Strain degradation of saturated clay under cyclic loading

2001 ◽  
Vol 38 (1) ◽  
pp. 208-212 ◽  
Author(s):  
Jian Zhou ◽  
Xiaonan Gong
Keyword(s):  
Mathematical Model ◽  
Cyclic Loading ◽  
Stress Ratio ◽  
Axial Strain ◽  
Influence Factors ◽  
Cyclic Stress ◽  
Point Of View ◽  
Triaxial Tests ◽  
Cyclic Stress Ratio ◽  
Saturated Clay

Soil degradation is studied from the point of view of cyclic axial strain through stress-controlled triaxial tests on Hangzhou normally consolidated clay. Different influence factors on strain, such as cyclic stress ratio, overconsolidation ratio, and frequency, are studied. Degradation index is redefined according to the tests. A mathematical model for strain degradation is presented and verified.Key words: cyclic loading, saturated clay, strain degradation, mathematical model.

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

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.

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

2020 ◽  
Vol 8 (4) ◽  
pp. 287 ◽  
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.

Laboratory study on subgrade fluidization under undrained cyclic triaxial loading

2020 ◽  
Vol 57 (11) ◽  
pp. 1767-1779 ◽  
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.

scholarly journals Shear modulus and damping ratio of a nonplastic silt at large shear strains

2019 ◽  
Vol 92 ◽  
pp. 08007
Author(s):  
Alper Sezer ◽  
Eyyub Karakan ◽  
Nazar Tanrinian
Keyword(s):  
Shear Modulus ◽  
Relative Density ◽  
Shear Strain ◽  
Stress Ratio ◽  
Damping Ratio ◽  
Cyclic Stress ◽  
Triaxial Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Cyclic Stress Ratio

Site response analyses and solution of dynamic soil-structure interaction problems need determination of variation of shear modulus and damping ratio with shear strain. Since many studies in literature concern evaluation of behavior of sands and silty sands, a series of cyclic triaxial tests were performed to determine the variation of shear modulus and damping ratio of a nonplastic silt with shear strain. Stress controlled cyclic triaxial tests on silt specimens of initial relative densities ranging among 30%, 50% and 70% were performed. Tests were carried out on identical samples under different CSR levels, and the confining pressure was selected as 100 kPa. Variation of shear modulus and damping ratio of silts with cyclic stress ratio amplitude, relative density and number of cycles were investigated. It was understood that soil relative density and cyclic stress ratio amplitude has a significant influence on shear modulus and damping ratio of silts. It was also observed that, as the cyclic stress ratio amplitude is increased, greater shear modulus and lower damping ratio values were obtained.

Effects of frequency and cyclic stress ratio on creep behavior of clay under cyclic loading

2016 ◽  
Vol 35 (2) ◽  
pp. 281-291 ◽  
Author(s):  
Huayang Lei ◽  
Jingjin Liu ◽  
Min Liu ◽  
Zhipeng Zhang ◽  
Mingjing Jiang
Keyword(s):  
Cyclic Loading ◽  
Creep Behavior ◽  
Stress Ratio ◽  
Cyclic Stress ◽  
Cyclic Stress Ratio

Effects of Vibration Frequency on Dynamic Properties of Undisturbed Structural Marine Soil

2012 ◽  
Vol 193-194 ◽  
pp. 925-930
Author(s):  
Xiao Ling Chen ◽  
Dong Li ◽  
Rui Min Liu
Keyword(s):  
Pore Pressure ◽  
Vibration Frequency ◽  
Stress Ratio ◽  
Dynamic Strength ◽  
Cyclic Stress ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Threshold Values ◽  
Cyclic Stress Ratio ◽  
Common View

Due to influence by many factors like soil classification, viscosity property and vibration frequency, there is no common view yet about the effect of frequency on dynamic pore pressure and characteristics. In order to study the development of pore pressure, strain and dynamic strength of Hangzhou Bay undisturbed structural silty clay under different vibration frequencies, cyclic triaxial tests were performed. The test results indicate that the frequency has little influence on pore pressure and strain when they didn’t reach the threshold values, but once they exceeded the threshold values the frequency will has strong influence. There is critical cyclic stress ratio when the cyclic stress ratio has not reached that value, the frequency has no influence on dynamic strength. For the given cycles, the higher the frequency is, the bigger the dynamic strength is. And with the increment of frequency, the influence on dynamic is decreased eventually.

Application of the R-Curve Concept to Fatigue Crack Growth

1978 ◽  
Vol 100 (4) ◽  
pp. 416-420 ◽  
Author(s):  
D. P. Wilhem ◽  
M. M. Ratwani
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Extension ◽  
Stress Ratio ◽  
Cyclic Stress ◽  
Crack Growth Resistance ◽  
Resistance Curve ◽  
Cyclic Stress Ratio ◽  
Wide Range

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.

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

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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