef limestone-concrete combination specimen

Biological and biochemical geneses bring complex structures to coral reef limestone (CRL), leading to pronounced anisotropy and heterogeneity. The stress field concentration induced by pore structure introduces a considerable dispersion in mechanical parameters and reduce the strength of CRL significantly. The CRL-C specimens were made using coral reef limestone to conduct uniaxial compression tests with loading rate of 0.002 mm/s, revealing the controlling mechanism of interface inclination angle for the strength of CRL-C specimens. The experiment results shows that the peak strength, peak strain, and modulus of elasticity of the combination all tend to lessen and then grow with increasing the interfacial inclination angle. The achieved results indicate that the tensile damage occurs in specimens with 0°, 15°, and 90° inclination angles, whereas the tension-shear stress damage takes place for specimens with 30° inclination angle. In turn, the shear damage occurs along the interface for specimens with 45°, 60°, and 75° inclination angles. The strength of combination specimens underwent the shear failure is noticeably smaller than that of the combination specimens damaged across the interface. Additionally, the cement mortar at the interface has a remarkable reinforcing effect on the interface strength, and the CRL-C interface possesses the highest cohesion and a lower internal friction angle compared to terrestrial rocks. Simultaneously, the parameters of the CRL-C specimens in the single-interface model are appropriately determined based on the interface strength. The inclination range of the combination specimen damaged along the interface is 35.58°<α < 85.83°. The predicted strength parameters based on the Coulomb model and the single-interface model provide a solid reference for the engineering design of CRL-C.

Influence of interface inclination angle and load impact velocity on dynamic splitting tensile behavior and dissipated energy of geopolymer-concrete composites

The application of geopolymer has great potential in repairing damaged concrete. In engineering construction, the repaired structure is often affected by dynamic loading. Experimental research on the dynamic mechanical behavior and energy dissipation of geopolymer-concrete composites (GCC) is of great significance for understanding the bonding performance between geopolymer and concrete. In this paper, dynamic splitting experiment was performed on GCC under different interface inclination angles and load impact velocities by using the split Hopkinson pressure bar (SHPB). Then, the influence of interface inclination angle and load impact velocity on dynamic splitting tensile behavior and dissipated energy of GCC were discussed. Finally, the failure modes and strain field were analyzed based on digital image correlation (DIC) technique. The results indicate that the static peak load of GCC is roughly distributed around 26.0 kN and the dynamic peak load is 263.0 kN. The dynamic peak load measured by GCC is more than 10 times the static peak load. As the interface inclination angle increases from 0° to 90°, the dynamic peak load, static peak load and energy dissipation rate increase linearly, while the tensile sensitivity coefficient decreases. The energy dissipation ratio of GCC is kept between 0.30 and 0.40. In addition, the dynamic peak load, tensile sensitivity coefficient and dissipated energy increase gradually as the load impact velocity increases. A transition from interface failure to tensile failure can be found in GCC with the inclination angle increases.

Assessment of p-y response of a laterally loaded single pile embedded in two-layered cohesionless substrata with inclined interface

ABSTRACT Laterally loaded piles embedded in multi-layered soil strata comprising inclined substratum presents a complex soil-structure interaction problem. Based on three-dimensional finite element analysis, this paper reports the response of a laterally loaded single pile embedded in two-layered cohesionless medium comprising inclined substrata. The overlying soil wedge is considered relatively weaker than the underlying stratum, and that the inclination of the wedge is considered varying along the direction of the applied lateral load. The pile-soil interaction is portrayed through p-y response at specified depths, load-deformation behaviour of the pile head and the lateral deflection profile of the pile. The outcomes manifest that the behaviour of laterally loaded pile, especially the p-y responses, is significantly influenced by the interface inclination angle, direction of loading and length-to-diameter ratio of pile. Further, the marked influence of strength and stiffness of the multi-layered strata on the p-y response of the laterally loaded pile are elucidated.

Static and dynamic fracture behavior of rock-concrete bi-material disc with different interface crack inclinations

The fracture behavior of rock-concrete bi-material structures with interface crack is of great significance to the stability of construction projects in rock engineering. Dynamic testing of cracked straight-through Brazilian disc (CSTBD) samples was performed using a split-Hopkinson pressure bar (SHPB) system. The fracture development of rock-concrete bi-material was monitored by the digital image correlation (DIC) technique. A static fracture test using the MTS322 hydraulic servo-controlled testing system was also carried out for comparison. The results show that three typical fracture patterns can be identified for CSTBD samples under both static and dynamic loading. At a smaller interface inclination angle, the disk samples fracture along the interface, while at a larger interface inclination angle, the samples suffer tensile fracture along the loading direction. The increase of strain rate leads to an increase in the number of secondary cracks. As the inclination of interface increases from 0° to 75°, the dissipated energy increases gradually. When the inclination exceeds 75°, the dissipated energy turns to weaken. The difference in peak dissipated energy between different inclination angles weakens as the strain rate increases. The dimensionless stress intensity factors (SIFs) at the two crack tips are different, and increasing the crack length-diameter ratio will enlarge the difference. The interface inclination angle has a significant effect on both the static and dynamic fracture toughness of CSTBD samples. As the inclination of the interface increases, the difference between mixed-mode static and dynamic fracture toughness also increases. The dependence of dynamic fracture toughness on inclination is significantly higher than that of static fracture toughness, and the ratio between dynamic and static fracture toughnesses increases with increasing loading rate.

Departure of Nitrogen Bubbles at the Solid–Liquid Interface during the Solidification of Duplex Stainless Steels

The departure of nitrogen bubbles from duplex stainless steel (DSS) is essential for studying the precipitation behavior of bubbles during solidification. In the current work, the numerical and theoretical derivation of analytical formula were used to study the bubble departure at the solid–liquid interface. In the paper, the departure radius of bubbles was deduced by numerical analysis. Based on the works of subcooled boiling flow, the forces of bubbles were analyzed at the solid–liquid interface. The critical condition of bubble departure was theoretically obtained. The effects of various factors on bubble departure and slip were also analyzed. The results showed that the critical radius of the bubble departure increased at the solid–liquid interface when reducing the interface inclination angle, the depth of liquid steel, the contact angle, the flow velocity of liquid steel, and the gas pressure on the surface of liquid steel. Moreover, when the interface inclination angle equaled zero, there was no slip in the interface direction before bubble departure, letting the bubbles float directly. However, when the interface inclination angle equaled π/4 or π/2, the bubbles slid along the interface before bubble departure in the x negative direction, which was more likely to cause the bubbles to be trapped.

Experimental study on factors influencing ERC-NSC interface bonding performance

The short-term behavior and long-term durability of materials for structural strengthening are significantly affected by their bond properties and compatibility with the existing substrate. In this study, the bonding performance between a normal strength concrete (NSC) substrate and an epoxy resin concrete (ERC) layer was investigated by applying direct tensile, splitting tensile, bi-shear, and slant shear tests, and the interfacial bond strength and corresponding failure modes were explored. Several factors that may affect the interfacial bond strength, including the ERC age, substrate moisture degree, and interface inclination angle, were examined to explore their influences. The results reveal that the increase in ERC age resulted in various degrees of increment for the bond strength among the four tests. The saturated surface dry (SSD) preparation method slightly increased the bond strength by 3 % in the splitting tensile tests. However, moisture at the substrate interface reduced the bond values by 25.5 %, 29.67 %, and 16.9 % in the direct tensile, bi-shear, and slant shear tests, respectively. As the inclination angle increased, the bonding strength of the slant shear test increased, while a larger inclination angle reduced the likelihood of interfacial failure. Furthermore, the minimum cohesion and shear friction coefficients were determined to be 2.26 MPa and 1.68 for air surface dry preparation and 1.62 MPa and 1.48 for SSD preparation.

Dynamic splitting tensile behavior of rock–concrete bimaterial disc with multiple material types under different interface inclination angle

AbstractThe experimental investigation on the dynamic mechanical properties and failure behavior of rock–concrete composite is of great significance for understanding the mechanical response of rock–shotcrete supporting structures. In the paper, impact splitting tests were performed on Brazilian disc specimens of the rock–concrete bimaterial with different interface inclination angles. Effects of interface inclination angle and material type on dynamic response and failure behavior under dynamic impact were analyzed experimentally. The results show that the dynamic splitting strength and energy dissipation ratio increase with the increase of interface inclination angle. However, the incorporation of fibers will reduce the splitting tensile strength. The crack‐resisting effect of sandstone–fiber concrete is more obvious, and the hysteresis plateau phenomenon appears in the post‐peak section of the stress‐time curve. The interface failure behavior is related to the stress state of the interface and can be divided into three patterns: tensile fracture, shear fracture, and interface non‐ fracture.

Fracture evolution of artificial composite rocks containing interface flaws under uniaxial compression

Composite rock with interfaces is widely distributed in nature. Its mechanical properties are significantly different from those of a single layer rock, which has become one of the highlighted issues in engineering design and operation. In this study, uniaxial compression tests are performed on rock-like specimens with two dissimilar layers. The evolution process of the apparent strain field of the specimen is analysed by digital image correlation (DIC). Acoustic emission (AE) technology is used to analyse the damage evolution process of specimens based on energy dissipation theory and the damage evolution model. The research results show that with the increase in the interface angle, the peak compressive strength of the specimen decreases slowly first and then decreases rapidly, increasing when reduced to the minimum. When the inclination angle of the specimen interface is 60°, its strength is the lowest. The higher the overall strength of the specimen is, the more obvious the above phenomenon. DIC technology captures the apparent strain field characteristics of each stage of specimen failure, which provides a basis for the analysis of the specimen failure mode. The failure modes of the specimens can be divided into five categories. When the inclination angles of the interface are 0°, 60°, 75° and 90°, the failure modes of the specimens are mainly affected by the inclination angle. When the inclination angles are 15°, 30° and 45°, the failure modes are affected by the inclination angle and the rock matrix strength. The damage evolution process of most specimens is divided into four stages. Some specimens only show three stages, such as those specimens with an interface inclination angle of 60°.

Research on the influence of ultraviolet aging on the interfacial cracking characteristics of warm mix crumb rubber modified asphalt mortar

In order to study the effect of ultraviolet (UV) aging on the interfacial cracking of SDYK surfactant warm mix crumb rubber modified asphalt mortar (CRS-WAM), EM viscosity reducer warm mix crumb rubber modified asphalt mortar (CRE-WAM) and hot mix crumb rubber modified asphalt mortar (CR-HAM), the digital image correlation (DIC) technology was applied to the single-edge notch bending (SENB) test of warm mix crumb rubber modified asphalt mortar(CR-WAM). Firstly, the effect of UV aging on the interface crack growth rate between CR-WAM and CR-HAM is analyzed. Secondly, based on DIC horizontal strain field (Exx) and statistical principle, a new interface damage factor DI is proposed. Finally, the influence factors of interface crack propagation path of asphalt mortar are analyzed by finite element method. The results show that the interfacial crack growth rate of asphalt mortar becomes faster after UV aging, and the crack propagation rate becomes faster and faster with the increase of UV aging time. DI can reflect the interfacial damage of asphalt mortar in real time, with the increase of UV aging time, the cumulative speed of DI value becomes faster and faster, and the interfacial bond strength becomes lower and lower. The crack growth rate and DI value of two kinds of CR-WAM are always lower than that of CR-HAM, CRS-WAM has the best interfacial bond strength and crack growth resistance, followed by CRE-WAM. The SENB test finite element model has a higher degree of agreement with the DIC results, the greater the interfacial adhesion, the smaller the fracture energy, the shorter the interface and the greater the interface inclination angle, the asphalt mortar is less likely to crack.

Experimental investigation of the Rock–Concrete bi materials influence of inclined interface on strength and failure behavior

Experimental observations and measurements on strength and failure behavior of rock-concrete bi materials are important to correctly understand the response of concrete structure-rock foundation. In this context, a large number of experimental investigations have been carried out in order to identify the interaction at rock-concrete interface, but the influence of inclined interface on strength and failure behavior has not been addressed by adequate experimental studies. The main objective of this investigation is to experimentally investigate the response of the rock-concrete interface at different inclination angles. The effect of inclined interface on strength and failure behavior of rock-concrete bi specimens were investigated under uniaxial compression (UCS), splitting tensile (ST) and point loading (PLS). The variation in strength and failure patterns with respect to the inclination angles of rock-concrete interface were generally observed in all test conditions. The measured strengths and observed failure behaviors during the UCS test were compared with those obtained from ST and PLS tests. It was found that the relation between PLS and interface inclination angle is remarkable in so far as in the case ST conditions in which tensile strength vary as a function of inclination angle. However, these both indirect tests does not provide satisfactory results in determination of the strength variation of specimens when inclination angle of weakness interface starts to become parallel to the loading direction.

Valley amplification of horizontal ground strain

It is recognized that seismic damages to segmented buried pipelines depend in part upon transient ground strain due to seismic wave propagation. Such wave propagation damage seems to be larger at sites with variable subsurface conditions, because of drastic changes in seismic wave characteristics as they propagates in heterogeneous rock and soil layers. This paper intends to investigate the amplification of horizontal ground strains in a valley subjected to vertically incident SH waves. A 2D model with an inclined soil-rock interface is established to simulate conditions of the valley subject to seismic wave propagation. A procedure for evaluating the ground strain amplification is developed by consideration of travel path effects. Three amplification/de-amplification mechanisms are specifically considered, the ground velocity amplification, ground strain amplification due to the change in the propagation direction, and de-amplification due to a lack of total reflection at the soil-rock interface. The analysis results show that the maximum amplification factor is mainly affected by the interface inclination angle and shear wave velocity ratio between the valley soil and the base rock. For a given number of wave cycles, the amplification factor grows with the increment of the inclination angle and declines with the growth of shear wave velocity ratio. The de-amplification at inclined interface is likely to nullify the amplification generated by travel path effects.

Interfacial dynamic impermeable cracks analysis in dissimilar piezoelectric materials under coupled electromechanical loading with the extended finite element method

Interfacial dynamic impermeable cracks analysis of dissimilar piezoelectric solids under coupled electromechanical impact loadings by the extended finite element method (X-FEM) is presented. The dynamic X-FEM approach recently developed by the authors is further extended to analyze transient responses of interfacial impermeable cracks in dissimilar piezoelectric structures. The mechanical displacements and electrical potential are approximated by appropriate enrichment functions that are not only for the crack-face and crack-tips, but also for the materials interfaces. In this work, we develop a new set of electro-mechanical enrichment functions for interfacial crack-tip in piezoelectric bimaterials, which is modified from the pure mechanical twelve-fold interfacial crack-tip enrichment functions used for mechanical problems. Unlike the pure mechanical set, the new modified enrichment functions contain the electric-mechanical factor, which is determined from the electro-mechanical fields of interfacial cracks in piezoelectric bimaterials. We also present asymptotic crack-tip fields in piezoelectric bimaterials based on the Stroh’s formalism, and then apply them in the evaluation of generalized dynamic intensity factors (GDIFs) via the interaction integrals. The accuracy of the proposed approach is validated by comparing the obtained GDIFs with the ones derived from boundary element method. Numerical dynamic results of interfacial cracks in piezoelectric bimaterials are investigated and some aspects of the influences of poling angles, interface inclination, impact loading, etc. on the GDIFs are analyzed. There are many important issues have found such as the accuracy of the GDIFs obtained by the present formulation is high; a pure electrical impact immediately induces non-zero GDIFs, while the elastic waves caused by the mechanical impact need some time to reach and excite the crack; the effect of polarization on the GDIFs is significant; the behaviors of the GDIFs are complicated and their peak values decrease with increasing poling angles; the interface inclination angle of cracks greatly alters the GDIFs; and the interfacial crack growth may be delayed either by the effects of polarization or the electrical impacts.

Simulations and Analysis of the Reshocked Inclined Interface Richtmyer–Meshkov Instability for Linear and Nonlinear Interface Perturbations

A computational study of the Richtmyer–Meshkov instability (RMI) is presented for an inclined interface perturbation in support of experiments being performed at the Texas A&amp;M shock tube facility. The study is comprised of 2D, viscous, diffusive, compressible simulations performed using the arbitrary Lagrange Eulerian code, ARES, developed at Lawrence Livermore National Laboratory. These simulations were performed to late times after reshock with two initial interface perturbations, in the linear and nonlinear regimes each, prescribed by the interface inclination angle. The interaction of the interface with the reshock wave produced a complex 2D set of compressible wave interactions including expansion waves, which also interacted with the interface. Distinct differences in the interface growth rates prior to reshock were found in previous work. The current work provides in-depth analysis of the vorticity and enstrophy fields to elucidate the physics of reshock for the inclined interface RMI. After reshock, the two cases exhibit some similarities in integral measurements despite their disparate initial conditions but also show different vorticity decay trends, power law decay for the nonlinear and linear decay for the linear perturbation case.

Investigation of the initial perturbation amplitude for the inclined interface Richtmyer–Meshkov instability

A simulation studying the effects of inclination angle and incident shock Mach number on the inclined interface Richtmyer–Meshkov instability is presented. Interface inclination angle is varied from 30° to 85°, with incident shock Mach numbers of 1.5, 2.0 and 2.5 for an air over SF6 interface. The simulations were performed in support of experiments to be performed in the Texas A&M shock tube facility, and were created with the ARES code developed at Lawrence Livermore National Laboratory. The parametric cases are separated by inclination angle into nonlinear and linear initial perturbation cases. A linear initial perturbation is defined as when the interface amplitude over wavelength is less than 0.1. Density, pressure gradient and vorticity plots are presented for a nonlinear and a linear case to highlight the differences in the flow field evolution. It is shown that the nonlinear case contains strong secondary compressible effects which reverberate through the interface until late times, while in the linear case these waves are almost completely absent. The inclined interface scaling method presented in previous work (McFarland et al 2011 Phys. Rev. E 84 026303) is tested for its ability to scale the mixing width growth rate for linear initial perturbation cases. This model was shown in the previous work to collapse data well for varying Mach numbers and nonlinear inclination angles. The scaled data is presented to show that a regime change occurs in the mixing width growth rate near an inclination angle of 80° which corresponds to the transition from a linear to nonlinear initial perturbation.

Interface Behavior between Two Fluids Vertically Oscillated in a Circular Cylinder under Nonlinear Contact Line Condition (1st Report, Measurement and Modeling of the Contact Line Behavior)

The development of waves on a fluid-fluid interface, excited by a vertical, relative motion of a solid wall enclosing the fluids, is affected significantly by the mobility of the interface on the wall. The effective, cycle-averaged mobility depends on the amplitudes of excitation and waves, because of a non-linear dependence of the velocity of the fluid-fluid-wall contact line on the angle of the interface hitting the wall. At higher amplitudes of excitation and waves, moreover, the interface motion is tied to the low mobility of the contact line only for a limited fraction of each cycle; for the rest of the cycle the interface is virtually untied from the wall, being connected to the contact line only through the surface of a thin, flat liquid film left on the wall. An analytical model is developed on the wall surface boundary conditions for the interface profile, in terms of non-linear relationship between the interface velocity along the wall and the near-wall inclination angle of interface. The model is based on optical data taken in a quasi-static experiment where measurements of near-wall interface configuration were essentially unaffected by wave generation on the interface. Numerical simulation with this model reproduces successfully the changes in the near-wall configuration of the interface in the experiment, including development and depletion of a liquid film on the wall associated with relative motion between the contact line and the interface elevation away from the wall.

Interface Behavior between Two Fluids Vertically Oscillated in a Circular Cylinder under Nonlinear Contact Line Condition (1st Report, Measurement and Modelling of the Contact Line Behavior)

The development of waves on a fluid-fluid interface, excited by a vertical, relative motion of a solid wall enclosing the fluids, is affected significantly by the mobility of the interface on the wall. The effective, cycle-averaged mobility depends on the amplitudes of excitation and waves, because of a non-linear dependence of the velocity of the fluid-fluid-wall contact line on the angle of the interface hitting the wall. At higher amplitudes of excitation and waves, moreover, the interface motion is tied to the low mobility of the contact line only for a limited fraction of each cycle ; for the rest of the cycle the interface is virtually untied from the wall, being connected to the contact line only through the surface of a thin, flat liquid film left on the wall. An analytical model is developed on the wall surface boundary conditions for the interface profile, in terms of non-linear relationship between the interface velocity along the wall and the near-wall inclination angle of interface. The model is based on optical data taken in a quasi-static experiment where measurements of near-wall interface configuration were essentially unaffected by wave generation on the interface. Numerical simulation with this model reproduces successfully the changes in the near-wall configuration of the interface in the experiment, including development and depletion of a liquid film on the wall associated with relative motion between the contact line and the interface elevation away from the wall.