Dynamic Shear Modulus and Damping Ratio for Threshold Strain in Cohesionless Soils

Based on modern ideas of thermomechanics, small strain dynamic dissipation function of Hardin-Drnevich model for soils is formulated using the assumptions of the beeline and the skeleton curve shift laws. Fundamentally, for cohesionless soils, two types of cyclic strain thresholds are identified: first threshold strain and second threshold strain represent boundaries between fundamentally different dynamic characteristics of cyclic soil behavior. Comparison between the two threshold shear strain values and dynamic degradation curves obtained on exactly the same soils, the results showed that the ratio of secant modulus and maximum dynamic shear modulus for the first threshold strain are almost 1.0, and the damping ratio is almost constant. When dynamic strain level exceeds the second threshold strain, the soil behavior is considerably at nonlinear, and the primary deformation mechanism is related to fabric changes during cyclic loading. The first and the second threshold strains are therefore essential for the understanding and solving soil dynamic problems.

Download Full-text

Study on Dynamic Characteristics of Rubber-Red Clay Mixtures

Advances in Materials Science and Engineering ◽

10.1155/2020/2343242 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Kaisheng Chen ◽

Qinqin Wang ◽

Dipu Luo ◽

Bo Zhou ◽

Kun Zhang

Keyword(s):

Particle Size ◽

Shear Modulus ◽

Vibration Frequency ◽

Damping Ratio ◽

Rubber Particle ◽

Confining Pressure ◽

Dynamic Strain ◽

Dynamic Shear Modulus ◽

Dynamic Shear ◽

Red Clay

Rubber powder formed from discarded tire rubber is mixed with red clay to form a rubber-red clay mixture. The dynamic triaxial test was carried out on the mixtures under different conditions. The effects of rubber content, rubber particle size, moisture content of mixed soil, compactness, confining pressure, and vibration frequency on shear strain relation, dynamic shear modulus, and damping ratio of the mixture were investigated. The results show that under the same dynamic strain, the dynamic shear stress-strain curve of rubber mixed soil decreases with the increase in rubber particle content and moisture content and decrease in rubber particle size. On the other hand, it increases with the increase in compactness, confining pressure, and vibration frequency, and as the dynamic strain increases, the τd-γd curve becomes more nonlinear. In addition, with the increase in the rubber particle content, the dynamic shear modulus decreased while the damping ratio increased. When the content was 2%, the change was fastest. After continued addition, it gradually became stable, and when the decrease in rubber particle size also shows the same pattern, 2.00 mm rubber-red clay mixture shows better structure. The water content has great influence on dynamic shear modulus and damping ratio of rubber-red clay mixtures. With the increase in compactness, confining pressure, and vibration frequency, the interaction between mixed soil particles was enhanced, the dynamic shear modulus increased, and the damping ratio decreased.

Download Full-text

Threshold Shear Strain for Dynamic Ramberg-Osgood Model in Soils Based on Thermomechanics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1065-1069.255 ◽

2014 ◽

Vol 1065-1069 ◽

pp. 255-259

Author(s):

Xiao Xia Guo ◽

Xiang Sun

Keyword(s):

Friction Coefficient ◽

Shear Modulus ◽

Shear Strain ◽

Dynamic Characteristics ◽

Fundamental Property ◽

Small Strain ◽

Dissipation Function ◽

Dynamic Shear Modulus ◽

Soil Behavior ◽

Skeleton Curve

The threshold shear strain is a fundamental property of the soil behavior subjected to cyclic loading. Starting from the unloading and reloading hysteretic curves of dynamic Ramberg-Osgood model, construct small-strain dynamic dissipation function and explain small-strain dynamic characteristics by use of the skeleton curve back stress assumption. The plotting results of yield curves in true stress space indicate that there exist two threshold shear strains which are defined as the first threshold shear strain and the second threshold shear strain respectively which represent boundaries between fundamentally different dynamic characteristics of cyclic soil behavior. The yields of soil are controlled by the constant friction coefficient, the variable friction coefficient and dilatancy-related microstructural changes respectively. Both the first threshold shear strain and the second threshold shear strain do depend significantly on the maximum dynamic shear modulus coefficient and exponent. Comparison between the two threshold shear strain values and shear modulus reduction curves obtained on exactly the same soils confirms that the soil behavior is considerably at nonlinear at , the secant shear modulus,Gs, of the four soils studied is between 0.6 and 0.8 of its maximum value.

Download Full-text

Dynamic shear modulus and damping ratio of clay mixed with waste rubber using cyclic triaxial apparatus

Soil Dynamics and Earthquake Engineering ◽

10.1016/j.soildyn.2020.106435 ◽

2021 ◽

Vol 140 ◽

pp. 106435 ◽

Cited By ~ 1

Author(s):

Davood Akbarimehr ◽

Kazem Fakharian

Keyword(s):

Shear Modulus ◽

Damping Ratio ◽

Dynamic Shear Modulus ◽

Dynamic Shear ◽

Cyclic Triaxial ◽

Triaxial Apparatus ◽

Waste Rubber

Download Full-text

Shear Modulus and Damping Ratio of Gravel Material

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.105-107.1426 ◽

2011 ◽

Vol 105-107 ◽

pp. 1426-1432 ◽

Cited By ~ 2

Author(s):

De Gao Zou ◽

Tao Gong ◽

Jing Mao Liu ◽

Xian Jing Kong

Keyword(s):

Shear Modulus ◽

Shear Strain ◽

Strain Amplitude ◽

Damping Ratio ◽

Confining Pressure ◽

Dynamic Shear Modulus ◽

Test Results ◽

Dynamic Shear ◽

Data Points ◽

Shear Strain Amplitude

Two of the most important parameters in dynamic analysis involving soils are the dynamic shear modulus and the damping ratio. In this study, a series of tests were performed on gravels. For comparison, some other tests carried out by other researchers were also collected. The test results show that normalized shear modulus and damping ratio vary with the shear strain amplitude, (1) normalized shear modulus decreases with the increase of dynamic shear strain amplitude, and as the confining pressure increases, the test data points move from the low end toward the high end; (2) damping ratio increases with the increase of shear strain amplitude, damping ratio is dependent on confining pressure where an increase in confining pressure decreased damping ratio. According to the test results, a reference formula is proposed to evaluate the maximum dynamic shear modulus, the best-fit curve and standard deviation bounds for the range of data points are also proposed.

Download Full-text

Experimental Study on Dynamic Characteristics of Ionic Soil Stabilizer Reinforcing Red Clay

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.374-377.1391 ◽

2011 ◽

Vol 374-377 ◽

pp. 1391-1395

Author(s):

Xue Song Lu ◽

Wei Xiang

Keyword(s):

Shear Modulus ◽

Shear Strain ◽

Dynamic Condition ◽

Damping Ratio ◽

Confining Pressure ◽

Natural Soil ◽

Dynamic Shear Modulus ◽

Dynamic Shear ◽

Red Clay ◽

Soil Stabilizer

Based on the red clay of Wuhan reinforced by Ionic Soil Stabilizer, the red clay soil is treated by different matches of ISS at first, then is tested in the Atterberg limits test and dynamic triaxia test. The results show that the plastic index decreases, and the red clay were greatly improved under the dynamic condition, the maximum dynamic shear modulus ratio acquired an incensement of 27.72% on average after mixing the ISS into the red clay. In addition, It was concluded that the confining pressure influenced the dynamic shear modulus and damping ratio to a certain extent. Given the same strain conditions, with the incensement of confining pressure increases, the dynamic shear modulus increased and the damping ratio decreased. Moreover, when plotting the dynamic shear modulus versus the dynamic shear strain, the similar curve can be formed for both the natural soil and the modified one, the dynamic shear modulus monotonously decreased with the incensement of the dynamic shear strain. However, the value of dynamic shear modulus differed in the same shear strain between the natural soil and the soil modified by ISS.

Download Full-text

Characterization of the Dynamic Properties of Clay–Gravel Mixtures at Low Strain Level

Sustainability ◽

10.3390/su12041616 ◽

2020 ◽

Vol 12 (4) ◽

pp. 1616 ◽

Cited By ~ 3

Author(s):

Xianwen Huang ◽

Aizhao Zhou ◽

Wei Wang ◽

Pengming Jiang

Keyword(s):

Shear Modulus ◽

Shear Strain ◽

Mechanical Performance ◽

Dynamic Properties ◽

Damping Ratio ◽

Confining Pressure ◽

Strain Level ◽

Dynamic Shear Modulus ◽

Dynamic Shear ◽

Gravel Content

In order to support the dynamic design of subgrade filling engineering, an experiment on the dynamic shear modulus (G) and damping ratio (D) of clay–gravel mixtures (CGMs) was carried out. Forty-two groups of resonant column tests were conducted to explore the effects of gravel content (0%, 10%, 20%, 30%, 40%, 50%, and 60%, which was the mass ratio of gravel to clay), gravel shape (round and angular gravels), and confining pressure (100, 200, and 300 kPa) on the dynamic shear modulus, and damping ratio of CGMs under the same compacting power. The test results showed that, with the increase of gravel content, the maximum dynamic shear modulus of CGMs increases, the referent shear strain increases linearly, and the minimum and maximum damping ratios decrease gradually. In CGMs with round gravels, the maximum dynamic shear modulus and the maximum damping ratio are greater, and the referent shear strain and the minimum damping ratio are smaller, compared to those with angular gravels. With the increase of confining pressure, the maximum dynamic shear modulus and the referent shear strain increase nonlinearly, while the minimum and maximum damping ratios decrease nonlinearly. The predicting equation for the dynamic shear modulus and the damping ratio of CGMs when considering confining pressure, gravel content, and shape was established. The results of this research may put forward a solid foundation for engineering design considering low-strain-level mechanical performance.

Download Full-text