Confining stress and static shear effects in cyclic liquefaction

2001 ◽  
Vol 38 (3) ◽  
pp. 580-591 ◽  
Author(s):  
Y P Vaid ◽  
J D Stedman ◽  
S Sivathayalan
Keyword(s):  
Initial Density ◽  
Confining Pressure ◽  
Empirical Method ◽  
Shear Stresses ◽  
Confining Stress ◽  
Liquefaction Resistance ◽  
Sand Liquefaction ◽  
Cyclic Resistance ◽  
Cyclic Resistance Ratio ◽  
Static Shear

Liquefaction resistance of a sand under cyclic loading is assessed and the effects of the levels of confining pressure and static shear on resistance to liquefaction are investigated. Site-specific values of the resistance under specified levels of confining and static shear stresses are measured in the laboratory. The measured values are compared with those which would be predicted by the application of empirical multiplying factors Kσ and Kα to the reference resistance at 100 kPa effective confining stress with no static shear. It is shown that Kσ and Kα are not independent, as assumed in current practice. The combined factor Kσ × Kα resulting from the empirical method is shown to underestimate the cyclic resistance ratio regardless of the initial density and confining and static shear levels. The degree of conservatism is most dramatic at looser density states.Key words: sand, liquefaction, static, cyclic, static shear, confining stress.

Effect of overburden pressure on liquefaction resistance of sand

1994 ◽  
Vol 31 (1) ◽  
pp. 53-60 ◽  
Author(s):  
V.S. Pillai ◽  
P.M. Byrne
Keyword(s):  
Published Data ◽  
Confining Stress ◽  
Liquefaction Resistance ◽  
Overburden Pressure ◽  
Site Specific ◽  
Indirect Approach ◽  
Cyclic Resistance ◽  
Wide Range ◽  
Cyclic Resistance Ratio ◽  
A Site

The effect of overburden pressure on liquefaction resistance of sand is studied and results of a site-specific investigation are presented. When estimating liquefaction resistance of sand from the indirect approach using the chart suggested by Seed et al. (1984) a correction factor Kσ is applied to account for vertical effective overburden stresses larger than 1 tsf. Published data indicate a decrease in Kσ with increased confining stress but with a wide range of Kσ values for the same confining stresses, predicting significantly differing liquefaction resistance. The effect of confining stresses on liquefaction resistance was investigated as part of a comprehensive seismic assessment of Duncan Dam in British Columbia. The results indicate that Kσ is dependent on confining stresses and the relative density of the soil, and values are generally significantly higher than much of the previously published data. Key words : liquefaction, sand, confining stress, density, cyclic resistance ratio.

Evaluation of liquefaction potential of foundation soils at Duncan Dam

1994 ◽  
Vol 31 (6) ◽  
pp. 951-966 ◽  
Author(s):  
V.S. Pillai ◽  
R.A. Stewart
Keyword(s):  
Engineering Properties ◽  
Soil Parameters ◽  
Confining Stress ◽  
Undisturbed Soil ◽  
Liquefaction Potential ◽  
Sand Liquefaction ◽  
Cyclic Resistance ◽  
And Performance ◽  
Design Earthquake ◽  
The Right

A comprehensive program of field, laboratory, and analytical investigations was carried out to evaluate the potential of liquefaction for the foundation soils at Duncan Dam. Duncan Dam was completed in 1967 under the Columbia River Treaty in southeastern British Columbia. The 39 m high zoned embankment dam is founded on a sequence of sands, silts, and gravels. Some of the foundation soils may liquefy during earthquake loading and this would affect the stability and performance of the dam. The liquefaction studies were carried out in two phases to characterize the engineering properties of the foundation soils and to assess its potential for triggering liquefaction using the total stress approach. This paper describes methods of assessment of liquefaction potential using soil parameters based on field penetration data (Seed's method) and laboratory testing of undisturbed soil samples obtained in situ after freezing the ground (Lab method) and presents the results of triggering analysis. Influence of confining stress (Kσ) and initial static shear stress (Kα) on liquefaction were investigated and site-specific Kσ and Kα curves were developed.For the design earthquake (M 6.5, PGA = 0.12g) both the Lab method and Seed's method predict a significant extent of liquefaction of the foundation soils under the downstream slope in the right half of the dam. Key words : sand, liquefaction, confining stress, density, cyclic resistance ratio.

scholarly journals Analysis of potential liquefaction of sandy soils using effective confining pressure

2020 ◽  
Vol 156 ◽  
pp. 02013
Author(s):  
Siti Nur Indah Sari
Keyword(s):  
Safety Factor ◽  
Sandy Soil ◽  
Sandy Soils ◽  
Confining Pressure ◽  
Resistance Ratio ◽  
Liquefaction Potential ◽  
Cyclic Resistance ◽  
The World ◽  
Cyclic Resistance Ratio ◽  
Central Sulawesi

Earthquake disasters are some of the most frequent disasters in the world. One of the impacts of earthquakes is liquefaction. Indonesia is earthquake-prone and has been negatively impacted by liquefaction. Recently liquefaction resulting from an earthquake in Palu, Central Sulawesi caused losses in terms of material and lives motivating a more detailed study of this risk to reduce it in the future. In this study, an analysis of the liquefaction potential of sandy soil was carried out by varying the effective confining pressure to produce a graph relating fine contents (FC) to cyclic resistance ratio (CRR).The value of the cyclic resistance ratio is needed to determine the safety factor for potential liquefaction.

A laboratory investigation of the dynamic properties of tailings

2011 ◽  
Vol 48 (11) ◽  
pp. 1587-1600 ◽  
Author(s):  
Michael James ◽  
Michel Aubertin ◽  
Dharma Wijewickreme ◽  
G. Ward Wilson
Keyword(s):  
Dynamic Properties ◽  
Cyclic Stress ◽  
Test Results ◽  
Liquefaction Resistance ◽  
Cyclic Stress Ratio ◽  
Cyclic Resistance ◽  
Direct Simple Shear ◽  
Cyclic Resistance Ratio ◽  
Modulus Reduction

The dynamic response of tailings from a gold mine located in western Quebec was evaluated using cyclic laboratory testing. These tailings are classified as nonplastic silt and sand. Specimens of the tailings were prepared as slurries, consolidated to vertical effective stresses of 100–400 kPa, and subjected to cyclic direct simple shear testing with cyclic stress ratio, CSR, values between 0.075 and 0.15. The shear modulus reduction of the tailings under cyclic loading was found to be fairly similar to that described for clean sands in the literature. The cyclic resistance ratio, CRR (which reflects the liquefaction resistance), of the samples was not significantly affected by the effective consolidation stress (in the range considered here). Analysis of test results with the simplified method of liquefaction evaluation indicates that this method may be applicable to these tailings. However, other factors, such as the possible effects of layering and ageing of the tailings in situ, should also be considered in such an assessment.

scholarly journals Undrained Cyclic Response and Resistance of Saturated Calcareous Sand considering Initial Static Shear Effect

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Baojian Li ◽  
Panpan Guo ◽  
Gaoyun Zhou ◽  
Zhe Wang ◽  
Gang Lei ◽  
...  
Keyword(s):  
Shear Stress ◽  
Relative Density ◽  
Shear Stresses ◽  
Loose Sand ◽  
Calcareous Sand ◽  
Cyclic Shear ◽  
Cyclic Response ◽  
Dense Sand ◽  
Cyclic Resistance ◽  
Static Shear

Sand elements in the natural or manmade field have often undergone initial static shear stresses before suffering cyclic loading. To explore the effect of static shear stress, a series of undrained cyclic triaxial tests were performed on dense and loose calcareous sand under different initial and cyclic shear stresses. The triaxial test results are used to describe the effect of static shear stress on the cyclic response of the calcareous sand with different relative density. Cyclic mobility, flow deformation, and residual deformation accumulation are the three main failure modes under varying static and cyclic shear stress levels. The cyclic resistance of dense sand is greater than that of loose sand, but the initial static stress has different effects on the cyclic resistance of the two kinds of sand. The dense sand owns a higher cyclic resistance with SSR increasing, while for the loose sand, 0.12 is the critical SSR corresponding to the lowest value of the cyclic resistance. The dense sand has more fast accumulation of dissipated energy, compared with loose sand. Additionally, an exponential relationship is established between static shear stress, relative density, and normalized energy density.

scholarly journals Liquefaction Characteristics of Sands Based on Cyclic Direct Simple Shear Test

2020 ◽  
Vol 20 (4) ◽  
pp. 239-249
Author(s):  
Byongyoun Hwang ◽  
Tae-Young Kwak ◽  
Jongkwan Kim ◽  
Jin-Tae Han
Keyword(s):  
Simple Shear ◽  
Evaluation Method ◽  
Resistance Ratio ◽  
Test Results ◽  
Liquefaction Resistance ◽  
Ottawa Sand ◽  
Cyclic Resistance ◽  
Direct Simple Shear ◽  
Cyclic Resistance Ratio ◽  
Particle Shapes

In this study, a series of cyclic direct simple shear tests were conducted on Pohang sand, Jumunjin sand, and Ottawa sand. The cyclic resistance ratio (CRR) was derived on the basis of the test results obtained. For verification of the effect of particle distribution on liquefaction resistance, the simplified method for evaluation of the possibility of liquefaction was used to assess these sands. The test results showed that the cyclic resistance ratio of Pohang sand was the lowest, which was consistent with the result of the simplified evaluation method for determining the possibility of liquefaction. In addition, the results showed that the liquefaction resistance increased for particle shapes being more angular than round. Normalization was subsequently applied to minimize the effects of the different factors, and the correlation between the CRR<sub>N=10</sub> normalization curve and the CRR<sub>N=15</sub> normalization curve was confirmed.

scholarly journals Correlation between shear wave velocity and effective confining pressure using cyclic triaxial testing apparatus

2019 ◽  
Vol 92 ◽  
pp. 04009
Author(s):  
Guojun Liu ◽  
Noriyuki Yasufuku ◽  
Ryohei Ishikura ◽  
Qiang Liu
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Effective Stress ◽  
Shear Wave Velocity ◽  
Confining Pressure ◽  
Similar Rate ◽  
Bender Elements ◽  
Confining Stress ◽  
Liquefaction Resistance ◽  
Ground Shaking

The 2016 Kumamoto earthquakes struck Kumamoto and Ōita regions and caused several devastating liquefaction induced damages. The primary damage was due to the extreme ground shaking of the foreshock and main shock sequence. Therefore, it is essential to develop a quick reliable approach with a high accuracy to assess the ground situation after foreshock or several shocks. Velocity of small shear wave (Vs) was widely used for evaluating the potential liquefaction. This study investigates the possibility of using Vs as a new indicator of the stress state in the soil after earthquake and evaluation of post liquefaction resistance of soil. Cyclic tri-axial apparatus equipped with bender elements were used to conduct two consecutives liquefaction tests on sandy soil. The Vs measured by bender elements was discussed on the relationship with effective stress during the liquefying processes. The results showed that for the sandy soils, a) Vs could not clearly reflect the significant reduction in resistance at re-liquefaction stages by directly comparing the Vs at the end of consolidation between first and stages, b) The shear wave velocity is significantly affected by effective confining pressure c) the shear wave velocity of 190 m/s was at confining pressure of 100 kPa. The shear wave velocity reaches to after 100 m/s after consolidations and re-consolidations. The shear wave velocity was found to reduce to 100 m/s when the effective confining stress reaches to 0 and to around 25 m/s when the double amplitude reaches to 5%; d) the velocity and effective stress decreases with a similar rate in liquefying process.

Application of machine learning algorithms to predict permeability in tight sandstone formations

Nafta-Gaz ◽  
2021 ◽  
Vol 77 (5) ◽  
pp. 283-292
Author(s):  
Tomasz Topór ◽  
Keyword(s):  
Machine Learning ◽  
Oil And Gas ◽  
Learning Algorithms ◽  
Confining Pressure ◽  
Machine Learning Algorithms ◽  
Core Material ◽  
Confining Stress ◽  
Tight Sandstone ◽  
Oil And Gas Exploration ◽  
Better Than

The application of machine learning algorithms in petroleum geology has opened a new chapter in oil and gas exploration. Machine learning algorithms have been successfully used to predict crucial petrophysical properties when characterizing reservoirs. This study utilizes the concept of machine learning to predict permeability under confining stress conditions for samples from tight sandstone formations. The models were constructed using two machine learning algorithms of varying complexity (multiple linear regression [MLR] and random forests [RF]) and trained on a dataset that combined basic well information, basic petrophysical data, and rock type from a visual inspection of the core material. The RF algorithm underwent feature engineering to increase the number of predictors in the models. In order to check the training models’ robustness, 10-fold cross-validation was performed. The MLR and RF applications demonstrated that both algorithms can accurately predict permeability under constant confining pressure (R2 0.800 vs. 0.834). The RF accuracy was about 3% better than that of the MLR and about 6% better than the linear reference regression (LR) that utilized only porosity. Porosity was the most influential feature of the models’ performance. In the case of RF, the depth was also significant in the permeability predictions, which could be evidence of hidden interactions between the variables of porosity and depth. The local interpretation revealed the common features among outliers. Both the training and testing sets had moderate-low porosity (3–10%) and a lack of fractures. In the test set, calcite or quartz cementation also led to poor permeability predictions. The workflow that utilizes the tidymodels concept will be further applied in more complex examples to predict spatial petrophysical features from seismic attributes using various machine learning algorithms.

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