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.

Shear Strength of Sand–Clay Interfaces Through Large-Scale Direct Shear Tests

2020 ◽  
Vol 45 (5) ◽  
pp. 4343-4357
Author(s):  
Zhong-Liang Zhang ◽  
Zhen-Dong Cui ◽  
Ling-Zi Zhao
Keyword(s):  
Shear Strength ◽  
Large Scale ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests

scholarly journals SCALE EFFECT ON THE SHEAR STRENGTH OF TWO-LAYER SOIL REINFORCED BY GEOGRID

2018 ◽  
Vol 30 (1) ◽  
Author(s):  
Sakine Tamassoki ◽  
Reza Z. Moayed ◽  
Mohammad Ashkani ◽  
Hamidreza Rahimi
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Scale Effect ◽  
Large Scale ◽  
Direct Shear ◽  
Shear Tests ◽  
Element Analysis ◽  
Direct Shear Tests ◽  
Granular Base ◽  
Shear Box

Geosynthetics are used to reinforce soils and improve their mechanical characteristics,especially when soft low-bearing capacity soils are encountered in civil engineering projects.Particularly, in roads, geosynthetics are placed between the interface of granular materials andsoft-soil sub grade to improve composite layers’ bearing capacity. This paper presents the resultsof the finite element analysis of the two-layer soil(granular base-clayey sub grade) reinforced bygeogrid and discusses the effect of the reinforcement on the shear strength. As the primary aim ofthe study, the numerical model was calibrated in comparison with the experimental results oflarge scale direct shear tests. The results showed that the shear strength improved in the two-layersoil which had been reinforced by geogrid. The predictions made by the developed model werefound to be in line with the experimental data obtained from large scale direct shear tests. Asanother aim of the study, different dimensions of shear box were used for modelling in order toinvestigate the scale effect on the shear strength of double-layered soil (clay-sand). The resultsshowed that the increase in the dimensions of the reinforced shear box leads to the enhancementof peak shear strength. Moreover, several analyses were conducted on geogrid in shear box withdifferent dimensions in fixed and unfixed states. The results demonstrated that the shear strengthof treated geogrid was higher than the shear strength of those in which untreated geogrid wasutilized.

scholarly journals Using Post-Harvest Waste to Improve Shearing Behaviour of Loess and Its Validation by Multiscale Direct Shear Tests

2019 ◽  
Vol 9 (23) ◽  
pp. 5206 ◽  
Author(s):  
Wen-Chieh Cheng ◽  
Zhong-Fei Xue ◽  
Lin Wang ◽  
Jian Xu
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Strain Hardening ◽  
Gradual Increase ◽  
Small Scale ◽  
Optimal Dosage ◽  
Direct Shear ◽  
Shear Tests ◽  
Post Harvest ◽  
Direct Shear Tests

Loess and PHW (post-harvest waste) are easily accessible in the Chinese Loess Plateau and have been widely applied to construction of residential houses that have been inhabited for decades under the effect of freeze-thaw cycles. Although many researchers have recognised that the addition of fibers to loess soil is effective in preventing soil erosion and stabilising slopes, a consensus on this claim has not been reached yet. This study investigates the shearing behaviour of the loess-PHW mixture using small-scale and large-scale direct shear (SSDS and LSDS) tests. Four typical shear stress versus horizontal displacement curves from the multiscale direct shear tests are recognised where one is featured with strain-softening shape and the other three with a strain-hardening shape. Two out of the three curves with strain-hardening shape show a gradual increase in the shear stress at additional and larger displacements, respectively, in which some factor starts to have an influence on the shearing behaviour. Comparisons of the shear strength measured in SSDS and LSDS are made, indicating that there are differences between SSDS and LSDS. The effect of PHW addition on shear strength is assessed in order to determine the optimal dosage. The improvement of shear strength is attributed to the effect of particle inter-locking, resulting from the addition of PHW to loess specimens, and takes effect as the water content surpassed a threshold, i.e., >14%, that facilitates particle rearrangement. Particle-box interaction behaviour is assessed at the same time, and the findings satisfactorily address the main cause of the gradual increase in shear stress following the curve inflection point. The improved shearing behaviour proves the ability of the loess-PHW mixture to resist the seepage force and consequently stratum erosion.

Large Scale Laboratory Direct Shear Tests on Ice

1975 ◽  
Vol 12 (2) ◽  
pp. 169-178 ◽  
Author(s):  
W. D. Roggensack
Keyword(s):  
Large Scale ◽  
Stress Conditions ◽  
Direct Shear ◽  
Shear Tests ◽  
Principal Stresses ◽  
Lake Ice ◽  
Direct Shear Tests ◽  
Strength Determination ◽  
Crystal Diameter ◽  
Shear Box

This paper presents the results of a series of large scale direct shear tests performed on lake ice. Test specimens were oriented with the principal stresses acting in the plane of the ice sheet, approximately normal to the long axes of the columnar crystals. Sample dimensions were large in comparison with mean crystal diameter, reducing the possibility of deviations introduced by size effects. Although a number of assumptions are made concerning stress conditions at failure, results for uniform, artificially ‘seeded’ test pond ice indicate a failure mechanism that is frictional and consistent with triaxial test data reported elsewhere. Post-peak shear resulted in the formation of a distinct failure zone that also displayed a frictional response. The direct shear test described is robust and simple, does not require elaborate sample preparation, and may present an alternative method of strength determination for ice mechanics problems where the shear box configuration duplicates field stress conditions and constraints.

Effect of fibre content and structure on anisotropic elastic stiffness and shear strength of peat

2012 ◽  
Vol 49 (4) ◽  
pp. 403-415 ◽  
Author(s):  
Michael T. Hendry ◽  
Jitendra S. Sharma ◽  
C. Derek Martin ◽  
S. Lee Barbour
Keyword(s):  
Shear Strength ◽  
Confining Pressure ◽  
Deviatoric Stress ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
A Value ◽  
Frictional Strength ◽  
Fibrous Peat ◽  
Interparticle Friction

This paper presents the results of a laboratory testing program involving consolidated undrained triaxial tests and direct shear tests on remoulded peat, remoulded peat fibre, and Shelby specimens of peat obtained from a field site located in the Edson subdivision of the Canadian National railway in Alberta, Canada. These results were analyzed within the frameworks of elastic behaviour of cross-anisotropic materials and shear strength of fibre-reinforced soil. Shelby specimens were found to be inherently cross-anisotropic, whereas the remoulded peat and peat fibre specimens showed a transition from isotropic to cross-anisotropic with increasing vertical strain and effective confining pressure. The horizontal stiffness of Shelby specimens was found to be 2.6 to 2.9 times their vertical stiffness. The shear strength of intact peat is made up of interparticle friction as well as tension in the peat fibres. A novel procedure for estimating the interparticle frictional strength of fibrous peat from CU triaxial test results is proposed. It involves extrapolating the linear strain-hardening portion of the stress–strain curve to obtain the deviatoric stress at zero axial strain and plotting the deviatoric stress values thus obtained against initial mean effective confining pressure to obtain the frictional strength. Using this procedure, a value of 31° was obtained for the interparticle friction, which compares favourably with a value of 31° obtained from direct shear tests. It is recommended that further studies be undertaken to assess if interparticle frictional strength is an appropriate strength parameter for evaluation of the stability of structures founded on fibrous peat.

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