Cyclic strength of loose anisotropically-consolidated calcareous sand under standing waves and assessment using the unified cyclic stress ratio

Crack growth resistance for both static (rising load) and for cyclic fatigue crack growth has been shown to be a continuous function over a range of 0.1 μm to 10 cm in crack extension for 2024-T3 aluminum. Crack growth resistance to each fatigue cycle of crack extension is shown to approach the materials ordinary undirectional static crack resistance value when the cyclic stress ratio is zero. The fatigue crack extension is averaged over many cycles and is correlated with the maximum value of the crack tip stress intensity, Kmax. A linear plot of crack growth resistance for fatigue and static loading data shows similar effects of thickness, stress ratio, and other parameters. The effect of cyclic stress ratio on crack growth resistance for 2219 aluminum indicates the magnitude of differences in resistance when plotted to a linear scale. Prediction of many of these trends is possible using one of several available crack growth data correlating techniques. It appears that a unique resistance curve, dependent on material, crack orientation, thickness, and stress/physical environment, can be developed for crack extensions as small as 0.076 μm (3 μ inches). This wide range, crack growth resistance curve is seen of immense potential for use in both fatigue and fracture studies.

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Experimental Study on the Combined Effect of Cyclic and Static Loads on the Mechanical Properties of the Saturated Soft Clay Material

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.723.843 ◽

2016 ◽

Vol 723 ◽

pp. 843-848

Author(s):

Yi Wei ◽

Ying Zhu ◽

Jing Ni

Keyword(s):

Mechanical Properties ◽

Cyclic Load ◽

Stress Ratio ◽

Axial Strain ◽

Soft Clay ◽

Cyclic Stress ◽

Excess Pore Pressure ◽

Static Loads ◽

Cyclic Stress Ratio ◽

Excess Pore

The combined effect of cyclic and static loads on the mechanical properties of the soft clay was experimentally investigated by conducting undrained cyclic triaxial tests on Shanghai clay. The results show that an increment in either static or cyclic load increases excess pore pressures and axial strains. For a given value of combined cyclic and static loads, the mechanical properties of the soft clay are more sensitive to the cyclic load. Furthermore, the accumulated excess pore pressure and axial strain for a larger cyclic stress ratio and a lower combined stress ratio might overcome that for a lower cyclic stress ratio and a higher combined stress ratio. The mechanical properties of the soft clay after the cyclic load was unloaded were also discussed. It was observed that the excess pore pressure and axial strain under the static load alone decrease gradually with time. The trend of them largely depends on the ratio of cyclic load to static load.

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Experimental and Estimation Studies of Resilient Modulus of Marine Coral Sand under Cyclic Loading

Journal of Marine Science and Engineering ◽

10.3390/jmse8040287 ◽

2020 ◽

Vol 8 (4) ◽

pp. 287 ◽

Cited By ~ 3

Author(s):

Shao-Heng He ◽

Qiong-Fang Zhang ◽

Zhi Ding ◽

Tang-Dai Xia ◽

Xiao-Lu Gan

Keyword(s):

Cyclic Loading ◽

South China Sea ◽

Effective Stress ◽

South China ◽

Stress Ratio ◽

Resilient Modulus ◽

Cyclic Stress ◽

Marine Transportation ◽

Cyclic Stress Ratio ◽

Coral Sand

Coral sand is an important filler resource that can solve the shortage of terrestrial fillers in coastal areas. Recently, the foundations of many infrastructures in the South China Sea have been built with coral sand as fillers, which have been subjected to wave and traffic cyclic loads. Resilient modulus (Mr) is an important design parameter in marine engineering, but there are few studies on the resilient modulus response of coral sand under cyclic loading. A series of drained cyclic triaxial tests were carried out to investigate the effects of the initial mean effective stress (p0) and cyclic stress ratio (ζ) on the resilient modulus response of the coral sand from the South China Sea. The change of fractal dimension (αc) can reflect the rule of particle breakage evolution. The αc of coral sand shows a tendency of almost maintaining stable and then increasing rapidly with the increase of mean effective stress p0 under each cyclic stress ratio ζ. There is a threshold of p0, when the p0 exceeds this threshold, αc will increase significantly with the increase of p0. The increase of p0 has a beneficial effect on the improvement of the Mr, while the increase of ζ has both beneficial and detrimental effects on the improvement of the Mr. A new prediction model of the Mr considering particle breakage was established, which can better predict the Mr of coral sand in the whole stress interval. The research results can provide guidance for the design of marine transportation infrastructures, which can promote the development of marine transportation industry and energy utilization.

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Laboratory study on subgrade fluidization under undrained cyclic triaxial loading

Canadian Geotechnical Journal ◽

10.1139/cgj-2019-0350 ◽

2020 ◽

Vol 57 (11) ◽

pp. 1767-1779 ◽

Cited By ~ 4

Author(s):

Buddhima Indraratna ◽

Mandeep Singh ◽

Thanh Trung Nguyen ◽

Serge Leroueil ◽

Aruni Abeywickrama ◽

...

Keyword(s):

Stress Ratio ◽

Confining Pressure ◽

Cyclic Stress ◽

Triaxial Tests ◽

Loading Conditions ◽

Cyclic Triaxial ◽

Cyclic Stress Ratio ◽

Upward Migration ◽

Efficient Operation ◽

Mud Pumping

A long-term issue that has hampered the efficient operation of heavy-haul tracks is the migration of fluidized fines from the shallow soft subgrade to the overlying ballast, i.e., mud pumping. This paper presents a series of undrained cyclic triaxial tests where realistic cyclic loading conditions were simulated at low confining pressure that is typical of shallow subgrade beneath a ballast track. Subgrade soil specimens with a low-plasticity index collected from a field site with recent history of mud pumping were tested at frequencies from 1.0 to 5.0 Hz and a cyclic stress ratio (CSR) from 0.1 to 1.0. The experimental results indicate that under adverse loading conditions of critical cyclic stress ratio (CSRc) and frequency, there is upward migration of moisture and the finest particles towards the specimen top and this causes the uppermost part of the soil specimen to soften and fluidize. Conversely, a smaller value of CSR tends to maintain stability of the specimen despite the increasing number of loading cycles. It is noteworthy that for any given combination of CSR and frequency, the relative compaction has a significant influence on the cyclic behaviour of the soil and its potential for fluidization.

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Experimental Study on Strength Weakening of Silty Soil of Subaqueous Yellow River Delta Under Cyclic Loadings

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 1 ◽

10.1115/omae2010-20769 ◽

2010 ◽

Author(s):

Huixin Liu ◽

Guohui Xu ◽

Qingpeng Zhao ◽

Xin Wang ◽

Yueqian Yu

Keyword(s):

Stress Ratio ◽

Yellow River ◽

Yellow River Delta ◽

Cyclic Stress ◽

River Delta ◽

Engineering Structures ◽

Cyclic Stress Ratio ◽

Cyclic Shear ◽

Silty Soil ◽

Critical Cyclic Stress Ratio

Silty soil seabed of Yellow River Delta is prone to sliding and liquefaction, which usually leads to geological hazards including landslides of seabed and failures of marine structures. The failure of silty soil is closely correlated with its strength change induced by wave actions. In this paper, silty soil samples of various clay contents were prepared, and cyclic triaxial experiments modeling wave actions were carried out on the samples to study the relationship between cyclic shear stress and number of cycles of silty soil taken from Subaqueous Yellow River Delta. Research results indicated that there existed a critical value in the cyclic stress exerting on the soil; the cyclic stress could cause failure of soil only when it’s value was higher than that of the critical stress; in this paper, critical cyclic stress ratio was defined as Kcr = ((σd+σ1)/σ3)cr, where Kcr is critical cyclic stress ratio, σd is axial pressure, σ1 is cyclic stress, σ3 is confining pressure. For the sake of the safety of design and construction of marine engineering structures, 1.30 was taken as the critical cyclic stress ratio of remolded silty soil in the Yellow River Delta, and 1.40 as that of the undisturbed silty soil. Also the results show that the dynamic strength weakening of silty soil followed the rule of power function attenuation. In addition, cyclic loading vibration experiments in a soil tank were carried out to study the weakening law of shear strength and penetration resistance with the variation of oscillation times.

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Experimental Study on the Fatigue Properties and Reliability for the Steel of Elastic Oil Sump

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.300-301.1377 ◽

2013 ◽

Vol 300-301 ◽

pp. 1377-1380

Author(s):

Bin Li ◽

Zong De Liu ◽

Peng Duan

Keyword(s):

Large Scale ◽

Stress Ratio ◽

Cyclic Stress ◽

Probabilistic Methods ◽

Life Assessment ◽

Fatigue Properties ◽

Test Results ◽

Design Data ◽

Cyclic Stress Ratio ◽

Fatigue Design

The elastic oil sump is commonly used as support parts in large-scale thrust bearing. It often operates under fluctuating load conditions during service. So, fatigue analysis of the material of the elastic oil sump is of great significance. In order to obtain the fatigue design data of the material of the elastic oil sump, the systematic tests on uniaxial tension-compression fatigue at room temperature are made. The fatigue limits and the fatigue life curves of the steel of the elastic oil sump are determined at different cyclic stress ratio. The P-S-N equations are calculated by the probabilistic methods. The test results provide a theoretical basis for the safety of life assessment of the elastic oil sump.

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Cyclic Degradation Characteristics of Undisturbed Soft Clay considering Anisotropy

Advances in Materials Science and Engineering ◽

10.1155/2021/3978415 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Miaomiao Sun ◽

Jiangang Yu ◽

Shaoheng He ◽

Zhi Ding

Keyword(s):

Plastic Strain ◽

Stress Ratio ◽

Soft Clay ◽

Stress Path ◽

Cyclic Stress ◽

Loading Frequency ◽

Degradation Index ◽

Cyclic Stress Ratio ◽

Stress Ratios ◽

Logarithmic Relationship

The stress-strain characteristics of soil depend primarily on the previous stress history and stress path, thus related to both the stress magnitude and direction. To have a better understanding of the response of soft clay under heart-shaped stress paths, 18 cyclic hollow cylinders tests were performed on undisturbed Hangzhou soft clay under different cyclic stress ratios, deviatoric consolidation ratios (K0), and loading frequencies. The result shows that as the vertical dynamic stress amplitude, K0 value, and loading frequency increase, the degradation index gradually decreases. Moreover, the degradation index of the soil under the cyclic torsion shear (CTS) test is always higher than that under the cyclic triaxial (CT) test. The increase in the amplitude of the cyclic stress ratio (CSR), K0 value, and the decrease in the loading frequency will promote the initial accumulative plastic strain and accelerate the failure rate of the soil sample; it shows that the effects of cyclic stress ratio amplitude, deviatoric consolidation ratios K0, and loading frequency on the accumulative plastic deformation of soil cannot be ignored. On the basis of the test results, a logarithmic relationship between the degradation index and the loading frequency is determined. A new empirical formula of accumulative plastic strain degradation of soft clay has been established, and its accuracy has been further verified by test data. The research results can provide theories for predicting and calculating the long-term settlement and deformation of clay foundation.

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