Yield strength ratios, critical strength ratios, and brittleness of sandy soils from laboratory tests

2011 ◽  
Vol 48 (3) ◽  
pp. 493-510 ◽  
Author(s):  
Abouzar Sadrekarimi ◽  
Scott M. Olson
Keyword(s):  
Yield Strength ◽  
Critical State ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Silty Sand ◽  
Strength Ratio ◽  
Critical Strength ◽  
Initial Void Ratio ◽  
Ring Shear ◽  
Particle Damage

In this study, we performed 26 undrained triaxial compression and 32 constant-volume ring shear tests on two clean sands and one silty sand. We then used these results to evaluate the critical states, and shear strength ratios mobilized at yield and at critical state. We obtained yield strength ratios that ranged from 0.16 to 0.32 and from 0.20 to 0.35 in triaxial compression and ring shear, respectively. Critical strength ratios mobilized prior to particle damage ranged from 0.01 to 0.26 in triaxial compression and from 0.04 to 0.22 in ring shear. Particle damage and shear displacement increased the slopes of the critical-state lines during ring shear testing, and consequently the critical strength ratios incorporating particle damage decreased from 0.02 to 0.12. In addition, specimen brittleness (before particle damage) increases with initial void ratio and state parameter and is affected by initial fabric and particle shape. However, particle damage and crushing considerably increases sand brittleness, making it essentially independent of initial void ratio. A unique relation is found between sand brittleness and critical strength ratio independent of sand type, mode of shear, fabric, and particle damage, which indicates an upper bound critical strength ratio of about 0.3 for mildly contractive sands.

Experimental Study on Shear Strength Considering Initial Void Ratio and Plasticity Index

2013 ◽  
Vol 405-408 ◽  
pp. 63-67
Author(s):  
Xing Chen Wang ◽  
Ri Qing Xu ◽  
Jian Feng Zhu
Keyword(s):  
Shear Strength ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Deviatoric Stress ◽  
Plasticity Index ◽  
Test Results ◽  
Compression Tests ◽  
Functional Relationships ◽  
Initial Void Ratio

A series of drained triaxial compression tests under different conditions were performed to quantitatively study the influence of the initial void ratio and plasticity index on the shear strength of remolded saturated clays. The test results show that both the peak stress friction angle and peak deviatoric stress decrease with increasing initial void ratio and plasticity index of the soil under the same confining pressure; whereas, they increase with increasing confining pressure of the soil under the same initial void ratio and plasticity index. A new synthesized physical parameter λ, which simultaneously represent both the type and the condition of remolded saturated clays, is defined based on the test results in this work. The functional relationships among the parameters φd and peak deviatoric stress in Mohr-Coulomb equation and the parameter λ are established to develop a modified Mohr-Coulomb equation by considering physical properties of soil. In this equation, only two input parameters, i.e., λ and the confine pressure, are needed to predict the shear strength of the soil. In order to check the accuracy of the proposed equation, laboratory tests were conducted to evaluate against the predicted results. The results show that the peak shear strength of remolded saturated clays can be well described by the proposed equation. Key words: shear strength; Mohr-Coulomb equation; remolded saturated clays; initial void ratio; plasticity index.

Influence of silt size and content on liquefaction behavior of sands

2011 ◽  
Vol 48 (6) ◽  
pp. 931-942 ◽  
Author(s):  
Mehmet Murat Monkul ◽  
Jerry A. Yamamuro
Keyword(s):  
Void Ratio ◽  
Triaxial Compression ◽  
Relative Size ◽  
Silty Sand ◽  
Engineering Practice ◽  
Compression Tests ◽  
Confining Stress ◽  
Liquefaction Potential ◽  
Fines Content ◽  
Triaxial Compression Tests

This study investigates the fines content influence on liquefaction potential of a single base sand mixed with three different essentially nonplastic silts through strain-controlled monotonic undrained triaxial compression tests. Confining stress (30 kPa) and deposition method (dry funnel deposition) were kept the same, while fines content was varied, to solely focus on how different silts and their contents influence the undrained response of the sand under comparable conditions. It was found that if the mean grain diameter ratio (D50-sand/d50-silt) of the sand grains to silt grains is sufficiently small, the liquefaction potential of the sand increases steadily with increasing fines content for the studied range (0%–20%). As D50-sand/d50-silt increases, the liquefaction potential of the silty sand might actually be less than the liquefaction potential of the clean sand. Test results also revealed that commonly used comparison bases (i.e., void ratio, intergranular void ratio, relative density) are not sufficient for assessing the influence of fines on liquefaction potential of silty sands. Finally, relative size of the silt grains should also be considered in geotechnical engineering practice in addition to content and plasticity of fines to characterize the influence of silt on liquefaction potential of sands.

scholarly journals Deformation induced by wetting: a simple model

2012 ◽  
Vol 49 (8) ◽  
pp. 954-960 ◽  
Author(s):  
Francesca Casini
Keyword(s):  
Simple Model ◽  
Void Ratio ◽  
Simple Expression ◽  
Silty Sand ◽  
Water Retention Curve ◽  
Retention Curve ◽  
Initial Void Ratio ◽  
Homogeneous Soil ◽  
Gravimetric Water Content ◽  
Compression Line

This paper presents a simple model for predicting the deformation induced by wetting. The objective is to quantify the deformation induced by saturation of an unsaturated layer of homogeneous soil, causing variation of the initial void ratio and gravimetric water content. The soil is a low-plasticity silty sand. A simple expression for the normal compression line (NCL), which depends on the parameter χ and one more parameter, will be proposed. The model may capture the progressive degradation induced by loading and wetting by linking the dependency of NCL by the parameter χ and water retention curve by porosity.

Isotropic yielding of unsaturated cemented silty sand

2013 ◽  
Vol 50 (8) ◽  
pp. 807-819 ◽  
Author(s):  
M. Arroyo ◽  
M.F. Amaral ◽  
E. Romero ◽  
A. Viana da Fonseca
Keyword(s):  
Water Content ◽  
Water Retention ◽  
Void Ratio ◽  
Dry Weight ◽  
Silty Sand ◽  
Initial Void Ratio ◽  
Naturally Occurring ◽  
Experimental Campaign ◽  
Hardening Mechanisms ◽  
Designed Materials

Unsaturated cemented soils are frequent both as designed materials and as naturally occurring layers. Both desiccation and cementation act separately as hardening mechanisms, but it is not clear how exactly their effects combine. Do they enhance one another? Are they mutually reinforcing? This study presents results from an experimental campaign aimed at answering these questions. Five different mixtures of soil (a granite saprolite) and cement (with cement contents in the range 0% to 7% on a dry weight basis) are tested in isotropic compression at four different water content levels. Initial void ratio is also controlled, using two initial compaction densities. Loading is performed at constant water content and suction is inferred from a set of water retention curves obtained from parallel psychrometric and pore-size distribution measurements. The range of yield stresses explored in this study covers almost two orders of magnitude and extends up to 7 MPa at suction values of up to 14 MPa. Both desiccation and cementation increase yield stress, but their effects are less marked when both act together, and therefore they are not mutually reinforcing.

Use of laboratory data to confirm yield and liquefied strength ratio concepts

2003 ◽  
Vol 40 (6) ◽  
pp. 1164-1184 ◽  
Author(s):  
Scott M Olson ◽  
Timothy D Stark
Keyword(s):  
Shear Strength ◽  
Steady State ◽  
Yield Strength ◽  
Triaxial Compression ◽  
Sandy Soils ◽  
Friction Angle ◽  
Strength Ratio ◽  
Case Histories ◽  
Direct Simple Shear ◽  
Flow Failure

A laboratory database of triaxial compression test results was collected to examine the use of strength ratios for liquefaction analysis. Specifically, the database was used to: (i) validate the yield strength ratio concept (or yield friction angle); (ii) demonstrate the parallelism of the consolidation line and steady state line of many sandy soils; and (iii) validate the liquefied strength ratio concept. The yield strength ratio of contractive sandy soils in triaxial compression ranges from approximately 0.29 to 0.42 (corresponding to yield friction angles of 16°–23°), while the yield strength ratio from flow failure case histories (which correspond approximately to direct simple shear conditions) ranges from 0.23 to 0.31 (or yield friction angles of 13°–17°). As expected, the yield friction angle is greatest in triaxial compression, smaller in direct simple shear, and likely smallest in triaxial extension. The steady state line and consolidation line of many contractive sandy soils are parallel for a wide range effective stresses, steady state line slopes, fines contents, and grain sizes and shapes that are applicable to many civil engineering structures. As such, the liquefied strength ratio is a constant for many sandy soils deposited in a consistent manner. The liquefied strength ratio is inversely related to state parameter and ranges from approximately 0.02 to 0.22 in laboratory triaxial compression tests. Flow failure case histories fall near the middle of this range.Key words: liquefaction, liquefied shear strength, yield shear strength, collapse surface, steady state line, penetration resistance.

Effect of depositional method on the undrained response of silty sand

2008 ◽  
Vol 45 (11) ◽  
pp. 1525-1537 ◽  
Author(s):  
Fletcher M. Wood ◽  
Jerry A. Yamamuro ◽  
Poul V. Lade
Keyword(s):  
Dry Deposition ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Silty Sand ◽  
Compression Tests ◽  
Strain Behavior ◽  
Silt Content ◽  
Isotropic Consolidation ◽  
Undrained Behavior ◽  
Triaxial Compression Tests

The results from a laboratory experimental study on silty sand are presented. Undrained triaxial compression tests were performed on Nevada sand containing nonplastic silt. All specimens underwent monotonic loading after isotropic consolidation to 25 kPa. Various depositional techniques were used to create specimens to compare their stress–strain behavior within three separate density ranges and three different silt contents. As density increased, the effect of the depositional method on the undrained behavior decreased. The influence of the depositional method on specimen behavior also was found to increase with silt content, particularly at lower densities. These findings therefore are of special interest with regard to laboratory testing for the purpose of characterizing liquefaction potential, where loose, silty sands may be encountered. A description and analysis of five different depositional techniques is provided. These methods include: dry funnel deposition, water sedimentation, slurry deposition, mixed dry deposition, and air pluviation. The results of the undrained testing are analyzed using void ratio after consolidation and silt content as the bases of comparison.

scholarly journals Definition and experimental determination of a soil-water retention surface

2010 ◽  
Vol 47 (6) ◽  
pp. 609-622 ◽  
Author(s):  
S. Salager ◽  
M. S. El Youssoufi ◽  
C. Saix
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Void Ratio ◽  
Silty Sand ◽  
Soil Water Retention ◽  
Initial Void Ratio ◽  
Hydromechanical Behaviour ◽  
Determination Methods

This paper deals with the definition and determination methods of the soil-water retention surface (SWRS), which is the tool used to present the hydromechanical behaviour of soils to highlight both the effect of suction on the change in water and total volumes and the effect of deformation with respect to the water retention capability. An experimental method is introduced to determine the SWRS and applied to a clayey silty sand. The determination of this surface is based on the measurement of void ratio, suction, and water content along the main drying paths. These paths are established for five different initial states. The experimental results allow us to define the parametric equations of the main drying paths, expressing both water content and void ratio as functions of suction and initial void ratio. A model of the SWRS for clayey silty sand is established in the space (void ratio – suction – water content). This surface covers all possible states of the soil inside the investigated range for the three variables. Finally, the SWRS is used to study the relations between water content and suction at a constant void ratio and between void ratio and suction at a constant water content.

scholarly journals SHEAR STRENGTH AND VOID RATIO OF UNSATURATED SOIL WITH DIFFERENT INITIAL VOID RATIO AT FAILURE, CRITICAL STATE

2008 ◽  
Vol 64 (2) ◽  
pp. 197-208
Author(s):  
Katsuo SASAHARA ◽  
Naoki SAKAI ◽  
Junichi KURIHARA
Keyword(s):  
Shear Strength ◽  
Unsaturated Soil ◽  
Critical State ◽  
Void Ratio ◽  
Initial Void Ratio

scholarly journals Influence of Initial Void Ratio on Critical State Behaviour of Poorly Graded Fine Sands

2020 ◽  
Vol 50 (5) ◽  
pp. 689-699
Author(s):  
Abdullah Ekinci ◽  
Mohamad Hanafi ◽  
Pedro Miguel Vaz Ferreira
Keyword(s):  
Critical State ◽  
Void Ratio ◽  
Initial Void Ratio ◽  
State Behaviour
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