Journal articles on the topic 'Shear-sliding mechanism'
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1
Li, Rong Jian, Qiang Xu, Wen Zheng, and Hung Chou Lin. "The Instability Mechanism of the Down TuDiLing Landslide." Advanced Materials Research 393-395 (November 2011): 1558–61. http://dx.doi.org/10.4028/www.scientific.net/amr.393-395.1558.
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By making use of the developed strength reduction finite element codes based on which the matric suction can be considered, the sliding mechanism of the Down TuDiLing slope is analyzed. The results show that the stability of the Down TuDiLing slope is stable under the condition of employing the peak shear strength of soil and the lose of matric suction, but under the condition of the residual shear strength, the safety factor of the slope is decreasing to instability with the weakening of the matric suction, and a local sliding surface occurs. Through the strength reduction finite element computation, the position of the local sliding surface of slope can be differentiated and determined, so the problem of the local sliding should be paid to more attention in the reinforcement design.
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Saitoh, Ken-ichi, Tomohiro Sato, Masanori Takuma, Yoshimasa Takahashi, and Ryuketsu Chin. "Molecular Dynamics Study on Lubrication Mechanism in Crystalline Structure between Copper and Sulfur." Journal of Materials 2015 (October 26, 2015): 1–13. http://dx.doi.org/10.1155/2015/963257.
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To clarify the nanosized mechanism of good lubrication in copper disulfide (Cu2S) crystal which is used as a sliding material, atomistic modeling of Cu2S is conducted and molecular dynamics (MD) simulations are performed in this paper. The interatomic interaction between atoms and crystalline structure in the phase of hexagonal crystal of Cu2S are carefully estimated by first-principle calculations. Then, approximating these interactions, we originally construct a conventional interatomic potential function of Cu2S crystal in its hexagonal phase. By using this potential function, we perform MD simulation of Cu2S crystal which is subjected to shear loading parallel to the basal plane. We compare results obtained by different conditions of sliding directions. Unlike ordinary hexagonal metallic crystals, it is found that the easy-glide direction does not always show small shear stress for Cu2S crystal. Besides, it is found that shearing velocity affects largely the magnitude of averaged shear stress. Generally speaking, higher velocity results in higher resistance against shear deformation. As a result, it is understood that Cu2S crystal exhibits somewhat liquid-like (amorphous) behavior in sliding condition and shear resistance increases with increase of sliding speed.
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Gevaert, Matthew R., Martine LaBerge, Jennifer M. Gordon, and John D. DesJardins. "The Quantification of Physiologically Relevant Cross-Shear Wear Phenomena on Orthopaedic Bearing Materials Using the MAX-Shear Wear Testing System." Journal of Tribology 127, no. 4 (June 1, 2005): 740–49. http://dx.doi.org/10.1115/1.2000272.
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Background: The occurrence of multi-directional sliding motion between total knee replacement bearing surfaces is theorized to be a primary wear and failure mechanism of ultra-high molecular weight poly(ethylene) (UHMWPE). To better quantify the tribologic mechanisms of this cross-shear wear, the MAX-Shear wear-testing system was developed to evaluate candidate biomaterials under controlled conditions of cross-shear wear. Method of approach: A computer controlled traveling x-y stage under a 3 degree-of-freedom statically loaded pin is used to implement the complex multi-directional motion pathways observed during TKR wear simulation. A MHz collection of dynamic x-y friction was available on all six environmentally controlled stations. The functionality of this testing platform was proven in a 100,000 cycle, 11.6 MPa, wear test using 15.0 mm diameter polished stainless steel spheres against flat GUR4150 UHMWPE. A five-pointed star wear pattern was used to incorporate the physiologically relevant cross-shear sliding conditions of stop/start, 50mm∕s entraining velocity and five crossing angles of 72°. Using normalized volumetric reconstruction of the resulting surface damage, a direct quantitative relationship between linear and cross-shear surface damage intensity was obtained. Results: Cross-shear surface damage volume loss was found to be 2.94 (±0.88) times that associated with linear sliding under identical tribologic conditions. SEM analysis of linear wear damage showed consistent fibril orientation along the direction of sliding while cross-shear wear damage showed multi-directional fibril orientations and increased surface roughness. Significant increases in discrete crossing-point friction coefficients were recorded throughout testing. Conclusions: This scientific approach to quantifying the tribologic effects of cross-shear provides fundamental wear mechanism data that are critical in evaluating potential biomaterials for use as in vivo bearings. Relevant multi-axis, cross-shear wear testing is necessary to provide quantifiable measures of complex biomaterials wear phenomena.
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Ma, Minghui, Fenhua Ren, and Wensheng Liu. "Experimental Investigation on Shear Failure Mechanism of Rock Mass with Intermittent Joints." Advances in Civil Engineering 2021 (March 16, 2021): 1–10. http://dx.doi.org/10.1155/2021/6623148.
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There are a large number of discontinuous weak planes distributed in the natural rock mass, which makes the sliding failure of rock mass along the intermittent structural plane very complex. To investigate the shear failure mechanism of rock mass with intermittent joints and study the influence of different joint heights on the shear failure mode of the rock mass, direct shear tests were carried out by presetting a series of jointed rock specimens with different undulating heights. During the shear loading, digital image correlation (DIC) technology was employed to monitor the surface strain field of the specimens in real time. The results show that the fluctuation height has a significant effect on the evolution of shear strain. With the increase of shear load, the maximum shear strain of the jointed specimens with different undulating heights first increases slowly and then increases rapidly. When the undulating height is 5 mm, the failure of the specimen is dominated by the rock sliding along prefabricated joints. When the undulating height is larger than 10 mm, the shear fracture of the rock becomes dominant. With the increase of the undulating height, more penetrating cracks perpendicular to the preexisting joints appear between the serrated surfaces, and the shear fracture phenomenon is more obvious.
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Zhu, Yuxuan, Fuchu Dai, and Xin Yao. "Preliminary understanding of the emplacement mechanism for the Tahman rock avalanche based on deposit landforms." Quarterly Journal of Engineering Geology and Hydrogeology 53, no. 3 (October 8, 2019): 460–65. http://dx.doi.org/10.1144/qjegh2019-079.
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Based on remote sensing interpretation, detailed field investigation of the deposit landforms and previous research, we propose that the emplacement mechanism of the Tahman rock avalanche, a giant Holocene rock avalanche, can be divided into three distinct phases: an extension-dominated sliding phase, a lateral shear-dominated sliding phase and a compression-dominated sliding phase.
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Li, Jun, Bin Li, Kai He, Yang Gao, Jiawei Wan, Weile Wu, and Han Zhang. "Failure Mechanism Analysis of Mining-Induced Landslide Based on Geophysical Investigation and Numerical Modelling Using Distinct Element Method." Remote Sensing 14, no. 23 (November 30, 2022): 6071. http://dx.doi.org/10.3390/rs14236071.
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Underground mining activity in the karst mountain in southwestern China has induced several large-scale rocky landslides and has caused serious casualties. At present, there is a lack of systematic research on the formation mechanism of landslides in this area using multi-method fusion technology. First, the orthophoto images of the landslide area obtained by UAV photography were used to analyze the deformation characteristics of the landslide. Second, the failure characteristics of the strata overlying the goaf were analyzed by geophysical detection. Finally, the deformation response characteristics of the mountain under underground mining were analyzed by UDEC numerical simulation. The results revealed that during the underground mining, the failure process of the mountain occurred in four stages: fracture expansion, subsidence and collapse, shear sliding, and multi-level sliding. Gently dipping soft–hard alternant strata and a blocky rock mass structure formed the geological foundation of the landslides. Underground mining accelerated the fracturing of the overlying strata and the formation of a stepped penetrating sliding surface. Tensile movement of the structural planes of hard sandstone in the free face, and shear sliding of the weak mudstone layer, were the main causes of the landslides. The slope instability mode was tension-shear fracturing, shear sliding, back toppling, and compressive shear failure. In addition, the fracture propagation in the overlying strata and damaged geological structure revealed by the geophysical detection were consistent with the simulation results. This study provides ideas for the precise countermeasures of disaster prevention and mitigation for similar landslides in this area.
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Nie, Lei, Min Zhang, and He Qing Jian. "Study on the Mechanism of the Landslide of Heda Expressway K377." Advanced Materials Research 255-260 (May 2011): 3437–43. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.3437.
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During the construction of Heda expressway, the Ermi landslide, which occurred on section K377, has interrupted the construction of the expressway. Additional engineering geological investigation became necessary. The direct economic losses are over 3 million US dollars. This paper analyzed the Ermi landslide from the aspects of formation process, engineering geological conditions, the structural characteristics and stability analysis of the landslide. The results show that the formation of the Ermi landslide is mainly due to geological conditions in project area. Because the structure of the sliding body is loose and some weak interlayer exists in the slope, the shear strength of the sliding surface and sliding body is low. As cut-slope excavating, the resistant of the slope body reduced. Eventually the slope lost its stability and a landslide formed. In the stability analysis of the slope, the shear strength parameters of the sliding surface was determined by anti-analysis. Therefore, the result of the evaluation is closer to the actual conditions. Analyzing the stability of the three sliding surfaces respectively, the stability factors for initial slope are between 1.211 and 1.468, and the stability factors for current slope are between 0.958 and 1.076. Hence, the cut-slope excavation is the direct cause of the landslide.
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Xie, Wan-li, Qianyi Guo, Jason Y. Wu, Ping Li, Hui Yang, and Maosheng Zhang. "Analysis of loess landslide mechanism and numerical simulation stabilization on the Loess Plateau in Central China." Natural Hazards 106, no. 1 (January 15, 2021): 805–27. http://dx.doi.org/10.1007/s11069-020-04492-w.
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AbstractLoess landslides have complicated deformation mechanisms. Accurately describing the internal failure deformation of loess landslides and establishing a theoretical method of landslide instability evaluation for the prevention of subsequent landslides have become important topics in western development project construction in China. This paper presents a case study of the Zhonglou Mountain landslide in Shaanxi Province, China. Based on field investigation results, a two-dimensional stability analysis model was constructed using the finite element method. Taking the deformation characteristics of the landslide as the research basis, the distribution laws of the displacement, stress, and shear strain of this landslide were identified with the strength reduction finite element numerical simulation method. Additionally, the safety factor was evaluated under normal and storm conditions. The numerical simulation results show that the horizontal tensile stress of the landslide was mainly distributed in the middle and upper parts of the landslide under normal conditions, while the vertical tensile stress was distributed near the sliding surface. Under heavy rainfall, the sliding force increased, and the anti-sliding force and anti-sliding section decreased; the location of the maximum shear strain shifted down from the middle and upper parts of the landslide body to the area with a shear crack, and the plastic shear strain area expanded along nearly the entire the sliding surface, leading to the occurrence of a landslide. Thus, the use of anti-slide piles to stabilize the landslide was proposed and tested. Monitoring points were arranged along the sliding surface to evaluate the displacement, stress, and strain responses. The on-site observation results agreed with the modeling results. The use of anti-slide piles was demonstrated to be an effective stabilization method for the Zhonglou Mountain landslide.
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Hooyer, Thomas S., and Neal R. Iverson. "Flow mechanism of the Des Moines lobe of the Laurentide ice sheet." Journal of Glaciology 48, no. 163 (2002): 575–86. http://dx.doi.org/10.3189/172756502781831160.
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AbstractRapid flow of the Des Moines lobe of the Laurentide ice sheet may have been related to its unlithified substrate. New reconstructions of the lobe, based on moraine elevations, sediment subsidence during moraine deposition, and flow-direction indicators, indicate that the lobe may have been ∼3 times thicker than in previous reconstructions. Nevertheless, implied basal shear stresses are <15 kPa, so internal ice deformation was not significant. Instead, the lobe likely moved by a combination of sliding, plowing of particles through the bed surface, and bed shear. Consolidation tests on basal till yield preconsolidation stresses of 125–300 kPa, so effective normal stresses on the bed were small. A model of sliding and plowing indicates that at such stresses most particles gripped by the ice may have plowed easily through the till bed, resulting in too small a shear traction on the bed to shear it at depth. Consistent with this prediction, measurements of orientations of clasts in basal till yield a weak fabric, implying pervasive bed shear strain less than ∼2, although some stronger fabrics have been reported by others. We infer, tentatively, that movement was principally at the bed surface by plowing.
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Guo, Wei, Yao Hu, Wenqi Hou, Xia Gao, Dan Bu, and Xu Xie. "Seismic Damage Mechanism of CRTS-II Slab Ballastless Track Structure on High-Speed Railway Bridges." International Journal of Structural Stability and Dynamics 20, no. 01 (November 22, 2019): 2050011. http://dx.doi.org/10.1142/s021945542050011x.
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China Railway Track System II (CRTS II) slab ballastless track structure is one of commonly adopted track systems on the high-speed railway bridge, which has been found seismically vulnerable under strong earthquakes. To investigate the earthquake-induced damage mechanism of the CRTS II slab ballastless track structure, a nonlinear numerical model of typical 7-span simply supported bridge–track system was established by the finite element software OpenSees and well calibrated by the test data and relative literatures. The nonlinear time history analysis was employed to calculate seismic responses of bridge and track parts under a suite of 10 seismic records. Results demonstrate that the sliding layer in the track structure is the most damage-prone component, especially at the bridge-subgrade transition section, and the shear alveolar may also sustain earthquake-induced fail. By analyzing the seismic damage mechanism of the track structure, this paper reveals that the nonuniform displacement responses of the girders and friction plate at the bridge-subgrade transition section are main factors that result in the extensive damage of the sliding layer and failure of the shear alveolar. However, the damage of these two components are beneficial to reduce the seismic responses of other components in the track structure and protect them from being damaged. From the perspective of engineering safety, the sliding layer and shear alveolar should be rigorously designed because the residual displacement of the sliding layer increases along with the maximum displacement and the failure of the shear alveolar may make the whole track structure failed.
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Tyfour, Wa’il R., Mohammed T. Hayajneh, Amer Momani, and Manar B. AL-Hajji. "Sliding wear mechanism of ductile materials – Effect of sliding direction reversal." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 3 (June 13, 2017): 315–25. http://dx.doi.org/10.1177/1350650117713878.
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The work presented in this paper tries to shed more light on the mechanism by which ductile surfaces fail and leave the contact surface during loaded pure sliding contact. An extensive experimental program was designed aimed at exploring the role of plastic shear strain accumulation in surface failure. Reversing the direction of strain during testing was the main variable which was facilitated by reversing the sliding direction. Changes in structure deformation morphology and accumulated plastic strain were analyzed. The effect of different sliding direction reversal regimes during testing, compared to unidirectional sliding to the same sliding distance, was thoroughly investigated. Results came to support that plastic strain accumulation is responsible for contact surface failure and, as a result, material loss from the ductile surface during sliding. It was evident, under the test conditions used, that reversing the sliding direction at different predefined sliding distances has resulted in delaying surface failure, resulting in lower wear loss compared to that found under unidirectional sliding. Multiple strain direction reversals resulted in higher beneficial effect in delaying failure. Furthermore, the earlier the sliding reversal is carried out, the better its effect of delaying failure. Findings have been explained in terms of plastic strain accumulation that leads to failure of the surface layer after reaching a certain strain to failure limit.
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Chang, Peng, Qiuge Feng, Nannan Wu, and Na Yang. "Research on Interface Slip Characteristics of Heritage Composite Timber Columns under Inclined Deformation." Applied Sciences 12, no. 14 (July 21, 2022): 7351. http://dx.doi.org/10.3390/app12147351.
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In order to study the mechanical performance and friction slip mechanism of the interface of a composite timber column under inclined deformation, the unilateral contact mechanical model of an ancient composite timber column under inclined deformation is proposed in this paper. According to the limit of the inclination angle of slip point and the limit of the inclination angle of slip surface, the failure modes of the combination’s interface can be divided into three stages: the fully sticky stage, the partially sticky stage and the sliding stage. The theoretical results of the sliding displacement and shear stiffness of the combination’s interface under the effect of iron hoops were obtained by using the elastic mechanics method. Based on the shear sliding test of a composite timber column’s interface under the effect of iron hoops, the influences of different parameters on the shear sliding performance of the combination’s interface were investigated. The test results show that the number and the spacing of the iron hoops and the inclination angle of the interface are important factors affecting the shear strength of the combination’s interface. The shear strength of the interface increased with the increase in the number of iron hoops and the inclination angle of the interface. Since hoop spacing that is too large or too small cannot effectively improve the shear capacity of the interface, there is an optimal value for the hoop spacing.
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Lin, Hung-Ming, Jian-Hong Wu, and Erik Sunarya. "Consolidated and Undrained Ring Shear Tests on the Sliding Surface of the Hsien-du-shan Landslide in Taiwan." Geofluids 2018 (October 30, 2018): 1–12. http://dx.doi.org/10.1155/2018/9410890.
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A new consolidated undrained ring shear test capable of measuring the pore pressures is presented to investigate the initiation mechanism of the Hsien-du-shan rock avalanche, triggered by Typhoon Morakot, in southern Taiwan. The postpeak state of the landslide surface between the Tangenshan sandstone and the remolded landslide gouge is discussed to address the unstable geomorphological precursors observed before the landslide occurred. Experimental results show that the internal friction angle of the high water content sliding surface in the total stress state, between 25.3 and 26.1°, clarifies the reason of the stable slope prior to Typhoon Morakot. In addition, during the ring shear tests, it is observed that the excess pore pressure is generated by the shear contractions of the sliding surface. The remolded landslide gouge, sheared under the high normal stress, rendered results associated with high shear strength, small shear contraction, low hydraulic conductivity, and continuous excess pore pressure. The excess pore pressure feedback at the sliding surface may have accelerated the landslide.
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Zhang, Xiao Ping, C. S. H. Lim, Yiu Wing Mai, and Yao Wu Shi. "Thermal Fatigue and Creep Fracture Behaviors of a Nanocomposite Solder in Microelectronic/Optoelectronic Packaging." Key Engineering Materials 312 (June 2006): 237–42. http://dx.doi.org/10.4028/www.scientific.net/kem.312.237.
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Thermal fatigue performance and creep resistance of soldered connections are crucial to the integrity and reliability of microelectronics, optoelectronics and photonics packaging systems. In this work, creep and thermal fatigue behaviours of lap shear joints soldered by a tin-based nanocomposite solder were characterized at different temperatures, with a comparison to a traditional Sn60Pb40 solder. The results show that the nano-composite solder has much better creep resistance and thermal creep fatigue property than the Sn60Pb40 solder. This is mainly due to the uniformly dispersed nano-sized Ag particles that have provided effective impediment to dislocation movement and grain boundary sliding, in addition to the alloying effect. The creep fractography analysis by SEM shows that a progressive shear deformation occurred as the main creep fracture mechanism. Sn60Pb solder joints deform dominantly by transgranular sliding, while the nano-composite solder joints creep by intergranular mechanism through grain boundary sliding and voids growth.
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Cai, Z., and R. J. Bathurst. "Seismic-induced permanent displacement of geosynthetic-reinforced segmental retaining walls." Canadian Geotechnical Journal 33, no. 6 (December 1, 1996): 937–55. http://dx.doi.org/10.1139/t96-123.
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This paper describes the application of conventional displacement methods to estimate seismic-induced permanent displacements of geosynthetic-reinforced segmental retaining walls constructed on firm foundations. Permanent displacements associated with three sliding mechanisms are investigated: (1) external sliding along the base of the total wall structure; (2) internal sliding along a reinforcement layer and through the facing column; and (3) block interface shear between facing column units. A pseudostatic method based on the Mononobe-Okabe earth pressure theory is used to determine the value of critical acceleration associated with each potential failure mechanism. Newmark's sliding block displacement method and a number of emperical methods are briefly summarized and can be used to estimate the permanent displacements of segmental retaining walls. An example is given to illustrate the application of the methods presented. Key words: segmental retaining walls, geosynthetics, seismic, Newmark, sliding block, displacement methods.
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Karachevtseva, Iuliia, Arcady V. Dyskin, and Elena Pasternak. "Generation and propagation of stick-slip waves over a fault with rate-independent friction." Nonlinear Processes in Geophysics 24, no. 3 (July 11, 2017): 343–49. http://dx.doi.org/10.5194/npg-24-343-2017.
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Abstract. Stick-slip sliding is observed at various scales in fault sliding and the accompanied seismic events. It is conventionally assumed that the mechanism of stick-slip over geo-materials lies in the rate dependence of friction. However, the movement resembling the stick-slip could be associated with elastic oscillations of the rock around the fault, which occurs irrespective of the rate properties of the friction. In order to investigate this mechanism, two simple models are considered in this paper: a mass-spring model of self-maintaining oscillations and a one-dimensional (1-D) model of wave propagation through an infinite elastic rod. The rod slides with friction over a stiff base. The sliding is resisted by elastic shear springs. The results show that the frictional sliding in the mass-spring model generates oscillations that resemble the stick-slip motion. Furthermore, it was observed that the stick-slip-like motion occurs even when the frictional coefficient is constant. The 1-D wave propagation model predicts that despite the presence of shear springs the frictional sliding waves move with the P wave velocity, denoting the wave as intersonic. It was also observed that the amplitude of sliding is decreased with time. This effect might provide an explanation to the observed intersonic rupture propagation over faults.
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Zhang, Hao. "Atomistic simulation of sliding of [1010] tilt grain boundaries in Mg." Journal of Materials Research 24, no. 11 (November 2009): 3446–53. http://dx.doi.org/10.1557/jmr.2009.0422.
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A series of molecular dynamics simulations was performed to study grain boundary sliding of three types of [101¯0] tilt grain boundaries in a magnesium bicrystal. In particular, a near Σ11 twin boundary, an asymmetric near Σ11 twin boundary, and a θ = 40.3° general [101¯0] tilt grain boundary were studied. Simulations showed that grain boundary sliding (a rigid motion of two grains relative to each other along boundary plane) did not occur over the stress range applied; instead, coupled shear motion (grain boundary sliding induced boundary migration) was dominant. Although the measured coupling coefficient, the ratio of boundary tangential displacement to boundary normal displacement, was in good agreement with theoretical prediction, the detailed shear behavior was different, depending on types of grain boundary, magnitude of applied shear stress, and temperature. It was also noted that grain boundary twining was the predominant mechanism that allowed the coupled shear motion to occur in hexagonal close-packed (HCP) magnesium.
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Ivanisenko, Yulia, and Hans Jörg Fecht. "Cooperative Grain Boundary Sliding and Shear Banding at High Strains in Ultrafine Grained and Nanocrystalline Pd Alloys." Materials Science Forum 667-669 (December 2010): 649–56. http://dx.doi.org/10.4028/www.scientific.net/msf.667-669.649.
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Instrumented high pressure torsion, i.e. mechanical test in a torsion mode under high pressure, allows interesting possibility of materials testing, because materials mechanical response can be studied in a practically unlimited shear strain range. We have studied microstructures formed in initially coarse crystalline and nanocrystalline (nc) Pd and its alloys after instrumented HPT up to shear strain 300, and revealed signatures of similar processes occurring in all these materials. In particular, we found traces of cooperative grain boundary sliding in the form of aligned in parallel segments of boundaries of several grains with straightened triple points. Fracture surfaces contained shear bands. Texture measurements revealed lower dislocation activity in nanocrystalline state as compared with coarse crystalline one. Therefore we argue that cooperative grain boundary sliding is an important deformation mechanism at large strain which develops in both ultrafine grained (ufg) and nanocrystalline materials. In nc and ufg materials planes of cooperative grain boundary sliding act as precursors of shear bands and shear occurs along planes formed by numerous grain boundaries.
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Wang, Jiugen, and Jianrong Tan. "Numerical Simulation of Traction in Rolling/Sliding Contacts." Journal of Tribology 119, no. 4 (October 1, 1997): 869–74. http://dx.doi.org/10.1115/1.2833898.
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A new model of traction in elastohydrodynamically lubricated contact is presented to study shear stress distributions. Results of full numerical analyses of elliptical contacts under rolling and sliding are presented. This study is confined to elastohydrodynamically lubricated contacts of relatively low load. Effects of dimensionless parameters such as speed, normal load, and elliptical parameter and coefficient of limiting shear stress on shear stress distributions have been analyzed. Moreover, the influence of slide-roll ratio on visualized shear stress in EHD contacts has been studied. It has been found that the higher slide-roll ratios induce higher maximum shear stress. Shear stresses in fluid film and those on surfaces vary with many factors that reveal the mechanism of traction in EHD conjunction zones.
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Zhu, Lei, Xin Jiang Song, and Bao Ning Hong. "Analysis of Shallow Landslides Stability of Coal Measure Soil through Contact Elastic-Plastic FEM." Advanced Materials Research 243-249 (May 2011): 2076–83. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2076.
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In order to reveal the mechanism of deformation, disintegration and failure of shallow landslides of coal measure soil, through contact elastic-plastic FEM with shear strength reduction, the paper analyzes shallow landslides stability, calculates shallow landslides safety factors, and reveals the mechanism of deformation, disintegration and failure of shallow landslide of coal measure soil. The results are shown as follows: during shallow landslides of coal measure soil, the displacement of sliding mass sliding along sliding surface, the plastic strain of sliding mass and sliding mass sliding state along sliding surface don’t change simultaneously; adopting contact elastic-plastic FEM algorithm may better reflect the actual state and sliding process of shallow landslides of coal measure soil. It can help faithfully reflect real situations of shallow landslides like deformation, disintegration and failure of shallow landslide of coal measure soil, and it may afford one method that can be used as a reference of the stability analysis, accurate evaluation and forecast of this type of landslide.
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Sagapuram, Dinakar, Koushik Viswanathan, Anirban Mahato, Narayan K. Sundaram, Rachid M'Saoubi, Kevin P. Trumble, and Srinivasan Chandrasekar. "Geometric flow control of shear bands by suppression of viscous sliding." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2192 (August 2016): 20160167. http://dx.doi.org/10.1098/rspa.2016.0167.
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Shear banding is a plastic flow instability with highly undesirable consequences for metals processing. While band characteristics have been well studied, general methods to control shear bands are presently lacking. Here, we use high-speed imaging and micro-marker analysis of flow in cutting to reveal the common fundamental mechanism underlying shear banding in metals. The flow unfolds in two distinct phases: an initiation phase followed by a viscous sliding phase in which most of the straining occurs. We show that the second sliding phase is well described by a simple model of two identical fluids being sheared across their interface. The equivalent shear band viscosity computed by fitting the model to experimental displacement profiles is very close in value to typical liquid metal viscosities. The observation of similar displacement profiles across different metals shows that specific microstructure details do not affect the second phase. This also suggests that the principal role of the initiation phase is to generate a weak interface that is susceptible to localized deformation. Importantly, by constraining the sliding phase, we demonstrate a material-agnostic method—passive geometric flow control—that effects complete band suppression in systems which otherwise fail via shear banding.
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Jiang, Hai-ming, Jie Li, Shu-xin Deng, De-rong Wang, and Xiao Zhao. "Experimental Investigation and Analysis of Triggering Mechanism for Fault-Slip Bursts of the Tunnel Surrounding Rock with External Disturbance." Shock and Vibration 2018 (September 25, 2018): 1–11. http://dx.doi.org/10.1155/2018/1687519.
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Shear-slip type rockburst is one of the most common geohazards confronted in deep underground excavations, which can easily occur after external disturbances. Owing to the sudden occurrence and significant damage caused, investigating the mechanism of these shear-slip type disasters is of tremendous significance in ensuring the safety of underground construction projects. In this paper, our attentions are mainly paid to investigate the necessary conditions and critical energy conditions of fault-slip bursts of the tunnel surrounding rock triggered by external disturbances. First, a simplified model for simulating the sliding instability phenomenon occurring in a blocky rock system under external disturbance is established. Next, using a newly developed testing system for the dynamic behaviour of blocky rock masses, a series of experiments to reproduce the sliding instability phenomenon are conducted; the purple sandstone block system is subjected to the combined effect of a vertical impact load and horizontal constant force. The influence of vertical impact energy on the sliding instability is analysed. The experimental results show that the critical energy of the impact load triggering the blocky rock mass slip instability depends on the shear force, and the higher the shear force, the lower is the external disturbance required. Furthermore, a one-dimensional dynamic calculation model is established to develop a better insight regarding the mechanism of the slip instability induced by external disturbances. A dimensionless energy parameter was introduced to quantifiably characterize the critical conditions of different types of fault-slip events. Theoretical analysis and calculations are presented, and the results agree with experimental observations.
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Zhang, Yunhe, Sian Wang, Xiwang Zhao, Fanming Wang, and Gaohui Wu. "In Situ Study on Fracture Behavior of Z-Pinned Carbon Fiber-Reinforced Aluminum Matrix Composite via Scanning Electron Microscope (SEM)." Materials 12, no. 12 (June 17, 2019): 1941. http://dx.doi.org/10.3390/ma12121941.
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Inside a scanning electron microscope (SEM) chamber, we performed an in situ interlaminar shear test on a z-pinned carbon fiber-reinforced aluminum matrix composite (Cf/Al) fabricated by the pressure the infiltration method to understand its failure mechanism. Experiments show that introducing a stainless-steel z-pin increases the interlaminar shear strength of Cf/Al composite by 148%. The increase in interlaminar shear strength is attributed to the high strength of the stainless-steel z-pin and the strong bonding between the z-pin and the matrix. When the z-pin/matrix interface failed, the z-pin can still experience large shear deformation, thereby enhancing delamination resistance. The failure mechanism of composite includes interfacial debonding, aluminum plough, z-pin shear deformation, frictional sliding, and fracture. These results in this study will help us understand the interlaminar strengthening mechanism of z-pins in the delamination of metal matrix composites.
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Basha, B. Munwar, and G. L. Sivakumar. "Analysis of Passive Earth Pressure and Displacements of Retaining Walls Using Pseudo-Dynamic Approach." International Journal of Geotechnical Earthquake Engineering 1, no. 1 (January 2010): 88–109. http://dx.doi.org/10.4018/jgee.2010090806.
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Using additional dynamic parameters in the pseudo-static method like shear wave and primary wave velocities of soil, phase change in the shear and primary waves, and soil amplification for seismic accelerations, one can benefit from another useful tool called pseudo-dynamic method to solve the problem of earth pressures. In this study, the pseudo-dynamic method is used to compute the seismic passive earth pressures on a rigid gravity retaining wall by considering both the planar failure and composite failure (log-spiral and planar) mechanisms. To validate the present formulation, passive earth pressure computed by the present method are compared with those given by other authors. Seismic passive earth pressure coefficients are provided in tabular form for different parameters. The sliding and rotational displacements are also computed and results of the comparative study showed that the assumption of planar failure mechanism for rough soil-wall interfaces significantly overestimates passive earth pressure and underestimate the sliding and rotational displacements.
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Feng, Shi-Jin, Jie-Ni Chen, Hong-Xin Chen, Xin Liu, T. Zhao, and Annan Zhou. "Analysis of sand – woven geotextile interface shear behavior using discrete element method (DEM)." Canadian Geotechnical Journal 57, no. 3 (March 2020): 433–47. http://dx.doi.org/10.1139/cgj-2018-0703.
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The interaction between soil and geotextile is essential for the performance of reinforced soil. This study reveals the microscopic mechanism of interface shear between sand and geotextile based on the discrete element method (DEM). The surface characteristics of geotextile are simulated by overlapped particles. The micromechanical parameters of sand, geotextile, and interface are calibrated effectively using laboratory test results. Three types of shear tests on the sand–geotextile interface are simulated; namely, interface direct shear test (IDST), double-sided interface shear test (D_IST), and interface direct shear test with periodic boundary (PBST). For IDST, the results show that the thickness of shear band is 2.4∼3.0 times the average particle diameter (D50); the contact force, percentage of sliding contact, and contact normal anisotropy inside the shear band are larger than those outside the shear band, whereas the coordination number is smaller inside the shear band. The mechanical response of D_IST is similar to that of IDST. However, D_IST has a shear band thickness of 3.0D50, and greater coordination number, percentage of sliding contact, and contact normal anisotropy. The results of PBST indicate that the peak stress and the shear band no longer appear without boundary constraint and the contact distribution is uniform.
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Wei, Jihong, Yan Men, Shaorui Sun, Huilin Le, and Feng Zhu. "Experimental Study on 3D Roughness and Shear Failure Mechanism of Rock Mass Discontinuity." Advances in Civil Engineering 2018 (2018): 1–20. http://dx.doi.org/10.1155/2018/7358205.
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A set of systematic experimental methods, including 3D accuracy scanning and identification of discontinuous surface topography, physical model construction, and laboratory direct shear experiment under different directions and normal stresses, was proposed to research the influence of discontinuity roughness on strength and deformation of discontinuity. During physical model construction of discontinuity, three types of discontinuity and rough natural rock joint surface models were constructed and moulded. Meanwhile, many influence factors of discontinuity surface topography, such as asperity inclination angle (AIA), asperity height (AH), normal stress (NS), and shear direction (SD), were considered during the direct shear experiment. On the basis of the experimental results, it can be found that there were two types of failure modes under different loading conditions, which were named “failure by shearing through the asperities” and “failure by sliding over the asperities”. The obvious stress concentration phenomenon, climbing, and cutting effects appeared in the process of the direct shear experiment. In addition, the accurate identification of surface topography of natural rough rock joint surface was carried out using three-dimensional sensing system (3DSS) and self-programming software before and after the experiment. The subsamples with the same surface topography as the original samples were moulded using a self-developed instrument. Then, the mechanical behavior of the original samples and subsamples for the natural rough rock joint surface under different shear directions and normal stresses was studied. The results show that the shear displacement under different shear directions and normal stresses is very large before it reaches the failure state. And the residual strength of the original samples is higher than that of the subsamples. In addition, failure modes of the subsamples are main failure by shearing through the asperities due to the significant difference between peak shear strength and residual strength. The failure modes for parts of the original samples are failure by sliding over the asperities. The change ratio of area for the discontinuity after the experiment depends on surface topography, strength of heave on the surface of discontinuity, and particle size of minerals on the surface of discontinuity.
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Iverson, Neal R. "Coupling between a glacier and a soft bed: II Model results." Journal of Glaciology 45, no. 149 (1999): 41–53. http://dx.doi.org/10.3189/s0022143000003026.
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Abstract The relation between the local effective pressure and shear stress on till beneath Storglaciären, Sweden, discussed in Iverson and others (1999), provides an empirical basis for studying the processes that control the strength of the ice/bed coupling. Particles in the bed that protrude into the glacier sole support shear stresses that are limited by either ploughing or the traditional sliding mechanisms. Model calculations, based on studies of cone penetration through fine-grained sediment and sliding theory, agree with the observed relation between shear stress and effective pressure if the water layer at the ice/bed interface is assumed to thicken rapidly as the effective pressure approaches zero. Studies of the hydraulics of linked cavities provide support for this assumption, if the mean thickness of the water layer reflects the extent of microcavity development at the interface. Comparison of the calculated shear stress with the ultimate strength of till suggests that bed deformation limits the shear stress on till beneath Storglaciären only at intermediate effective pressures; at very low effective pressures, like those inferred at the site of the tiltmeter discussed in Iverson and others (1999), and at sufficiently high effective pressures, ploughing and sliding should focus motion near the glacier sole. A calculation using parameter values appropriate for Ice Stream B, West Antarctica, suggests that ploughing may occur there at shear stresses not sufficient to deform the bed at depth. This conclusion is reinforced by the likelihood that pore pressures in excess of hydrostatic should develop down-glacier from ploughing particles, thereby weakening the bed near the glacier sole. However, given the apparent sensitivity of the ice/bed coupling to basal conditions that may be highly variable, any blanket assumption regarding the flow mechanism of ice masses on soft beds should probably be viewed with skepticism.
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Iverson, Neal R. "Coupling between a glacier and a soft bed: II Model results." Journal of Glaciology 45, no. 149 (1999): 41–53. http://dx.doi.org/10.1017/s0022143000003026.
Full textAbstract:
AbstractThe relation between the local effective pressure and shear stress on till beneath Storglaciären, Sweden, discussed in Iverson and others (1999), provides an empirical basis for studying the processes that control the strength of the ice/bed coupling. Particles in the bed that protrude into the glacier sole support shear stresses that are limited by either ploughing or the traditional sliding mechanisms. Model calculations, based on studies of cone penetration through fine-grained sediment and sliding theory, agree with the observed relation between shear stress and effective pressure if the water layer at the ice/bed interface is assumed to thicken rapidly as the effective pressure approaches zero. Studies of the hydraulics of linked cavities provide support for this assumption, if the mean thickness of the water layer reflects the extent of microcavity development at the interface. Comparison of the calculated shear stress with the ultimate strength of till suggests that bed deformation limits the shear stress on till beneath Storglaciären only at intermediate effective pressures; at very low effective pressures, like those inferred at the site of the tiltmeter discussed in Iverson and others (1999), and at sufficiently high effective pressures, ploughing and sliding should focus motion near the glacier sole. A calculation using parameter values appropriate for Ice Stream B, West Antarctica, suggests that ploughing may occur there at shear stresses not sufficient to deform the bed at depth. This conclusion is reinforced by the likelihood that pore pressures in excess of hydrostatic should develop down-glacier from ploughing particles, thereby weakening the bed near the glacier sole. However, given the apparent sensitivity of the ice/bed coupling to basal conditions that may be highly variable, any blanket assumption regarding the flow mechanism of ice masses on soft beds should probably be viewed with skepticism.
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Meng, Fanjing, and Kun Liu. "The stick-slip mechanism for granular flow lubrication." Industrial Lubrication and Tribology 71, no. 1 (January 14, 2019): 139–45. http://dx.doi.org/10.1108/ilt-07-2018-0295.
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Purpose Granular flow lubrication is developed in recent years as a new lubrication method which can be used in extreme environments, while the stick-slip mechanisms of granular flow lubrication are an urgent obstacle remains unsolved in fully establishing the granular flow lubrication theory. Design/methodology/approach A granular flow lubrication research model is constructed by the discrete element method. Using this numerical model, the mesoscopic and macroscopic responses of stick-slip that influenced by the shear velocity, and the influence of the shear velocity and the normal pressure on the vertical displacement are studied. Findings Research results show that movement states of granular flow lubrication medium gradually transform from the stick-slip state to the sliding state with increased shear velocity, in which these are closely related to the fluctuations of force chains and friction coefficients between granules. The stick-slip phenomenon comes up at lower shear velocity prior to the appearance of granular lift-off between the two friction pair, which comes up at higher shear velocity. Higher normal pressure restrains the dilatation of the granular flow lubrication medium, which in turn causes a decrease in the displacement. Originality/value These findings reveal the stick-slip mechanism of granular flow lubrication and can also offer the helpful reference for the design of the new granular lubrication bearing.
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Liu, Huanrong, Zehui Jiang, Benhua Fei, Chungyun Hse, and Zhengjun Sun. "Tensile behaviour and fracture mechanism of moso bamboo (Phyllostachys pubescens)." Holzforschung 69, no. 1 (January 1, 2015): 47–52. http://dx.doi.org/10.1515/hf-2013-0220.
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Abstract The present work is aiming at the elucidation of the tensile behaviour and fracture performance of moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) by means of digital speckle correlation method (DSCM) and microscopic techniques. Results indicated that fibres play a major role in longitudinal tension and impeding crack radial propagation. Hybrid I-II failure mode was observed, i.e., crack opening (in tensile stress) and shear sliding (in shear stress). According to microscopic fracture characteristics, fibres extraction and stretching, filament formation in parenchyma with fibres bridging, interface debonding and the helix fracture of fibres happened in tension, which created more interfaces and dissipated more energy. The graded composite structure of bamboo provides intrinsic and extrinsic toughening mechanisms which contribute to improved toughness and physical properties.
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Sun, Yan, Yiwen Ju, Wei Zhou, Hongtai Chao, Zhicai Wang, Lei Wang, Hongjian Zhu, and Kui Han. "Experimental Evidence and Characteristic Recognition of the Nanoweakening of Slip Deformation Zones." Journal of Nanoscience and Nanotechnology 21, no. 1 (January 1, 2021): 788–94. http://dx.doi.org/10.1166/jnn.2021.18742.
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A central issue in the study of fault evolution is to identify shear weakening and its mechanism; currently, studies of fault weakening in narrow slip deformation zones, including those of various slipping planes such as schistosity, foliation, cleavage, joints and faults in rocks, are ongoing. To verify the nanoweakening in shear slipping, we carried out experiments: triaxial compression experiments on sandstones and uniaxial compression experiments on granites. Furthermore, on the basis of scanning electron microscopy (SEM) observations and experimental data analyses, we suggested three kinds of nanoweakening in terms of the corresponding strain stages: (1) The slip nanoweakening caused by the strain hardening deformation stage of the shear slip, which creates nanograins with dense coatings that may be due to the nanocoating on the shear planes, can result in rolling friction rather than with sliding friction, and the former is a principal mechanism of sliding nanoweakening. (2) The rheological nanoweakening caused by the strain softening deformation stage; in view of developing weakened deformation due to grain boundary migration (GBM), the flow of synkinematic minerals and melt coating phenomena lead to rheological nanoweakening. (3) The dynamic nanoweakening caused by thermal pressurization and fluid pressurization during the strain softening stage and strain degenerating stage. Thus, when these aspects are considered in defining the relationship between the nanoweakening at the slipping planes and the strain stages, the representative mechanism and its behavior rules can be obtained.
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Kou, Chang Huan, Shih Wei Ma, and Meng Wei Lai. "Mechanism of Debris Flows in Mountain Streams." Applied Mechanics and Materials 419 (October 2013): 883–88. http://dx.doi.org/10.4028/www.scientific.net/amm.419.883.
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This paper suggests the mechanism of occurrence of debris flow in mountain streams. It is found that the sliding of the undermined stream banks follows the exponential probability distribution function. This indicates that the major amount of debris is from an intensive sliding in the initial stage of flood flow development. This can be otherwise proved by the viscous flow boundary layer theory such as the shear stresses on the wall are initially very large. Through a relative dimensional analysis, a special dimensionless parameter K is grouped which has a very important effect on the occurrence of the acceleration of the heavy debris by the flow. It interprets, during the flood flow development, the amount of debris on the stream bed can only be accelerated when the kinetic energy of the flow is greater than the apparent work of the debris against the flow. Of course, as a transient behavior, once it starts, the sudden acceleration of a huge amount of debris flow bore will usually cause an unpredictable downstream disaster.
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Meng, Fanjing, Kun Liu, and Tao Qin. "Experimental investigations of force transmission characteristics in granular flow lubrication." Industrial Lubrication and Tribology 70, no. 7 (September 10, 2018): 1151–57. http://dx.doi.org/10.1108/ilt-07-2017-0211.
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Purpose Granular lubrication is a new lubrication method and can be used in extreme working conditions; however, the obstacle of force transmission characteristics needs to be urgently solved to fully understand the mechanical and bearing mechanisms of granular lubrication. Design/methodology/approach A flat sliding friction cell is developed to study the force transmission behaviors of granules under shearing. Granular material, sliding velocity, granule size and granule humidity are considered in these experiments. The measured normal and shear force, which is transmitted from the bottom friction pair to the top friction pair via the granular lubrication medium, reveals the influence of these controlling parameters on the force transmission characteristics of granules. Findings Experimental results show that a low sliding velocity, a large granule size and a low granular humidity increase the measured normal force and shear force. Besides, a comparison experiment with other typical lubrication styles is also carried out. The force transmission under granular lubrication is mainly dependent on the force transmission path, which is closely related to the deconstruction and reconstruction of the force chains in the granule assembly. Originality/value These findings reveal the force transmission mechanism of granular lubrication and can also offer the helpful reference for the design of the new granular lubrication bearing.
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Zhou, Jian Qiu, Ying Wang, and Shu Zhang. "Effect of Grain Rotation on the Strain-Softening Behavior in Nanocrystalline Materials." Advanced Materials Research 311-313 (August 2011): 516–20. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.516.
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We postulated a softening model involving grain rotation that results in diffusion-accommodated grain-boundary sliding. This numerical model was used to compute the proportion evolution of grains within shear bands and was also employed to predict the softening of nanocrystalline materials considering non-homogeneous plastic deformation due to shear bands. The effect of softening mechanism for total stress-strain relation and the grain size and mean maximum Schmid factor effect was also considered in our model.
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Bai, Zhiwen, Xiaohan Yan, Jian Yin, and Huaiyu Hou. "Influence of Chromium Atoms on the Shear-Coupled Motion of [110] Symmetric Tilt Grain Boundary in α-Iron: Atomic Simulation." Metals 12, no. 9 (August 30, 2022): 1451. http://dx.doi.org/10.3390/met12091451.
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Shear-coupled grain boundary motion (SCGBM) is an important mechanism of plastic deformation, especially in the cases of ultrafine-grained or nanocrystalline materials at low temperatures. Much research work has been focused on the geometric rules of coupling, the grain boundary migration mechanisms, or the temperature effect of SCGBM, but the effect of the alloy atoms is seldom involved. In this work, molecular dynamics (MD) simulations were carried out to examine the SCGBM of the Σ17[110](223) and Σ9[110](221) grain boundaries (GBs) in iron-chromium alloys containing from 1 at.% to 9 at.% Cr. A constant shear velocity corresponding to 10 m/s parallel to the boundary plane was applied to the models. Our simulation results indicate that the critical stress of GB migration reduces due to the addition of Cr atoms for the Σ17(223) GB. As for the Σ9(221) GB, sliding occurs simultaneously with coupling in the shear process when the atomic amount of Cr reaches 3%. This phenomenon was also observed in the Σ9(221) GB in pure Fe when the temperature was elevated to 300 K, which was studied in our previous simulation work. The existence of new structural units was demonstrated to be responsible for the sliding of the grain boundary.
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Chang, Muhsiung. "A 3D slope stability analysis method assuming parallel lines of intersection and differential straining of block contacts." Canadian Geotechnical Journal 39, no. 4 (August 1, 2002): 799–811. http://dx.doi.org/10.1139/t02-020.
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A three-dimensional (3D) method of analysis of the stability of slopes was developed based on the sliding mechanism observed in the 1988 failure of the Kettleman Hills landfill slope (Kettleman City, California) and the associated model studies. By adopting a limit equilibrium concept, the method assumes the sliding mass as a block system in which the contacts between blocks are inclined. The lines of intersection of the block contacts are assumed to be parallel, which enables the sliding kinematics. In consideration of the differential straining between blocks, the shear stresses on the slip surface and the block contacts are evaluated based on the degree of shear strength mobilization on these contacts. The overall factor of safety is calculated based on the force equilibrium of the individual blocks and the entire block system as well. Based on comparisons with a series of hypothetical 3D and 2D problems with known solutions, the method was generally found to be accurate in predicting the stability of slopes involving a translational type of sliding failure. For rotational sliding failures in clays, however, the method appears to slightly overestimate the calculated factor of safety; up to as much as 10% in a typical problem examined in this study.Key words: slope stability, 3D method, limit equilibrium, block kinematics, strain incompatibility.
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Ge, Decheng, Fuxing Jiang, Cunwen Wang, Yang Chen, Chunyu Dong, Sitao Zhu, Zhaoyi Wang, and Fei Han. "Sliding Impact Mechanism of Square Roadway Based on Complex Function Theory." Shock and Vibration 2021 (January 31, 2021): 1–12. http://dx.doi.org/10.1155/2021/6655694.
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To clarify the process of stress change and plastic zone evolution of square roadways under high-stress conditions, the rotational square expansion plastic zone evolution model of square roadway was established by theoretical analysis, numerical simulation, and engineering verification. The shear slip impact stress criterion of square roadway based on complex variable function theory was studied, and the law of surrounding rock stress distribution, plastic zone expansion, elastic energy density, local energy release rate (LERR), and total energy release of square roadway were analyzed. The results show that the compressive stress is concentrated in the four corners of the roadway after the roadway excavated and transfers with the change of plastic zone. Main shear failures start from the four corners and develop in a rotating square shape, forming square failure zones I and II. The square failure zone I is connected with the roadway contour and rotated 45°. The square failure zone II is connected with the square failure zone I and rotated 45°. When the original rock stress is low, the surrounding rock tends to be stable after the square shear slip line field formed. When the original rock stress is high, the shear failure of the surrounding rock continues to occur after the square failure zone II formed, showing a spiral slip line. Corners of the square roadway and square failure zones I and II are the main energy accumulation and release areas. The maximum elastic energy density and LERR increase exponentially with the ratio of vertical stress to uniaxial compressive strength (Ic). When square corners of the roof are changed to round corners, the plastic zone of the roof expands to form an arch structure. The maximum elastic energy density decreases by 22%, which reduces the energy level and possibility of rock burst. This study enriches the failure mechanism of roadway sliding impact. It can provide a basic theoretical reference for the design of the new roadway section and support form based on the prevention of rock burst.
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WANG, Gonghui, Akira SUEMINE, and Guangqi CHEN. "Retraction: Residual shear behavior of serpentinite in Shiraishi landslide, Tokushima Prefecture and sliding mechanism." Journal of the Japan Landslide Society 47, no. 5 (2010): 265–73. http://dx.doi.org/10.3313/jls.47.265.
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Lu, Kunquan, Zexian Cao, Meiying Hou, Zehui Jiang, Rong Shen, Qiang Wang, Gang Sun, and Jixing Liu. "The mechanism of earthquake." International Journal of Modern Physics B 32, no. 07 (March 5, 2018): 1850080. http://dx.doi.org/10.1142/s0217979218500807.
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The physical mechanism of earthquake remains a challenging issue to be clarified. Seismologists used to attribute shallow earthquake to the elastic rebound of crustal rocks. The seismic energy calculated following the elastic rebound theory and with the data of experimental results upon rocks, however, shows a large discrepancy with measurement — a fact that has been dubbed as “the heat flow paradox”. For the intermediate-focus and deep-focus earthquakes, both occurring in the region of the mantle, there is not reasonable explanation either. This paper will discuss the physical mechanism of earthquake from a new perspective, starting from the fact that both the crust and the mantle are discrete collective system of matters with slow dynamics, as well as from the basic principles of physics, especially some new concepts of condensed matter physics emerged in the recent years. (1) Stress distribution in earth’s crust: Without taking the tectonic force into account, according to the rheological principle of “everything flows”, the normal stress and transverse stress must be balanced due to the effect of gravitational pressure over a long period of time, thus no differential stress in the original crustal rocks is to be expected. The tectonic force is successively transferred and accumulated via stick-slip motions of rock blocks to squeeze the fault gouge and then exerted upon other rock blocks. The superposition of such additional lateral tectonic force and the original stress gives rise to the real-time stress in crustal rocks. The mechanical characteristics of fault gouge are different from rocks as it consists of granular matters. The elastic moduli of the fault gouges are much less than those of rocks, and they become larger with increasing pressure. This peculiarity of the fault gouge leads to a tectonic force increasing with depth in a nonlinear fashion. The distribution and variation of the tectonic stress in the crust are specified. (2) The strength of crust rocks: The gravitational pressure can initiate the elasticity–plasticity transition in crust rocks. By calculating the depth dependence of elasticity–plasticity transition and according to the actual situation analysis, the behaviors of crust rocks can be categorized in three typical zones: elastic, partially plastic and fully plastic. As the proportion of plastic portion reaches about 10% in the partially plastic zone, plastic interconnection may occur and the variation of shear strength in rocks is mainly characterized by plastic behavior. The equivalent coefficient of friction for the plastic slip is smaller by an order of magnitude, or even less than that for brittle fracture, thus the shear strength of rocks by plastic sliding is much less than that by brittle breaking. Moreover, with increasing depth a number of other factors can further reduce the shear yield strength of rocks. On the other hand, since earthquake is a large-scale damage, the rock breaking must occur along the weakest path. Therefore, the actual fracture strength of rocks in a shallow earthquake is assuredly lower than the average shear strength of rocks as generally observed. The typical distributions of the average strength and actual fracture strength in crustal rocks varying with depth are schematically illustrated. (3) The conditions for earthquake occurrence and mechanisms of earthquake: An earthquake will lead to volume expansion, and volume expansion must break through the obstacle. The condition for an earthquake to occur is as follows: the tectonic force exceeds the sum of the fracture strength of rock, the friction force of fault boundary and the resistance from obstacles. Therefore, the shallow earthquake is characterized by plastic sliding of rocks that break through the obstacles. Accordingly, four possible patterns for shallow earthquakes are put forward. Deep-focus earthquakes are believed to result from a wide-range rock flow that breaks the jam. Both shallow earthquakes and deep-focus earthquakes are the energy release caused by the slip or flow of rocks following a jamming–unjamming transition. (4) The energetics and impending precursors of earthquake: The energy of earthquake is the kinetic energy released from the jamming–unjamming transition. Calculation shows that the kinetic energy of seismic rock sliding is comparable with the total work demanded for rocks’ shear failure and overcoming of frictional resistance. There will be no heat flow paradox. Meanwhile, some valuable seismic precursors are likely to be identified by observing the accumulation of additional tectonic forces, local geological changes, as well as the effect of rock state changes, etc.
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Molinari, A., Y. Estrin, and S. Mercier. "Dependence of the Coefficient of Friction on the Sliding Conditions in the High Velocity Range." Journal of Tribology 121, no. 1 (January 1, 1999): 35–41. http://dx.doi.org/10.1115/1.2833808.
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The velocity, normal pressure, and slider size dependence of the coefficient of dry friction of metals in the range of high sliding velocities (V ≥ 1 m/s) is investigated theoretically. Failure of the adhesive junctions by adiabatic shear banding is considered as the underlying process. The concept of asperity shearing by the adiabatic shear banding mechanism represents a new approach to unlubricated high velocity friction. Analytical solutions of a coupled thermomechanical problem are given for two constitutive relations. Numerical solutions for steel-on-steel friction showing a decrease of the coefficient of friction with the sliding velocity for different normal pressures are presented. The model is considered to be adequate in the velocity range of 1–10 m/s where friction enhanced oxidation or surface melting are believed not to interfere with the asperity shearing process.
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Min, Gyeongjo, Daisuke Fukuda, Sewook Oh, Gyeonggyu Kim, Younghun Ko, Hongyuan Liu, Moonkyung Chung, and Sangho Cho. "Three-Dimensional Combined Finite-Discrete Element Modeling of Shear Fracture Process in Direct Shearing of Rough Concrete–Rock Joints." Applied Sciences 10, no. 22 (November 12, 2020): 8033. http://dx.doi.org/10.3390/app10228033.
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A three-dimensional combined finite-discrete element element method (FDEM), parallelized by a general-purpose graphic-processing-unit (GPGPU), was applied to identify the fracture process of rough concrete–rock joints under direct shearing. The development process of shear resistance under the complex interaction between the rough concrete–rock joint surfaces, i.e., asperity dilatation, sliding, and degradation, was numerically simulated in terms of various asperity roughness under constant normal confinement. It was found that joint roughness significantly affects the development of overall joint shear resistance. The main mechanism for the joint shear resistance was identified as asperity sliding in the case of smoother joint roughness and asperity degradation in the case of rougher joint asperity. Moreover, it was established that the bulk internal friction angle increased with asperity angle increments in the Mohr–Coulomb criterion, and these results follow Patton’s theoretical model. Finally, the friction coefficient in FDEM appears to be an important parameter for simulating the direct shear test because the friction coefficient affects the bulk shear strength as well as the bulk internal friction angle. In addition, the friction coefficient of the rock–concrete joints contributes to the variation of the internal friction angle at the smooth joint than the rough joint.
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Wang, Peng, Yu Xiao, and Nan Wu. "Electrical Power Generation Using Dynamic Piezoelectric Shear Deformation Under Friction." Acta Mechanica Solida Sinica 34, no. 6 (November 26, 2021): 977–88. http://dx.doi.org/10.1007/s10338-021-00291-3.
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AbstractA new electrical power generation device based on high-frequency dynamic piezoelectric shear deformation under friction is developed. During the operation of a moving plate compressed and sliding on the top of a piezoelectric patch with constant velocity, dynamic shear deformation of the elastic piezoelectric patch is excited by periodic friction force and status (sliding and stick) variation. The dynamic piezoelectric shear strain can then generate continuous electrical power for energy absorbing and harvesting applications. The design of the piezoelectric couple device is first provided, and its mechanism, dynamic response and electric power generation under friction are described by a detailed iteration model. By comparing with previous experimental results, the accuracy of the proposed model is proven. Through numerical studies, the influences of the equivalent mass of the system, the velocity of the sliding object, the static friction coefficient and its lower limit, as well as the friction force delay rate on the power generation are obtained and discussed. The numerical results show that with the proposed design, up to 50-Watt maximum electrical power could be generated by a piezoelectric patch with a dimension of $$20\times 2\times 6$$ 20 × 2 × 6 cm under continuous friction with the moving plate at the velocity of 15 m/s. The possible bi-linear elastic stiffness variation of the system is also introduced, and the threshold of bi-linear elastic deformation, where the system stiffness changes, can be optimized for obtaining the highest power generation.
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Zhao, Na, Yibin Zhang, Haibin Miao, and Lixin Meng. "Study on the Creep and Fracture Evolution Mechanism of Rock Mass with Weak Interlayers." Advances in Materials Science and Engineering 2022 (February 10, 2022): 1–14. http://dx.doi.org/10.1155/2022/5004306.
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To study the influence of weak interlayers on the creep failure characteristics of rock masses, based on the continuous-discontinuous method (CDEM), the uniaxial compression creep experiments of rock masses containing weak layers were numerically simulated; and the weakened rock masses under different conditions were analyzed in detail. We focused on the final failure mode and creep curve of the rock mass with a weak interlayer (θ = 30°, d = 20 mm, c = 1) as examples by selecting the crack distribution state of the model during compression at different time steps. We analyzed the propagation and convergence mode of cracks in a rock mass with weak layers. The research results show that the existence of weak interlayers affects the integrity of the rock mass and the creep failure mode. With the increase in the inclination of the weak interlayer, the failure mode of the rock mass changes from shear failure through the weak layer to slip along the weak layer. For shear failure, the total strain and steady-state creep rate of the rock mass first decrease and then increase, showing a U-shaped distribution; as the thickness of the weak interlayer increases, the rock mass always follows the shear in the weak layer. Creep failure occurs on the fracture surface, and the total strain and steady-state creep rate of the rock mass are positively correlated with the thickness. If the thickness continues to increase, there is no significant difference in the creep characteristics of the rock mass; the volume occupied by the soft rock in the body increases, the overall rigidity of the rock mass decreases, and the plastic deformation increases. The form of creep failure of the rock mass changes from sliding shear failure along the weak layer to sliding shear failure through the weak interlayer. The total strain and steady-state creep rate of the rock mass increase with the increase in the number of weak layers; the greater the distance between the weak layers, the smaller the total strain and steady-state creep rate of the rock mass. The slower the crack growth rate, the less likely the rock mass to undergo creep damage.
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Sakuma, H., K. Kawai, I. Katayama, and S. Suehara. "What is the origin of macroscopic friction?" Science Advances 4, no. 12 (December 2018): eaav2268. http://dx.doi.org/10.1126/sciadv.aav2268.
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What is the origin of molecular friction, and how can macroscopic friction be explained in terms of molecular friction? To elucidate the origins of molecular and macroscopic friction, we conducted density functional theory calculations and double-direct shear tests at normal stresses ranging from 5 to 60 MPa for mica surfaces. Frictional forces between mica surfaces were theoretically predicted to oscillate periodically every 30° of sliding direction, in agreement with previous experimental findings. This result affirms that the potential energy roughness of mica under sliding is the origin of molecular friction, which depends on the normal stress and sliding direction. The discovered mechanism of molecular friction can quantitatively explain experimentally observed macroscopic friction of mica when the presence of wear particles is taken into consideration.
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Mundl, R., G. Meschke, and W. Liederer. "Friction Mechanism of Tread Blocks on Snow Surfaces." Tire Science and Technology 25, no. 4 (October 1, 1997): 245–64. http://dx.doi.org/10.2346/1.2137543.
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Abstract Evaluation of tread pattern designs with respect to performance of winter tires on snow is still predominantly based on empirical knowledge. To gain greater insight into the complex interaction between the elastic tread block and the inelastically deforming snow, numerical simulations by means of the Finite Element Method (FEM) were carried out in conjunction with experimental investigations. An elastoplastic material model for snow was developed. Calibration of the model parameters is based on shear and compression tests conducted on specimens made of natural and artificial snow. Good correlation is obtained between results from laboratory experiments and from numerical simulations with respect to the deformations and the frictional behavior of a single rubber block sliding on snow.
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WU, AIQING, QIGUI YANG, GUISHENG MA, BO LU, and XIAOJUN LI. "STUDY ON THE FORMATION MECHANISM OF TANGJIASHAN LANDSLIDE TRIGGERED BY WENCHUAN EARTHQUAKE USING DDA SIMULATION." International Journal of Computational Methods 08, no. 02 (June 2011): 229–45. http://dx.doi.org/10.1142/s0219876211002563.
Full textAbstract:
Wenchuan earthquake, Ms 8.0 in magnitude and occurred on May 12, 2008 in Sichuan Province, China, triggered a lot of landslides, rock collapses, debris flow, etc. The Tangjiashan landslide, with its total volume 20.37 million m3, was the biggest and the most notable one for its effects. Based on the field geological investigation and the typical acceleration records of the main shock obtained in the period of the earthquake, numerical simulation of the whole sliding process of Tangjiashan landslide has been carried out by DDA method. It is shown that the Tangjiashan landslide was a high-speed landslide, behaved with nonlinear features in the whole sliding process. The total duration of the landslide was about 30 s while nearly all of their slipping displacements were carried out in the beginning 25 s, with the maximum sliding velocity about 30 m/s, and the average 15–17 m/s in the beginning 25 s. The crash of rock blocks induced a much higher stresses near the middle and lower parts of the landslide, with the maximum value of 6–7 MPa. The dynamic earthquake load caused an incessant deformation of the landslide, resulting in the reduction of mechanical parameters, especially the shear strength on the sliding surface and the ratio of friction coefficient on sliding surface in kinematical and static conditions are no more than 0.35. DDA simulation considering the displacement-based parameter reduction has been developed in the original DDA code, and its results primarily reflect the evolvement process of a landslide under strong seismic loads.
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Hu, Huihua, Xing Zhang, Jianxin Qin, and Hang Lin. "Influence of Morphology Characteristics on Shear Mechanical Properties of Sawtooth Joints." Buildings 12, no. 7 (June 22, 2022): 886. http://dx.doi.org/10.3390/buildings12070886.
Full textAbstract:
The interface problem exists widely in building. Joints are interfaces of rock mass structures. To further study the influence of morphological characteristics on the shear mechanical properties of sawtooth joints, this paper prepared rock-like materials based on the similarity principle and carried out direct shear tests of sawtooth joints. The results showed that: (1) the peak shear displacement of joints first increases and then decreases with increasing normal stress, but the normal trend of stress during turning is different under different sawtooth angles. When the sawtooth angle of the joints is small, the decrease in shear stress between shear strength and residual shear strength is not obvious, and the rate of decrease is also small. (2) The shear strength of joints is positively correlated with normal stress. Using the Mohr–Coulomb criterion to analyze the shear strength of joints, it was found that the cohesion c and internal friction angle α of joints increased nonlinearly with increasing sawtooth angle, but their increasing trends were different. By introducing the function relation between cohesion, internal friction angle, and sawtooth angle into the classical shear strength equation, an empirical equation for the shear strength of joints was established in consideration of sawtooth angle. (3) There are two modes of shear failure for serrated joints: the “saw-toothed sliding gnawing failure mechanism” (SSG) and the “tensile fracture mechanism” (TFM). In the SSG, the shear failure mode of joints evolves in a slipping–gnawing–complete gnawing mechanism with increasing sawtooth angle and normal stress. The TFM mainly occurs at high sawtooth angles. This study provides a theoretical reference for the prediction and prevention of geological disasters.
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Tang, Xiao Song, Ying Ren Zheng, and Jian Ping Xin. "Experimental Study and Numerical Simulation on the Large-Sized Models of Micro Anti-Slide Piles." Advanced Materials Research 919-921 (April 2014): 670–77. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.670.
Full textAbstract:
Micro antislide pile is more and more widely used in the emergent repair of landslide. But systematic and complete understanding about its antislide and failure mechanism is still insufficient; in addition, the theoretical study lags far behind the practical application. Through largesized physical model experiment and numerical simulation, the paper analyses the failure mechanism and failure mode of micro antislide piles in soil slope. The experiment and numerical simulation prove the fine antislide effects of micro piles, which allows large displacement of sliding mass and can delay the collapse of slope effectively, so it is applicable for emergent repair. The deformation of micro antislide pile is “S” shape, which is the tensile failure and shearcompression failure of concrete by bending deformation. At the same time, tensileshear failure happens on the reinforced bars. The largest shear of pile is located on the sliding surface and all the largest bending moment is above the sliding surface. The bending moment on the first row of plies is the largest followed by the third row and that on the second row is the smallest.
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Xiang, Xing Hua, Zhi Yuan Li, and Xiao Ting Zhang. "Influence of Rainfall Infiltration on Landslide Treatment Engineering." Advanced Materials Research 709 (June 2013): 936–41. http://dx.doi.org/10.4028/www.scientific.net/amr.709.936.
Full textAbstract:
Rainfall infiltration can induce landslides and influence engineering treatment effects. With a landslide uncounted in expressway construction in Shanxi province as an example, the bad effect of water was analyzed. Based on changes in soil strength caused by rainfall infiltration and shear experiments of undisturbed and water-saturated sliding zone soil under several conditions, the calculation parameters of soil were determined. Distribution of the maximum principal stress and shear stress inside the supported landslide before and after the rain was calculated through FEM numerical simulation and then deformation and failure mechanism of landslide was analyzed; the results reveal that for the supported landslide, the principal stress is mainly caused by gravity before and after the rain, meanwhile infiltration can induce increase in instantaneous strain and dramatic change in maximum shearing stress which is focused on the sliding surface adjacent to the bedding plane. As mentioned above, the drainage of surface water and groundwater in landslide treatment can delay landslide deformation effectively.
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Sammonds, Peter R., Daniel C. Hatton, and Daniel L. Feltham. "Micromechanics of sea ice frictional slip from test basin scale experiments." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2086 (February 13, 2017): 20150354. http://dx.doi.org/10.1098/rsta.2015.0354.
Full textAbstract:
We have conducted a series of high-resolution friction experiments on large floating saline ice floes in an environmental test basin. In these experiments, a central ice floe was pushed between two other floes, sliding along two interfacial faults. The frictional motion was predominantly stick–slip. Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High-resolution measurements during a single stick–slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. This is slip-weakening behaviour. We have therefore characterized what we consider to be a key deformation mechanism in Arctic Ocean dynamics. In order to understand the micromechanics of sea ice friction, we have employed a theoretical constitutive relation (i.e. an equation for shear stress in terms of temperature, normal load, acceleration, velocity and slip displacement) derived from the physics of asperity–asperity contact and sliding (Hatton et al. 2009 Phil. Mag. 89 , 2771–2799 ( doi:10.1080/14786430903113769 )). We find that our experimental data conform reasonably with this frictional law once slip weakening is introduced. We find that the constitutive relation follows Archard's law rather than Amontons' law, with (where τ is the shear stress and σ n is the normal stress) and n = 26/27, with a fractal asperity distribution, where the frictional shear stress, τ = f fractal T ml w s , where f fractal is the fractal asperity height distribution, T ml is the shear strength for frictional melting and lubrication and w s is the slip weakening. We can therefore deduce that the interfacial faults failed in shear for these experimental conditions through processes of brittle failure of asperities in shear, and, at higher velocities, through frictional heating, localized surface melting and hydrodynamic lubrication. This article is part of the themed issue ‘Microdynamics of ice’.