Instability and liquefaction of granular soils under undrained and partially drained states

1998 ◽  
Vol 35 (6) ◽  
pp. 1053-1062 ◽  
Author(s):  
Y P Vaid ◽  
A Eliadorani
Keyword(s):  
Experimental Investigation ◽  
Triaxial Test ◽  
Void Ratio ◽  
Granular Soils ◽  
Saturated Sand ◽  
Stress Space ◽  
Sand Liquefaction ◽  
Undrained Shear

An experimental investigation of the initiation of instability (liquefaction) in saturated sand under partially drained conditions is presented. The domain of stress space in which this instability develops is identified under various degrees of drainage, and its relationship to the zone of instability observed under undrained shear is explored. It is shown that partially drained conditions may render sand unstable that would otherwise be stable in a completely undrained state. Extremely small void ratio increases that cannot be regarded as physical loosening of sand, if sand is partially drained, contribute to instability. Implications of the findings are discussed in practical problems of liquefaction.Key words: sand, liquefaction, undrained, partially drained, instability, triaxial test.

Stress path and steady state

1990 ◽  
Vol 27 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Y. P. Vaid ◽  
E. K. F. Chung ◽  
R. H. Kuerbis
Keyword(s):  
Steady State ◽  
Effective Stress ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Stress Path ◽  
Stress Space ◽  
Sand Liquefaction ◽  
State Strength ◽  
The Difference ◽  
State Stress

The effect of stress path on the steady state line of a liquefiable sand is investigated. Results from undrained triaxial compression and extension tests on water-deposited sands show that the steady state line of a given sand, though unique in the effective stress space, is not so in the void ratio – effective stress space. The sand is contractive over a much larger range of void ratios in extension than in compression. While a single steady state line emerges for compression loading, extension loading yields several lines, each characteristic to a given deposition void ratio. All these extension lines lie to the left of the compression line in void ratio – effective stress space. Thus at a given void ratio, steady state strength is smaller in extension than in compression, the difference increasing as the sand becomes looser. The implications of the results are discussed in relation to practical design. Key words: sand, liquefaction, steady state, stress path.

scholarly journals Experimental Investigation on Small-Strain Stiffness of Marine Silty Sand

2020 ◽  
Vol 8 (5) ◽  
pp. 360 ◽  
Author(s):  
Qi Wu ◽  
Qingrui Lu ◽  
Qizhou Guo ◽  
Kai Zhao ◽  
Pen Chen ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Void Ratio ◽  
Reduction Rate ◽  
Confining Pressure ◽  
Small Strain ◽  
Silty Sand ◽  
Bender Element ◽  
Small Strain Stiffness ◽  
Alternative State ◽  
State Index

The significance of small-strain stiffness (Gmax) of saturated composite soils are still of great concern in practice, due to the complex influence of fines on soil fabric. This paper presents an experimental investigation conducted through comprehensive bender element tests on Gmax of marine silty sand. Special attention is paid to the influence of initial effective confining pressure ( σ c 0 ′ ), global void ratio (e) and fines content (FC) on Gmax of a marine silty sand. The results indicate that under otherwise similar conditions, Gmax decreases with decreasing e or FC, but decreases with increasing FC. In addition, the reduction rate of Gmax with e increasing is not sensitive to σ c 0 ′ , but obviously sensitive to changes in FC. The equivalent skeleton void ratio (e*) is introduced as an alternative state index for silty sand with various FC, based on the concept of binary packing material. Remarkably, the Hardin model is modified with the new state index e*, allowing unified characterization of Gmax values for silty sand with various FC, e, and σ c 0 ′ . Independent test data for different silty sand published in the literature calibrate the applicability of this proposed model.

scholarly journals Vertical ground motion and its effects on liquefaction resistance of fully saturated sand deposits

2016 ◽  
Vol 472 (2192) ◽  
pp. 20160434 ◽  
Author(s):  
Vasiliki Tsaparli ◽  
Stavroula Kontoe ◽  
David M. G. Taborda ◽  
David M. Potts
Keyword(s):  
Vertical Component ◽  
Vertical Motion ◽  
Soil Liquefaction ◽  
Elastic Response ◽  
Saturated Sand ◽  
Liquefaction Resistance ◽  
Sand Liquefaction ◽  
Variable Permeability ◽  
Lower Amplitude ◽  
Input Motion

Soil liquefaction has been extensively investigated over the years with the aim to understand its fundamental mechanism and successfully remediate it. Despite the multi-directional nature of earthquakes, the vertical seismic component is largely neglected, as it is traditionally considered to be of much lower amplitude than the components in the horizontal plane. The 2010–2011 Canterbury earthquake sequence in New Zealand is a prime example that vertical accelerations can be of significant magnitude, with peak amplitudes well exceeding their horizontal counterparts. As research on this topic is very limited, there is an emerging need for a more thorough investigation of the vertical motion and its effect on soil liquefaction. As such, throughout this study, uni- and bidirectional finite-element analyses are carried out focusing on the influence of the input vertical motion on sand liquefaction. The effects of the frequency content of the input motion, of the depth of the deposit and of the hydraulic regime, using variable permeability, are investigated and exhaustively discussed. The results indicate that the usual assumption of linear elastic response when compressional waves propagate in a fully saturated sand deposit does not always hold true. Most importantly post-liquefaction settlements appear to be increased when the vertical component is included in the analysis.

Numerical Simulation of Pile-Soil Interaction Considering Sand Liquefaction under Earthquake

2012 ◽  
Vol 226-228 ◽  
pp. 1019-1022 ◽  
Author(s):  
Pei Zhen Li ◽  
Dong Ya Ma ◽  
Da Ming Zeng ◽  
Xi Lin Lu
Keyword(s):  
Numerical Simulation ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Clay ◽  
Soil Liquefaction ◽  
Engineering Practice ◽  
Saturated Sand ◽  
Acceleration Response ◽  
Sand Liquefaction ◽  
Vibration Time

Liquefaction is one of the most important damages in pile foundation under earthquake. However, it is very difficult to analyze. Numerical simulation of pile-soil interaction considering saturated sand liquefaction under earthquake is conducted using OpenSees program. In this model, the soil is divided into soft clay soil and saturated sand, and the single pile is embedded in the soil. The results show that the pore water pressure rises and the soil liquefied as vibration time increases. With the nonlinear of the soil develop, the stiffness, bearing capacity and the acceleration response of the soil and the pile decrease, while the displacement response of the soil increases. Therefore, it is necessary to consider the soil liquefaction in the design and analysis in the engineering practice.

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