Effects of inclusion contents on resilient modulus and damping ratio of unsaturated track-bed materials

2017 ◽  
Vol 54 (12) ◽  
pp. 1672-1681 ◽  
Author(s):  
Han-Lin Wang ◽  
Yu-Jun Cui ◽  
Francisco Lamas-Lopez ◽  
Jean-Claude Dupla ◽  
Jean Canou ◽  
...  
Keyword(s):  
Resilient Modulus ◽  
Damping Ratio ◽  
Triaxial Tests ◽  
Dynamic Parameters ◽  
Subgrade Soils ◽  
In Situ Investigation ◽  
Coarse Grains ◽  
The Matrix ◽  
Variation Rate ◽  
Number Of Cycles

For the French conventional railway lines, a layer, namely interlayer, was created in the substructure mainly by the interpenetration of ballast grains and subgrade soils. The in situ investigation indicated that the content of coarse grains decreases over depth. In this study, the resilient modulus and damping ratio of the unsaturated lower part of the interlayer soil were investigated at six different volumetric inclusion contents fv (volumetric ratio of dry coarse grains to the whole sample) by carrying out cyclic triaxial tests following a multi-step loading procedure. The results show that the two dynamic parameters (resilient modulus and damping ratio) change significantly at the beginning of loading and the variation rate decreases as the number of cycles increases. Besides, a mean characteristic volumetric inclusion content fv–cha ranging from 27.8% to 28.9% was identified, separating two zones with different inclusion effects. To verify this observation, X-ray microcomputed tomography (μCT) scans were conducted on as-compacted samples. The results obtained strongly support the existence of fv–cha: when fv ≤ fv–cha, the matrix of fines constitutes the skeleton of the sample with inclusions floating in it, leading to slight changes of the two dynamic parameters with fv. By contrast, when fv > fv–cha, the inclusions dominate the skeleton of the sample, giving rise to significant changes of the two dynamic parameters with fv.

scholarly journals Influence of Humidity State on Dynamic Resilient Modulus of Subgrade Soils: Considering Repeated Wetting-Drying Cycles

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Gongfeng Xin ◽  
Anshun Zhang ◽  
Zijian Wang ◽  
Quanjun Shen ◽  
Minghao Mu
Keyword(s):  
Resilient Modulus ◽  
Confining Pressure ◽  
Service Performance ◽  
Triaxial Tests ◽  
Road Engineering ◽  
Groundwater Level Fluctuations ◽  
Subgrade Soils ◽  
Deviator Stress ◽  
Complicated Conditions ◽  
Satisfactory Prediction

The service performance of subgrade depends on the dynamic resilient modulus (MR) of subgrade soils. Meanwhile, due to complicated conditions such as rainfall infiltration, high temperature evaporation, and groundwater level fluctuations, it can be safely said that the humidity state and repeated wetting-drying (WD) cycles affect the MR of subgrade soils. The object of this study is to conduct a series of dynamic triaxial tests after WD cycles to investigate the characteristics of the MR under various factors. The main results are as follows: (i) the MR decreased with the increase of deviator stress and rose with the growth of confining pressure; (ii) the humidification effect caused by the increase in moisture content attenuated the MR; (iii) the accumulation of WD cycles damaged the MR; however the decline rate was gradually retarded until it was stable with WD cycles 5 times; (iv) the satisfactory prediction model for the MR of subgrade soils considering WD cycles was proposed and verified. It is expected that the findings can provide valuable contributions for road engineering.

scholarly journals Dynamic Parameters and Hysteresis Loop Characteristics of Frozen Silt Clay under Different Cyclic Stress Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Furong Liu ◽  
Zhiwei Zhou ◽  
Wei Ma ◽  
Shujuan Zhang ◽  
Zhizhong Sun
Keyword(s):  
Hysteresis Loop ◽  
Phase Difference ◽  
Resilient Modulus ◽  
Axial Stress ◽  
Damping Ratio ◽  
Hysteresis Loops ◽  
Confining Pressure ◽  
Stress Path ◽  
Cyclic Stress ◽  
Dynamic Parameters

In cold regions, the long-term stability of engineering facilities is unavoidably influenced by the negative temperature, freeze-thaw process, dry-wet process, and dynamic loading conditions induced by earthquakes and traffic loads. In order to investigate the effects of different cyclic stress paths on the evolution of dynamic mechanical properties of frozen silt clay, a series of cyclic triaxial tests with variation confining pressure (VCP) or constant confining pressure (CCP) were performed. Triaxial low-temperature apparatus (MTS-810) was taken advantage of to simulating various cyclic stress paths by changing cyclic loading conditions of axial stress and confining pressure. In this paper, the evolution features of the axial resilient modulus, damping ratios, and the shape of hysteresis loops with an increase in the number of load cycles under different dynamic stress paths are comprehensively studied. The results show that the loading angle of cyclic stress path and the phase difference between cyclic axial stress and confining pressure are the main factors that remarkably affect the development characteristics of the resilient modulus and damping ratio. With increasing of the loading angle and phase difference, the resilient modulus increases, but damping ratio increases with increasing of loading angle and with decreasing of phase difference. With the continuous increase in the number of loading cycles, the samples of frozen soil show compacting and hardening characteristics. With an increase in the number of load cycles, the shape of hysteresis loop becoming narrows, the resilient modulus decreases at the initial stage and then gradually increases, and the damping ratio stably decreases. According to contrastively analyzing the evolution of dynamic parameters and the shape features of hysteresis loops under various cyclic stress paths, it can be clearly discovered that the evolution of sample microstructure and the development of dynamic characteristics of frozen samples have obvious dependence on the cyclic stress path. Therefore, the effects of variable confining pressure (VCP) on dynamic behaviors of frozen soils are nonnegligible in practical cold region engineering.

scholarly journals Deformation and Damping Characteristics of Lightweight Clay-EPS Soil under Cyclic Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Yundong Zhou ◽  
Mingdong Li ◽  
Qibao He ◽  
Kejun Wen
Keyword(s):  
Ground Improvement ◽  
Damping Ratio ◽  
Compressive Strain ◽  
Negative Relationship ◽  
Dynamic Strain ◽  
Triaxial Tests ◽  
Damping Characteristics ◽  
Practical Engineering ◽  
Number Of Cycles ◽  
Soft Ground Improvement

Lightweight Clay-EPS Soil (LCES) is a newly developed material which has many merits such as the adjustability of strength and density, simplicity for construction, and economical efficiency. It has been widely applied in practical engineering, e.g., soft ground improvement, the solvent of bridge head jump, earthfill of pipeline, and broadening of highway. Meanwhile, construction castoff and industrial waste can be recycled as a major ingredient in LCES. The dynamic deformation characteristics of LCES and clay were comprehensively studied using laboratory dynamic triaxial tests. It was found that the compressive strain of LCES increased while the growth rate of strain decreased with the increasing number of cycles, which conformed to a hyperbola model. The dynamic secant elastic modulus of LCES decreased with the increase of dynamic strain, which was represented by strain softening. The dynamic modulus of clay decreased sharply, while that of LCES decreased marginally. Moreover, the damping ratio of LCES tended to increase with the increasing dynamic strain. The damping ratio of LCES was lower than that of clay at the same strain level. It was also found that cement content had a negative relationship with the damping ratio of LCES, while the effect of EPS beads content was adverse. The damping ratio of both LCES and clay decreased moderately.

Soil behavior during freezing and thawing using variable and constant confining pressure triaxial tests

2001 ◽  
Vol 38 (4) ◽  
pp. 863-875 ◽  
Author(s):  
Erik Simonsen ◽  
Ulf Isacsson
Keyword(s):  
Resilient Modulus ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Soil Behavior ◽  
Freezing And Thawing ◽  
Mean Values ◽  
Freeze Thaw ◽  
Subgrade Soils ◽  
Thaw Cycle ◽  
Significant Difference

Although variable confining pressure (VCP) triaxial tests are generally preferred to constant confining pressure (CCP) triaxial tests due to the more realistic stress application, VCP tests have never been utilized when investigating freeze–thaw effects on unbound road materials. In this study, three soils were investigated for resilient behavior during freezing and thawing utilizing both VCP and CCP triaxial testing. The soils were tested at selected temperatures between +20 and –10°C during one full freeze–thaw cycle. The results were analyzed in terms of the traditionally used resilient modulus and Poisson's ratio, as well as volumetric and shear components, and indicate a significant difference in moduli computed from CCP and VCP data. However, resilient moduli display compatible values when interpreted in terms of mean values of deviator stress and mean normal stress. With regard to freezevthaw effects on resilient moduli, the results are inconsistent with previous findings. However, this can be explained by the different test conditions applied.Key words: freeze–thaw, triaxial tests, unbound pavement materials, subgrade soils, resilient modulus.

scholarly journals Empirical Method for Evaluating Resilient Modulus of Saturated Silty Clay under Cyclic Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhen Zhang ◽  
Yong Chen ◽  
Guanbao Ye ◽  
Peilin Xiang ◽  
Yan Xiao ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Stress Ratio ◽  
Resilient Modulus ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Empirical Method ◽  
Traffic Load ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Test Results

Resilient modulus of soil is crucial for the design of a structure on a foundation subjected to a cyclic loading (e.g., traffic load or machine vibration load). This paper conducted a series of dynamic triaxial tests of saturated silty clay, considering the influence of the factors of cyclic stress ratio (CSR), static deviatoric stress ratio (SDR), and overconsolidation ratio (OCR) on the resilient modulus and dynamic damping ratio of the soil. A cyclic loading with a form of half sine wave was used to model the traffic loading. The results showed that the soil was prone to failure under a higher SDR, even though the applied CSR was less than the critical CSR. The saturated silty clay performed a strain softening behavior and its dynamic properties deteriorated significantly when higher CSR and SDR and lower OCR were involved. Based on the test results, an empirical method with a form of exponential function was proposed to evaluate the resilient modulus of the soil, considering the combined effects of CSR and SDR and OCR. The proposed method was verified through a comparison with the test results in this study and from literatures, and some recommendations for its application were offered.

scholarly journals A Methodology for Determination of Resilient Modulus of Asphaltic Concrete

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
A. Patel ◽  
M. P. Kulkarni ◽  
S. D. Gumaste ◽  
P. P. Bartake ◽  
K. V. K. Rao ◽  
...  
Keyword(s):  
Resilient Modulus ◽  
Triaxial Tests ◽  
Asphaltic Concrete ◽  
Empirical Relationships ◽  
Cyclic Triaxial Tests ◽  
Electronic Circuitry ◽  
Quality Check ◽  
R Value ◽  
Vast Variation

Resilient modulus, , is an important parameter for designing pavements. However, its determination by resorting to cyclic triaxial tests is tedious and time consuming. Moreover, empirical relationships, correlating to various other material properties (namely, California Bearing Ratio, CBR; Limerock Bearing Ratio, LBR; R-value and the Soil Support Value, SSV), give vast variation in the estimated results. With this in view, an electronic circuitry, which employs bender and extender elements (i.e., piezo-ceramic elements), was developed. Details of the circuitry and the testing methodology adopted for this purpose are presented in this paper. This methodology helps in determining the resilient modulus of the material quite precisely. Further, it is believed that this methodology would be quite useful to engineers and technologists for conducting quality check of the pavements, quite rapidly and easily.

Evaluation of Seasonal Effects on Subgrade Soils

2003 ◽  
Vol 1821 (1) ◽  
pp. 47-55 ◽  
Author(s):  
Andrew G. Heydinger
Keyword(s):  
Seasonal Variations ◽  
Resilient Modulus ◽  
Monitoring Program ◽  
Test Site ◽  
Pavement Design ◽  
Seasonal Effects ◽  
Pavement Performance ◽  
Climatic Effects ◽  
Subgrade Soils ◽  
Frost Penetration

One objective of the FHWA’s Long-Term Pavement Performance (LTPP) program is to determine climatic effects on pavement performance. The LTPP instrumentation program includes seasonal monitoring program (SMP) instrumentation to monitor the seasonal variations of moisture, temperature, and frost penetration. Findings from the SMP instrumentation are to be incorporated into future pavement design procedures. Data from SMP instrumentation at the Ohio Strategic Highway Research Program Test Road (US-23, Delaware County, Ohio) and other reported results were analyzed to develop empirical equations. General expressions for the seasonal variations of average daily air temperature and variations of temperature and moisture in the fine-grained subgrade soil at the test site are presented. An expression for the seasonal variation of resilient modulus was derived. Average monthly weighting factors that can be used for pavement design were computed. Other factors such as frost penetration, depth of water table, and drainage conditions are discussed.

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