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 A semi-empirical relationship for the small-strain shear modulus of soft clays

2019 ◽  
Vol 92 ◽  
pp. 04005
Author(s):  
Vashish Taukoor ◽  
Cassandra J. Rutherford ◽  
Scott M. Olson
Keyword(s):  
Shear Modulus ◽  
Effective Stress ◽  
Void Ratio ◽  
Empirical Relationship ◽  
Small Strain ◽  
High Plasticity ◽  
Bender Element ◽  
Stress History ◽  
Small Strain Shear Modulus ◽  
Semi Empirical

The small-strain shear modulus (Gmax) is a soil property that has many practical applications. The authors compiled a database of Gmax measurements for 40 normally consolidated to slightly overconsolidated low to high plasticity clays. Using these data, the authors propose a semi-empirical relationship between Gmax, effective stress (σ'v or σ'c), preconsolidation stress (σ'p) and in-situ void ratio (e0) for four ranges of plasticity index (Ip): Ip < 30%, 30% ≤ Ip < 50%, 50% ≤ Ip < 80% and 80% ≤ Ip < 120%. With results from bender element tests on a Gulf of Mexico clay subjected to multiple load-unload consolidation loops, the authors were able to validate the proposed relationships for 30% ≤ Ip < 50% and 50% ≤ Ip < 80%. The proposed relationship for 30% ≤ Ip < 50% and 50% ≤ Ip < 80% captures changes in laboratory Gmax resulting from variations in effective stress (σ'c), maximum past stress (σ'v,max), and void ratio. The proposed relationships are a simple and efficient tool that can provide independent insight on Gmax if the stress history of a clay is known, or on stress history if Gmax is known.

scholarly journals Laboratory Characterization of a Compacted–Unsaturated Silty Sand with Special Attention to Dynamic Behavior

2020 ◽  
Vol 10 (7) ◽  
pp. 2559
Author(s):  
Andrzej Głuchowski ◽  
Zdzisław Skutnik ◽  
Marcin Biliniak ◽  
Wojciech Sas ◽  
Diego Lo Presti
Keyword(s):  
Shear Modulus ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Bender Element ◽  
State Dependent ◽  
Laboratory Characterization ◽  
Dynamic Excitations

The dynamic properties of compacted non-cohesive soils are desired not only because of the risk of natural sources of dynamic excitations such as earthquakes, but mostly because of the anthropogenic impact of machines that are working on such soils. These soils are often unsaturated, which positively affects the soil’s mechanical properties. The information about the values of these parameters is highly desirable for engineers. In this article, we performed a series of tests, including oedometric tests, resonant column tests, bender element tests, and unsaturated triaxial tests, to evaluate those characteristic parameters. The results showed that sandy silt soil has a typical reaction to dynamic loading in terms of shear modulus degradation and the damping ratio curves’ characteristics, which can be modeled by using empirical equations. We found that the compaction procedure caused an over-consolidation state dependent on the moisture content during compaction effort. The article analyzed the soil properties that impact the maximum shear modulus G0 value. Those properties were suction s, confining pressure σ3, and compaction degree represented by the void ratio function f(e).

Small to intermediate strain properties of fly ashes with various carbon and biomass contents

2016 ◽  
Vol 53 (1) ◽  
pp. 35-48 ◽  
Author(s):  
H. Choo ◽  
N.N. Yeboah ◽  
S.E. Burns
Keyword(s):  
Void Ratio ◽  
Small Strain ◽  
Interparticle Contact ◽  
Bender Elements ◽  
Fly Ashes ◽  
Small Strain Stiffness ◽  
Initial Void Ratio ◽  
Constrained Modulus ◽  
Stiffness Anisotropy ◽  
Biomass Particles

High-carbon-content fly ashes with biomass particles are typically landfilled in accordance with the ASTM C618 regulation. To quantify their geotechnical properties relating to storage and disposal, this study evaluates the small to intermediate strain properties of fly ashes with various carbon and biomass contents. Tested fly ashes had carbon contents ranging from 1.1% to 9.6%, resulting from co-combusting coal with biomass (biomass contents ranging from 0% to 8.2% by weight). The small-strain stiffness and intermediate-strain constrained modulus were evaluated using consolidation tests performed in a modified oedometer cell equipped with bender elements. It was found that initial void ratio governed the compressibility (or constrained modulus) of fly ashes, and with an increase in carbon and biomass contents, the small-strain stiffness of fly ashes decreased due to the decrease in number of direct contacts between microspheres. In addition, the interfine void ratio, ef, was employed instead of global void ratio to capture the alteration of interparticle contact or interparticle coordination between microspheres, due to the change in carbon and biomass contents. Finally, the stiffness in an overconsolidated state and the stiffness anisotropy of fly ashes were evaluated.

scholarly journals Effect of Inter-granular Void Ratio on Volume Compressibility and Undrained Shear Response of Base-sand and Natural Silty-sand of Kutch

2019 ◽  
Vol 92 ◽  
pp. 06002 ◽  
Author(s):  
Majid Hussain ◽  
Ajanta Sachan
Keyword(s):  
Void Ratio ◽  
Confining Pressure ◽  
Deviatoric Stress ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Sand Sample ◽  
Shear Response ◽  
Volume Compressibility ◽  
Consolidation Phase ◽  
Undrained Shear

In this article, effect of inter-granular void ratio (eg) on the volume compressibility and undrained shear strength behaviour of a natural silty-sand and base-sand is explored. Natural silty-sand sample was collected from Fatehgarh dam in Kutch region of India and the specimens prepared were subjected to isotropically consolidated undrained compression (CIUC) triaxial tests under two scenarios. In scenario one, silty-sand collected from Fatehgarh dam was used to perform CIUC triaxial tests at in-situ density. However, scenario two was based on CIUC triaxial tests on base-sand, which was extracted from Fatehgarh dam silty-sand soil by removing fines. It was ensured that the two specimens (silty-sand, base-sand) had the same void ratio (e = 0.704) but different inter-granular void ratios (eg-silty-sand = 1.156 and eg-base-sand = 0.704). Volume compressibility during isotropic consolidation phase of specimens was strongly reduced in the base-sand as compared to silty-sand. The undrained shear response of base-sand showed an increase in peak deviatoric stress by a factor of 1.8, 1.6 and 1.7 as compared to silty-sand at an initial effective confining pressure of 100 kPa, 200 kPa and 300 kPa respectively. The angle of friction mobilized at peak deviatoric stress and the work done per unit volume increased with the decrease in the inter-granular void ratio (eg), although the void ratio (e) was same.

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