scholarly journals Undrained Dynamic Behavior of Reinforced Subgrade under Long-Term Cyclic Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Min Geng ◽  
Debin Wang ◽  
Peiyong Li
Keyword(s):  
Elastic Modulus ◽  
Cyclic Loading ◽  
Dynamic Behavior ◽  
Vibration Frequency ◽  
Dynamic Stress ◽  
Stress Amplitude ◽  
Confining Pressure ◽  
Reinforced Soil ◽  
Dynamic Elastic Modulus

To study the dynamic behavior of reinforced subgrade, a series of undrained cyclic triaxial tests of reinforced soil (the specimen a height of 50 cm and a diameter of 20 cm) were performed in this paper. The specimens were tested by varying confining pressure, vibration frequency, dynamic stress amplitudes, and reinforced layers. Orthogonal experiment is a better way to optimize the process of experiment. Impact on dynamic behavior of the reinforced soil specimens is discussed through orthogonal design of experiments in four factors and three levels. This study has demonstrated that the order of dynamic elastic modulus of reinforced soil is influenced by dynamic stress amplitude, frequency, reinforced layer, and confining pressure within changing in factor level. The dynamic stress amplitude has great influence on the dynamic elastic modulus of reinforced soil. The bearing capacity and dynamic elastic modulus of reinforced subgrade decrease slightly with the increase of dynamic strain. Frequency has an influence on the dynamic elastic modulus. It is shown that the cumulative strain of reinforced soil is related to the vibration frequency. The test results also exemplify the reinforced subgrade restrict lateral displacement of subgrade and reduce settlement of subgrade under long-term cyclic loading.

The Deformation Characteristics of Soft Clay under Cyclic Loading

2012 ◽  
Vol 446-449 ◽  
pp. 1709-1712 ◽  
Author(s):  
Yong Zhang ◽  
Li Wan ◽  
Xiong Wei Li
Keyword(s):  
Elastic Modulus ◽  
Cyclic Loading ◽  
Elastic Strain ◽  
Dynamic Stress ◽  
Stress Amplitude ◽  
Soft Clay ◽  
Dynamic Elastic Modulus ◽  
Deformation Characteristics ◽  
Cycle Number ◽  
Critical Type

Through the undrained dynamic triaxial experiment, the deformation characteristics of saturated soft clay under cyclic loading are investigated. The cyclic loading was simplified as sine wave. It is found that under different dynamic stress, the deformation patterns of specimen in this experiment can be divided into three kinds, such as dense compressed, tensile break-up and shear failure type. In the process of vibration, the deformation forms of samples can also be divided into three types by dynamic stress amplitude, such as stable, destructive and critical type. The dynamic stress amplitude corresponding to the critical type is called critical dynamic stress. With the dynamic elastic strain increasing gradually, the dynamic elastic modulus decreases and rigidity softening occurs. Furthermore, dynamic elastic modulus and dynamic elastic strain curve decrease while the cyclic number is increasing. Finally, to establish the equation of the relationship between dynamic elastic modulus and dynamic elastic strain, the factor of cycle number should be considered.

scholarly journals Dynamic Behavior and Constitutive Relationship of Mudstone Slip Zone of Landslide with Weak Interlayer

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jingjing Zhou ◽  
Fasuo Zhao ◽  
Yanbo Zhu ◽  
Wenqi Dong ◽  
Ziguang He
Keyword(s):  
Elastic Modulus ◽  
Dynamic Behavior ◽  
Empirical Model ◽  
Dynamic Stress ◽  
Stress Amplitude ◽  
Damping Ratio ◽  
Constitutive Relationship ◽  
Dynamic Elastic Modulus ◽  
Loading Frequency ◽  
Mountain Area

Sliding zone dynamics in the Qinling-Daba mountain area under different dynamic parameters have not been studied extensively. In this study, we investigated the dynamic behavior of the sliding zones of a high-steep rock landslide in the Qinling-Daba mountain area under the influence of dynamic stress amplitude and frequency and proposed an empirical model of the dynamic constitutive relationship. The dynamic behavior was studied based on a cyclic triaxial test system. The results indicated that an increase in the dynamic stress amplitude decreased the dynamic elastic modulus linearly, increased the damping ratio, and increased the axial strain exponentially. Among these properties, the elastic strain was found to be more sensitive to the increase in the dynamic stress amplitude than the plastic strain. As the loading frequency increased, the dynamic elastic modulus increased, whereas the damping ratio decreased. Furthermore, the proposed empirical model of the dynamic constitutive relationship between the vibration number and loading frequency based on the dynamic elastic modulus could satisfactorily describe the dynamic stress-strain relationships of the samples from test stability and failure zones. These findings are expected to make a significant contribution toward further revealing the sliding mechanism of such landslides.

scholarly journals Study on the Mechanical Properties of Chlorine Saline Soil under the Interaction of Multiple Factors

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Anhua Xu ◽  
Pengcheng Wang ◽  
Jianhong Fang
Keyword(s):  
Elastic Modulus ◽  
Moisture Content ◽  
Mechanical Characteristics ◽  
External Environment ◽  
Confining Pressure ◽  
Dynamic Elastic Modulus ◽  
Dynamic Strain ◽  
Saline Soils ◽  
Loading Frequency ◽  
Failure Strength

The distribution of chlorine saline soils is extensive in Haixi region of Qinghai Province in Northwest China. Its natural and geographical conditions are unique, and the external environment varies greatly. To study the effects of variable external environment on the mechanical characteristics of chlorine saline soils, a number of unconsolidated undrained (UU) dynamic triaxial tests under different confining pressure, moisture content, and loading frequency were carried out. The dynamic stress–dynamic strain, failure strength, dynamic elastic modulus, and parameter of shear strength were analyzed. The triaxial test results demonstrated that the stress–strain curves of the soil were strain-hardening. The failure strength and dynamic elastic modulus increased with the increasing of confining pressure; the law with moisture content and loading frequency were inconsistent. The dynamic cohesion and dynamic friction angle increased with the increasing of loading frequency, but decreased with the increasing of moisture content. Besides, the significance analysis theory was used to analyze the effect degree of different factors. It found that the effects of confining pressure, loading frequency, and the interaction between confining pressure and frequency on mechanical characteristics were significant, but the moisture content had less effect.

Comparing Tests on the Durability of Concrete after Long-Term Immersion in Different Salt Solution

2014 ◽  
Vol 501-504 ◽  
pp. 1087-1091 ◽  
Author(s):  
Xiao Ping Su ◽  
Li Zhang
Keyword(s):  
Elastic Modulus ◽  
Salt Solution ◽  
Saline Soil ◽  
Salt Water ◽  
Dynamic Elastic Modulus ◽  
Salt Crystallization ◽  
Soluble Salts ◽  
Concrete Damage ◽  
Damage Law

The western region of Jilin province is one of the areas with the most serious saline soil, which is the type of inland soda salt. In order to study the damage law of concrete under the condition of long-term erosion by the soluble salts in saline soil or groundwater or saturated salt water, three groups of salt solution, Na2SO4, NaCl, NaHCO3 solution, were made according to the content of soluble salts in saline soil of Daan city in spring, and water was as a comparison. The comparing tests of long-term immersion were conducted on the normal concrete specimens with the size of 40mm×40mm×160mm. The results show that there is little change on the appearance, mass and dynamic elastic modulus of concrete soaked in water. But for the concrete soaked in salt solution, the loss rate of mass changes from reduction to growth, the relative dynamic elastic modulus of concrete grows at first and declines later. Through analysis of electron microscope scanning, energy spectrum and chemical composition of concrete samples, concrete damage caused by salts includes chemical erosion and salt crystallization damage. Na2SO4 mainly influences the dynamic elastic modulus of concrete, NaCl mainly influences the mass of concrete due to its strong penetration, while NaHCO3, ranking between the two salts above, largely influences not only the mass of concrete, but also the dynamic elastic modulus of concrete.

Failure Characteristic of Granite under Cyclic Loading with Different Frequencies

2014 ◽  
Vol 638-640 ◽  
pp. 1967-1970
Author(s):  
Xiao Hui Ni
Keyword(s):  
Elastic Modulus ◽  
Cyclic Loading ◽  
Nuclear Power ◽  
Damping Ratio ◽  
Research Result ◽  
Testing Machine ◽  
Dynamic Elastic Modulus ◽  
Dynamic Strain ◽  
Response Analysis ◽  
Cyclic Frequency

The uniaxial cyclic fatigue tests on granite coming from the ChangJiang of Hainan nuclear power first-stage construction conventional island were done on the RMT-150B multi-function automatic rigid rock servo material testing machine. Stress amplitude of 10 MPa and sine wave cyclic loads with five different frequencies of 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 Hz were adopted as dynamic disturbance. The law between cyclic frequency and dynamic stress-dynamic strain hysteretic curve, dynamic elastic modulus and damping ratio are researched. The results showed that the curves of strain and stress for loading and unloading are not superposition under cyclic loading, but hysteretic loops. When cyclic frequency changes between 0.01 and 1.0 Hz, the granite hysteretic loop area, dynamic elastic modulus and damping ratio are increased with frequency increasing. The research result offered great reference value to seismic response analysis and site safety evaluation of the changjiang nuclear power.

DEGRADATION EFFECT OF SEAWATER ON THE LONG-TERM DYNAMIC BEHAVIOR OF ARTIFICIALLY CEMENTED SAND

2013 ◽  
Vol 07 (04) ◽  
pp. 1350031 ◽  
Author(s):  
BO LI ◽  
YUANQIANG CAI ◽  
XIANGWU ZENG ◽  
LINYOU PAN
Keyword(s):  
Shear Modulus ◽  
Dynamic Behavior ◽  
Tap Water ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Resonant Column ◽  
Cyclic Triaxial Tests ◽  
Cemented Sand

The dynamic behavior of lightly cemented sand under long-term seawater attack was evaluated in this study. Resonant column and cyclic triaxial tests were employed to investigate the evolution of the shear modulus and damping ratio of cemented sand with respect to soaking period (SP), confining pressure, and cement content (CC). The results of this study show that the cementation of the sand is affected by soaking in seawater to a greater extent than by soaking in tap water. The shear modulus of the cemented sand soaked in seawater was smaller than that of the cemented sand soaked in tap water. The damping ratio increased significantly, as the SP increased and was greater for the cemented sand soaked in seawater than for the cemented sand soaked in tap water. The dynamic behavior of nonhomogenous specimens was examined. Crystallization of salts could be clearly observed and probably explains the evolution of the dynamic behavior of the cemented sand. Finally, the shear modulus was fitted using Rollins' Law [Rollins et al., 1998], which demonstrates that the parameters used in the equation can be reasonably fitted linearly over a range of SPs.

scholarly journals SHPB Testing and Analysis of Bedded Shale under Active Confining Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Guoliang Yang ◽  
Jingjiu Bi ◽  
Xuguang Li ◽  
Jie Liu ◽  
Yanjie Feng
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Peak Stress ◽  
Confining Pressure ◽  
Dynamic Mechanical Properties ◽  
Dynamic Elastic Modulus ◽  
Peak Strain ◽  
Dynamic Mechanical ◽  
Bedding Angle

Shale gas is the most important new energy source in the field of energy, and its exploitation is very important. The research on the dynamic mechanical properties of shale is the premise of exploitation. To study the dynamic mechanical properties of shale from the Changning-Weiyuan area of Sichuan Province, China, under confining pressure, we used a split Hopkinson pressure bar (SHPB) test system with an active containment device to carry out dynamic compression tests on shale with different bedding angles. (1) With active confining pressure, the shale experiences a high strain rate, and its stress-strain curve exhibits obvious plastic deformation. (2) For the same impact pressure, the peak stress of shale describes a U-shaped curve with an increasing bedding angle; besides, the peak stress of shale with different bedding angles increases linearly with rising confining pressure. The strain rate shows a significant confining pressure enhancement effect. With active confining pressure, the peak strain gradually decreases as the bedding angle increases. (3) As a result of the influence of different bedding angles, the dynamic elastic modulus of shale has obvious anisotropic characteristics. Shale with different bedding angles exhibits different rates of increase in the dynamic elastic modulus with rising confining pressure, which may be related to differences in the development of planes of weakness in the shale. The results of this study improve our understanding of the behavior of bedded shale under stress.

The Study on Dynamic Mechanical Response under Staged Loading

2014 ◽  
Vol 501-504 ◽  
pp. 115-119
Author(s):  
Fei Luo ◽  
Zhan Yuan Zhu ◽  
Lin Zhi Cui ◽  
Gao Min Li ◽  
Yi Ting He
Keyword(s):  
Energy Dissipation ◽  
Residual Strain ◽  
Dynamic Stress ◽  
Mechanical Response ◽  
Stress Amplitude ◽  
Testing Machine ◽  
Morphological Characteristics ◽  
Confining Pressure ◽  
Dynamic Mechanical ◽  
Microscopic Damage

Based on MTS-810 type vibration testing machine, morphological characteristics of hysteretic curves of frozen clay are quantitatively studied, and dynamic mechanical response are analyzed consisting of stiffness, viscosity, degree of microscopic damage, residual strain and energy dissipation. The studies have shown that the higher vibration frequencies are, the greater the stiffness is, while the smaller viscosity, the degree of microscopic damage, residual strain and energy dissipation are. Stiffness, viscosity, degree of microscopic damage, residual strain and energy dissipation are less affected by confining pressure. With increasing dynamic stress amplitude, stiffness decreases gradually, while viscosity, degree of microscopic damage, residual strain and energy dissipation increase gradually.

scholarly journals Elastic-Viscoplastic Constitutive Model of Soil under Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yuan Ma ◽  
Hua Liang ◽  
Yongxue You ◽  
Weiguang Zhang ◽  
Limin Guo ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Dynamic Stress ◽  
Stress Amplitude ◽  
Yield Criterion ◽  
Case Analysis ◽  
Research Field ◽  
Constant Amplitude ◽  
Bingham Model ◽  
Viscoplastic Model ◽  
Flow Criterion

The creep problems are often involved in soil under cyclic loading, and its behaviors of soil under cyclic loading sparks many arguments in current research field. To propose one new model to demonstrate these creep behaviors of soil under cyclic loading, the cyclic loading was simplified equivalently, and the elastic-viscoplastic model (EVPM) for soil under cyclic loading was established based on the Bingham model. The yield criterion for soil under cyclic loading with constant amplitude was proposed following the simplified load. A constitutive equation based on the EVPM was constructed by using the flow criterion related to the yield criterion. Meanwhile, the parameters of EVPM were identified and discussed. In addition, the case analysis of the EVPM was also performed. The results indicate that the stable and destructive creep behaviors of soil under cyclic loading could be well described by the recommended EVPM, and the obtained parameters in the model exhibited a clear regularity with the increase of dynamic stress amplitude. Besides, the established model could be selected to predict the stable and destructive creep behavior of soil under cyclic loading.

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