Stress–strain behaviour of weathered weak rock in middle-sized triaxial tests

2006 ◽  
Vol 43 (10) ◽  
pp. 1096-1104 ◽  
Author(s):  
De'an Sun ◽  
Tugen Feng ◽  
Hajime Matsuoka
Keyword(s):  
Triaxial Test ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Weak Rock ◽  
Test Results ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Undisturbed Samples ◽  
Strain Relationship

A middle-sized triaxial test apparatus for a specimen 20 cm in height and 10 cm in diameter was developed to measure the deformation and strength of weak rock or gravel. High-quality undisturbed samples of a weathered weak rock were taken from a dam site by a core drilling method. To avoid damage to the structure of the weak rock due to saturation of specimens as a result of measuring volume change through the water change in a burette, the lateral deformation of specimens was directly measured in the unsaturated condition using three rings mounted on the specimen. Using the developed triaxial test apparatus, isotropic compression tests and consolidated–drained triaxial compression tests were performed on unsaturated or saturated undisturbed samples under confining pressures of 49, 98, 196, 392, 539, and 683 kPa. The test results show that the stress–strain relationship of the weathered weak rock under both unsaturated and saturated conditions is strongly influenced by the confining pressure when the confining pressure is less than 392 kPa, and the stress–strain behaviour becomes similar to that of normally consolidated clay when the confining pressure is greater than 392 kPa. Comparison of results of triaxial tests on unsaturated and saturated specimens shows that the saturated samples become somewhat weak. The test results also show that the bonding and stress history largely influence the stress–strain relationship at small strain levels.Key words: weathered weak rock, microstructure, undisturbed sample, deformation, strength, triaxial test, unsaturated sample.

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.

Dynamic Stress-Strain Relationship of Saturated Clay by Dynamic Triaxial Test

2011 ◽  
Vol 250-253 ◽  
pp. 3183-3186
Author(s):  
Jian Yi Yuan
Keyword(s):  
Triaxial Test ◽  
Dynamic Stress ◽  
Soft Clay ◽  
Confining Pressure ◽  
Dynamic Shear ◽  
Stress Strain ◽  
Dynamic Triaxial Test ◽  
Wide Range ◽  
Strain Relationship ◽  
Relationship Of

Subgrade diseases are exposed more and more serious with raising speed of existing railway in wide range. Fro the complexity of dynamic stress-strain relationship of soil, dynamic triaxial test was used to analyze .the dynamic mechanics behavior under cyclic train load for saturated soft clay in Yangtze Delta region. Compaction coefficient, confining pressure, dynamic shear strsss ratio, inputing stimulus and loading frequence were taken into account in test. The results show that the dynamic stress-strain curves of soil specimen are provided with prominent hysteretic characteristics and area surrounded by hysteretic curves gradually augment and slope of hysteretic curve decreases with the increase of dynamic shear train amplitude. The strong correlation exists between dynamical stress and strain.

scholarly journals Effect of Geotextile Reinforcement on Shear Strength of Sandy Soil: Laboratory Study

2016 ◽  
Vol 38 (4) ◽  
pp. 3-13 ◽  
Author(s):  
Sidali Denine ◽  
Noureddine Della ◽  
Muhammed Rawaz Dlawar ◽  
Feia Sadok ◽  
Jean Canou ◽  
...  
Keyword(s):  
Shear Strength ◽  
Mechanical Behaviour ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Loose Sand ◽  
Test Results ◽  
Compression Tests ◽  
Confining Stress ◽  
Natural Sand ◽  
Confining Pressures

Abstract This paper presents results of a series of undrained monotonic compression tests on loose sand reinforced with geotextile mainly to study the effect of confining stress on the mechanical behaviour of geotextile reinforced sand. The triaxial tests were performed on reconstituted specimens of dry natural sand prepared at loose relative density (Dr = 30%) with and without geotextile layers and consolidated to three levels of confining pressures 50, 100 and 200 kPa, where different numbers and different arrangements of reinforcement layers were placed at different heights of the specimens (0, 1 and 2 layers). The behaviour of test specimens was presented and discussed. Test results showed that geotextile inclusion improves the mechanical behaviour of sand, a significant increase in the shear strength and cohesion value is obtained by adding up layers of reinforcement. Also, the results indicate that the strength ratio is more pronounced for samples which were subjected to low value of confining pressure. The obtained results reveal that high value of confining pressure can restrict the sand shear dilatancy and the more effect of reinforcement efficiently.

Laboratory Triaxial Test Study on Soil Reinforced with Roots of Manilagrass

2011 ◽  
Vol 250-253 ◽  
pp. 1366-1370 ◽  
Author(s):  
Kai Fu Liu ◽  
Xiang Ru Yang ◽  
Xin Yu Xie ◽  
Chang Fu Wu ◽  
Yong Hai Liu
Keyword(s):  
Shear Strength ◽  
Triaxial Test ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Research Results ◽  
Test Study ◽  
Strain Relationship ◽  
Optimal Quantity ◽  
Better Than

Laboratory triaxial tests of the soil reinforced with roots of Manilagrass were carried out in order to understand the stress-strain relationship. The change of shear strength indexes of the soil reinforced with roots of Manilagrass was investigated with the quantity of grassroots planted in the soil specimens. The results of laboratory triaxial tests show that the strength and capacity for resisting the deformation of soil reinforced with roots are better than those of unreinforced soil. And under the certain number of grassroots layers, the strength and capacity for resisting the deformation of soil reinforced with roots increase firstly and then reduce with the increasing of Manilagrass roots quantity. In other words, there is an optimal quantity of Manilagrass roots affecting the strength and capacity for resisting the deformation of soil reinforced with roots. The research results are important for understanding the mechanism and use of vegetation protection for slope.

scholarly journals A Stress-Strain Model for Brick Prism under Uniaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Keun-Hyeok Yang ◽  
Yongjei Lee ◽  
Yong-Ha Hwang
Keyword(s):  
Strain Curve ◽  
Peak Stress ◽  
Test Results ◽  
Compression Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Proposed Model ◽  
Relationship Model ◽  
Strain Relationship ◽  
Strain Model

This study proposes a simple and rational stress-strain relationship model applicable to brick masonry under compression. The brick prism compression tests were conducted with different mortar strengths and with constant brick strength. From the observation of the test results, shape of the stress-strain curve is assumed to be parabola. In developing the stress-strain model, the modulus of elasticity, the strain at peak stress, and the strain at 50% of the peak stress on the descending branch were formulated from regression analysis using test data. Numerical and statistical analyses were then performed to derive equations for the key parameter to determine the slopes at the ascending and descending branches of the stress-strain curve shape. The reliability of the proposed model was examined by comparisons with actual stress-strain curves obtained from the tests and the existing model. The proposed model in this study turned out to be more accurate and easier to handle than previous models so that it is expected to contribute towards the mathematical simplicity of analytical modeling.

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 Comparative Study in Method of Compaction by Consolidated Drained and Direct Shear Test

2020 ◽  
Vol 78 (2) ◽  
pp. 143-152
Author(s):  
Abdul Samad Abdul Rahman ◽  
N. Sidek ◽  
Juhaizad Ahmad ◽  
N. Hamzah ◽  
M. I. F. Rosli
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Triaxial Test ◽  
Direct Shear Test ◽  
Shear Test ◽  
Void Ratio ◽  
Direct Shear ◽  
Test Results ◽  
Stress Strain ◽  
Strain Behaviour

Soil compaction has been a common practice in the construction of highways, embankments, earth dams and other related structures where the condition of the soil is high in void ratio and therefore having a very low in bearing capacity. Therefore, the soil needs to be compacted in order to minimize the void ratio and in the same time would results in having a very high bearing capacity to sustain load. Nevertheless, only a few researches have been done to investigate the method of compaction using different energy on the behavior of shear strength by consolidated drained and direct shear test. In this research, the effect of different compaction in energy of 25 number of blows compared to 40 number of blows on the stress-strain behaviour of drained triaxial test has been done and findings of the data are to be compared with direct shear test. Results reveal that there is an increase in soil unit weight by using different energy in compaction with an increase of 5% from 1790 kg/m3 to 1880 kg/m3 for 25 and 40 number of blows respectively. However, the stress-strain behaviour of the specimens shows differently when compared between consolidated drained triaxial and direct shear test. The shear strength for direct shear-stress is at higher value compared to drained triaxial test. For drained triaxial test, results reveal that the effective friction angles are increase only about 1% from 37° to 38°. This is due to the soil particles rearranging itself with the different applied pressures thus eliminating the effects of different energy on the shear strength of the specimens. However, for direct shear test, the shear strength increases drastically from 29° to 32°. The increase of the shear strength is more likely influence by the soil particle arrangement due to the impact of the energy of the no of blows to the desired specimen.

scholarly journals Studying Shear Performance of Flax Fiber-Reinforced Clay by Triaxial Test

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Qiang Ma ◽  
Yicong Yang ◽  
Henglin Xiao ◽  
Wenwen Xing
Keyword(s):  
Shear Strength ◽  
Triaxial Test ◽  
Confining Pressure ◽  
Fiber Content ◽  
Flax Fiber ◽  
Triaxial Tests ◽  
Fiber Reinforced ◽  
Shear Performance ◽  
Strain Relationship ◽  
Reinforced Clay

Laboratory triaxial tests were carried out to investigate the reinforcement mechanism, to study the characteristics of flax fiber-reinforced clay, and to discuss the effect on stress-strain relationship and shear strength parameters of flax fiber-reinforced clay in different flax fiber content and different confining pressure. Respectively, the ratio of fiber content to clay by weight is 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%, and the confining pressure is 100 kPa, 200 kPa, and 300 kPa in triaxial test. The test results show that, the shear strength of flax fiber-reinforced clay is greater than that of pure clay. Compared with the pure clay, the shear strength of flax fiber-reinforced clay increased as the cohesion and friction increased; while the increase of the friction is relatively small, the increase of cohesion is large. The shear strength firstly increased and then reduced with the increase of flax fiber content. When the fiber content was 0.8%, the shear strength reached a peak value, and the shear strength reduced with the further increase of fiber content.

Study on Stress-Strain Behaviour of Mud Stone from Triaxial Test

2011 ◽  
Vol 197-198 ◽  
pp. 1425-1429
Author(s):  
Bao Tian Xu ◽  
Chang Hong Yan
Keyword(s):  
Elastic Strain ◽  
Polynomial Function ◽  
Confining Pressure ◽  
Stress Strain ◽  
Failure Pressure ◽  
Strain Behaviour ◽  
Strain Fracture ◽  
Strain Relationship ◽  
Relationship Of ◽  
The Relationship

This paper systematically analysis the stress-strain behaviour of mud stone under different confining pressure. The relationship between the mechanical behaviour of mud stone and confining pressure is established, and the curves of stress-strain relationship of mud stone are fitted. The results indicate that the failure pressure and the elastic modulus increase with the increasing of confining pressure conforming to the linear function. The stress- strain of mud stone is divided into four different stages which are fracture closing, elastic strain, fracture expanding and plastic strain stage. The stress-strain behaviour in different stage has different function law, the stage of fracture closing can be fitted by polynomial function, the stage of fracture expanding can be fitted by hyperbola function, the fitting result is ideal.

Effect of consolidation history and stress path on hyperbolic stress–strain relations

1985 ◽  
Vol 22 (2) ◽  
pp. 172-176 ◽  
Author(s):  
Y. P. Vaid
Keyword(s):  
Stress Path ◽  
Triaxial Tests ◽  
Soil Deformation ◽  
Test Results ◽  
Stress Strain ◽  
Deviator Stress ◽  
Strain Behaviour ◽  
Stress Variable ◽  
Anisotropic Consolidation ◽  
Soil Behaviour

The hyperbolic approximation of the stress–strain behaviour of soil based on the results of conventional triaxial tests, which is used in incremental elastic analysis of soil deformation problems, is shown to be inapplicable for representing soil behaviour under anisotropic consolidation and different stress paths. Test results on a normally consolidated clay are presented to show that a separate hyperbolic representation of stress–strain behaviour is possible for each consolidation history and stress path if increment in deviator stress after consolidation, rather than deviator stress, is used as the stress variable. Hyperbolic parameters are thus shown to depend on test type.

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