Peak Undrained Resistance of Loose Sands

1997 ◽  
Vol 1569 (1) ◽  
pp. 65-76
Author(s):  
G. Norris ◽  
R. Madhu ◽  
M. Ashour ◽  
R. Valceschini
Keyword(s):  
Volumetric Strain ◽  
Confining Pressure ◽  
Triaxial Testing ◽  
Loose Sand ◽  
Failure Envelope ◽  
Change Measurement ◽  
Deviator Stress ◽  
Coulomb Failure ◽  
Volume Change Measurement ◽  
Liquefaction Analysis

The peak undrained resistance (σ d,upeak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure ([Formula: see text]) and an increasing stress level ( SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σ d) versus volumetric strain (ε v) as assessed from a drained triaxial test. A method is presented whereby a single drained test with volume change measurement can be used to assess this undrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only drained triaxial testing.

Mechanical behaviour of powders using a medium pressure flexible boundary cubical triaxial tester

2003 ◽  
Vol 217 (3) ◽  
pp. 233-241 ◽  
Author(s):  
F Li ◽  
V M Puri
Keyword(s):  
Shear Modulus ◽  
Mechanical Behaviour ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Alumina Powder ◽  
Medium Pressure ◽  
Mean Pressure ◽  
Confining Pressures

A medium pressure (<21 MPa) flexible boundary cubical triaxial tester was designed to measure the true three-dimensional response of powders. In this study, compression behaviour and strength of a microcrystalline cellulose powder (Avicel® PH102), a spray-dried alumina powder (A16SG), and a fluid-bed-granulated silicon nitride based powder (KY3500) were measured. To characterize the mechanical behaviour, three types of triaxial stress paths, that is, the hydrostatic triaxial compression (HTC), the conventional triaxial compression (CTC), and the constant mean pressure triaxial compression (CMPTC) tests were performed. The HTC test measured the volumetric response of the test powders under isostatic pressure from 0 to 13.79MPa, during which the three powders underwent a maximum volumetric strain of 40.8 per cent for Avicel® PH102, 30.5 per cent for A16SG, and 33.0 per cent for KY3500. The bulk modulus values increased 6.4-fold from 57 to 367MPa for Avicel® PH102, 3.7-fold from 174 to 637 MPa for A16SG, and 8.1-fold from 74 to 597MPa for KY3500, when the isotropic stress increased from 0.69 to 13.79 MPa. The CTC and CMPTC tests measured the shear response of the three powders. From 0.035 to 3.45MPa confining pressure, the shear modulus increased 28.7-fold from 1.6 to 45.9MPa for Avicel® PH102, 35-fold from 1.7 to 60.5MPa for A16SG, and 28.5-fold from 1.5 to 42.8MPa for KY3500. In addition, the failure stresses of the three powders increased from 0.129 to 4.41 MPa for Avicel® PH102, 0.082 to 3.62 MPa for A16SG, and 0.090 to 4.66MPa for KY3500, respectively, when consolidation pressure increased from 0.035 to 3.45MPa. In addition, the shear modulus and failure stress values determined from the CTC test at 2.07, 2.76, and 3.45MPa confining pressures are consistently greater than those from the CMPTC test at the same constant mean pressures. This observation demonstrates the influence of stress paths on material properties. The CTT is a useful tool for characterizing the three-dimensional response of powders and powder mixtures.

Experimental investigation of the effect of compliant pores on reservoir rocks under hydrostatic and triaxial compression stress states

2019 ◽  
Vol 56 (7) ◽  
pp. 983-991
Author(s):  
Hua Yu ◽  
Kam Ng ◽  
Dario Grana ◽  
John Kaszuba ◽  
Vladimir Alvarado ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Triaxial Compression ◽  
Matrix Material ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Differential Pressure ◽  
Sandstone Sample ◽  
Stress States ◽  
Rock Springs ◽  
Stage 1

The presence of compliant pores in rocks is important for understanding the stress–strain behaviors under different stress conditions. This paper describes findings on the effect of compliant pores on the mechanical behavior of a reservoir sandstone under hydrostatic and triaxial compression. Laboratory experiments were conducted at reservoir temperature on Weber Sandstone samples from the Rock Springs Uplift, Wyoming. Each experiment was conducted at three sequential stages: (stage 1) increase in the confining pressure while maintaining the pore pressure, (stage 2) increase in the pore pressure while maintaining the confining pressure, and (stage 3) application of the deviatoric load to failure. The nonlinear pore pressure – volumetric strain relationship governed by compliant pores under low confining pressure changes to a linear behavior governed by stiff pores under higher confining pressure. The estimated compressibilities of the matrix material in sandstone samples are close to the typical compressibility of quartz. Because of the change in pore structures during stage 1 and stage 2 loadings, the estimated bulk compressibilities of the sandstone sample under the lowest confining pressure decrease with increasing differential pressure. The increase in crack initiation stress is limited with increasing differential pressure because of similar total crack length governed by initial compliant porosity in sandstone samples.

scholarly journals Triaxial Compressive Failure Characteristics and Constitutive Model Study of Jurassic-Cretaceous Weakly Cemented Sandstone

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jinlong Cai ◽  
Wei Zou
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Ductile Failure ◽  
Mathematical Expression ◽  
Confining Pressure ◽  
Mining Area ◽  
Peak Strength ◽  
Correction Coefficient

A conventional triaxial compression test of Jurassic-Cretaceous typical weakly consolidated sandstone from a mining area in Ordos, China, was conducted using an MTS816 tester. Results showed that, before the peak, the rock had a distinct yield stage. When the specimen reached its peak strength, the strength decreased rapidly and showed an obvious brittle failure. When the confining pressure was increased to 15 MPa, the decrease of strength was slow and the rock tended toward ductile failure. With the increase of confining pressure, the cyclic strain initially increased slightly, whereas the volumetric strain increased greatly and the rock sample was in a compression state. When the load reached a critical value, the curve was reversely bent, resulting in volume expansion, whereas the peak strength, residual strength, and elastic modulus increased with confining pressure, and Poisson’s ratio decreased with the confining pressure. In the model based on macroscopic failure rock, the expression of the relationship between fracture angle and confining pressure provided a solid theoretical basis for the direction and failure mode of the macroscopic crack. Based on the rock strength theory and Weibull random distribution assumption of rock element strength, the damage variable correction coefficient was introduced when the residual strength was considered. Then, the mathematical expression of the 3D damage statistical constitutive model was established. Finally, the theoretical curve of the established constitutive model was compared with the triaxial test curve, which showed a high degree of coincidence.

scholarly journals Influence of fissure inclination and confining pressure on the local behaviour of natural clays

2019 ◽  
Vol 92 ◽  
pp. 03004
Author(s):  
Erika Tudisco ◽  
Claudia Vitone ◽  
Cristina Mondello ◽  
Gioacchino Viggiani ◽  
Stephen A. Hall ◽  
...  
Keyword(s):  
Volumetric Strain ◽  
Confining Pressure ◽  
Image Correlation ◽  
Compression Tests ◽  
Confinement Pressure ◽  
Santa Croce ◽  
Deformation Processes ◽  
Natural Clays ◽  
Scaly Clay

In this experimental study the influence of fissuring orientation and confinement pressure on the mechanical behaviour of natural clays is investigated. The tested material, the scaly clay from Santa Croce di Magliano (south of Italy), is characterised by an intense network of pre-existing fissures of single orientation. Several plane strain compression tests have been conducted, under different confinement pressures (i.e., from 50 to 600 kPa), on specimens having fissures with vertical, medium and horizontal inclination. Digital Image Correlation has been used to follow the deformation processes of the specimens throughout the tests by measuring incremental shear and volumetric strain maps. The results showed a strong coupling between the total confinement and the fissure inclination, that is controlling both the onset and the development of the patterns of the localisation processes. The new results have been compared with previous ones carried out on the same material without confinement. The comparison shed light on the role of total confinement that becomes particularly relevant from certain levels of pressures and fissuring inclination.

scholarly journals Computed Tomography Assessment of Response to Therapy: Tumor Volume Change Measurement, Truth Data, and Error

2009 ◽  
Vol 2 (4) ◽  
pp. 216-222 ◽  
Author(s):  
Michael F. McNitt-Gray ◽  
Luc M. Bidaut ◽  
Samuel G. Armato ◽  
Charles R. Meyer ◽  
Marios A. Gavrielides ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Volume Change ◽  
Tumor Volume ◽  
Response To Therapy ◽  
Change Measurement ◽  
Volume Change Measurement

Modified state parameter for characterizing static liquefaction of sand with fines

2009 ◽  
Vol 46 (3) ◽  
pp. 281-295 ◽  
Author(s):  
D. C. Bobei ◽  
S. R. Lo ◽  
D. Wanatowski ◽  
C. T. Gnanendran ◽  
M. M. Rahman
Keyword(s):  
Critical State ◽  
Volumetric Strain ◽  
State Parameter ◽  
Confining Pressure ◽  
Log P ◽  
Test Results ◽  
Static Liquefaction ◽  
Isotropic Consolidation ◽  
Failure Line ◽  
Soil Behaviour

An experimental study was carried out to investigate the static liquefaction behaviour of sand with a small amount of plastic and nonplastic fines. Five series of tests were conducted in drained and undrained conditions. The drained test results indicate not only that the failure line coincides with the critical state, but also that the development of volumetric strain during shearing was not sensitive to the initial confining pressure. In both isotropically and anisotropically consolidated undrained tests, a so-called “reverse behaviour” was consistently observed. The results were also interpreted in the critical state framework. The critical and steady state (CS/SS) data were found to trace along the same curve in e–log( p′) space, irrespective of the stress history and effective stress paths. A comparison between the isotropic consolidation line (ICL) and critical state (CS) curve showed that a small amount of fines can significantly change the shape and position of the ICL relative to the CS curve. Furthermore, the soil behaviour manifested in both drained and undrained shearing led to the development of a modified state parameter.

Automated Digital Image Processing for Volume Change Measurement in Triaxial Cells

2007 ◽  
Vol 30 (2) ◽  
pp. 100309 ◽  
Author(s):  
LD Suits ◽  
TC Sheahan ◽  
P Gachet ◽  
F Geiser ◽  
L Laloui ◽  
...  
Keyword(s):  
Image Processing ◽  
Digital Image Processing ◽  
Volume Change ◽  
Digital Image ◽  
Change Measurement ◽  
Volume Change Measurement
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