Energy dissipation and dynamic behaviour of clay under cyclic loading

1992 ◽  
Vol 29 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Y. L. Cao ◽  
K. T. Law
Keyword(s):  
Shear Modulus ◽  
Pore Pressure ◽  
Dynamic Behaviour ◽  
Dynamic Strength ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Energy Concept ◽  
Excess Pore

A laboratory study has been conducted to investigate the dynamic behaviour of Champlain Sea clay from two locations in the Ottawa River valley region. The test program includes cyclic triaxial tests and resonant-column tests. The soil samples were consolidated at a range of pressures before the dynamic shear in order to cover the dynamic behaviour under both the overconsolidated and the normally consolidated states. An energy concept is introduced to interpret the test results. Mathematical relationships have been established for describing the various aspects of dynamic behaviour. These aspects include excess pore pressure, dynamic strength, dynamic shear modulus, and plastic strain. The study shows that the energy concept provides a promising way to analyze dynamic soil behaviour. Key words : energy, dynamic behaviour, clay, cyclic test, earthquake, excess pore pressure, shear modulus, strength.

scholarly journals New Structure for Strengthening Soil Embankments

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Fang Xu ◽  
Wuming Leng ◽  
Rusong Nie ◽  
Qishu Zhang ◽  
Qi Yang
Keyword(s):  
Shear Modulus ◽  
Large Scale ◽  
Dynamic Stress ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Additional Stress ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Critical Dynamic

A new prestressed reinforcement device (PRD) consisting of two lateral pressure plates (LPPs) and a reinforcement bar is developed to strengthen soil embankments by improving the soil confining pressure and providing lateral constraint on embankment slopes. The reinforcement effects of PRDs were demonstrated by investigating the beneficial effects of increasing confining pressure on the soil behavior via the performance of a series of large-scale static and cyclic triaxial tests on a coarse-grained embankment soil. The results show that PRDs can effectively improve the soil shear strength, bearing capacity, ability to resist elastic and plastic deformation, critical dynamic stress, and dynamic shear modulus, and empirical methods were also developed to determine the critical dynamic stress and initial dynamic shear modulus of the embankment soil. Moreover, 3D finite element analyses (FEAs) with an LPP width of 1.2 m were performed to analyze the additional stress field in a prestressed heavy-haul railway embankment. The FEAs showed that the additional stress at a given external distance from the border of an LPP first increased to a maximum value and then gradually decreased with increasing depth; the additional stress was transferred to the zones where the subgrade tends to have higher stresses with peak stress diffusion angles of 34° (slope direction) and 27° (longitudinal direction); and a continuous effective reinforcement zone with a minimum additional stress coefficient of approximately 0.2 was likely to form at the diffusion surface of the train loads, provided that the net spacing of the LPPs was 0.7 m. The reinforcement zone above the diffusion surface of the train loads can act as a protective layer for the zones that tend to have higher stresses. Finally, the advantages and application prospects of PRDs are discussed in detail. The newly developed PRDs may provide a cost-effective alternative for strengthening soil embankments.

Effects of Complex Initial Stress State Parameters on Dynamic Shear Modulus of Loess

2011 ◽  
Vol 243-249 ◽  
pp. 2601-2606 ◽  
Author(s):  
Zhi Jie Wang ◽  
Ya Sheng Luo ◽  
Hong Guo
Keyword(s):  
Stress State ◽  
Shear Modulus ◽  
Principal Stress ◽  
Initial Stress ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Initial Stress State ◽  
Foundation Soil ◽  
Stress States

The foundation soil of the buildings and structures is often in complex initial stress states. The dynamic torsional shear triaxial tests are carried out on undisturbed and remodeling loess under different complex initial stress states by using the remolded DTC-199 torsional cyclic load triaxial apparatus, and the effects of each complex initial stress state parameter on dynamic shear modulus of loess are discussed. Results show that, other conditions being the same, the influence of angles of initial principal stressα0on dynamic shear modulusGdof loess show a trend of the biggerα0is, the smallerGdis. The effect laws of efficient of initial intermediate principal stressb0onGdof loess are not obvious. When the dynamic shear strain is larger, the bigger initial deviator stress ratioη0is, the smallerGdof loess is. The influence of initial average principal stresspm0on loess is significant. The biggerpm0is, the biggerGdof loess is.Gdof undisturbed loess is greater than that of remodeling loess under the complex initial stress states.

Research on the Dynamic Deformation Characteristics of Tailings Silt in Zhuziqing Tailings Dam

2012 ◽  
Vol 524-527 ◽  
pp. 459-465
Author(s):  
Jian Bin Xie ◽  
Wen Lian Liu ◽  
Lin Hua Shi ◽  
Guo Hai Zhang ◽  
Jie Zhang
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Damping Ratio ◽  
Physical And Mechanical Properties ◽  
Dynamic Strength ◽  
Confining Pressure ◽  
Standard Penetration Test ◽  
Dynamic Shear Modulus ◽  
Tailings Dam ◽  
Dynamic Shear

In this paper, it has been studied that types and mechanical properties of tailings silt in Zhuziqing tailings dam based on the Zhuziqing tailings’ deposition characteristics, particles size distribution test, physical and mechanical properties test. Then it has been studied subsequently by the dynamic triaxial test, wave velocity test and standard penetration test for tailings silt that the dynamic characteristics, dynamic strength and vibration liquefaction of the tailing silt. Results show that the tailings silt in tailings pond is graded well. Under the condition of isotropic or anisotropic consolidation, dynamic shear modulus of tailings silt increase as the dynamic shear strain decreasing and increase as the increase of confining pressure or consolidation ratio. But the variation law on damping ratio of tailings silt is just opposite to that of dynamic shear modulus. Results also show that there is more liquefied possibility over the seventh sub-dam in the tailings dam, and the liquefied possibility position locates at the place from new sub-dam to deposited beach in tailing pond.

Numerical Simulation Study on Size Effect of Dynamic Properties of Coarse Materials

2011 ◽  
Vol 368-373 ◽  
pp. 2749-2754
Author(s):  
Gui Yang ◽  
Qi Yin Gao ◽  
De Qing Gao ◽  
Yan Chen Liu
Keyword(s):  
Shear Modulus ◽  
Sample Size ◽  
Scale Effect ◽  
Damping Ratio ◽  
Particle Diameter ◽  
Triaxial Tests ◽  
Hyperbolic Function ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Power Functions

Though the test level has improved highly, the original grading curve of coarse materials should be reduced in some scale in dynamic triaxial test. This method must affect the difference between the test results and the real results, which is called scale effect. In this paper, the scale effect was studied by using particle flow code (PFC) based on dynamic triaxial tests. The relationship between microscopic shear modulus and the maximum particle diameter can be simulated by hyperbolic function. The results show that the dynamic shear modulus and damping ratio are increased with the sample size increase. The normalized dynamic shear modulus vs. normalized dynamic shear strains of different size samples are located in a narrow space which can be simulated by modified Hardin-Drnevich model formula. The parameters of maximum shear modulus and damping ratio of different sample size can be simulated by power functions.

Effect of unloading duration on unconfined compressive strength

1999 ◽  
Vol 36 (1) ◽  
pp. 166-172 ◽  
Author(s):  
M A Fam ◽  
M B Dusseault
Keyword(s):  
Compressive Strength ◽  
Pore Pressure ◽  
Unconfined Compressive Strength ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Coefficient Of Consolidation ◽  
Unconfined Compression Test ◽  
Excess Pore

This note examines the effect of unloading duration on unconfined compression test results. Artificial clayey specimens were prepared using the slurry consolidation technique. Extracted specimens were loaded vertically under K0 conditions, and the load was kept constant until the end of primary consolidation. Specimens were unloaded and unconfined compression tests were carried out at different times after unloading. It is observed that the longer the unloading duration, the lower the measured unconfined strength. This behavior is attributed to the presence of negative excess pore pressure that dissipates with time, reducing the strength. Using the measured coefficient of consolidation, the degree of excess pore pressure dissipation and therefore the average mean effective stress near the failure zone can be calculated at the time of failure. Mohr circles are drawn tangential to the total shear envelope, using the calculated mean effective stresses. Reasonable agreement between predicted and measured unconfined compressive strengths has been observed, suggesting that consolidation theory can be adopted to assess the effect of unloading duration on unconfined compressive strength. Finally, engineering applications using a similar concept are briefly discussed.Key words: clays, unloading, consolidation, unconfined compression tests, triaxial tests.

scholarly journals Dynamic Shear Modulus and Damping Ratio of Sand–Rubber Mixtures under Large Strain Range

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4017 ◽  
Author(s):  
Jianfeng Li ◽  
Jie Cui ◽  
Yi Shan ◽  
Yadong Li ◽  
Bo Ju
Keyword(s):  
Shear Modulus ◽  
Volume Content ◽  
Damping Ratio ◽  
Rubber Particle ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Particle Sizes ◽  
Dynamic Shear ◽  
Confining Pressures ◽  
Shear Strains

Adding rubber into sands has been found to improve the mechanical behavior of sands, including their dynamic properties. However, ambiguous and even contradictory results have been reported regarding the dynamic behavior of sand–rubber mixtures, particularly in terms of the damping ratio. A series of cyclic triaxial tests were, therefore, performed under a large range of shear strains on sand–rubber mixtures with varying rubber volume contents, rubber particle sizes, and confining pressures. The results indicate the dynamic shear modulus decreases with increasing rubber volume content and with decreasing particle size and confining pressure. The relationship of the damping ratio to the evaluated parameters is complicated and strain-dependent; at shear strains less than a critical value, the damping ratio increases with increasing rubber volume content, whereas the opposite trend is observed at greater shear strains. Furthermore, sand–rubber mixtures with different rubber particle sizes exceed the damping ratio of pure sand at different rubber volume contents. A new empirical model to predict the maximum shear moduli of mixtures with various rubber volume contents, rubber particle sizes, and confining pressures is accordingly proposed. This study provides a reference for the design of sand–rubber mixtures in engineering applications.

scholarly journals Normalized Shear Modulus and Damping Ratio of Soil–Rock Mixtures With Different Volumetric Block Proportions

2021 ◽  
Vol 9 ◽  
Author(s):  
Shengnian Wang ◽  
Xinqun Gao ◽  
Honglei Hui ◽  
Wei Ma ◽  
Chong Shi ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Large Scale ◽  
Volume Fraction ◽  
Damping Ratio ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Confining Pressures ◽  
Gravelly Soils ◽  
Shear Behaviors

The volume fraction of rock blocks plays a particularly significant role in static/dynamic shear behaviors of soil–rock mixtures (SRM). Large-scale cyclic triaxial tests for SRM with different volumetric block proportions (VBPs) were performed at different confining pressures to investigate the reduction of dynamic shear modulus (G) and the increase of damping ratio (λ). Results indicate that VBP has a significant effect on the dynamic behaviors of SRM. The higher VBP is more likely to result in a gentler reduction of G and a faster increase of λ. The variations of dynamic shear modulus ratio (G/G0) and normalized damping ratio (λnor) fall within relatively narrow bands but are very different with gravelly soils and sands due to VBP with particle size larger than 2 mm. The G/G0 and λnor can be characterized by empirical functions about normalized shear strain amplitude (γnor).

scholarly journals Dynamic Nonlinear and Residual Deformation Behaviors of the Fly Ash-Modified Loess

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Qian Wang ◽  
Jun Wang ◽  
Xiumei Zhong ◽  
Haiping Ma ◽  
Xiaowei Xu
Keyword(s):  
Fly Ash ◽  
Shear Modulus ◽  
Shear Strain ◽  
Residual Strain ◽  
Damping Ratio ◽  
Ash Content ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Modulus Ratio

Metastable loess soils can deform, inducing geological and engineering disasters. Therefore, the behavior of the loess under dynamic load is gaining massive attention from researchers to improve the strength of the soils. Fly ash mixed with loess can improve strength and reduce construction costs and environmental pollution. Moreover, it has strong economic and social benefits. This paper investigates the influence of fly ash on the dynamic properties of the modified loess through a series of dynamic triaxial tests of the fly ash modified loess with different fly ash contents. The treated soil samples were prepared using a static compaction method in both ends and cured for 28 days. The dynamic shear modulus ratio, the damping ratio, and the dynamic residual strain of the modified loess were analyzed. The variation characteristics of the dynamic shear modulus ratio and damping ratio with the dynamic shear strain of the fly ash modified loess were obtained. The effect of fly ash content on the dynamic nonlinear parameters of the modified loess was also investigated. In addition, the relationship between the dynamic residual strain and the fly ash content was discussed. The results show that the dynamic shear modulus ratio of fly ash modified loess decreases nonlinearly with the increase in the dynamic shear strain. However, the attenuation rate difference of the curves is small. The damping ratio increases gradually with increasing dynamic shear strain. Under a certain dynamic shear strain level, the damping ratio decreases with the increase in the fly ash content. The dynamic residual strain increases with the increase in the dynamic stress. However, it decreases with the increase in the fly ash content. When the fly ash content is between 10% and 20%, the dynamic residual strain of fly ash modified loess is reduced rapidly. However, when the fly ash content exceeds 20%, the dynamic residual strain decreases slowly. The fly ash content of 20% could be suggested as an optimal content for seismic resistance of the loess foundation.

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