Triaxial Compression of a Cohesive Soil with Effective Octahedral Normal Stress Control

1965 ◽  
Vol 2 (1) ◽  
pp. 40-52 ◽  
Author(s):  
R L Kondner ◽  
J M Horner
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Triaxial Compression ◽  
Cohesive Soil ◽  
Deviatoric Stress ◽  
Strain Response ◽  
Compression Tests ◽  
Ultimate Shear Strength ◽  
Stress Strain ◽  
Stress Control

The influence of the first invariant of the effective stress tensor upon the deviatoric response of a cohesive soil is investigated. Triaxial compression tests with effective octahedral normal stress control show the deviatoric stress-strain response to be definitely affected by the value of the effective octahedral stress, [Formula: see text]. The values of [Formula: see text] range from 7.5 psi to 30.0 psi. For a constant value of strain, the deviatoric stress increases with an increase in [Formula: see text]. The ultimate shear strength can be approximated as a linear function of [Formula: see text]. Hyperbolic representation of the stress-strain response provides a convenient method for obtaining a measure of the ultimate shear strength using the response of stress states other than failure. The deviatoric stress-strain response as a function of the effective octahedral stress, [Formula: see text], can be expressed in the normalized form[Formula: see text]where ε is the strain, [Formula: see text] is a measure of the shear strength expressed in terms of [Formula: see text] , and A as well as B are numerical coefficients.

Experimental Study on Shear Strength Considering Initial Void Ratio and Plasticity Index

2013 ◽  
Vol 405-408 ◽  
pp. 63-67
Author(s):  
Xing Chen Wang ◽  
Ri Qing Xu ◽  
Jian Feng Zhu
Keyword(s):  
Shear Strength ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Deviatoric Stress ◽  
Plasticity Index ◽  
Test Results ◽  
Compression Tests ◽  
Functional Relationships ◽  
Initial Void Ratio

A series of drained triaxial compression tests under different conditions were performed to quantitatively study the influence of the initial void ratio and plasticity index on the shear strength of remolded saturated clays. The test results show that both the peak stress friction angle and peak deviatoric stress decrease with increasing initial void ratio and plasticity index of the soil under the same confining pressure; whereas, they increase with increasing confining pressure of the soil under the same initial void ratio and plasticity index. A new synthesized physical parameter λ, which simultaneously represent both the type and the condition of remolded saturated clays, is defined based on the test results in this work. The functional relationships among the parameters φd and peak deviatoric stress in Mohr-Coulomb equation and the parameter λ are established to develop a modified Mohr-Coulomb equation by considering physical properties of soil. In this equation, only two input parameters, i.e., λ and the confine pressure, are needed to predict the shear strength of the soil. In order to check the accuracy of the proposed equation, laboratory tests were conducted to evaluate against the predicted results. The results show that the peak shear strength of remolded saturated clays can be well described by the proposed equation. Key words: shear strength; Mohr-Coulomb equation; remolded saturated clays; initial void ratio; plasticity index.

scholarly journals Triaxial Testing on Geogrid-reinforced Granular Soils

2021 ◽  
Vol 1200 (1) ◽  
pp. 012030
Author(s):  
Tigo Mindiastiwi ◽  
Po-Kai Wu ◽  
Agus Bambang Siswanto ◽  
Mukhamad Afif Salim
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Reinforced Soil ◽  
Deviatoric Stress ◽  
Granular Soils ◽  
Peak Shear Strength ◽  
Compression Tests ◽  
Soil C ◽  
Dense Sand

Abstract Laboratory triaxial compression tests were carried out to investigate the mechanical behavior of dense sand and geogrid-reinforced granular soils. The tested sand having its mean particle size (D50) equal to 0.6 mm was adopted. Three geogrids with different longitudinal and transverse nominal strengths were used. The dimensions of the cylindrical soil specimen were 70 mm (diameter) × 160 mm (height). The relative density was equal to 70% for all tests. The reinforced sand specimens with one or two geogrid layers were sheared under effective confining pressures (σ′3) equal to 50 kPa. The test results of unreinforced sand indicate the general stress-strain behavior of dense sand when sheared, whereas the deviatoric stress reaches its peak value, after which it gradually decreases to ultimate value (σ1 - σ3)ult. The difference of effective confining pressure indicates that the peak of deviatoric stress Δσd = (σ1 - σ3) increases with the increase in effective confining pressure (σ′3), while the peak principal stress ratio (σ′1/σ′3) decreases with the increase (σ′3). The friction angle (ϕ′)and cohesion (c′), defined by analytical and graphical methods for unreinforced sand. Geogrid as reinforcement increasing peak shear strength. The increasing peak shear strength is more pronounced with a higher number of geogrid and the geogrid with higher stiffness. Increased in confining stress inside reinforced soil mass (Δσ3R) can be interpreted by cohesive reinforced soil (CR).

Shear Strength of a Cemented Paste Backfill Submitted to High Confining Pressure

2016 ◽  
Vol 858 ◽  
pp. 219-224 ◽  
Author(s):  
Eduardo Eiler Batista de Araújo ◽  
Dragana Simon ◽  
Fagner Alexandre Nunes de França ◽  
Osvaldo de Freitas Neto ◽  
Olavo Francisco dos Santos Jr.
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Binder Content ◽  
Cemented Paste Backfill ◽  
Compression Tests ◽  
Mining Operations ◽  
Geomechanical Properties ◽  
Confining Pressures ◽  
Paste Backfill ◽  
Curing Method

Deep mining operations require special measures in order to keep safe and economic aspects. After mine ore is extracted, voids are created and need to be filled with high-strength, low-cost materials. Cemented Paste Backfill (CPB) has recently become one of the main alternatives in filling stopes. Although numerous papers have mentioned the magnitudes of the strength of this material, its behavior under high confining pressures is still not well understood. Therefore, the purpose of this study is to increase the knowledge regarding the CPB behavior. Triaxial compression tests were performed using a Hoek Cell and Load Frame System under high confining pressures. Samples with two different binder contents were used in order to obtain the CPB strength improvement. Besides the self-weight consolidation curing method, samples were subjected to a different curing method that simulated a zero gravity condition (rotating wheel) in the first curing day to compare their mixture properties. The results suggested that both curing method and binder content have influenced the geomechanical properties of Cemented Paste Backfill. By increasing the curing time, the CPB shear strength has increased slightly, whereas specimens with higher binder content presented a significant increase in shear strength values.

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.

Prediction of Stress-Strain Response Using Rotational Multiple Yield Surface Framework in Malaysian Residual Soil

2020 ◽  
Vol 843 ◽  
pp. 132-137
Author(s):  
Asmidar Alias ◽  
Mohd Jamaludin Md Noor ◽  
Abdul Samad Abdul Rahman
Keyword(s):  
Shear Strength ◽  
Effective Stress ◽  
Volume Change ◽  
Yield Surface ◽  
Axial Strain ◽  
The Body ◽  
Residual Soil ◽  
Strain Response ◽  
Stress Strain ◽  
Soil Volume

Soil settlement is normally quantified using conventional soil volume change models which are solely based on the effective stress and the role of shear strength is ignored due to the difficulties to incorporate in the framework. The Rotational Multiple Yield Surface Framework (RMYSF) is a soil volume change model developed from the standpoint of the interaction between the effective stress and shear strength. RMYSF incorporates the development of mobilised shear strength within the body of the soil whenever the soil is subjected to anisotropic compression. Currently the framework has been applied to predict the soil anisotropic stress-strain behaviour at any effective stress. This paper present the enhancement of this volume change framework using normalisation of axial strain with the understanding that the failure axial strain is not unique, but increases as the effective stress increases. This technique has essentially produced a better accuracy in the prediction of the stress-strain response for Malaysian residual soils. A series of drained tri-axial tests under various effective stresses has been conducted using specimens of 50mm diameter and 100mm height and from the stress-strain curves the inherent mobilised shear strength envelopes at various axial strains have been determined. These mobilised shear strength envelopes were then applied for the prediction of the soil stress-strain response. An excellent agreement between the predicted and the actual stress-strain curves has been achieved.

scholarly journals Effect of Rock Particle Content on the Mechanical Behavior of a Soil-Rock Mixture (SRM) via Large-Scale Direct Shear Test

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Longqi Liu ◽  
Xuesong Mao ◽  
Yajun Xiao ◽  
Qian Wu ◽  
Ke Tang ◽  
...  
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Large Scale ◽  
Direct Shear Test ◽  
Shear Test ◽  
Volumetric Strain ◽  
Direct Shear ◽  
Stress Strain ◽  
Particle Content ◽  
Rock Particle

The mechanical strength of the landslide deposits directly affects the safety and operation of the roads in the western mountainous area of China. Therefore, the research is aimed at studying the mechanisms of a landslide deposit sample with different rock particle contents by analyzing its characteristics of the stress-strain behavior, the “jumping” phenomenon, the volumetric strain, and the shear strength parameters via a large-scale direct shear test. Stress-strain results show that stress-strain curves can be divided into 3 different stages: liner elastic stage, yielding stage, and strain-hardening stage. The shear strength of SRM behaves more like “soil” at a lower rock particle content and behaves more like “rock joints” at a higher rock particle content. Characteristics of the “jumping” phenomenon results show that the “intense jumping” stage becomes obvious with the increasing rock particle content and the normal stress. However, the lower the rock particle content is, the more obvious the “jumping” phenomenon under the same normal stress is. Volumetric strain results show that the sample with a lower rock particle content showed a dilatancy behavior under the low normal stress and shrinkage behavior under the high normal stress. The dilatancy value becomes smaller with the increasing normal stress. The maximum shear stress value of the rock particle content corresponds to the maximum value of dilatancy or shrinkage. We also conclude that the intercept of the Mohr failure envelope of the soil-rock mixture should be called the “equivalent cohesion,” not simply called the “cohesion.” The higher the normal stress and rock particle content are, the bigger the equivalent cohesion and the internal friction angle is.

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