Shear Slide Research Articles

Interlayer Shear Sliding Behaviors during the Fracture Process of Thick Sandstone Roof and Its Mechanism Leading to Coal Mine Tremors

To explore the causes of mine tremors in coal mines with sandstone roofs, a three-point bending loading experiment was designed for composite sandstone layers, and the fracture and interlayer shear slip characteristics of the composite sandstone layers were studied using optical measurement and acoustic emission techniques. The results show that the bending of the rock layers led to interlayer sliding deformation, while the fracturing greatly promoted interlayer sliding. The maximum interlayer slip accelerations during bending deformation and fracturing were 0.6 mm/s2 and 3.8 mm/s2, respectively. During the fracturing of the rock layers, the proportion of acoustic emission shear fracture events increased with the continuous occurrence of long-lasting and high-amplitude acoustic emission events. The mechanism of mine tremors in thick sandstone roofs is as follows: the increase in the area of the goaf causes rock bending deformation and fracturing, accompanied by interlayer shear slip, fracturing of the sandstone layer, and friction dislocation at the cementation surface of the adjacent sandstone layers, which jointly cause vibration of the roof.

A failure criterion for shale considering the anisotropy and hydration based on the shear slide failure model

A failure criterion fully considering the anisotropy and hydration of shale is essential for shale formation stability evaluation. Thus, a novel failure criterion for hydration shale is developed by using Jaeger’s shear failure criterion to describe the anisotropy and using the shear strength reduction caused by clay minerals hydration to evaluate the hydration. This failure criterion is defined with four parameters in Jaeger’s shear failure criterion (S1, S2, α and φ), three hydration parameters (k, ωsh and σs) and two material size parameters (d and l0). The physical meanings and determining procedures of these parameters are described. The accuracy and applicability of this failure criterion are examined using the published experimental data, showing a cohesive agreement between the predicted values and the testing results, R2 = 0.916 and AAREP (average absolute relative error percentage) of 9.260%. The error (|Dp|) is then discussed considering the effects of β (angle between bedding plane versus axial loading), moisture content and confining pressure, presenting that |Dp| increases when β is closer to 30°, and |Dp| decreases with decreasing moisture content and with increasing confining pressure. Moreover, |Dp| is demonstrated as being sensitive to S1 and being steady with decrease in the data set when β is 0°, 30°, 45° and 90°.

Experimental study on seismic behavior of reinforced concrete shear walls with low shear span ratio

Shear span ratio (SSR) is a key factor affecting the structural and seismic behavior of shear walls. Existing experimental studies on the seismic behavior of shear walls with SSR less than 1.0 are limited. In order to study the seismic behavior of squat reinforced concrete (RC) shear walls, 16 specimens (of which four specimens were subjected to coupled tension-shear force) with SSR of 0.5, 0.75, and 1.0 were fabricated and subjected to horizontal low-cycle repeated loading tests. The parameters considered in the test included the SSR, axial load ratio (ALR), and horizontal reinforcement ratio (HRR). The seismic behavior of the 16 squat RC shear wall specimens was investigated by analyzing their failure modes, hysteretic behaviors, and energy dissipation capacities. This study also assessed the validity of shear strength capacity formulae for shear walls with low SSR adopted in the design codes used currently in China, America, Canada and Europe. Five failure modes were observed in the 16 specimens, namely, diagonal compression-sliding (DCS) failure, diagonal compression (DC) failure, shear-bending (SB) failure, shear sliding (SS) failure, and tensile shear (TS) failure. For the specimens under compression, the failure mode of the specimens changed from shear failure to shear-bending failure with the increase in SSR. Also, the shear strength capacity was significantly reduced as SSR increased, while the deformation capacity and energy dissipation capacity increased significantly. The specimens under tension with SSR of 0.5 suffered TS failure. Vertical tension significantly decreased the shear strength capacity and energy dissipation capacity of the shear walls, however their ductility factor and ultimate displacement increased. The increase in ALR from 0.3 to 0.5 enhanced the shear strength capacity of the shear walls but the energy dissipation capacity reduced. With the increase in HRR, the shear strength capacity and energy dissipation capacity of the shear walls improved slightly. The shear strength capacities of shear walls assessed according to the four design codes were all conservative for the specimens suffering DC failure and DCS failure, while the opposite was true for the specimens with TS failure. For the specimens suffering SB failure, only the ACI 318-19 calculation results were not conservative compared to the test results.

Micromechanical Modeling of Unreinforced Masonry Arches Accounting for Flexural Hinges and Shear Slidings

ABSTRACT This paper investigates the structural response of unreinforced masonry arches subjected to asymmetrical vertical concentrated loads, by studying global force-displacement response curves and collapse mechanisms. The micromechanical modeling approach is adopted, which describes the detailed arrangement, geometry and mechanical properties of the masonry constituents. This is introduced in a 2D finite element procedure modified and enriched to describe masonry curved geometry and the occurring damage and friction mechanisms. Linear elastic behavior is assumed for bricks, whereas a damage-friction law is considered for the mortar to describe flexural and shear failure mechanisms. First, to prove the efficiency of the adopted model, the response of experimentally tested arches is numerically reproduced. Then, a parametric analysis is performed to analyze the effect of the geometric parameters on the global structural response. It is proved that, as the thickness/internal radius ratio increases, the failure mechanism moves from the formation of flexural hinges to shear sliding, leading to a more brittle response. Moreover, influence of relevant material parameters is investigated and the numerical outcomes are compared with those obtained by the classical limit analysis approach. It appears that the maximum predicted load generally exceeds the limit analysis collapse value, depending on the material properties mostly influencing the failure mechanisms.

1-g shaking table tests of precast horseshoe segmental tunnel: Experimental design, dynamic properties, deformation mode and damage pattern

A novel precast horseshoe segmental tunnel (PHST) structure was applied in the construction of the west extending project of Beijing Subway Line 6. The seismic performance of the PHST was one of the critical difficulties for the engineering project. A series of investigations were conducted to deal with the problem, including the 1-g shaking table model tests of the PHST buried in sand. In the present study, the experimental setup, construction of the PHST model (tube), dynamic properties of the soil-tube system, deformation mode and damage patterns of the tube were introduced. The preliminary results show that the tube had a very slight influence on the dynamic properties of the soil-tube system, which was consistent with the traditional learning. Under seismic motions with the precautionary intensity of the prototype site, the dynamic properties of the soil-tube system were not varied. The seismic responses of the tube were within the linear range. With the increasing seismic intensity, the predominant frequencies of the soil-tube system were firstly decreasing and then tended to be rather steady; meanwhile, the viscous damping ratio was firstly increasing and then rather steady. Under the excitations of the rare seismic motions, the non-linear responses of the tube were observed. The connection regions were damaged and tended to failures. Under the effects of the very rare motions, the thorough failures were observed at the connections. The tube was developed as a multi-hinge mechanism. The damage patterns at the connections were flexural damage and shear slide between segments. After the actions of strong motions, the tube kept horizontally expanding and vertically shrinking.

Experimental Study on Seepage Properties of Postpeak Fractured Rocks under Cyclic Loading-Unloading Confining Stress and Axial Stress

Excavation in rock masses always encounters safety problems from rock fracture seepage in water-rich areas, which needs to be paid much attention, especially for fractured rocks under complicated stress state. For this reason, the permeability of fractured sandstone and granite is experimentally investigated under cyclic loading-unloading confining stress and axial stress. The variation of permeability coefficient and seepage flow with increasing and decreasing the confining stress and axial stress are comprehensively analyzed. Results show that the changing patterns of permeability with loading-unloading cycles of confining stress for both fractured sandstone and granite are similar. The permeability is most sensitive to the initial loading-unloading stages. After several loading-unloading cycles, the confining stress has little effect on permeability. The seepage flow decreases as the confining stress is unloaded to the same level in the loading process, indicating a hysteresis effect on the recovery of seepage capacity. The seepage properties under cyclic loading-unloading the axial stress are quite different from those under the confining stress. The permeability of fractured sandstone is most sensitive to the first cycle of loading-unloading of axial stress. The irrecoverable shear slide between fractures under the axial stress causes dilatancy or contraction, which makes the permeability coefficient to consecutively decrease at the subsequent cycles. The permeability of granite first decreases during the first loading of axial stress, while this trend is disordered at the subsequent stages no matter loading or unloading the axial stress. This is because of the accumulation of breakage fragments between fractures, which further disturbs the seepage flow. These findings may be useful for further understanding the seepage properties of fractured granite and sandstone under complex loading-unloading history.

The Effect of Shear Sliding of Vertical Contraction Joints on Seismic Response of High Arch Dams with Fine Finite Element Model

The contraction joints of arch dams with and without shear keys are simplified to be with no‐slip condition and with relative sliding condition, respectively. Based on the Lagrange multiplier method, a contact model considering the manner of independent cantilever dead load type with no‐slip condition and relative sliding condition is proposed to model the nonlinearities of vertical contraction joins, which is special to the nonlinear analysis of arch dams considering the manner of dead load type. Different from the conventional Gauss iterative method, the strategy of the alternating iterative solution of normal force and tangential force is employed. The parallelization based on overlapping domain decomposition method (ODDM) and explicit message passing using distributed memory parallel computers is employed to improve the computational efficiency. An existing high arch dam with fine finite element model is analyzed to investigate the effect of shear sliding of vertical joints on seismic response of the arch dam. The result shows that the values of maximum principal tensile stress under relative sliding condition are significantly greater than those under no‐slip condition.

Unique interfacial reaction and so-induced change in mechanical performance of Sn–3.0Ag–0.5Cu/Cu solder joints formed during undercooled and eutectic liquid soldering processes

A novel technique is proposed to prepare Sn–3.0Ag–0.5Cu/Cu joints at three different processing temperatures, which are called undercooled liquid (UL, 213.0 °C), eutectic liquid (EL, 217.0 °C) and normal liquid (NL, 231.0 °C) soldering temperatures correspondingly, and each of them is lower than, equal to and higher than Sn–3.0Ag–0.5Cu solder’s melting point (217.0 °C), respectively. The interfacial reaction, intermetallic compound growth and mechanical performance of Sn–3.0Ag–0.5Cu/Cu joints formed during UL, EL and NL soldering processes were investigated systematically. Results show that for Sn–3.0Ag–0.5Cu solder as the undercooled liquid melt or eutectic liquid melt or normal liquid melt in the formation of joints, the thickness of interfacial intermetallic compound (IMC) layer in the joints increases with prolonging dwelling time. For three different liquid soldering processes, the change tendency of the interfacial IMC layer thickness is distinct. For joints formed at UL and EL temperatures, the excessive growth of primary Cu6Sn5 and interfacial IMC (mainly Cu6Sn5) can be suppressed during isothermally dwelling in the liquid state for more than 5 min. Ball shear test results show that solder joints formed at UL and EL temperatures have lower value of the maximum shear force (MSF) than those formed during the NL soldering process. For UL and EL types of joints, the fracture occurs either by shear slide fracture totally along the shear tool tip movement plane (i.e., in-plane shear slide fracture) or by shear slide fracture initially along the shear tool tip movement plane and afterwards shear deformation fracture in the solder matrix under the plane (i.e., out-of-plane shear slide and deformation mixed-mode fracture), while the fracture takes place in NL joints only by in-plane shear slide fracture mode.

EXPERIMENTS AND FEM MODELS ON SEMI-COMPOSITE BEHAVIOR OF SRC STRUCTURES

Analytical models were prepared and results from these models were compared with experimental results to confirm the adequate modeling of steel-reinforced concrete members used in rockfall-protection galleries or rock-sheds. Static loading tests of steel-reinforced concrete members (a girder and a slab) were conducted on a simply supported beam. The analytical models have different contact conditions to verify which condition can express a semi-composite behavior and shear slide. Three types of contact conditions were applied: normal, tied, and tiebreak contact. Tiebreak contact can express the occurrence of gaps by defining shear bond strength. Consequently, analytical models that applied tiebreak contact showed comparatively good agreement with experimental results. Analytical models that applied the tiebreak contact condition showed a correlation of 97% (girder) and 101% (slab) with the experimental results for the maximum load-carrying capacity. Therefore, considering that slippage occurs between different materials, the model is good for expressing the behavior of complicated structures such as steel-reinforced concrete members that are used as a rock-shed.

A method for fast safety screening of explosives in terms of crystal packing and molecular stability.

Safety prediction is crucial to the molecular design or the material design of explosives, and the predictions based on any single factor alone will cause much inaccuracy, leading to a desire for a method on multi-bases. The presented proposes an improved method for fast screening explosive safety by combining a crystal packing factor and a molecular one, that is, steric hindrance against shear slide in crystal and molecular stability, denoted by intermolecular friction symbol (IFS) and bond dissociation energy (BDE) of trigger linkage respectively. Employing this BDE-IFS combined method, we understand the impact sensitivities of 24 existing explosives, and predict those of two energetic-energetic cocrystals of the observed CL-20/BTF and the supposed HMX/TATB. As a result, a better understanding is implemented by the combined method relative to molecular stability alone, verifying its improvement of more accurate predictions and the feasibility of IFS to graphically reflect molecular stacking in crystals. Also, this work verifies that the explosive safety is strongly related with its crystal stacking, which determines steric hindrance and influences shear slide.

Evaluation of storm wave-induced silty seabed instability and geo-hazards: A case study in the Yellow River delta

Models based on the theoretical framework of soil mechanics are presented to evaluate storm wave-induced silty seabed instability and geo-hazards through a case study in the Yellow River delta. First, the transient and residual mechanisms of wave-induced pore pressure are analyzed. Three typical models (i.e., elastic model, pore pressure development mode and elasto-plastic model) are proposed to calculate wave-induced stresses in the seabed. Next, mechanisms and calculation methods of wave-induced seabed instability modes such as scour, liquefaction, seepage instability and shear slide are proposed. Typical results of storm wave-induced excess pore pressure and seabed instability are given and relevant discussions are made. At last, the formation mechanism of geo-hazards in the Yellow River delta is analyzed based on the proposed mechanism and calculated results. Results and analysis indicate that both transient and residual mechanisms are important to storm wave-induced response of silty seabed and hence the elasto-plastic model is more appropriate. Complete liquefaction does not happen, while other types of instability occur mostly within 2–6m under the seabed surface. Wave-induced scour, seepage instability and shear slide are all possible instability modes under the 1-year storm waves, and scour is predominant for the 50-year storm waves. The formation mechanism of geo-hazards such as shallow slide and storm wave reactivation, pockmarks, silt flow and gully, disturbed stratum and hard crust in the Yellow River are well explained based on the proposed mechanisms and calculated results of storm wave-induced silty seabed instability.

Stability analysis of crack slope considering nonlinearity and water pressure

The soil slopes tend to induce the appearance of tension cracks at the top of slope under various factors, which poses an adverse impact on slope stability. Based on Power-Law nonlinear failure criterion, kinematical approach is adopted in this paper to investigate the effects of underground water and vertical tension cracks on stability of slopes. Notice that the tension cracks tend to propagate vertically, and thus a novel failure mechanism composed by the tension crack and logarithmic spiral shear slide plane is postulated. Theoretically, the worst position of crack propagation makes the stability factor minimal, and the failure surfaces can be obtained under different conditions through optimization. According to the proposed mechanism and nonlinear Mohr-Coulomb strength criterion, the stability factor and safety coefficient of slopes are derived. Subsequently, sensitivity analysis with respect to specific examples is conducted to analyze the influence of tension cracks, nonlinear strength parameters and pore water pressure on the slope stability. The results indicate that slope stability weakens gradually at the presence of tension cracks, and the changing degree is more evident with the increase of the slope angle. Meanwhile, nonlinear parameters have more significant impact on the safety factor with the decreasing value of the slope angle. However, the bigger the slope angle, the greater the height of tension cracks, and therefore the more obvious influence of pore water pressure on slope stability. When the slope angle approaches to be vertical, the height of tension cracks increases sharply. As a matter of fact, the height of tension cracks is highly related to geometrical conditions, strength parameters and water effect, which build a mutual relationship to determine slope stability.

Research on Shear Bearing Capacity and Sliding Performance of Modified Mortar Isolation Sliding Layer for Rural Construction

This paper studied the cracking and sliding working performance of modified mortar isolation sliding layer in a sliding isolation technique suitable for the rural construction. The technology realizes the sliding isolation by setting the up and down ring beams at the outdoor ground bonded by low-grade modified mortar and the shear deformation limit by setting rubber beams. Through the compression-shear tests on different grades of modified mortar which mixed with graphite and talc, the horizontal shear strength of different modified mortars have been acquired. the friction performances of different modified mortars have been Compared by the friction coefficient tests,. Through calculating, the sliding performances of modified mortar layer under the seismic actions of different seismic fortification intensities have been achieved. The research shows that the modified mortar sliding layer has well sliding performance, and it is able to meet the demand of sliding isolation of the rural construction.

Research on chip formation parameters of aluminum alloy 6061-T6 based on high-speed orthogonal cutting model

Chip formation, an important aspect of the high-speed cutting (HSC) mechanism, is generally accepted as the result of shear deformation in the shear zone and tool-chip friction. In order to accurately study chip formation process in HSC, a theoretical model for the high-speed orthogonal cutting of aluminum alloy 6061-T6 was built, which can be used to calculate the important parameters of chip formation, such as shear angle, friction angle, length of shear plane, tool-chip contact length, and width of the first shear zone. A series of orthogonal cutting experiments, with the YG6 carbide tool and on a wide range of cutting speed (100–1,900 m/min) and feed (0.06–0.15 mm/r), were performed in order to obtain the parameters required in the model, including the cutting forces, the chip thickness, and the shear slip distance. Seven kinds of chip formation parameters were obtained with different cutting parameters in the experiment, and the built theoretical model can well explain the formation process and the morphology characteristics of these chips, which proves that the combined method of theoretical model and orthogonal cutting experiment is an effective and easy approach to obtain the parameters of chip formation in HSC, avoiding the cutting speed limitation and the safety risk in quick-stop test. Within the range of parameters set in the experiments, the chip mainly appears to be continuous chip, curling chip, or discontinuous chip. And the chip thickness, friction angle, length of shear plane, and width of the first shear zone decrease with the increase of the cutting speed; meanwhile, the shear slide distance and shear angle increase.

FATURES OF ORIGIN AND DEVELOPMENT OF TECHNOGENIC LANDSLIDES ARE IN DISTRICT OF BALAKLAVA (SOUTH-WEST CRIMEA)

Практично всі сучасні зсувні ділянки в околицях Балаклави приурочені до грабенів. Найбільший у Криму зсув утворився в результаті техногенного впливу.

Understanding the desensitizing mechanism of olefin in explosives: shear slide of mixed HMX-olefin systems

We simulated the shear slide behavior of typical mixed HMX-olefin systems and the effect of thickness of olefin layers (4-22 Å) on the behavior at a molecular level by considering two cases: bulk shear and interfacial shear. The results show that: (1) the addition of olefin into HMX can reduce greatly the shear sliding barriers relative to the pure HMX in the two cases, suggesting that the desensitizing mechanism of olefin is controlled dominantly by its good lubricating property; (2) the change of interaction energy in both systoles of shear slide is strongly dominated by van der Waals interaction; and (3) the thickness of olefin layers in the mixed explosives can influence its desensitizing efficiency. That is, the excessive thinness of olefin layers in the mixed explosive systems, for example, several angstroms, can lead to very high sliding barriers.

Shear Sliding Stress at the Interface of Members of a Japanese-style Bow

Shear Sliding Stress at the Interface of Members of a Japanese-style Bow

Numerical Simulation of Rock Burst in Circular Tunnels Under Unloading Conditions

Rock burst in a circular tunnel under high in-situ stress conditions was investigated with a numerical method coupled the rock failure process theory (RFPA) and discontinuous deformation theory (DDA). Some numerical tests were carraied out to investigate the failuer patterns of circular tunnel under unloading conditions. Compared the results under loading conditions, the shapes of failure zones are more regular under the unloading conditions. The failure patterns in the same type of rock mass are clearly different because of non-homogeneity of the rock material. The extension of cracks shows some predictability with an increasing of in-situ stress. When the homogeneity index of rocks (m) is either relatively high or low and lateral pressure coefficients (λ) is high, the number of regular shear slide cracks decreases and the probability of a rock burst also becomes lower. Our numerical simulation results show that the stability of surface rock and the natural bedding stratification of rock material greatly affect rock bursts. Installing bolts with due diligence and suitably can effectively prevent rock bursts. However, it is not effective to control rock bursts by releasing the strain energy with normal pre-boreholes.

Pressure Dependence of Shear Strength and Sliding Friction

Pressure Dependence of Shear Strength and Sliding Friction