Triaxial Characterization of Minnesota Road Research Project Granular Materials

1997 ◽  
Vol 1577 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Navneet Garg ◽  
Marshall R. Thompson
Keyword(s):  
Shear Strength ◽  
Granular Materials ◽  
Resilient Modulus ◽  
Axial Strain ◽  
Confining Pressure ◽  
Engineering Properties ◽  
Shear Tests ◽  
Road Project ◽  
Load Tests ◽  
Repeated Load

Six granular materials were used as base and subbase materials in the flexible pavement test sections for the Minnesota Road Research (Mn/ROAD) project. Crushed/fractured particles are not allowed in aggregate classes CL-1Fsp, CL-1Csp, CL-3sp, and CL-4sp. Ten to 15 percent crushed/fractured particles are required for CL-5sp. One hundred percent crushed/ fractured particles are required for CL-6sp. A comprehensive laboratory testing program was established to determine pertinent engineering properties of the granular materials. Rapid shear tests and repeated-load tests were conducted to determine the shear strength parameters (friction angle and cohesion), resilient modulus, rutting potential, stress history effects on shear strength, and moisture susceptibility. The results from the rapid shear tests and permanent deformation tests show that the rutting potential of a granular material can be characterized from rapid shear test at a confining pressure of 15 psi (103.35 kPa). The rutting parameter A was a function of the shear strength of the granular materials. The shear strength results obtained from rapid shear tests performed at a confining pressure of 15 psi reflect the rutting trends observed in the low-volume road test sections at the Mn/ROAD project. Results from repeated-load tests were used to develop the parameters for K-θ, UT-Austin, and Uzan’s models for evaluating the resilient modulus of granular materials. The axial strain values calculated from the resilient modulus models appear to be in good agreement with the measured axial strain values, except for the very low shear strength material CL-1Csp.

Characterization of granular materials for pavements

1989 ◽  
Vol 26 (4) ◽  
pp. 725-730 ◽  
Author(s):  
A. Nataatmadja ◽  
A. K. Parkin
Keyword(s):  
Granular Materials ◽  
Resilient Modulus ◽  
Confining Pressure ◽  
Elastic Model ◽  
Deviator Stress ◽  
Repeated Load Triaxial Test ◽  
Materials Modelling ◽  
Repeated Load ◽  
Repeated Load Triaxial

For design and analysis of flexible pavements, a simple elastic model that does not require cumbersome calculation and also can rank materials according to their performance is clearly desirable. Early studies indicated that the resilient modulus of a granular material can be taken to be a function of the first invariant of stress, θ, although there is evidence that it is also dependent on the repeated deviator stress, qr. The limitations of some earlier models are discussed herein and a simple model for granular materials is proposed. The model is empirical in nature and based on repeated load triaxial testing with constant confining pressure. The application of this model in situations where the confining pressure is pulsed in phase with the deviator stress is also discussed. Key words: repeated load, triaxial test, resilient modulus, granular materials, modelling, pavement.

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.

Study on Shear Strength of Artificial Methane Hydrate

2010 ◽  
Author(s):  
Feng Yu ◽  
Yongchen Song ◽  
Weiguo Liu ◽  
Yanghui Li ◽  
Jiafei Zhao
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Shear Strength ◽  
Strain Rate ◽  
Methane Hydrate ◽  
Confining Pressure ◽  
Test System ◽  
Secant Modulus ◽  
Shear Tests ◽  
Hydrate Reservoir

The production of methane from hydrate reservoir may induce deformation of the hydrate-bearing strata. The research on mechanical properties of methane hydrate and establishing an efficient methane exploitation technology appear very important. In this paper, a low-temperature high-pressure triaxial test system including pressure crystal device (sample preparation system) was developed. A series of triaxial shear tests were carried out on artificial methane hydrate samples. The mechanical behavior was analyzed. The preliminary results show that the shear strength of methane hydrate increases with the increase of confining pressure and strain rate. While it increases with the decrease of temperature. Moreover, the secant modulus increases with the enhancement of strain rate and the decrease of confining pressure.

scholarly journals Comparison of Mechanical Properties of Fiber-Reinforced Sand under Triaxial Compression and Direct Shear

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Reza Noorzad ◽  
Seyed Taher Ghoreyshi Zarinkolaei
Keyword(s):  
Shear Strength ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Polypropylene Fiber ◽  
Triaxial Tests ◽  
Direct Shear ◽  
Test Results ◽  
Peak Reduction ◽  
Shear Tests ◽  
Direct Shear Tests

AbstractThis research investigates the behavior of sand reinforced with polypropylene fiber. To do this, 40 direct shear tests and 40 triaxial tests were performed on the coastal beaches of Babolsar, a city in the North of Iran. The effect of parameters such as fiber content, length of fiber and normal or confining pressure on the behavior of Babolsar sand have been studied. In this study, four various fiber contents (0, 0.25, 0.5 and 1 percent), three different lengths of fiber (6, 12 and 18 mm) and four normal or confining pressures (50, 100, 200 and 400 kPa) have been employed. The test results show that fiber inclusion has a significant effect on the behavior of sand. In both direct shear and triaxial tests, the addition of fibers improved shear strength parameters (C, '), increased peak shear strength and axial strain at failure, and also limited the amount of post-peak reduction in shear resistance. The comparison of the test results revealed that due to better fiber orientation toward the direction of principal tensile strain in triaxial test as compared to direct shear tests, the fiber efficiency and its effect on soil behavior is much more significant in triaxial specimens.

Study on Mechanical Property of Structural Damaged Expansive Soil with CT-Triaxial Shear Test

2012 ◽  
Vol 599 ◽  
pp. 811-814
Author(s):  
Lang Jing Shi ◽  
Xian Li ◽  
Zhen Peng ◽  
Shi Ji Wang ◽  
Fan Wu
Keyword(s):  
Mechanical Property ◽  
Axial Stress ◽  
Axial Strain ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Ct Images ◽  
Shear Tests ◽  
Triaxial Shear Test ◽  
Damage Area ◽  
Damage Degree

A series of CT-triaxial shear tests were conducted on expancive soil specimens under controlled suction and confining pressure as 50kPa and 100kPa. The derivative and axial stress in each stage and CT images of inner structure of specimens were obtained .The results show that the different damage location and damage degree on expansive soil samples have different effect on soil mechanical property. The deviatoric stress of smaller damage area sample is larger than of bigger damage area specimen when the damage locates at the same place. The deviatoric strain is independent of the damage degree of samples. The CT images show that with the axial strain increasing, the fissures in soil close gradually, the density of soil increases, and the deformation of samples gets larger with the increase of confining pressure.

scholarly journals Influence of particle size and gradation on shear strength–dilation relation of granular materials

2019 ◽  
Vol 56 (2) ◽  
pp. 208-227 ◽  
Author(s):  
Samaneh Amirpour Harehdasht ◽  
Mahmoud N. Hussien ◽  
Mourad Karray ◽  
Varvara Roubtsova ◽  
Mohamed Chekired
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Shear Strength ◽  
Granular Materials ◽  
Plane Strain ◽  
Computer Code ◽  
Direct Shear ◽  
Shear Tests ◽  
Empirical Formulas ◽  
Direct Shear Tests

Upon close scrutiny of data reported in the literature, taking into account particle-scale characteristics to optimize the precision of the well-known empirical Bolton’s equations and imposing particle-size limits on them is recommended. The present paper examines the potential influence of particle size and grading on the shear strength–dilation relation of granular materials from the results of 276 symmetrical direct shear tests. The applicability of physical symmetrical direct shear tests to interpret the plane strain frictional shearing resistance of granular materials has been widely discussed using the discrete element method (DEM) computer code SiGran. Sixteen different grain-size distribution curves of three different materials were tested at different normal pressures and initial relative densities. It is demonstrated that while the contribution of dilatancy to shear strength is not influenced by the variation in the coefficient of uniformity, Cu, in the investigated range, it significantly decreases with increasing mean particle size, D50. The coefficients of Bolton’s equations have been, therefore, adjusted to account for D50. A comparison of the predictions by the proposed empirical formulas with plane strain friction angle, [Formula: see text], and dilation angle, ψ, data from the literature shows that accounting for the grain size yields more accurate results.

scholarly journals Effect of the Surface Roughness on the Shear Strength of Granular Materials in Ring Shear Tests

2019 ◽  
Vol 9 (15) ◽  
pp. 2977 ◽  
Author(s):  
Sueng-Won Jeong ◽  
Sung-Sik Park
Keyword(s):  
Surface Roughness ◽  
Shear Strength ◽  
Granular Materials ◽  
Rough Surfaces ◽  
Shear Velocity ◽  
Shear Tests ◽  
Ring Shear ◽  
Ring Shear Tests ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

Surface roughness plays an important role in estimating the shear strength of granular materials. A series of ring shear tests with different surface roughnesses (i.e., smooth and rough surfaces) were performed. A large-sized ring shear device, which is applicable for fine- and coarse-grained sediments, was developed to examine the shear strength of large particle sizes (i.e., commercial gravels with a mean grain size of 6 mm). In terms of surface roughness, the drainage- and shear-velocity-dependent shear strengths of the granular materials were examined. In this study, different shear velocities of 0.1, 0.5, and 1 mm/s were applied under drained and undrained conditions. The test results clearly show that shear stress is affected by drainage, shear velocity, and surface roughness. In particular, a typical strain-hardening behavior is exhibited regardless of the drainage and shear velocity condition. The measured shear strength obtained from both drained and undrained conditions increased with increasing shear velocity. All tests showed a large fragmentation using rough surfaces compared to the smooth surfaces of the device. The grain crushing was significant during shearing, even when normal stress was not applied. For a given shear velocity, surface roughness is an important feature in determining the shear strength of granular materials.

scholarly journals Modeling Sea Ice fracture at very high resolution with VP rheologies

2018 ◽  
Author(s):  
Damien Ringeisen ◽  
Nils Hutter ◽  
Martin Losch ◽  
L. Bruno Tremblay
Keyword(s):  
Shear Strength ◽  
High Resolution ◽  
Sea Ice ◽  
Granular Materials ◽  
Yield Curve ◽  
Confining Pressure ◽  
Shear Resistance ◽  
Flow Rule ◽  
Normal Flow ◽  
Strength Parameters

Abstract. Recent high resolution pan-Arctic sea ice simulations show fracture patterns (Linear Kinematic Features – LKFs) that are typical of granular materials but with intersection (fracture) angles wider than those observed from high-resolution satellite images (with a modal value of θ = 20°). In this article, We investigate the mechanism of formation and parameter dependencies of ice fracture in simple numerical bi-axial test on a 8 km x 25 km ice floe at an unprecedented resolution of 25m for two different yield curves: an elliptical (VP) and a Coulombic yield curve both with normal flow rule. In the standardVP model, the simulated angle of fracture is θ = 33.9°, compared to 20° in observations. The dependence of the angle of fracture on the ice shear strength is also contrary to that of typical granular materials with larger angle of fracture for higher shear strength – think of a wet sand castle with steeper walls than a dry sand castle. In this model, the divergence along the fracture lines (or LKFs) is entirely dictated by the ice shear strength used in the model with high shear strength resulting in convergence along LKFs and low shear strength resulting in divergence along LKFs. This is again contrary to typical granular materials where divergence (or dilation) is linked with the orientation of contacts normals that oppose the flow with divergence present for larger shear resistance and convergence for lower shear resistance. Moreover, the angle of fracture depends on the confining pressure in the uni-axial test with more convergence as the confining pressure increases, again contrary to granular material that have an angle of fracture that is independent of the confining pressure. We note that all three behaviors of the VP model are linked with the use of an associative (normal) flow rule. In the Coulombic model, the angle of fracture is smaller (θ = 23.5°), but the solution is unstable when the compressive stresses are too large because of the discontinuity between the straight limbs of the yield curve and the elliptical capping. Our results show that while the VP model gives angles of fracture that are visually correct, the bias in the magnitude of the angle of fracture and the physical dependencies of the angle of fracture on mechanical strength parameters and stress fields couple the sea ice mechanical strength parameters, the sea-ice drift, sea-ice deformation (strain-rate) field in an inconsistent way. We consider this evidence to move away from the elliptical yield curve and associative (normal) flow rule, a deformation law that is not applicable to pressure-sensitive and dilatant granular material such as sea ice.

scholarly journals Shear strength behaviour of sand-bentonite mixtures with pumice additivite under high temperature

2020 ◽  
Vol 205 ◽  
pp. 04004
Author(s):  
Esra Güneri ◽  
Yeliz Yükselen Aksoy
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Room Temperature ◽  
Engineering Properties ◽  
Direct Shear ◽  
Test Results ◽  
Soil Behavior ◽  
Shear Tests ◽  
Volume Deformation ◽  
Direct Shear Tests

Depending on increase in the number and type of energy geostructures, studies on the change in soil behavior against heat increase becomes more important. The engineering properties such as permeability, volume deformation of surrounding soils around energy structures mustn’t alter in the presence of heat and thermal cycles. Pumice is a material used in many fields especially for thermal insulation. For that reason, pumice can be used for increasing the resistance of soils in the presence of heat. In this study, the shear strength behavior of sand-bentonite mixtures was investigated with pumice additive under high temperature. In the experiments, 10% and 20% pumice were added to 10% and 20% sand-bentonite mixtures and compaction, direct shear tests were conducted. The direct shear tests were performed both room temperature and under 80°C. The results have shown that the pumice additive increased the shear strength of sand-bentonite mixtures under high temperature when compared the test results under room temperature.

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