scholarly journals Stress-Dilatancy for Soils. Part II: Experimental Validation for Triaxial Tests

2016 ◽  
Vol 38 (4) ◽  
pp. 59-65 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Test Data ◽  
Experimental Validation ◽  
Triaxial Compression ◽  
Shear Resistance ◽  
State Theory ◽  
Triaxial Tests ◽  
Macro Scale ◽  
Undrained Conditions ◽  
Particle Rolling ◽  
Drained And Undrained Conditions

Abstract Different forms of the stress-dilatancy relations obtained based on the frictional theory for the triaxial condition are presented. The analysed test data show that the shear resistance of many soils is purely frictional. The angle Φ0 represents the resistance of the soil as a combined effect of sliding and particle rolling on the macro-scale during shear at the critical frictional state. The stress-plastic dilatancy relations differ not only for triaxial compression and extension but also for drained and undrained conditions. The experiment investigated shows the correctness of the frictional state theory in the triaxial condition.

scholarly journals Stress-strain behaviour of Toyoura sand in undrained triaxial compression

2019 ◽  
Vol 92 ◽  
pp. 15010 ◽  
Author(s):  
Katarzyna Dołżyk-Szypcio
Keyword(s):  
Stress Ratio ◽  
Triaxial Compression ◽  
State Parameter ◽  
State Theory ◽  
Natural State ◽  
Strain Behaviour ◽  
Characteristic Points ◽  
Toyoura Sand ◽  
Undrained Conditions ◽  
Parameter Values

The stress-plastic dilatancy relationship for Toyoura sand sheared under undrained triaxial conditions was analysed by use of Frictional State Theory. Under undrained conditions, plastic strain increments are counterbalanced by elastic strain increments. The linear stress ratio-plastic dilatancy relationships at different stages of sand shear were obtained by assuming that Poisson's ratio is a function of shear strain. Contrary to a drained condition, natural state parameter values are not special for characteristic points of sand behaviour under undrained conditions.

Failure, instability, and the second work increment in loose silty sand

2011 ◽  
Vol 48 (6) ◽  
pp. 943-955 ◽  
Author(s):  
Mehmet Murat Monkul ◽  
Jerry A. Yamamuro ◽  
Poul V. Lade
Keyword(s):  
Triaxial Compression ◽  
Failure Surface ◽  
Stress Path ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Stability Conditions ◽  
Stability And Instability ◽  
Constant Shear Stress ◽  
The Mean ◽  
Undrained Conditions

Triaxial tests have been performed to demonstrate the conditions for stability and instability in loose silty sand. Drucker (1951) and Hill (1958) stability conditions in terms of the sign of the second work increment were employed in the design of the stress paths used in the triaxial compression and extension tests performed with quasi-constant shear stress while the mean normal stress was reduced until failure occurred. It is shown that the sand is completely stable under drained conditions for any stress path and irrespective of the sign of the second work increment. This is demonstrated by completely stopping the change in stresses and observing the stable behavior in the range of stresses where the sand contracts and where it dilates. Once the effective stress failure surface is passed, the sand becomes unstable, and the sign of the second work increment is always negative. Run-away instability can occur inside the failure surface for loose silty sand under undrained conditions for which the sand tends to contract, pore pressures continue to develop, and the second work increment is negative. Liquefaction may follow if the loose silty sand is sufficiently loose.

scholarly journals Stress–dilatancy of gravel for triaxial compression tests

2018 ◽  
Vol 50 (2) ◽  
pp. 119-128 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Shear Strain ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
State Theory ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Stress Strain ◽  
Characteristic Points ◽  
Triaxial Compression Tests

Abstract The stress–plastic dilatancy relationships for gravel are analyzed based on drained triaxial tests experiments described in literature. For this, Frictional State Theory is used. The characteristic points and stages of shearing may be defined from the analysis of η–Dp relationship. The characteristic points and stages of shearing cannot be identified from ordinary stress–strain, volumetric strain–shear strain relationships that are shown in literature.

Steady-state lines of sand–silt mixtures

2006 ◽  
Vol 43 (11) ◽  
pp. 1213-1219 ◽  
Author(s):  
S L Yang ◽  
R Sandven ◽  
L Grande
Keyword(s):  
Steady State ◽  
Key Words ◽  
Friction Angle ◽  
Triaxial Tests ◽  
Fines Content ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions ◽  
Intergranular Void

The steady-state lines (SSLs) for sand–silt mixtures with various fines contents (0%, 5%, 10%, 15%, 20%, 30%, 50%, 70%, and 94%) were studied. It was indicated that the location of the SSL in the e–p′ space is different for each mixture, but the SSLs are parallel. In the e – ln p′ plot, the SSLs are similar for the mixtures with a fines content of less than the transitional fines content (TFC) when tested under drained and undrained conditions and the intergranular and interfine void ratios are used. The data diverge when the fines contents are equal to or greater than the TFC, even though the interfine void ratios are used. The results of the tests conducted under drained and undrained conditions produced a unique SSL in the p′–q space for each material. Different SSLs in the p′–q space were observed for the studied materials, and the friction angle at steady state varied in the range of 37.3°–42.2°. The study showed that the SSLs can be represented by one line in tests under drained conditions if the fines contents are less (0%–30%) than the TFC and the corrected intergranular void ratios are used. The lines can also be represented by one line for sand–silt mixtures with high fines contents (50%–94%) if the corrected interfine void ratios are used instead of void ratios. Key words: steady-state line, sand–silt mixtures, transitional fines content, drained and undrained triaxial tests.

scholarly journals Experimental study on fibre reinforced sandy soils behaviour under static loadings - drained and undrained conditions

2019 ◽  
Vol 92 ◽  
pp. 12002
Author(s):  
Jorge Hernán Flórez-Gálvez ◽  
Lucas Festugato ◽  
Nilo Cesar Consoli
Keyword(s):  
Experimental Study ◽  
Sandy Soils ◽  
Friction Angle ◽  
The Other ◽  
Triaxial Tests ◽  
Polypropylene Fibres ◽  
Undrained Conditions ◽  
Positive Effect ◽  
Drained And Undrained Conditions ◽  
Sustained Increase

The effect of the addition of 0.5% of randomly distributed polypropylene fibres in a round grained sand, composed mainly of silica, is presented on laboratory scale. The samples were compacted with two void ratios (0.75 and 0.63), corresponding to values of relative density of 50% and 90% respectively. 24 monotonic triaxial tests were performed, with initial effective mean pressures of 20, 100 and 200 kPa. Half of samples were tested in drained conditions, and the other half in undrained conditions. For the samples subjected to drained conditions, the effect of the fibres was identified at the post-failure stage, by showing sustained increase of strength. The positive effect of fibres could also be observed through the increase of material friction angle. In the samples subjected to undrained tests, the addition of fibres reduced the contractive behaviour, mainly for those more compacted.

Three-dimensional cyclic behavior of saturated clays: comparison between undrained and partly drained conditions

2021 ◽  
Author(s):  
Yanlin Zhang ◽  
Chuan Gu ◽  
Jun Wang ◽  
Yuanqiang Cai
Keyword(s):  
Resilient Modulus ◽  
Three Dimensional ◽  
Cyclic Stress ◽  
Cyclic Behavior ◽  
Triaxial Tests ◽  
Cyclic Stress Ratio ◽  
True Triaxial ◽  
Deformation Behaviors ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

The cyclic response of subgrade clays under traffic loadings is likely to be partly drained rather than undrained, and the traffic-induced dynamic stress field is three-dimensional rather than axisymmetric. To compare the three-dimensional deformation behaviors of saturated clays between partly drained and undrained conditions, a large number of cyclic true triaxial tests were conducted. Experimental results show that partly drained condition leads to a remarkable increase of permanent major principal strain ( ) compared to undrained condition, and the differences of between the two drainage conditions are affected greatly by the factors of cyclic stress ratio (CSR), overconsolidation ratio (OCR), and coefficient of cyclic intermediate principal stress (bcyc). The increase of bcyc induces a linear reduction of in undrained condition, while it causes a first increase and then a decrease of in partly drained condition. The clays undergo stiffness softening and hardening in partly drained and undrained conditions, respectively, and the effects of bcyc and CSR on the stiffness evolution are very different between the two drainage conditions. The mechanism of the complex and resilient modulus behaviors in three-dimensional state and partly drained condition is further discussed. In addition, two different empirical models are employed to predict in partly drained and undrained conditions, respectively.

Hydromechanical behaviour of overconsolidated unsaturated soil in undrained conditions

2019 ◽  
Vol 56 (11) ◽  
pp. 1609-1621 ◽  
Author(s):  
Shengshen Wu ◽  
Annan Zhou ◽  
Jie Li ◽  
Jayantha Kodikara ◽  
Wen-Chieh Cheng
Keyword(s):  
Effective Stress ◽  
Unsaturated Soils ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Conventional Triaxial Compression ◽  
Hydromechanical Behaviour ◽  
Undrained Conditions

Hydromechanical behaviour of an unsaturated silt with various suctions and different overconsolidated ratios (OCRs) was investigated through a series of undrained triaxial tests (constant water contents, CW). All the samples were prepared from the slurry state. Different OCRs (= 1, 2, 4, and 8 in net stress) were achieved by unloading the samples to 400, 200, 100, and 50 kPa from an initial confining net pressure of 400 kPa. Then the samples were dried to various suctions (0, 100, 200, 300, and 400 kPa). Unsaturated samples with different OCRs were then sheared at CW conditions following the conventional triaxial compression (CTC) paths. Full hydromechanical responses including the changes in deviator stress, stress ratio, volumetric strain, suction, and degree of saturation with axial strain were monitored and are presented in this paper. Some key findings include (i) the critical state for unsaturated soils with different OCRs can be well defined by Bishop’s effective stress; (ii) the peak strength in Bishop’s effective stress increases with increase of OCR, but decreases with increase of suction in the undrained condition; and (iii) the volume change of unsaturated soils in undrained conditions is related to OCRs and the volume of pore air.

scholarly journals Recommended Procedures to Assess Critical State Locus from Triaxial Tests in Cohesionless Remoulded Samples

Geotechnics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 95-127
Author(s):  
António Viana da Fonseca ◽  
Diana Cordeiro ◽  
Fausto Molina-Gómez
Keyword(s):  
Critical State ◽  
Review Paper ◽  
State Theory ◽  
Soil Freezing ◽  
Triaxial Tests ◽  
Cohesionless Soils ◽  
Saturation Condition ◽  
Testing Procedures ◽  
Laboratory Procedures ◽  
Soil Behaviour

The critical state theory is a robust conceptual framework for the characterisation of soil behaviour. In the laboratory, triaxial tests are used to assess the critical state locus. In the last decades, the equipment and testing procedures for soil characterisation, within the critical state framework, have advanced to obtain accurate and reliable results. This review paper summarises and describes a series of recommended laboratory procedures to assess the critical state locus in cohesionless soils. For this purpose, results obtained in the laboratory from different cohesionless soils and triaxial equipment configurations are compiled, analysed and discussed in detail. The procedures presented in this paper reinforce the use of triaxial cells with lubricated end platens and an embedded connection piston into the top-cap, together with the verification of the full saturation condition and the measurement end-of-test water content—preferable using the soil freezing technique. The experimental evidence and comparison between equipment configurations provide relevant insights about the laboratory procedures for obtaining a reliable characterisation of the critical state locus of cohesionless geomaterials. All the procedures recommended herein can be easily implemented in academic and commercial geotechnical laboratories.

Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

2020 ◽  
Vol 57 (3) ◽  
pp. 448-452 ◽  
Author(s):  
A.S. Lees ◽  
J. Clausen
Keyword(s):  
Triaxial Compression ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Failure Envelope ◽  
Element Analysis ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Triaxial Compression Tests ◽  
Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

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