Meaning, Measurement, and Field Application of Fully Softened Shear Strength of Stiff Clays and Clay Shales

2021 ◽  
Author(s):  
Gholamreza Mesri ◽  
Cai Wang ◽  
Thierno Kane
Keyword(s):  
Shear Strength ◽  
Slip Surface ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Field Application ◽  
Slope Failures ◽  
Stiff Clays ◽  
Clay Shales ◽  
First Time ◽  
Fully Softened Shear Strength

Fully softened shear strength mobilized in first-time slope failures, introduced by Skempton in 1970, corresponds to a random edge-face arrangement and interaction of clay particles in an entirely destructured fabric of stiff clays and clay shales. A series of triaxial compression tests was conducted on reconstituted normally consolidated specimens of 15 stiff clay and clay shale compositions. Based on the laboratory results an empirical correlation for secant fully softened friction angle, ϕ'fssσ'n, was developed for clay compositions with plasticity index in the range of 10 to 250%, in effective normal stress range of 10 to 700 kPa. The laboratory measurements confirm an empirical equation for fully softened shear strength in terms of parameters ϕ'fss100 and mfs. The field application of secant fully softened friction angle was examined by stability analyses of 63 first-time slope failures in 38 geologic materials. These include 45 slope failures with a segment of observed slip surface at residual condition and the back-scarp mobilizing fully softened shear strength, and 18 slope failures with entire observed slip surface at fully softened condition. The back-calculated fully softened secant friction angles for first-time slope failures are in good agreement with ϕ'fssσ'n correlation based on laboratory tests.

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.

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.

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.

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.

Influence of Density on the Hydraulic and Mechanical Properties of Sands

2014 ◽  
Vol 580-583 ◽  
pp. 659-664
Author(s):  
Osvaldo de Freitas Neto ◽  
Olavo Francisco dos Santos Jr. ◽  
Ricardo Nascimento Flores Severo
Keyword(s):  
Shear Strength ◽  
Hydraulic Conductivity ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Coarse Fraction ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Strength Tests ◽  
Constant Head ◽  
Direct Shear Testing

This article aims at assessing the influence of relative density on the hydraulic conductivity and shear strength of two sands, denominated S01 and S02, derived from different regions and formation processes. S01 is wind-blown and S2 alluvial. The results of characterization and hydraulic conductivity in constant head tests were presented for both samples. The results of direct shear tests with sand S01 prepared with 5 different void ratios were also presented, for a vertical stress of 100kPa. The S02 sample was prepared with 4 different void ratios and these underwent direct shear testing with vertical stresses of 25kPa and 150kPa. This sample was prepared with the maximum and minimum void ratio and submitted to strength tests at CD triaxial compression with confining stresses of 50kPa, 100kPa and 200kPa. Results showed that even with different grain sizes, and under different density conditions, there were no significant variations in the permeability of the materials. With respect to shear strength, sand S01 obtained higher angle of friction values than sand S02, even though the latter had a higher percent coarse fraction. Sand S02 was relatively similar in terms of friction angle values obtained in direct shear and triaxial compression strength tests.

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