scholarly journals LIQUEFACTION BEHAVIOR OF LOOSE SAND CONTAINING NON-PLASTIC FINES UNDER INITIAL SHEAR STRESSES -INVESTIGATION BY CYCLIC AND MONOTONIC LOADING TORTIONAL SHEAR TESTS-

2013 ◽  
Vol 69 (1) ◽  
pp. 80-90
Author(s):  
Takuya KUSAKA ◽  
Takaji KOKUSHO ◽  
Ryotaro ARAI
Keyword(s):  
Monotonic Loading ◽  
Shear Stresses ◽  
Loose Sand ◽  
Shear Tests

Reliability analysis of static liquefaction of loose sand using the random finite element method

2015 ◽  
Vol 32 (7) ◽  
pp. 2100-2119 ◽  
Author(s):  
Ali Johari ◽  
Jaber Rezvani Pour ◽  
Akbar Javadi
Keyword(s):  
Finite Element ◽  
Pressure Ratio ◽  
Monotonic Loading ◽  
Unit Weight ◽  
Soil Parameters ◽  
Loose Sand ◽  
Element Analysis ◽  
Content Type ◽  
Static Liquefaction ◽  
Random Finite Element

Purpose – Liquefaction of soils is defined as significant reduction in shear strength and stiffness due to increase in pore water pressure. This phenomenon can occur in static (monotonic) or dynamic loading patterns. However, in each pattern, the inherent variability of the soil parameters indicates that this problem is of a probabilistic nature rather than being deterministic. The purpose of this paper is to present a method, based on random finite element method, for reliability assessment of static liquefaction of saturated loose sand under monotonic loading. Design/methodology/approach – The random finite element analysis is used for reliability assessment of static liquefaction of saturated loose sand under monotonic loading. The soil behavior is modeled by an elasto-plastic effective stress constitutive model. Independent soil parameters including saturated unit weight, peak friction angle and initial plastic shear modulus are selected as stochastic parameters which are modeled using a truncated normal probability density function (pdf). Findings – The probability of liquefaction is assessed by pdf of modified pore pressure ratio at each depth. For this purpose pore pressure ratio is modified for monotonic loading of soil. It is shown that the saturated unit weight is the most effective parameter, within the selected stochastic parameters, influencing the static soil liquefaction. Originality/value – This research focuses on the reliability analysis of static liquefaction potential of sandy soils. Three independent soil parameters including saturated unit weight, peak friction angle and initial plastic shear modulus are considered as stochastic input parameters. A computer model, coded in MATLAB, is developed for the random finite element analysis. For modeling of the soil behavior, a specific elasto-plastic effective stress constitutive model (UBCSAND) was used.

scholarly journals Cyclic and Permanent Shear Strains of a Soft Cohesive Soil Subjected to Combined Static and Cyclic Loading

2020 ◽  
Vol 10 (23) ◽  
pp. 8433
Author(s):  
Hernán Patiño ◽  
Rubén Galindo ◽  
Claudio Olalla Marañón
Keyword(s):  
Simple Shear ◽  
Cohesive Soil ◽  
Mediterranean Coast ◽  
Vertical Stress ◽  
Experimental Program ◽  
Shear Stresses ◽  
Shear Tests ◽  
Cyclic Shear ◽  
Shear Strains ◽  
Number Of Cycles

This paper refers to cyclic shear strains (γc) and permanent shear strains (γp) of a soft cohesive soil, when both monotonic shear stresses (τo) and cyclic shear stresses (τc) are applied. The research is backed by an extensive experimental program with 139 cyclic simple shear tests that included identification and classification tests. These cyclic simple shear tests were conducted under different levels of stresses, τo, before the cyclic phase. Laboratory tests were carried out on undisturbed samples from the Port of Barcelona, located in Spain on the Mediterranean coast, and characterized by a monotonic strength (τmax) approximately equal to 30% of the initial effective vertical stress (σ′ov). The samples were taken at depths between 29 and 52 m and correspond to an initial effective vertical stress between 277 and 413 kPa, respectively. In general, the results indicate that: (a) the combination of τo and τc controls the generation of γc and γp, (b) it is not always true that when τo/σ′ov + τc/σ′ov ≈ τmax/σ′ov, the soil reaches failure cyclically, and (c) empirical relations useful for design can be established between γc, γp, and the number of cycles (N), for different relationships varying (τo/σ′ov) between 0% and 25%.

Measurement of soil strength in simple shear tests

1991 ◽  
Vol 28 (2) ◽  
pp. 255-262 ◽  
Author(s):  
J. H. Atkinson ◽  
W. H. W. Lau ◽  
J. J. M. Powell
Keyword(s):  
Simple Shear ◽  
Shear Test ◽  
Triaxial Tests ◽  
Shear Stresses ◽  
Shear Tests ◽  
Laboratory Equipment ◽  
Simple Shear Test ◽  
Failure Envelopes ◽  
London Clay ◽  
Normal And Shear Stresses

During a simple shear test the axes of stress rotate and, in a conventional apparatus in which the only stresses measured are the normal and shear stresses on horizontal planes, it is not possible to define the stress state completely. As a result, the measured failure stresses may not represent the true strength of the soil. Examination of possible Mohr's circles for soils at failure in simple shear tests demonstrates that the measured strength for a given soil depends on, among other things, the ratio of the horizontal and vertical effective stresses at failure. Results of laboratory tests on Cowden Till and on blue London Clay show the differences between strengths measured in simple shear and triaxial tests. A consequence of the conventional interpretation of the simple shear test is that effective stress failure envelopes have a false cohesion intercept with friction angles smaller than those measured in triaxial tests. Key words: clays, laboratory equipment, shear strength, shear tests, triaxial tests.

scholarly journals Influence of Plant Roots On Slope Stabilization: A Geotechnical Investigation

2021 ◽  
Author(s):  
Thounaojam Joyraj Singh ◽  
Soibam Ibotombi ◽  
Maisnam Pradipchandra Singh
Keyword(s):  
Shear Strength ◽  
Plant Species ◽  
Root Density ◽  
Plant Roots ◽  
Shear Stresses ◽  
Shear Tests ◽  
Reinforced Soils ◽  
Direct Shear Tests ◽  
Lateral Branches ◽  
Strength Increment

Abstract Direct shear tests conducted on soil samples reveal that soils with plant roots show an increase in cohesive factor but increase in frictional angle is insignificant. Displacement and shear strength graphs, however, indicate that soil with plant roots can withstand more shear stresses. Among the three plant species selected for the present study, Chimonobambusa sp. has the highest shear strength increment, ∆C = 5.0 KN/m2 followed by Cymbopogon sp., and Pseudosasa japonica with 4.5KN/m2 and 1.0KN/m2 shear strength increments respectively. An increase in shear strength is also observed in the reinforced soils with increase in number of roots of these plant species. Cymbopogon sp. has higher root density near the surface but decreases with increasing depth and absent at 320mm depth, Pseudosasa japonica has the lowest root density but penetrates deeper up to 530mm while Chimonobambusa sp. penetrates deepest at 700mm with lateral branches extending up to 650mm. Cymbopogon sp., and Pseudosasa japonica may be useful as a bioengineering tool to mitigate soil erosion while Chimonobambusa sp. to mitigate both erosion and shallow landslides.

scholarly journals Undrained Cyclic Response and Resistance of Saturated Calcareous Sand considering Initial Static Shear Effect

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Baojian Li ◽  
Panpan Guo ◽  
Gaoyun Zhou ◽  
Zhe Wang ◽  
Gang Lei ◽  
...  
Keyword(s):  
Shear Stress ◽  
Relative Density ◽  
Shear Stresses ◽  
Loose Sand ◽  
Calcareous Sand ◽  
Cyclic Shear ◽  
Cyclic Response ◽  
Dense Sand ◽  
Cyclic Resistance ◽  
Static Shear

Sand elements in the natural or manmade field have often undergone initial static shear stresses before suffering cyclic loading. To explore the effect of static shear stress, a series of undrained cyclic triaxial tests were performed on dense and loose calcareous sand under different initial and cyclic shear stresses. The triaxial test results are used to describe the effect of static shear stress on the cyclic response of the calcareous sand with different relative density. Cyclic mobility, flow deformation, and residual deformation accumulation are the three main failure modes under varying static and cyclic shear stress levels. The cyclic resistance of dense sand is greater than that of loose sand, but the initial static stress has different effects on the cyclic resistance of the two kinds of sand. The dense sand owns a higher cyclic resistance with SSR increasing, while for the loose sand, 0.12 is the critical SSR corresponding to the lowest value of the cyclic resistance. The dense sand has more fast accumulation of dissipated energy, compared with loose sand. Additionally, an exponential relationship is established between static shear stress, relative density, and normalized energy density.

Failure state of a sand in simple shear

1988 ◽  
Vol 25 (2) ◽  
pp. 395-400 ◽  
Author(s):  
Muniram Budhu
Keyword(s):  
Stress State ◽  
Shear Strain ◽  
Simple Shear ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Shear Tests ◽  
Failure State ◽  
Failure Loads ◽  
Test Soil ◽  
Geotechnical Problems

The stress state in many practical geotechnical problems is analogous to simple shear strain. However, the devices available to test soil samples in simple shear strain impose nonuniform stress and strain fields. Consequently, the interpretation of results from simple shear tests is often questioned. In this article, results of tests on loose and dense Leighton Buzzard sand from two specially instrumented simple shear devices–Cambridge University's device and a Norwegian Geotechnical Institute type–are used to interpret the failure mode and the failure stress state. The data were obtained from the centre of the samples, a region removed from stress concentrations. Failure was observed to be initiated on vertical planes and occurred very soon after shear displacement was applied. However, neither these vertical planes nor the horizontal planes were the planes of maximum stress obliquity mobilized during the tests. Key words: deformation, failure, loads, sand, shear tests, simple shear, stresses.

Instability of loose sand in constant volume direct simple shear tests in relation to particle shape

2020 ◽  
Vol 15 (9) ◽  
pp. 2507-2527 ◽  
Author(s):  
A. Lashkari ◽  
S. R. Falsafizadeh ◽  
P. T. Shourijeh ◽  
M. J. Alipour
Keyword(s):  
Simple Shear ◽  
Particle Shape ◽  
Constant Volume ◽  
Loose Sand ◽  
Shear Tests ◽  
Direct Simple Shear

scholarly journals Analysis of contact interaction of polymer honeycomb core and CFRP base layers in sandwich-core constructions

2021 ◽  
Vol 20 (1) ◽  
pp. 87-96
Author(s):  
S. A. Pavlova
Keyword(s):  
Contact Interaction ◽  
Composite Structures ◽  
High Strength ◽  
Complex Stress ◽  
Shear Stresses ◽  
Honeycomb Core ◽  
Shear Tests ◽  
Reinforced Plastics ◽  
Four Point Bending ◽  
Sandwich Core

The article considers the challenge of studying the mechanical properties of composite sandwich constructions at the interface between the base layers and the lightweight core. The results of strength tests are presented for specimens of sandwich-core panels with coats made of high-strength carbon fiber-reinforced plastics (CFRP) and polymer honeycomb core considering various loading conditions. It is noted that a discrepancy in the values of shear stresses occurs in four-point bending and shear tests due to the complex stress-strain state of the specimens during bending. In order to interpret the experimental data, numerical analysis of the area of contact interaction between the coats and the filler of the sandwich-core composite structures is carried out. It is noted that in the presence of significant normal stresses in the adhesive coat the base layers separate from the core during shear tests and there is underestimation of the values of shear stresses by about 20%. Recommendations for the assignment of ultimate shear stresses for the use in practical design of sandwich-core composite constructions are put forward.

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