On the “elastic” stiffness in a high-cycle accumulation model for sand: a comparison of drained and undrained cyclic triaxial tests

2010 ◽  
Vol 47 (7) ◽  
pp. 791-805 ◽  
Author(s):  
Torsten Wichtmann ◽  
Andrzej Niemunis ◽  
Theodor Triantafyllidis
Keyword(s):  
Bulk Modulus ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Volumetric Strain ◽  
Elastic Stiffness ◽  
Plastic Strain Rate ◽  
Triaxial Tests ◽  
Strain Accumulation ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests

High-cycle accumulation (HCA) models may be used for the prediction of settlements or stress relaxation in soils due to a large number of cycles (N > 103) with a relatively small-strain amplitude (εampl < 10−3). This paper presents a discussion of the elastic stiffness, [Formula: see text], used in the basic constitutive equation of an HCA model, [Formula: see text], where [Formula: see text] is the trend of effective stress, [Formula: see text] is the trend of strain, [Formula: see text] is the rate of strain accumulation, and [Formula: see text] is the plastic strain rate. [Formula: see text] interrelates the “trends” of stress and strain evolution. For the experimental assessment of the bulk modulus, [Formula: see text], the rate of pore-water pressure accumulation, [Formula: see text], in undrained cyclic triaxial tests and the rate of volumetric strain accumulation, [Formula: see text], in drained cyclic tests have been compared. The pressure-dependent bulk modulus, K, was quantified from 15 pairs of drained and undrained tests with different consolidation pressures and stress amplitudes. It is demonstrated that both the curves [Formula: see text] in the drained tests and u(N) in the undrained tests are well predicted by the authors’ HCA model if the elastic stiffness is determined using the method described in the present paper. A simplified determination of K from the unloading and reloading curve in an oedometric compression test is discussed.

scholarly journals Soil liquefaction as an identification test

2019 ◽  
Vol 92 ◽  
pp. 08008
Author(s):  
Bozana Bacic ◽  
Ivo Herle
Keyword(s):  
Pore Water ◽  
Laboratory Testing ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Initial Density ◽  
Soil Liquefaction ◽  
Triaxial Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Identification Test

Time-consuming and complicated investigations of soil liquefaction in cyclic triaxial tests are the most common way of laboratory analysis of this phenomenon. Moreover, the necessary equipment for the performance of cyclic triaxial tests is very expensive. Much simpler method for laboratory testing of the soil liquefaction has been developed at the Institute of Geotechnical Engineering at the TU Dresden. This method takes into account the pore water pressure build-up during cyclic shearing within a short time period. During the test, the soil sample is subjected to horizontal cyclic loading and the generated pore water pressure is measured. In the first series of these experiments, a dependence of the pore water pressure buildup on the initial density of soil could be observed, as expected. When comparing different soils, it is shown that the tendency to liquefaction depends also on the granulometric properties (e.g. grain size distribution) of the soil. The aim of the further development is to establish a simple identification test for laboratory testing of the soil liquefaction.

scholarly journals An appraisal of end conditions in advanced monotonic and cyclic triaxial testing on a range of geomaterials

2019 ◽  
Vol 92 ◽  
pp. 02007
Author(s):  
Ken Vinck ◽  
Tingfa Liu ◽  
Emil Ushev ◽  
Richard J. Jardine
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Sensors ◽  
Local Strain ◽  
Triaxial Tests ◽  
Triaxial Testing ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
End Conditions

Compressing samples between rigid platens, as in triaxial testing, induce non-uniform specimen stress, strain and pore water distributions. Although well recognised historically, the effects of such platen restraints are often disregarded or overlooked when performing or interpreting monotonic and cyclic experiments. This paper presents an updated appraisal of end conditions based on laboratory experiments run on sand, glacial till, intact and puttified chalk as part of offshore piling research projects. Monotonic and cyclic triaxial tests are reported that incorporated local strain and pore pressure sensors and a range of platen configurations. New insights are reported regarding the small-to-large behaviour and undrained cyclic pore water pressure measurement.

Pure elastic stiffness of sand represented by response envelopes derived from cyclic triaxial tests with local strain measurements

2020 ◽  
Vol 15 (8) ◽  
pp. 2075-2088 ◽  
Author(s):  
Lukas Knittel ◽  
Torsten Wichtmann ◽  
Andrzej Niemunis ◽  
Gerhard Huber ◽  
Edgar Espino ◽  
...  
Keyword(s):  
Local Strain ◽  
Elastic Stiffness ◽  
Triaxial Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Strain Measurements

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.

scholarly journals Evaluation of Liquefaction Potential in Saturated Sand under Different Drainage Boundary Conditions—An Energy Approach

2019 ◽  
Vol 7 (11) ◽  
pp. 411
Author(s):  
Chang-Rui Yao ◽  
Bo Wang ◽  
Zhi-Qiang Liu ◽  
Hao Fan ◽  
Fang-Hao Sun ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Water Pressure ◽  
Energy Approach ◽  
Triaxial Tests ◽  
Dissipated Energy ◽  
Dry Density ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Liquefaction Potential ◽  
Sand Liquefaction

Drainage conditions are supposed to have significant influence on sand liquefaction behavior. An infiltration device was utilized in cyclic triaxial tests to reproduce different drainage conditions by altering dry density of the within silt. Permeability coefficient ratio (kp) was utilized for quantifying the drainage boundary effect. Cyclic triaxial tests were conducted on saturated Fujian standard sand samples. Test results were used to evaluate the liquefaction potential by using the energy approach. It can be concluded that, if kp increases slightly bigger than zero, excess pore water pressure (EPWP) will respond more fiercely, and the dissipated energy that triggers sand liquefaction will be less. By considering kp, an energy-based database was built by taking kp into consideration and different neural network (NN) models were constructed to predict liquefaction potential by energy approaches accurately under different drainage boundary conditions. It was suggested that the neuro-fuzzy (NF)-based NN model has more satisfactory performance.

scholarly journals Experimental Research on Effect of Fines Content on Liquefaction Properties of Sand

2019 ◽  
Vol 8 (6S) ◽  
pp. 432-436
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Sandy Soils ◽  
Triaxial Tests ◽  
Liquefaction Resistance ◽  
Cyclic Triaxial Tests ◽  
Fines Content ◽  
Fine Grained ◽  
Cyclic Resistance

Liquefaction is a phenomenon mainly occurred in saturated fine grained soils under major earthquakes causes tremendous loss to infrastructure. From the literature it has been observed that liquefaction not only occurs in fine sands but also occurs in sands containing some amount of fines particles, which are of less than 75µ in size. Unfortunately there is no clear conclusions given as how effect the fines content on liquefaction resistance of sandy soils. In order to solve above mentioned problem this study was undertaken through stress-controlled cyclic triaxial tests to know the effect of fines content on liquefaction resistance of sandy soils. In this study the program of experimentation was done on base sand and sand mixed with four different combinations of fines like 10%, 20%, 30%, and 40% of fines with base sand by weight.. The main parameters changed in this work were percentage fines and shear stress ratio (CSR ), where the observed parameter was amount of pore water pressure and cycle of loading.. The result showed that, rate of pore water pressure generation during cyclic loading was largely affected by limiting silt content and density index. The trend observed as amount of pore water pressure is increased more than base sand with adding of fines content up to 20%, later the trend observed as reverse. And also noticed that more CSR value increases the pore water pressure generation and decreases the cyclic resistance

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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