Automatic Static and Cyclic Shear Testing Machine under Constant Normal Stiffness Boundary Conditions

Niktabar, S. M. Mahdi; Rao, K. Seshagiri; Shrivastava, Amit Kumar

doi:10.1520/gtj20170083

Cited by 6 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An automatic static and cyclic shear testing machine (Niktabar et al, 2018 [ 41 ]) under different boundary conditions was used to conduct cyclic shear tests under CNL and CNS with varying normal stiffness. The stiffness was provided by vertical hydraulic pressure based on joint dilation and servo valve feedback programming on the software of the apparatus.…”

Section: Experimental Methodologymentioning

confidence: 99%

Effect of Varying Normal Stiffness on Soft Rock Joints under Cyclic Shear Loads

et al. 2023

Self Cite

View full text Add to dashboard Cite

The evaluation of changes in shear resistance on soft (or weathered) rock joints under cyclic shear loads with constant normal load (CNL) and constant normal stiffness (CNS) significantly contributes to increasing the safety and stability of rock slopes and underground structures. In this study, a series of cyclic shear tests were conducted on simulated soft rock joints with regular (15°-15°, 30°-30°) and irregular (15°-30°) asperities under different normal stiffnesses (kn). The results indicated that the first peak shear stress increases with the increase in kn up to the normal stiffness of the joints (knj). Beyond knj, no significant change was observed in the peak shear stress. The difference in peak shear stress between regular (30°-30°) and irregular joints (15°-30°) increases as kn increases. The minimum difference of peak shear stress between regular and irregular joints was observed (8.2%) under CNL and the maximum difference was found (64.3%) on knj under CNS. The difference in peak shear stress between the first and subsequent cycles significantly increases as both the joint roughness and kn increases. A new shear strength model is developed to predict peak shear stress of the joints for different kn and asperity angles under cyclic shear loads.

show abstract

Section: Experimental Methodologymentioning

confidence: 99%

Effect of Varying Normal Stiffness on Soft Rock Joints under Cyclic Shear Loads

et al. 2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…Automatic static and cyclic shear testing machine (Niktabar et al 2018) was utilized in this experiments (Fig. 2).…”

Section: Shear Machine and Testing Proceduresmentioning

confidence: 99%

Effect of Load Frequency and Amplitude of Displacement on Soft Rock Joints under Cyclic Shear loads

Niktabar

Rao

Shrivastava

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

A series of cyclic shear tests was conducted on soft synthetic rock joints with 30°- 30° asperities. Large scale shear apparatus was used in the experiments to investigate effects of shear load frequency and amplitude of displacement on the joint behaviour. Varying load frequencies (0.01, 0.05 and 0.1 Hz,) and displacement amplitudes (±4, ±6, and ±8 mm) for three different normal stresses (0.1, 0.5 and 1 MPa) were applied. The results indicated that the first peak shear stress on the joint is significantly influenced by the frequency of cyclic shear load and subsequent peaks of shear stress are largely influenced by the amplitude of displacement. Reduction in peak shear stress at higher frequency of load is greater than the reduction at lower frequency of load under cyclic movements. Shear mechanism on the joint asperities at low normal stress demonstrate asperity diminishing does not depend on load direction at high frequency. Whereas, at low frequency of loads, it depends on direction of starting cyclic shear load. Low amplitude of displacement has no effect on asperity deformation under cyclic loads. As the amplitude rises, the diminishing of asperities increases significantly. Shear mechanism and asperity diminishing at low normal stress is similar for the both higher amplitude of displacement and lower frequency of load. Comparison of shear strength envelopes indicated an opposite behaviour of the joint at varying load frequencies and displacement amplitudes.

show abstract

“…Jafari et al [ 40 ] conducted cyclic shear tests on artificial joint interfaces to analyze the influence of shear cycle times and normal stress. Mirzaghorbanali et al [ 41 , 42 ], and Niktabar et al [ 43 ] carried out a series of cyclic shear tests under constant normal stiffness boundary conditions to explore the influence of initial normal stress and shear rate. Niktabar and Rao [ 43 ] developed a new type of large servo-controlled direct shear testing machine, on which the cyclic shear tests of different shear load frequency, amplitude, and normal stiffness under constant normal stiffness and constant normal stress boundary conditions can all be realized.…”

Section: Introductionmentioning

confidence: 99%

“…Mirzaghorbanali et al [ 41 , 42 ], and Niktabar et al [ 43 ] carried out a series of cyclic shear tests under constant normal stiffness boundary conditions to explore the influence of initial normal stress and shear rate. Niktabar and Rao [ 43 ] developed a new type of large servo-controlled direct shear testing machine, on which the cyclic shear tests of different shear load frequency, amplitude, and normal stiffness under constant normal stiffness and constant normal stress boundary conditions can all be realized. Liu and Dai [ 44 ] revealed the influences of loading frequency, maximum stress, and amplitude on the mechanical properties of rock interface through laboratory tests.…”

Section: Introductionmentioning

confidence: 99%

Apparent Deterioration Law and Shear Failure Mode of Rock–Mortar Interface Based on Topography-Sensing Technology

et al. 2023

View full text Add to dashboard Cite

As an advanced spatial technology, topography-sensing technology is comprehensive, macroscopic, and intuitive. It shows unique advantages for rock structure interpretation and has important guiding significance for the research of the shear performances of rock–mortar interface under cyclic load in rock mass engineering. In this paper, cyclic shearing tests combined with the shear surface topography-sensing technology are employed to investigate the evolution characteristics of the interface morphology and the strength deterioration of the rock–mortar interface. Primarily, mortar and three types of rocks are used to prepare different rock–mortar interfaces, which are then applied to cyclic shear loading under two constant normal stresses. Subsequently, the shear strength degradation and dilatancy characteristics of rock–mortar interfaces with varying shear times are discussed. In addition, on the basis of the non-contact three-dimensional topography-sensing technology, the apparent three-dimensional point–cloud coordinate information of rock–mortar interface before and after each shear loading is obtained, and the apparent three-dimensional topography parameters of rock–mortar interface are calculated, according to which the influences of normal stress and lithology on the topography of interface subjected to cyclic shearing loading are analyzed.

show abstract

Automatic Static and Cyclic Shear Testing Machine under Constant Normal Stiffness Boundary Conditions

Cited by 6 publications

References 12 publications

Effect of Varying Normal Stiffness on Soft Rock Joints under Cyclic Shear Loads

Effect of Varying Normal Stiffness on Soft Rock Joints under Cyclic Shear Loads

Effect of Load Frequency and Amplitude of Displacement on Soft Rock Joints under Cyclic Shear loads

Apparent Deterioration Law and Shear Failure Mode of Rock–Mortar Interface Based on Topography-Sensing Technology

Contact Info

Product

Resources

About