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.

scholarly journals Experimental Study on the Effects of Initial Shear Stress and Vibration Frequency on Dynamic Strength of Saturated Sands

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Jian Zhang ◽  
Jiuting Cao ◽  
Sijie Huang
Keyword(s):  
Shear Stress ◽  
Internal Friction ◽  
Vibration Frequency ◽  
Stress Ratio ◽  
Dynamic Strength ◽  
Friction Angle ◽  
Cyclic Stress ◽  
Internal Friction Angle ◽  
Shear Stresses ◽  
Cyclic Stress Ratio

The cyclic triaxial system is used to investigate the effects of confining pressure, initial shear stress, cyclic stress ratio, and vibration frequency on the dynamic strength characteristics of saturated sand in the Wenchuan area. Results show that when the vibration frequency is constant, the dynamic strength of sand increases with the increase of the consolidation ratio. However, when the consolidation ratio exceeds a certain value, the dynamic strength of sand decreases or increases slowly. The dynamic internal friction angle first increases and then decreases with the increase of consolidation ratio, and the dynamic internal friction angle under different initial shear stresses differs by a maximum of about 12%. When the failure cycles are constant, the dynamic strength and the dynamic internal friction angle of the sand increase with the increase of vibration frequency, and the dynamic internal friction angle at different frequencies differs by a maximum of about 7%. When the cyclic stress ratio is constant, the higher the vibration frequency, the greater the cycles required to achieve the failure. As the cyclic stress ratio decreases, the influence of the vibration frequency on the failure cycles is gradually reduced.

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.

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.

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.

scholarly journals Experimental Study on the Deformation and Strength Characteristics of Saturated Clay under Cyclic Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Jian Zhang ◽  
Yangguang Sun ◽  
Jiuting Cao
Keyword(s):  
Shear Stress ◽  
Vibration Frequency ◽  
Failure Strain ◽  
Dynamic Strength ◽  
Cyclic Stress ◽  
Strength Characteristics ◽  
Dynamic Strain ◽  
Cyclic Stress Ratio ◽  
Saturated Clay ◽  
Deformation And Strength Characteristics

The deformation and strength characteristics of saturated clay are studied through a cyclic triaxial test of clay in the Wenchuan earthquake area. Specifically, the effects of cyclic stress ratio, initial shear stress, and vibration frequency on the dynamic characteristics of saturated clay are analysed. Results show a failure strain in the dynamic strain development of saturated clay. Before the failure strain, the dynamic strain of soil develops slowly. After the failure strain, the soil strain increases sharply and leads to failure. Under the same confining pressure, the failure strain produced by different cyclic stress ratios has a linear relationship with the failure frequency. The dynamic strain development curve of saturated clay can be simplified to failure, transition, and stability types, which are mainly affected by the cyclic stress ratio. Initial shear stress and vibration frequency have significant effects on the deformation and strength characteristics of saturated clay. The larger the initial shear stress or the lower the vibration frequency is, the more sufficient the dynamic strain of soil develops and the fewer the number of cycles required to reach the same dynamic strain. Under the same number of cycles, the larger the initial shear stress or the lower the vibration frequency, the smaller the dynamic stress required to cause soil failure and the lower the dynamic strength of the soil. A turning point exists in the dynamic strength curve of clay. The smaller the initial shear stress or the higher the vibration frequency, the smoother the curve after the turning point and the smaller the tangent slope.

Cumulative Strain Behaviour of Saturated Clay Under Transit Cyclic Loading

2011 ◽  
Vol 422 ◽  
pp. 409-415
Author(s):  
Shun Hua Zhou ◽  
Jing Shan Shi ◽  
Quan Mei Gong ◽  
Chang Ji
Keyword(s):  
Plastic Strain ◽  
Pore Pressure ◽  
Triaxial Test ◽  
Cyclic Stress ◽  
Calculation Model ◽  
Triaxial Tests ◽  
Cyclic Stress Ratio ◽  
Dynamic Triaxial Test ◽  
Cumulative Strain ◽  
Cumulative Plastic Strain

Based on the dynamic triaxial test of typical soils in Hangzhou area, the existed empirical calculation formulas of cumulative pore pressure and cumulative plastic strain are analyzed to recharacterized variables such as the cyclic stress ratio and the static deviator stress, therefor the modified formulas are proposed. Parameters of cumulative deformation calculation model that suitable for this area are also determined according to dynamic triaxial tests. Thereafter the modified formulas is applied in a subway project under construction in Hangzhou. Results show that both the the cumulative plastic strain and cumulative pore pressure in dynamic triaxial test have the power exponential function relationship with the vibration number, and an inflection point appears in curve when amounts to approximately 1000. The improved formulas basicly tally with test results, of which the cumulative plastic strain formula coinsides better. The formulas work well in calculating the long-term settlement of subway projects in Hangzhou area.

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 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.

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