scholarly journals Relation between the Friction Angle of Sand at Triaxial Compression and Triaxial Extension and Plane Strain Conditions

Geosciences ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 29 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Plane Strain ◽  
Soil Mechanics ◽  
Triaxial Compression ◽  
Deformation Mode ◽  
Friction Angle ◽  
Failure Criteria ◽  
Compression Tests ◽  
Laboratory Test Results ◽  
Experimental Findings ◽  
Triaxial Extension

The strength of sand is usually characterized by the maximum value of the secant friction angle. The friction angle is a function of deformation mode, density, and stress level and is strongly correlated with dilatancy at failure. Most often, the friction angle is evaluated from results of conventional compression tests, and correlation between the friction angle of sand at triaxial compression and triaxial extension and plane strain conditions is a vital problem of soil mechanics. These correlations can be obtained from laboratory test results. The failure criteria for sand presented in literature also give the possibility of finding correlations between friction angles for different deformation modes. The general stress-dilatancy relationship obtained from the frictional state concept, with some additional assumptions, gives the possibility of finding theoretical relationships between the friction angle of sand at triaxial compression and triaxial extension and plane strain conditions. The theoretically obtained relationships presented in the paper are fully consistent with theoretical and experimental findings of soil mechanics.

scholarly journals Triaxial Testing of Geosynthetics Reinforced Tailings with Different Reinforced Layers

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1943
Author(s):  
Fu Yi ◽  
Changbo Du
Keyword(s):  
Triaxial Compression ◽  
Friction Angle ◽  
Confining Pressure ◽  
Test Results ◽  
Compression Tests ◽  
Strength Index ◽  
Stress Strain ◽  
High Confining Pressure ◽  
Zhang Model ◽  
Triaxial Compression Tests

To evaluate the shear properties of geotextile-reinforced tailings, triaxial compression tests were performed on geogrids and geotextiles with zero, one, two, and four reinforced layers. The stress–strain characteristics and reinforcement effects of the reinforced tailings with different layers were analyzed. According to the test results, the geogrid stress–strain curves show hardening characteristics, whereas the geotextile stress–strain curves have strain-softening properties. With more reinforced layers, the hardening or softening characteristics become more prominent. We demonstrate that the stress–strain curves of geogrids and geotextile reinforced tailings under different reinforced layers can be fitted by the Duncan–Zhang model, which indicates that the pseudo-cohesion of shear strength index increases linearly whereas the friction angle remains primarily unchanged with the increase in reinforced layers. In addition, we observed that, although the strength of the reinforced tailings increases substantially, the reinforcement effect is more significant at a low confining pressure than at a high confining pressure. On the contrary, the triaxial specimen strength decreases with the increase in the number of reinforced layers. Our findings can provide valuable input toward the design and application of reinforced engineering.

Influence of Water Contents on Shear Strength of Rammed Earth Wall of Earth-Building

2011 ◽  
Vol 382 ◽  
pp. 172-175
Author(s):  
Ren Wei Wu ◽  
Xing Qian Peng ◽  
Li Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Triaxial Compression ◽  
Friction Angle ◽  
World Heritage Site ◽  
Rammed Earth ◽  
Compression Tests ◽  
Rammed Earth Wall ◽  
Influence Of Water ◽  
Water Contents

As the "Fujian earth-building" have been inscribed by UNESCO in 2008 as World Heritage Site, attentions of protection about the "Fujian earth-building" has getting more and more. This article takes samples of a rammed-earth wall from Yongding earth-buildings and determines the shear strength of the samples with different water content through triaxial compression tests. The influence on shear strength of water content of rammed-earth samples is analyzed. Test results show that the shear strength of rammed-earth has much to do with the water content of the soil, the greater the water content is，the smaller the shear strength is. With water content increasing, cohesion and internal friction angle of rammed-earth were decreases, and its changing trend is of marked characteristic of stage. When water contents of rammed-earth is under some value, its cohesion changes in small ranges; when water contents of rammed-earth is over the value, its cohesion decreases with water content increasing.

scholarly journals Shear Characteristics of Cement-Stabilized Sand Reinforced with Waste Polyester Fiber Fabric Blocks

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiangfeng Lv ◽  
Hongyuan Zhou
Keyword(s):  
Low Cost ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Polyester Fiber ◽  
Peak Strain ◽  
Compression Tests ◽  
Initial Stiffness ◽  
Cemented Sand ◽  
Aspect Ratios ◽  
Fiber Fabric

The present paper is devoted to investigate the effects of waste polyester fiber fabric blocks on the strength and mechanical behavior of cemented sand. In the investigation, samples were prepared at four different percentages of waste polyester fiber fabric block content (0.0%, 0.5%, 1.0%, and 1.5% by weight of soil) and two different aspect ratios (2 : 1 and 3 : 1), and conventional triaxial compression tests were carried out after the curing period. The test results indicated that the addition of fibers increased peak and residual shear strengths of cemented sand and changed its brittle behavior to a more ductile one. As the fabric block content increased, the brittleness index and initial stiffness decreased, and the peak strain and internal friction angle increased. The optimal combination of the content and aspect ratio was determined to be 0.5% and 3 : 1. The integration of the fabric blocks with the cemented sand matrix was analyzed by using the scanning electron microscopy (SEM). It is found that the reinforcement effect is related to the bond strength and friction at the interface. The micromechanical properties of the fiber/matrix interface were influenced by the undulations between the fabric block components. In summary, this study presented a low-cost and environment-friendly method for reinforcing cement-stabilized sand.

scholarly journals Experimental Investigation on Failure Modes and Mechanical Properties of Rock-Like Specimens with a Grout-Infilled Flaw under Triaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Huilin Le ◽  
Shaorui Sun ◽  
Feng Zhu ◽  
Haotian Fan
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Epoxy Resin ◽  
Failure Modes ◽  
Shear Failure ◽  
Fractured Rock ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Confining Pressure ◽  
Compression Tests

Flaws existing in rock mass are one of the main factors resulting in the instability of rock mass. Epoxy resin is often used to reinforce fractured rock mass. However, few researches focused on mechanical properties of the specimens with a resin-infilled flaw under triaxial compression. Therefore, in this research, epoxy resin was selected as the grouting material, and triaxial compression tests were conducted on the rock-like specimens with a grout-infilled flaw having different geometries. This study draws some new conclusions. The high confining pressure suppresses the generation of tensile cracks, and the failure mode changes from tensile-shear failure to shear failure as the confining pressure increases. Grouting with epoxy resin leads to the improvement of peak strengths of the specimens under triaxial compression. The reinforcement effect of epoxy resin is better for the specimens having a large flaw length and those under a relatively low confining pressure. Grouting with epoxy resin reduces the internal friction angle of the samples but improves their cohesion. This research may provide some useful insights for understanding the mechanical behaviors of grouted rock masses.

Undrained triaxial strength and stress–strain characteristics of a glacial till soil

1988 ◽  
Vol 25 (3) ◽  
pp. 428-439 ◽  
Author(s):  
J. H. Atkinson ◽  
J. A. Little
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
Triaxial Compression ◽  
Practical Importance ◽  
Small Strain ◽  
Compression Tests ◽  
Triaxial Strength ◽  
Current State ◽  
Boulder Clay ◽  
Triaxial Compression Tests

Undrained triaxial compression tests were carried out on reconstituted and nominally undisturbed tubed samples of a lodgement till from the Vale of St. Albans in Hertfordshire, England. The soil is a matrix-dominant, chalky boulder clay of Anglian age with little discernable engineering fabric. Electron microscope observations showed the presence of crystalline calcite in tube samples.The test results were examined within the general framework of critical state soil mechanics using normalizing procedures to take account of the different states and stress histories of the samples. These analyses demonstrate the practical importance of accounting for the current state and stress history in the interpretation of soil test data.The present results form a self-consistent pattern of behaviour. Differences between reconstituted and tubed samples were found only at small strain and may be attributed to cementing in tubed samples, which is broken down during reconstitution and during relatively large straining in recompression and shearing. Key words: boulder clay, cemented soil, critical state, shear strength, soil mechanics, stiffness, till, triaxial test.

Isothermal modeling of sand–bentonite mixtures at elevated temperatures

1995 ◽  
Vol 32 (1) ◽  
pp. 78-88 ◽  
Author(s):  
B.E. Lingnau ◽  
J. Graham ◽  
N. Tanaka
Keyword(s):  
Shear Strength ◽  
Elevated Temperatures ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Compression Tests ◽  
Strain Behavior ◽  
Bentonite Buffer ◽  
State Boundary ◽  
Increasing Temperature ◽  
Triaxial Compression Tests

Two models are proposed for describing the stress–strain behavior of sand–bentonite (buffer) mixtures at elevated temperatures: (1) isothermal pseudoelasticity and (2) isothermal elastic-plasticity. Data to support the models come from consolidated undrained triaxial compression tests performed on dense saturated buffer specimens at effective confining stresses up to 9.0 MPa and temperatures of 26°, 65°, and 100 °C. Measurements indicate that volumes decrease with increasing temperature if the tests are carried out under drained conditions. These trends can be modelled by a family of hardening lines in semilog compression space. Power law relationships are presented for undrained shear-strength envelopes that increase in size with an increase in temperature. The slopes of unload-reload lines, κ, in semilog compression space vary with temperature and can be related to systematic variation in the friction angle [Formula: see text]. The shear modulus G50 at 50% peak strength also depends on temperature. Several plotting techniques are used to show the existence of different state boundary surfaces for each test temperature. Key words : sand–bentonite, buffer, compression, shear strength, temperature, modelling.

scholarly journals Characteristic parameters of soil failure criteria for plane strain conditions – experimental and semi-theoretical study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Justyna Sławińska-Budzich
Keyword(s):  
Plane Strain ◽  
Theoretical Study ◽  
Friction Angle ◽  
Failure Criteria ◽  
Flow Rule ◽  
Characteristic Parameters ◽  
True Triaxial ◽  
Soil Failure ◽  
Confining Pressures ◽  
Associated Flow Rule

Abstract The paper concerns the characteristic parameters of the selected isotropic failure criteria, i.e. Mohr–Coulomb, Drucker–Prager, Matsuoka–Nakai and Lade–Duncan. The parameters are determined directly from the failure criteria and stress measurements or by semi-theoretical approach, assuming that the soil obeys the associated flow rule and using the plane strain condition. In the latter case, the parameters can be expressed as functions of the plane strain internal friction angle, which is determined from measurements. The principal stress tensor components, corresponding to the soil peak strength and necessary to obtain the failure criteria parameters, are measured in a series of true triaxial, plane strain tests, on coarse Skarpa sand samples of different initial relative density, subjected to various confining pressures.

scholarly journals Stress-strain Relationship in Homogeneous and Two-layered Triaxial Test Specimens

2020 ◽  
Author(s):  
Gabriel Oliveira ◽  
Isabel Falorca
Keyword(s):  
Soil Mechanics ◽  
Triaxial Compression ◽  
Nonlinear Behavior ◽  
Confining Pressure ◽  
Test Method ◽  
Compression Tests ◽  
Stress Strain ◽  
Triaxial Apparatus ◽  
Strain Relationship ◽  
The Stability

The stress-strain relationship of a homogeneous specimen, obtained from triaxial compression test, allows to determine stiffness parameters for numerical-method based analyses in common geotechnical software. Stiffness parameters are defined as the ratio of stress to strain along an axis. However, when a heterogeneous specimen is tested, the equivalent elastic modulus that represents a simplification of the nonlinear behavior is complex. This paper presents a study intended to contribute to the debate about the degree to which conventional soil mechanics approaches can be applied to layered specimens. Triaxial compression tests were carried out on both homogeneous and two-layered specimens under a low effective confining pressure of 30 kPa. The triaxial apparatus was chosen since the applied stress and specimen boundary conditions are well defined, and the repeatability of the test method is good. The behavior of both specimens was studied in terms of the stress-strain relationship and stiffness. The main differences were crucial to understanding the composite soil-aggregate interaction, which is discussed and compared. The results indicate that the interface between composite soil and aggregate is important to keep the stability of the layer of aggregate over the soft composite soil, and practical methods of achieving that are suggested.

scholarly journals An Enhanced Ubiquitous-Joint Model for a Rock Mass With Conjugate Joints and Its Application on Excavation Simulation of Large Underground Caverns

2021 ◽  
Vol 9 ◽  
Author(s):  
Xianlun Leng ◽  
Chuan Wang ◽  
Qian Sheng ◽  
Jian Chen ◽  
Hailun Li
Keyword(s):  
Rock Mass ◽  
Failure Modes ◽  
Triaxial Compression ◽  
Local Coordinate System ◽  
Failure Criteria ◽  
Jointed Rock ◽  
Joint Model ◽  
Compression Tests ◽  
Mechanical Behaviors ◽  
Underground Caverns

A conjugate jointed rock mass (CJRM) is a rock mass with two sets of intersecting joints formed from intact rock under shear. Its mechanical properties and excavation-induced hazards of large underground caverns are different from those of common rock masses because of the unique geological origin thereof. To demonstrate numerically the excavation responses of CJRM, the ubiquitous-joint model is enhanced by consideration of the specific mechanical behaviors of the rock mass. In the enhanced model, CJRM is considered as the composite of columns of rock and two sets of weak planes of joints. The local coordinates, failure modes, and failure sequences of the rock columns and joints are redefined based on the composite characteristics of CJRM, and the failure criteria and plastic potential functions are accordingly modified. The enhanced model is verified numerically by triaxial compression tests and then employed to simulate the excavation of large underground caverns of a pumped storage power station in China. Results show that the modification of the local coordinate system, failure modes, and failure sequences made in the enhanced model is suited to the simulation of the mechanical behaviors of CJRM. Compared with the original ubiquitous-joint model, the enhanced model allows better predictions of the distribution of plastic zones and magnitudes of deformations in simulating underground excavations in CJRM and helps to assess the excavation-triggered hazards more accurately.

scholarly journals Numerical Triaxial Apparatus and Application

2013 ◽  
Vol 353-356 ◽  
pp. 3251-3255 ◽  
Author(s):  
Xiao Liang Wang ◽  
Jia Chun Li
Keyword(s):  
Granular Materials ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Good Prediction ◽  
Strain Response ◽  
Compression Tests ◽  
Dilatancy Angle ◽  
Triaxial Apparatus ◽  
Dem Model

A numerical triaxial apparatus based on discrete element method is developed on the platform of Yade using Python script. A DEM model with rolling resistance contact considered is proposed for dense granular materials, which is then applied in triaxial compression test of Chende sand. Stress-strain response and volume-axial strain response of the DEM model agree well with that of experiments, with a good prediction of dilatancy angle. Degradation of granular materials duo to particle erosion is also investigated using triaxial compression tests. It is indicated that peak friction angle decreases with the remove of particles if strong force network of granular materials is destroyed.

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