Moisture Effects on Degraded Ballast Shear Strength Behavior

2016 ◽  
Author(s):  
Yu Qian ◽  
Debakanta Mishra ◽  
Erol Tutumluer ◽  
Youssef M. A. Hashash ◽  
Jamshid Ghaboussi
Keyword(s):  
Shear Strength ◽  
Los Angeles ◽  
Large Scale ◽  
Coal Dust ◽  
Axial Strain ◽  
Dust Collection ◽  
Uniform Size ◽  
Classical Text ◽  
Fouled Ballast ◽  
Strength Behavior

Ballast consisting of large sized aggregate particles with uniform size distribution is an essential component of the track substructure, to facilitate load distribution and drainage. As freight tonnage accumulates with traffic, ballast will accumulate an increasing percentage of fines due to either aggregate breakdown or outside contamination such as subgrade soil intrusion and coal dust collection. According to the classical text by Selig and Waters [1], ballast degradation from traffic involves up to 76% of all fouling cases; voids will be occupied by fines from the bottom of ballast layer gradually causing ballast clogging and losing its drainage ability. When moisture is trapped within ballast, especially fouled ballast, ballast layer stability is compromised. In the recent studies at the University of Illinois, the focus has been to evaluate behavior of fouled ballast due to aggregate degradation using large scale triaxial testing. To investigate the effects of moisture on degraded ballast, fouled ballast was generated in the laboratory through controlled Los Angeles (LA) abrasion tests intended to mimic aggregate abrasion and breakdown and generate fouled ballast at compositions similar to those observed in the field due to repeated train loadings. Triaxial shear strength tests were performed on the fouled ballast at different moisture contents. Important findings of this preliminary study on characterizing wet fouled ballast are presented in this paper. Moisture was found to have a significant effect on the fouled ballast strength behavior. Adding a small amount of 3% moisture (by weight of particles smaller than 3/8 in. size or smaller than 9.5 mm) caused test specimens to indicate approximately 50% decrease in shear strength of the dry fouled ballast. Wet fouled ballast samples peaked at significantly lower maximum deviator stress values at relatively smaller axial strains and remained at these low levels as the axial strain was increased.

Effects of Ballast Degradation on Permanent Deformation Behavior From Large-Scale Triaxial Tests

2014 ◽  
Author(s):  
Yu Qian ◽  
Erol Tutumluer ◽  
Youssef M. A. Hashash ◽  
Jamshid Ghaboussi
Keyword(s):  
Los Angeles ◽  
Large Scale ◽  
Fine Particles ◽  
Coal Dust ◽  
Permanent Deformation ◽  
Triaxial Tests ◽  
Los Angeles Abrasion ◽  
Aggregate Breakdown ◽  
Fouled Ballast ◽  
Repeated Load

Consisting of large sized aggregate particles with uniform size distribution, ballast is an essential component of the track substructure to facilitate load distribution and drainage. As freight tonnage accumulates with traffic, ballast will get fouled increasingly due to either aggregate breakdown and degradation or contamination by other materials such as coal dust and subgrade soil intrusion. Fouling affects shear strength and load carrying ability of ballast layer especially under wet conditions. According to Selig and Waters [1], ballast fouling is often due to aggregate degradation, which covers up to 76% of all the fouling cases. To investigate the effects of ballast aggregate breakdown and degradation on the mechanical behavior of fouled ballast, a series of Los Angeles abrasion tests were performed in this study to generate fouled ballast materials caused by particle breakage and abrasion under a well-controlled laboratory environment. The change of particle shape properties during the Los Angeles abrasion tests was quantified and studied through image analysis technology. Large-scale triaxial tests were performed on specimens of new ballast, degraded ballast coarse particle fraction (without fines), and full gradation of degraded ballast (with fines) under repeated load application using a triaxial test device recently developed at the University of Illinois specifically for ballast size aggregate materials. The large-scale triaxial results indicated that the specimen having those degraded coarse particles yielded higher permanent deformation trends from repeated load triaxial testing when compared to the specimen with the new ballast gradation. As expected, the highest permanent deformation was obtained from the degraded ballast specimen having fine particles and the Fouling Index (FI) value of approximately 40.

Shear Strength and Drainage Characteristics of Elastomeric Polyurethane Treated Coal-Fouled Ballast

2021 ◽  
pp. 036119812110363
Author(s):  
Syed Khaja Karimullah Hussaini ◽  
Dinesh Gundavaram
Keyword(s):  
Shear Strength ◽  
Large Scale ◽  
Empirical Relationship ◽  
Direct Shear ◽  
Shear Tests ◽  
Contamination Index ◽  
Direct Shear Tests ◽  
Fouled Ballast ◽  
Constant Head ◽  
Fouling Materials

The shear behavior and drainage characteristics of coal-fouled ballast when treated with elastomeric polyurethane are assessed by means of large-scale direct shear and permeability tests. The results from direct shear tests confirmed that the shear strength of both stabilized and unstabilized coal-fouled ballast was highly influenced by the extent of fouling (VCI: void contamination index). The performance index (PI) of elastomer-stabilized coal-fouled ballast (ESFB), determined as the fraction of shear strength of fouled ballast to the shear strength of fresh and unstabilized ballast, lies in the range of 1.23 to 0.84. Moreover, the performance of ESFB having VCI ≥30% was found to be either similar to or poorer than that of clean ballast without any treatment, thus indicating that the elastomer treatment may be provided only to ballast with VCI ≤30%. The results from constant head permeability tests indicate that the hydraulic conductivity of ballast ( k) is highly influenced by the presence of fouling materials but is only slightly reduced as a result of the elastomer stabilization. The k of ballast decreased from 43 to 0.18 mm/s as the VCI increased from 0 to 75%. For VCI ≥ 45% the k of ballast was found to be lower than that recommended for sub-ballast. On the other hand, the k of ballast reduced slightly from 43 to 37 mm/s because of the elastomer stabilization. Furthermore, an empirical relationship is established between k and e to determine the k of both stabilized and unstabilized fouled ballast.

Experimental Study on the Shear Strength Characteristics of Municipal Solid Waste

2011 ◽  
Vol 219-220 ◽  
pp. 660-664 ◽  
Author(s):  
Zhen Ying Zhang ◽  
Da Zhi Wu
Keyword(s):  
Shear Strength ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Effective Stress ◽  
Large Scale ◽  
Void Ratio ◽  
Influence Factor ◽  
Axial Strain ◽  
Strength Characteristics ◽  
Initial Void Ratio

Basing on the traditional tri-axial test instrument with large scale specimen, the shear strength characteristics of municipal solid waste has been studied. The municipal solid waste is divided into three parts: the material that is easy to be biodegraded, reinforced material that is difficult to be biodegraded and the incompressible solid waste material. Two different proportions of these three parts, which are 50%, 15%, 35% and 65%, 10%, 25% is selected. A series of laboratory tests have been performed for different proportion of ingredients, different initial void ratios and different confining pressures. Testing results show that the initial void ratio and the proportion of ingredients are the main influence factor for the shear strength of the municipal solid waste. Besides, the principle effective stress increases with the axial strain and the confining pressure in a hardening increasing trend, and the principle effective stress decreases with the increase of the initial void ratio of the municipal solid waste.

Evaluation the Shear Strength Behavior of aged MSW using Large Scale In Situ Direct Shear Test, a case of Tabriz Landfill

2020 ◽  
Vol 18 (7) ◽  
pp. 717-733 ◽  
Author(s):  
Mohsen Keramati ◽  
Masoud Shahedifar ◽  
Mohammad Hosein Aminfar ◽  
Hasan Alagipuor
Keyword(s):  
Shear Strength ◽  
Large Scale ◽  
Direct Shear Test ◽  
Shear Test ◽  
Direct Shear ◽  
Strength Behavior

Shear strength behavior of Mont Terri Opalinus Claystone in fault zone

2015 ◽  
Vol 10 (1) ◽  
pp. 31-38
Author(s):  
Ildikó Buocz ◽  
Nikoletta Rozgonyi-Boissinot ◽  
Ákos Török
Keyword(s):  
Shear Strength ◽  
Fault Zone ◽  
Strength Behavior ◽  
Mont Terri

scholarly journals 214 Longitudinal Changes in Sleep Duration, Timing, Variability, and Stages during the COVID-19 Pandemic: Large-Scale Fitbit Data

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A86-A86
Author(s):  
Michael Grandner ◽  
Naghmeh Rezaei
Keyword(s):  
New York ◽  
Los Angeles ◽  
San Francisco ◽  
Sleep Duration ◽  
Large Scale ◽  
Age Groups ◽  
Population Level ◽  
Sleep Stages ◽  
Longitudinal Changes ◽  
Timing Variability

Abstract Introduction The COVID-19 pandemic has resulted in societal-level changes to sleep and other behavioral patterns. Objective, longitudinal data would allow for a greater understanding of sleep-related changes at the population level. Methods N= 163,524 deidentified active Fitbit users from 6 major US cities contributed data, representing areas particularly hard-hit by the pandemic (Chicago, Houston, Los Angeles, New York, San Francisco, and Miami). Sleep variables extracted include nightly and weekly mean sleep duration and bedtime, variability (standard deviation) of sleep duration and bedtime, and estimated arousals and sleep stages. Deviation from similar timeframes in 2019 were examined. All analyses were performed in Python. Results These data detail how sleep duration and timing changed longitudinally, stratified by age group and gender, relative to previous years’ data. Overall, 2020 represented a significant departure for all age groups and both men and women (P<0.00001). Mean sleep duration increased in nearly all groups (P<0.00001) by 5-11 minutes, compared to a mean decrease of 5-8 minutes seen over the same period in 2019. Categorically, sleep duration increased for some and decreased for others, but more extended than restricted. Sleep phase shifted later for nearly all groups (p<0.00001). Categorically, bedtime was delayed for some and advanced for others, though more delayed than advanced. Duration and bedtime variability decreased, owing largely to decreased weekday-weekend differences. WASO increased, REM% increased, and Deep% decreased. Additional analyses show stratified, longitudinal changes to sleep duration and timing mean and variability distributions by month, as well as effect sizes and correlations to other outcomes. Conclusion The pandemic was associated with increased sleep duration on average, in contrast to 2019 when sleep decreased. The increase was most profound among younger adults, especially women. The youngest adults also experienced the greatest bedtime delay, in line with extensive school-start-times and chronotype data. When given the opportunity, the difference between weekdays and weekends became smaller, with occupational implications. Sleep staging data showed that slightly extending sleep minimally impacted deep sleep but resulted in a proportional increase in REM. Wakefulness during the night also increased, suggesting increased arousal despite greater sleep duration. Support (if any) This research was supported by Fitbit, Inc.

Coal dust explosions in a large-scale vertical tube apparatus

1971 ◽  
Vol 17 (2) ◽  
pp. 159-170 ◽  
Author(s):  
K.N. Palmer ◽  
P.S. Tonkin
Keyword(s):  
Large Scale ◽  
Coal Dust ◽  
Vertical Tube ◽  
Dust Explosions

scholarly journals Large-Scale Fabrication of Ultrasensitive and Uniform Surface-Enhanced Raman Scattering Substrates for the Trace Detection of Pesticides

Nanomaterials ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 520 ◽  
Author(s):  
Jia Zhu ◽  
Guanzhou Lin ◽  
Meizhang Wu ◽  
Zhuojie Chen ◽  
Peimin Lu ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Large Scale ◽  
Capillary Flow ◽  
Surface Enhanced Raman Scattering ◽  
Ag Nps ◽  
Uniform Size ◽  
Sers Substrates ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering

Technology transfer from laboratory into practical application needs to meet the demands of economic viability and operational simplicity. This paper reports a simple and convenient strategy to fabricate large-scale and ultrasensitive surface-enhanced Raman scattering (SERS) substrates. In this strategy, no toxic chemicals or sophisticated instruments are required to fabricate the SERS substrates. On one hand, Ag nanoparticles (NPs) with relatively uniform size were synthesized using the modified Tollens method, which employs an ultra-low concentration of Ag+ and excessive amounts of glucose as a reducing agent. On the other hand, when a drop of the colloidal Ag NPs dries on a horizontal solid surface, the droplet becomes ropy, turns into a layered structure under gravity, and hardens. During evaporation, capillary flow was burdened by viscidity resistance from the ropy glucose solution. Thus, the coffee-ring effect is eliminated, leading to a uniform deposition of Ag NPs. With this method, flat Ag NPs-based SERS active films were formed in array-well plates defined by hole-shaped polydimethylsiloxane (PDMS) structures bonded on glass substrates, which were made for convenient detection. The strong SERS activity of these substrates allowed us to reach detection limits down to 10−14 M of Rhodamine 6 G and 10−10 M of thiram (pesticide).

Shear strength behavior of compacted unsaturated residual soil

2013 ◽  
Vol 7 (1) ◽  
pp. 1-9 ◽  
Author(s):  
F A M Marinho ◽  
O M Oliveira ◽  
H Adem ◽  
S Vanapalli
Keyword(s):  
Shear Strength ◽  
Residual Soil ◽  
Strength Behavior
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