Cyclic Pore Pressure Generation, Dissipation and Densification in Granular Mixes

2012 ◽  
pp. 66-84
Author(s):  
S. Thevanayagam ◽  
T. Shenthan
Keyword(s):  
Experimental Study ◽  
Pore Pressure ◽  
Triaxial Tests ◽  
Cyclic Tests ◽  
Contact Density ◽  
Coefficient Of Consolidation ◽  
Cyclic Triaxial Tests ◽  
Analysis Of Performance ◽  
Intergranular Void Ratio ◽  
Intergranular Void

Knowledge of cyclic load induced pore pressure generation, post-liquefaction dissipation and volumetric densification characteristics of sands, silty sands, and silts are important for the analysis of performance of loose saturated granular deposits in seismic areas. This article presents results from an experimental study of these characteristics for such soils containing 0 to 100% non-plastic silt. Pore pressure generation characteristics are studied using undrained cyclic triaxial tests. Pre- and post-liquefaction compressibility and coefficient of consolidation, and post-liquefaction volumetric densification characteristics are determined from consolidation data prior to cyclic tests and pore pressure dissipation tests following undrained cyclic tests. Effects of fines content on these characteristics compared to those of clean sands are examined in the context of intergranular void ratio and intergranular contact density concepts.

Cyclic Pore Pressure Generation, Dissipation and Densification in Granular Mixes

2010 ◽  
Vol 1 (1) ◽  
pp. 42-61 ◽  
Author(s):  
S. Thevanayagam ◽  
T. Shenthan
Keyword(s):  
Pore Pressure ◽  
Cyclic Load ◽  
Void Ratio ◽  
Triaxial Tests ◽  
Cyclic Tests ◽  
Contact Density ◽  
Coefficient Of Consolidation ◽  
Cyclic Triaxial Tests ◽  
Analysis Of Performance ◽  
Intergranular Void

Knowledge of cyclic load induced pore pressure generation, post-liquefaction dissipation and volumetric densification characteristics of sands, silty sands, and silts are important for the analysis of performance of loose saturated granular deposits in seismic areas. This article presents results from an experimental study of these characteristics for such soils containing 0 to 100% non-plastic silt. Pore pressure generation characteristics are studied using undrained cyclic triaxial tests. Pre- and post-liquefaction compressibility and coefficient of consolidation, and post-liquefaction volumetric densification characteristics are determined from consolidation data prior to cyclic tests and pore pressure dissipation tests following undrained cyclic tests. Effects of fines content on these characteristics compared to those of clean sands are examined in the context of intergranular void ratio and intergranular contact density concepts.

Effect of load shape on relationship between dissipated energy and residual excess pore pressure generation in cyclic triaxial tests

2013 ◽  
Vol 50 (11) ◽  
pp. 1118-1128 ◽  
Author(s):  
Carmine Polito ◽  
Russell A. Green ◽  
Erin Dillon ◽  
Changbum Sohn
Keyword(s):  
Pore Pressure ◽  
Water Pressure ◽  
Laboratory Data ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Dissipated Energy ◽  
Generation Model ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Load Shape

The energy dissipated in soil during cyclic loading can be used to predict the change in the pore-water pressure developed in the soil. To examine whether the energy required to cause liquefaction is dependent on or independent of the load shape applied, a series of 28 cyclic triaxial tests were performed using five different load shapes having a range of cyclic stress ratios. The five load shapes were applied to identically prepared specimens of clean sand and the dissipated energy – pore pressure generation characteristics examined. It was found that that the dissipated energy to cause initial liquefaction was normally distributed and independent of the load shape, although it is seemingly somewhat dependent on duration of loading. A corollary to this finding is that laboratory data from specimens tested using sinusoidal loadings can be used to calibrate the Green, Mitchell, and Polito (GMP) energy-based pore pressure generation model for use in predicting in situ pore pressures in soils subjected to nonsinusoidal loadings (e.g., earthquake loadings). Given the relative simplicity of the GMP model, these findings make the model an attractive alternative to implement in effective stress dynamic response codes.

Effect of unloading duration on unconfined compressive strength

1999 ◽  
Vol 36 (1) ◽  
pp. 166-172 ◽  
Author(s):  
M A Fam ◽  
M B Dusseault
Keyword(s):  
Compressive Strength ◽  
Pore Pressure ◽  
Unconfined Compressive Strength ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Coefficient Of Consolidation ◽  
Unconfined Compression Test ◽  
Excess Pore

This note examines the effect of unloading duration on unconfined compression test results. Artificial clayey specimens were prepared using the slurry consolidation technique. Extracted specimens were loaded vertically under K0 conditions, and the load was kept constant until the end of primary consolidation. Specimens were unloaded and unconfined compression tests were carried out at different times after unloading. It is observed that the longer the unloading duration, the lower the measured unconfined strength. This behavior is attributed to the presence of negative excess pore pressure that dissipates with time, reducing the strength. Using the measured coefficient of consolidation, the degree of excess pore pressure dissipation and therefore the average mean effective stress near the failure zone can be calculated at the time of failure. Mohr circles are drawn tangential to the total shear envelope, using the calculated mean effective stresses. Reasonable agreement between predicted and measured unconfined compressive strengths has been observed, suggesting that consolidation theory can be adopted to assess the effect of unloading duration on unconfined compressive strength. Finally, engineering applications using a similar concept are briefly discussed.Key words: clays, unloading, consolidation, unconfined compression tests, triaxial tests.

Experimental Study of Liquefaction Resistant Characteristics of Remodeled Clayey Sands

2011 ◽  
Vol 368-373 ◽  
pp. 2887-2890
Author(s):  
Yun Long Wang ◽  
Zhao Yan Li ◽  
Rui Sun ◽  
Xiao Ming Yuan
Keyword(s):  
Experimental Study ◽  
Pure Water ◽  
Clay Content ◽  
Triaxial Tests ◽  
Shear Stresses ◽  
Cyclic Triaxial ◽  
Liquefaction Resistance ◽  
Cyclic Triaxial Tests ◽  
Freezing Method ◽  
Wide Range

Cyclic triaxial tests were carried out for remodeled saturated clayey sands with the clay content varying in a relatively wide range from 0% to 40%. In the tests, saturated uniformity clayey sands were obtained by pre-freezing method, i.e. immersing samples in pure water for 12 hours under vacuum, and then, freezing the sample to -15°C for 6 hours. Experimental results indicate that the lowest liquefaction resistance in mixtures occurs when clay contents is of the order of 15%. The ratio of liquefaction shear stresses of the specimens obtained using pre-freezing method are larger than those obtained with the traditional deposit-in-water method.

Effect of the loading frequency on the sand liquefaction behaviour in cyclic triaxial tests

2021 ◽  
Vol 147 ◽  
pp. 106779
Author(s):  
Zhehao Zhu ◽  
Feng Zhang ◽  
Qingyun Peng ◽  
Jean-Claude Dupla ◽  
Jean Canou ◽  
...  
Keyword(s):  
Triaxial Tests ◽  
Loading Frequency ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Sand Liquefaction
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