scholarly journals Research on Shear Behavior of Sand–Structure Interface Based on Monotonic and Cyclic Tests

2021 ◽  
Vol 11 (24) ◽  
pp. 11837
Author(s):  
Pei Zhang ◽  
Shijia Ding ◽  
Kang Fei

In order to study the shear behavior of the interface between sand and structure, a series of shear tests were carried out using an HJ-1 ring shear apparatus (Nanjing, China). First, through the monotonic shear tests, the loose sand and dense sand were sheared at the steel interface with different roughnesses. The results showed that when the interface was relatively smooth, the shear stress–shear displacement curves of loose sand and dense sand both exhibit strain hardening characteristics. When the interface was rough, the dense sand showed strain softening. The initial shear stiffness of the sand–steel interface increased with the increase in normal stress, interface roughness, or sand relative density. Then, considering the influence of initial shear stress, through the cyclic shear test, this work analyzed the shape of the loading and unloading curves and the development law of cumulative normal deformation, and discussed the change of loading and unloading shear stiffness under different stress level amplitudes and the residual deformation generated during the cycle. The research results showed that loose sand and dense sand generally shrunk in volume during the cycle. The initial loading process was similar to the case of static loading. In the later dynamic loading process, the shear shrinkage per cycle was relatively small and continued to develop. Additionally, it was found that the unloading stiffness of the sand–steel interface is always greater than the initial loading stiffness. As the number of cycles increases, the loading stiffness increases, and it may eventually approach the unloading stiffness.

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Liu Xianshan ◽  
Li Man ◽  
Xu Ming ◽  
Kang Zhiyong

The hydrated shales under cyclic loading and unloading conditions are common for the shale reservoir development; corresponding mechanical properties and permeability evolution are very significant and should be deeply researched. Firstly, the experiments of the hydrated shales under the above conditions are discussed, showing that the peak strength is lower and corresponding permeability is higher for more days of hydrating treatment. Secondly, the damage theory is proposed to analyze the shale permeability evolution due to hydromechanical damage and get permeability variation under initial loading and unloading conditions, observing that the permeability in the loading process decreases with increasing confining pressure and increases in the unloading process with decreasing confining pressure; however, the former changes much greater than the latter considering the same confining pressure, indicating that the irreversible damage for the hydrated shales in this cyclic condition has resulted in obvious difference of the permeability. Furthermore, the curves between the permeability and confining pressure based on the experimental data are fitted as negative exponential functions under initial loading conditions and power functions under more cyclic loading conditions, showing that more loading process will change the permeability evolution model. However, the permeability while unloading changes smoothly and can be fitted as a power function with the confining pressure. And in addition, the loss ratio and recovery ratio of the permeability have been deeply researched under five cyclic loading and unloading conditions, thoroughly explaining the permeability decreasing variation with more cyclic processes. Finally, the sensitive coefficients of the permeability have been investigated to observe the largest coefficients under initial cyclic conditions and less and less with more cyclic processes, especially the coefficients while loading which are more sensitive to lower confining pressure and smaller while unloading, which is in accordance with the shale permeability loss and recovery variation, revealing the permeability evolution of the hydrated shale under complex extracted environment.


Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Baojian Li ◽  
Panpan Guo ◽  
Gaoyun Zhou ◽  
Zhe Wang ◽  
Gang Lei ◽  
...  

Sand elements in the natural or manmade field have often undergone initial static shear stresses before suffering cyclic loading. To explore the effect of static shear stress, a series of undrained cyclic triaxial tests were performed on dense and loose calcareous sand under different initial and cyclic shear stresses. The triaxial test results are used to describe the effect of static shear stress on the cyclic response of the calcareous sand with different relative density. Cyclic mobility, flow deformation, and residual deformation accumulation are the three main failure modes under varying static and cyclic shear stress levels. The cyclic resistance of dense sand is greater than that of loose sand, but the initial static stress has different effects on the cyclic resistance of the two kinds of sand. The dense sand owns a higher cyclic resistance with SSR increasing, while for the loose sand, 0.12 is the critical SSR corresponding to the lowest value of the cyclic resistance. The dense sand has more fast accumulation of dissipated energy, compared with loose sand. Additionally, an exponential relationship is established between static shear stress, relative density, and normalized energy density.


1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.


2019 ◽  
Vol 92 ◽  
pp. 16010
Author(s):  
Benjamin Cerfontaine ◽  
Jonathan Knappett ◽  
Michael Brown ◽  
Aaron Bradshaw

Plate and screw anchors provide a significant uplift capacity and have multiple applications in both onshore and offshore geotechnical engineering. Uplift design methods are mostly based on semi-empirical approaches assuming a failure mechanism, a normal and a shear stress distribution at failure and empirical factors back-calculated against experimental data. However, these design methods are shown to under- or overpredict most of the existing larger scale experimental tests. Numerical FE simulations are undertaken to provide new insight into the failure mechanism and stress distribution which should be considered in anchor design in dense sand. Results show that a conical shallow wedge whose inclination to the vertical direction is equal to the dilation angle is a good approximation of the failure mechanism in sand. This shallow mechanism has been observed in each case for relative embedment ratios (depth/diameter) ranging from 1 to 9. However, the stress distribution varies non-linearly with depth, due to the soil deformability and progressive failure. A sharp peak of normal and shear stress can be identified close to the anchor edge, before a gradual decrease with increasing distance along the shear plane. The peak stress magnitude increases almost linearly with embedment depth at larger relative embedment ratios. Although further research is necessary, these results lay the basis for the development of a new generation of design criteria for determining anchor capacity at the ultimate limiting state.


2017 ◽  
Vol 17 (10) ◽  
pp. 06017018 ◽  
Author(s):  
Vishwas N. Khatri ◽  
Jyant Kumar ◽  
Shamim Akhtar

2020 ◽  
Vol 44 (5) ◽  
pp. 20190471
Author(s):  
M. Konstadinou ◽  
A. Bezuijen ◽  
G. Greeuw ◽  
C. Zwanenburg ◽  
H. M. Van Essen ◽  
...  

2018 ◽  
Vol 26 (1) ◽  
pp. 9-18
Author(s):  
Dooyong Cho ◽  
Jinwoong Choi ◽  
Hoseong Jeong

When Perfobond Rib shear connectors are used as flexural materials in structures such as bridges, they show flexural shear behavior due to external force, rather than direct shear behavior. The aim of this study is thus to analyze the difference between both behaviors. First, we prepared a specimen to analyze direct shear behavior using Perfobond Rib shear connectors, analyzed the characteristics of behavior with a push-out test and proposed a formula of shear resistance assessment. Proposed formula shows a relatively good fit with less than 10% error. A flexural shear test was then conducted based on the result of the direct shear test. Based on the static flexural test it analyzed the flexural behavior and the flexural shear stress it calculated. Direct shear stress and EN 1994-1-1 to lead and be calculated, it compared the flexural shear stress and it analyzed in about the shear resistance stress which it follows in load direction. Finally, we compared both test results, and the comparison showed that the flexural shear stress is approximately 6% stronger than the direct shear stress.


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