Plastic modeling of porous rocks in drained and undrained conditions

2020 ◽  
Vol 117 ◽  
pp. 103277
Author(s):  
B. Han ◽  
W.Q. Shen ◽  
S.Y. Xie ◽  
J.F. Shao
Keyword(s):  
Porous Rocks ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

Effect of microstructure on undrained behaviour of sands

2001 ◽  
Vol 38 (1) ◽  
pp. 16-28 ◽  
Author(s):  
R G Wan ◽  
P J Guo
Keyword(s):  
Phase Transformation ◽  
Mathematical Modelling ◽  
Representative Elementary Volume ◽  
Elementary Volume ◽  
Sand Liquefaction ◽  
Proposed Model ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

This paper presents a mathematical modelling of the effects of initial fabric on the mechanical behaviour of sand. A stress-dilatancy model that incorporates microstructural aspects of sand is hereby obtained while writing energy conservation for an ensemble of particles over a representative elementary volume at micro- and macro-scales. The resulting stress-dilatancy model, when used within an elastoplastic framework, successfully reproduces certain aspects of sand behaviour that are reflective of its microstructure under both drained and undrained conditions. The role of microstructure in relation to the characterization of steady, quasi-steady, and phase-transformation states is discussed within the framework of the model. Numerical simulations obtained from the proposed model are generally very consistent with experimental observations and provide insightful information.Key words: sand, liquefaction, fabric, dilatancy, constitutive laws, granular materials, plasticity.

scholarly journals Modelling the monotonic and cyclic behaviour of sands using Artificial Neural Networks

2021 ◽  
Vol 249 ◽  
pp. 11015
Author(s):  
Weixian Chen ◽  
Andrés Alfonso Peña Olarte ◽  
Roberto Cudmani
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Good Prediction ◽  
Adaptive Neural Network ◽  
Cyclic Behaviour ◽  
Anisotropic Consolidation ◽  
Stress Cycles ◽  
Undrained Conditions ◽  
Artificial Neural ◽  
Drained And Undrained Conditions

In this study artificial neural networks (ANN) are used to simulate the monotonic and cyclic behaviour of sands observed in laboratory tests on Karlsruhe sand under drained and undrained conditions. A genetic algorithm (GA) is used to obtain an optimal framework for the ANN. The results show that the proposed genetic adaptive neural network (GANN) can effectively simulate drained and undrained monotonic triaxial behaviour of saturated sand under isotropic or anisotropic consolidation. The GANN is also able to predict satisfactorily the cyclic behaviour of sands under undrained triaxial test with strain and stress cycles. In addition, GANN is able to distinguish between monotonic drained and undrained conditions by delivering a good prediction when trained with the combined database.

scholarly journals Effect of the Surface Roughness on the Shear Strength of Granular Materials in Ring Shear Tests

2019 ◽  
Vol 9 (15) ◽  
pp. 2977 ◽  
Author(s):  
Sueng-Won Jeong ◽  
Sung-Sik Park
Keyword(s):  
Surface Roughness ◽  
Shear Strength ◽  
Granular Materials ◽  
Rough Surfaces ◽  
Shear Velocity ◽  
Shear Tests ◽  
Ring Shear ◽  
Ring Shear Tests ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

Surface roughness plays an important role in estimating the shear strength of granular materials. A series of ring shear tests with different surface roughnesses (i.e., smooth and rough surfaces) were performed. A large-sized ring shear device, which is applicable for fine- and coarse-grained sediments, was developed to examine the shear strength of large particle sizes (i.e., commercial gravels with a mean grain size of 6 mm). In terms of surface roughness, the drainage- and shear-velocity-dependent shear strengths of the granular materials were examined. In this study, different shear velocities of 0.1, 0.5, and 1 mm/s were applied under drained and undrained conditions. The test results clearly show that shear stress is affected by drainage, shear velocity, and surface roughness. In particular, a typical strain-hardening behavior is exhibited regardless of the drainage and shear velocity condition. The measured shear strength obtained from both drained and undrained conditions increased with increasing shear velocity. All tests showed a large fragmentation using rough surfaces compared to the smooth surfaces of the device. The grain crushing was significant during shearing, even when normal stress was not applied. For a given shear velocity, surface roughness is an important feature in determining the shear strength of granular materials.

Beach sediment mixing under drained and undrained conditions

2013 ◽  
Vol 165 ◽  
pp. 1503-1508 ◽  
Author(s):  
Paolo Ciavola ◽  
Pasquale Contestabile ◽  
Francesco Aristodemo ◽  
Diego Vicinanza
Keyword(s):  
Beach Sediment ◽  
Sediment Mixing ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

scholarly journals Compression mechanisms of unsaturated clay under high stresses

2015 ◽  
Vol 52 (12) ◽  
pp. 2099-2112 ◽  
Author(s):  
Woongju Mun ◽  
John S. McCartney
Keyword(s):  
Unsaturated Soils ◽  
Water Pressure ◽  
High Stress ◽  
Control Mode ◽  
Gradual Transition ◽  
Compression Tests ◽  
Suction Control ◽  
Unsaturated Clay ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

This paper investigates the compression behavior of unsaturated clay under mean stresses up to 160 MPa and different drainage conditions. A new isotropic pressure cell was developed that incorporates matric suction control using the axis-translation technique, and a high-pressure syringe pump operated in displacement-control mode was used to control the total stress and track specimen volume changes. In addition to presenting results from characterization tests on the cell, results from a series of isotropic compression tests performed on compacted clay specimens under drained and undrained conditions are presented. These results permit evaluation of the hardening mechanisms and transition points in the compression curve with increasing effective stress. As expected, specimens tested under undrained conditions were much stiffer than those tested under drained conditions. In the drained tests, the rate of compression was sufficient to permit steady-state dissipation of excess pore-water pressure except under the highest stress ranges. Suction-induced hardening was observed when comparing saturated and unsaturated specimens tested in the drained compression tests. In both the drained and undrained compression tests, the range of applied stresses was sufficient to cause collapse or dissolution of the air voids (pressurized saturation) and convergence of the virgin compression lines for unsaturated specimens with that measured for saturated specimens. A gradual transition to full-void closure was observed at high stresses when the compression curves were plotted on a natural scale, but the shapes of the compression curves at high stresses were not consistent with conventional soil mechanics models when plotted on a semilogarithmic scale. The results from this study provide insight into how constitutive models for unsaturated soils can be extended to high stress conditions for drained and undrained conditions.

scholarly journals Discussion on “Experimental Deformation of Opalinus Clay at Elevated Temperature and Pressure Conditions: Mechanical Properties and the Influence of Rock Fabric” of Schuster, V., Rybacki, E., Bonnelye, A., Herrmann, J., Schleicher, A.M., Dresen, G.

2021 ◽  
Author(s):  
Eleonora Crisci ◽  
Alessio Ferrari ◽  
Lyesse Laloui
Keyword(s):  
Mechanical Properties ◽  
Testing Procedure ◽  
Opalinus Clay ◽  
Strain Rates ◽  
Pressure Equilibrium ◽  
Experimental Deformation ◽  
Dry Conditions ◽  
Undrained Conditions ◽  
Temperature And Pressure ◽  
Drained And Undrained Conditions

AbstractThe testing procedure and results on saturated samples of Opalinus Clay in the work of Schuster et al. (Rock Mech Rock Eng https://doi.org/10.1007/s00603-021-02474-3, 2021) were conducted and presented using strain rates two to four orders of magnitudes higher than the rates needed to allow pore pressure equilibrium in the material, both in drained and undrained conditions. This leads to an erroneous estimation of the mechanical properties in saturated conditions. We discuss this aspect in the context of shale testing. We also discuss the effect of drying-induced fissuring on the mechanical properties of geomaterials tested in dry conditions.

scholarly journals Behavior of a Large Diameter Bored Pile in Drained and Undrained Conditions: Comparative Analysis

Geosciences ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 261
Author(s):  
Mohamed Ezzat Al-Atroush ◽  
Ashraf Hefny ◽  
Yasser Zaghloul ◽  
Tamer Sorour
Keyword(s):  
Numerical Models ◽  
Large Diameter ◽  
Field Measurements ◽  
Load Test ◽  
Design Parameters ◽  
Test Problems ◽  
Loading Test ◽  
Stiff Clay ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

Despite the difficulties in obtaining the ultimate capacity of the large diameter bored piles (LDBP) using the in situ loading test, this method is the most recommended by several codes and design standards. However, several settlement-based approaches, alongside the conventional capacity-based design approach for LDBP, are proposed in the event of the impossibility of performing a pile-loading test during the design phase. With that in mind, natural clays usually involve some degree of over consolidation; there is considerable debate among the various approaches on how to represent the behavior of the overconsolidated (OC)stiff clay and its design parameters, whether drained or undrained, in the pile-load test problems. In this paper, field measurements of axial loaded to failure LDBP load test installed in OC stiff clay (Alzey Bridge Case Study, Germany) have been used to assess the quality of two numerical models established to simulate the pile behavior in both drained and undrained conditions. After calibration, the load transfer mechanism of the LDBP in both drained and undrained conditions has been explored. Results of the numerical analyses showed the main differences between the soil pile interaction in both drained and undrained conditions. Also, field measurements have been used to assess the ultimate pile capacity estimated using different methods.

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.

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.

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