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.

Steady-State Strength, Relative Density, and Fines Content Relationship for Sands

1996 ◽  
Vol 1547 (1) ◽  
pp. 61-67 ◽  
Author(s):  
S. Thevanayagam ◽  
K. Ravishankar ◽  
S. Mohan
Keyword(s):  
Shear Strength ◽  
Steady State ◽  
Lower Bound ◽  
Relative Density ◽  
Sandy Soils ◽  
Friction Angle ◽  
Stability Evaluation ◽  
Fines Content ◽  
Seismic Slope Stability ◽  
State Strength

The appropriate choice of shear strength of liquefied sands is an important component in seismic slope stability evaluation. Several factors affect the undrained steady-state strength (Sus) of sands. The steady-state strengths of 24 sandy soils were analyzed. It is shown that fines content, relative density, and friction angle play important roles affecting Sus. Fines content was found to be the major factor affecting Sus. This was verified experimentally for one sand. When the Sus. data for sands were grouped into (a) relatively clean sands (<12 percent fines), (b) silty sands (12 to 50 percent fines), and (c) silts or sandy silts (>50 percent fines), at the same relative density, relatively clean sands showed the highest Sus. Silts showed the lowest Sus. Silty sands showed intermediate strengths. Lower-bound Sus-relative density relationships were established for relatively clean sands and silty sands.

Liquefied strength ratio from liquefaction flow failure case histories

2002 ◽  
Vol 39 (3) ◽  
pp. 629-647 ◽  
Author(s):  
Scott M Olson ◽  
Timothy D Stark
Keyword(s):  
Shear Strength ◽  
Back Analysis ◽  
Penetration Resistance ◽  
Standard Penetration Test ◽  
Strength Ratio ◽  
Penetration Test ◽  
Case Histories ◽  
Tip Resistance ◽  
Flow Failure ◽  
Vertical Effective Stress

The shear strength of liquefied soil, su(LIQ), mobilized during a liquefaction flow failure is normalized with respect to the vertical effective stress (σ 'vo) prior to failure to evaluate the liquefied strength ratio, su(LIQ)/σ 'vo. Liquefied strength ratios mobilized during 33 cases of liquefaction flow failure are estimated using a procedure developed to directly back-analyze the liquefied strength ratio. In ten cases, sufficient data regarding the flow slide are available to incorporate the kinetics, i.e., momentum, of failure in the back-analysis. Using liquefied strength ratios back-calculated from case histories, relationships between liquefied strength ratio and normalized standard penetration test blowcount and cone penetration test tip resistance are proposed. These relationships indicate approximately linear correlations between liquefied strength ratio and penetration resistance up to values of qc1 and (N1)60 of 6.5 MPa and 12 blows/ft (i.e., blows/0.3 m), respectively.Key words: liquefaction, flow failure, liquefied shear strength, stability analysis, kinetics, penetration resistance.

Liquefied Strength Ratio with Stress Densification and Low Stresses

2020 ◽  
Author(s):  
Timothy D Stark ◽  
Charles John MacRobert
Keyword(s):  
Shear Strength ◽  
Stability Analysis ◽  
Sandy Soils ◽  
Penetration Resistance ◽  
Vertical Stress ◽  
Strength Ratio ◽  
Case Histories ◽  
Remedial Measure ◽  
Initial Penetration ◽  
Expected Increase

This paper presents a comparison of four (4) assumptions or approaches for using a liquefied shear strength ratio for sandy soils in cases where there has been a large increase in effective vertical stress, e.g., structure raising or remedial measure, that is outside the effective stresses of the case histories used to develop the empirical liquefied shear strength ratio and penetration resistance correlations. Changes in penetration resistance due to an increase in effective vertical stress are used in an example to illustrate the following four (4) assumptions for determining a liquefied shear strength ratio in such a post-liquefaction stability analysis: (1) initial effective vertical stress and initial penetration resistance, (2) initial effective vertical stress and the expected increase in penetration resistance due to the increase in effective vertical stress, (3) final effective vertical stress and initial penetration resistance, which is suggested, and (4) final effective vertical stress and final penetration resistance. This paper also presents suggestions for using a liquefied strength ratio at low effective vertical stresses, e.g., approaching the toe of a dam or embankment, in a post-liquefaction stability analysis.

Mode of shear effects on yield and liquefied strength ratios

2008 ◽  
Vol 45 (4) ◽  
pp. 574-587 ◽  
Author(s):  
Scott M. Olson ◽  
Benjamin B. Mattson
Keyword(s):  
Simple Shear ◽  
Void Ratio ◽  
Triaxial Compression ◽  
State Parameter ◽  
Sloping Ground ◽  
Direct Simple Shear ◽  
Flow Failure ◽  
Triaxial Extension Test ◽  
Triaxial Extension ◽  
Rotational Shear

A database of 386 laboratory triaxial compression, direct simple shear, rotational shear, and triaxial extension test results was collected to examine yield and liquefied strength ratio concepts used in liquefaction analysis of sloping ground. These data envelope the yield and liquefied strength ratios obtained from back-analyses of liquefaction flow failure case histories. Generally, triaxial compression exhibits the highest yield and liquefied strength ratios, triaxial extension yields the lowest ratios, and direct simple shear – rotational shear shows intermediate responses. However, mode of shear appears to have a considerably smaller effect on laboratory-measured liquefied strength ratios for specimens with a positive state parameter (i.e., difference in consolidation void ratio and steady state void ratio at the same effective stress).

Influence of Water Contents on Shear Strength of Rammed Earth Wall of Earth-Building

2011 ◽  
Vol 382 ◽  
pp. 172-175
Author(s):  
Ren Wei Wu ◽  
Xing Qian Peng ◽  
Li Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Triaxial Compression ◽  
Friction Angle ◽  
World Heritage Site ◽  
Rammed Earth ◽  
Compression Tests ◽  
Rammed Earth Wall ◽  
Influence Of Water ◽  
Water Contents

As the "Fujian earth-building" have been inscribed by UNESCO in 2008 as World Heritage Site, attentions of protection about the "Fujian earth-building" has getting more and more. This article takes samples of a rammed-earth wall from Yongding earth-buildings and determines the shear strength of the samples with different water content through triaxial compression tests. The influence on shear strength of water content of rammed-earth samples is analyzed. Test results show that the shear strength of rammed-earth has much to do with the water content of the soil, the greater the water content is，the smaller the shear strength is. With water content increasing, cohesion and internal friction angle of rammed-earth were decreases, and its changing trend is of marked characteristic of stage. When water contents of rammed-earth is under some value, its cohesion changes in small ranges; when water contents of rammed-earth is over the value, its cohesion decreases with water content increasing.

scholarly journals Numerical Experiments on Triaxial Compression Strength of Soil-Rock Mixture

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Yanxi Zhao ◽  
Zhongxian Liu
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Friction Angle ◽  
Mechanical Parameters ◽  
Test Results ◽  
Data Statistics ◽  
Nonlinear Hardening ◽  
Properties Of Soil

Soil-rock mixture is a kind of unfavorable geologic material, and it is composed of low-strength soil particles and high-stiffness rock blocks. Mechanical properties of soil-rock mixture were controlled by the internal mesoscopic medium, thus resulting in great difficulties of determination of mechanical parameters. In this paper, influences of rock content, mesoscopic features, and random distribution of mixture in soil-rock mixture on its shear strength were discussed through discrete element numerical simulation of the laboratory triaxial test. Results demonstrated that, with the increase of rock content, the internal friction angle of soil-rock mixture increased continuously, while the cohesion of soil-rock mixture decreased firstly and then increased. The stress-strain curve belonged to a nonlinear hardening type, which was close to soil characteristic. However, the shear strength was affected by mesoscopic medium of mixture particles significantly, resulting in the strong discreteness of strength, and only by large amounts of data statistics can we get a better regularity of strength. The research results can provide references to determine mechanical parameters of soil-rock mixture.

Reconsideration of case histories for estimating undrained shear strength in sandy soils

1999 ◽  
Vol 36 (5) ◽  
pp. 907-933 ◽  
Author(s):  
C E (Fear) Wride ◽  
E C McRoberts ◽  
P K Robertson
Keyword(s):  
Shear Strength ◽  
Sandy Soils ◽  
Standard Penetration Test ◽  
Undrained Shear Strength ◽  
Soil Liquefaction ◽  
Penetration Test ◽  
Case Histories ◽  
Original Case ◽  
Undrained Strength ◽  
Undrained Shear

When sandy soils respond in a strain-softening manner to undrained loading, an estimation of the resulting undrained shear strength (Su) is required to determine the potential for flow liquefaction at a given site. One of the most commonly used methods for estimating the undrained strength of liquefied sand is an empirical standard penetration test (SPT) based chart (originally proposed by H.B. Seed), which was developed using a number of case histories. The original interpretations of these case histories are viewed by many workers and regulatory agencies as the most authoritative measure of the liquefied strength of sand. Consequently, in comparison, other less conservative methods are generally held in an unfavourable light. This paper reexamines the original database of case histories in view of some more recent concepts regarding soil liquefaction. The objectives of this paper are to explore and reassess the issues involved in the original assessment and to offer alternative views of the case records. The conclusions presented here indicate that alternative explanations of the liquefied strength of sand are not inconsistent with the original case histories. Key words: sandy soils, soil liquefaction, undrained strength, standard penetration test (SPT).

Isothermal modeling of sand–bentonite mixtures at elevated temperatures

1995 ◽  
Vol 32 (1) ◽  
pp. 78-88 ◽  
Author(s):  
B.E. Lingnau ◽  
J. Graham ◽  
N. Tanaka
Keyword(s):  
Shear Strength ◽  
Elevated Temperatures ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Compression Tests ◽  
Strain Behavior ◽  
Bentonite Buffer ◽  
State Boundary ◽  
Increasing Temperature ◽  
Triaxial Compression Tests

Two models are proposed for describing the stress–strain behavior of sand–bentonite (buffer) mixtures at elevated temperatures: (1) isothermal pseudoelasticity and (2) isothermal elastic-plasticity. Data to support the models come from consolidated undrained triaxial compression tests performed on dense saturated buffer specimens at effective confining stresses up to 9.0 MPa and temperatures of 26°, 65°, and 100 °C. Measurements indicate that volumes decrease with increasing temperature if the tests are carried out under drained conditions. These trends can be modelled by a family of hardening lines in semilog compression space. Power law relationships are presented for undrained shear-strength envelopes that increase in size with an increase in temperature. The slopes of unload-reload lines, κ, in semilog compression space vary with temperature and can be related to systematic variation in the friction angle [Formula: see text]. The shear modulus G50 at 50% peak strength also depends on temperature. Several plotting techniques are used to show the existence of different state boundary surfaces for each test temperature. Key words : sand–bentonite, buffer, compression, shear strength, temperature, modelling.

Gravel Content Effect on the Shear Strength of Clay-Gravel Mixtures

2011 ◽  
Vol 71-78 ◽  
pp. 4685-4688 ◽  
Author(s):  
Chen Wang ◽  
Chuan Ni Zhan
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Triaxial Compression ◽  
Constant Strain Rate ◽  
Friction Angle ◽  
Confining Pressure ◽  
Internal Friction Angle ◽  
Compression Tests ◽  
Gravel Content ◽  
Confining Pressures

Gravel content is an important factor affecting the mechanical properties of clay-gravel mixtures. To study the effects of gravel content on the shear strength of clay-gravel mixtures, constant-strain-rate drained triaxial compression tests were conducted for various mixtures. The gravel contents were 30%, 40%, 50% and 70%. The confining pressures were varied from 50kPa to 300kPa. Test results indicate that the deviator stress at failure under the same confining pressure increases with the increase in gravel content. As the gravel content in the mixtures is between 30% and 50%, the shear strength is jointly attributed by clay and gravel. An increase in gravel content results in slight increases in both the cohesion intercept and internal friction angle. At gravel content of up to 70%, the shear strength of the mixture is controlled by that of the gravel, and the cohesion intercept and the internal friction angle increase sharply.

Exploring the effects of nanoscale zero-valent iron (nZVI) on the mechanical properties of lead-contaminated clay

2019 ◽  
Vol 56 (10) ◽  
pp. 1395-1405 ◽  
Author(s):  
Yong-Zhan Chen ◽  
Wan-Huan Zhou ◽  
Fuming Liu ◽  
Shuping Yi
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Morphological Characteristics ◽  
Friction Angle ◽  
Zero Valent Iron ◽  
Compression Tests ◽  
Shear Tests ◽  
Nanoscale Zero Valent Iron ◽  
Triaxial Compression Tests ◽  
Oedometer Tests

Nanoscale zero-valent iron (nZVI) is a well-known efficient nanomaterial for the immobilization of heavy metals and has been widely applied in the remediation of contaminated groundwater and soils. In this study, a series of field emission scanning electron microscopy (FESEM) analyses, vane shear tests, triaxial compression tests, and oedometer tests was conducted on lead-contaminated clay using four dosages of nZVI treatment (0.2%, 1%, 5%, and 10%). The geotechnical properties, including basic index properties, stiffness, shear strength, and compressibility, were assessed after the reaction procedure. FESEM analysis was performed to explore the potential mechanisms of nZVI treatment in terms of morphological characteristics. It was found that the plasticity index decreased gradually with increasing nZVI dosage. Treating contaminated soil with nZVI caused an increase in the vane shear strength, stiffness, and friction angle. The compression index increased gradually because of the nZVI treatment. Based on the FESEM analysis, a conclusion can be deduced that larger aggregates and conjoined structures resulting from nZVI treatment can lead to the strengthening of lead-contaminated clay.

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