scholarly journals Mechanical behaviour of Panzhihua iron tailings

2019 ◽  
Vol 56 (3) ◽  
pp. 420-435 ◽  
Author(s):  
W. Li ◽  
M.R. Coop
Keyword(s):  
High Risk ◽  
Rate Of Convergence ◽  
Mechanical Behaviour ◽  
Critical State ◽  
Preparation Method ◽  
Tailings Impoundment ◽  
Tailings Dams ◽  
Different Shapes ◽  
Compression Line ◽  
Normal Compression

Safety problems have concerned many researchers studying tailings dams in recent years, as they have a high risk of failure due to liquefaction. Existing analysis of liquefaction in tailings within a critical state framework has relied on the critical state line (CSL) being unique in the volumetric plane. However, recent advances have highlighted a so-called “transitional” behaviour in which the location of the normal compression line (NCL) and CSL is a function of the density of the soils at deposition. This paper presents a detailed investigation of the mechanics of tailings taken from three locations of an iron tailings impoundment. Reconstituted samples were prepared by different methods and at different densities. No transitional behaviour was found, although the results show that the rate of convergence of the compression curves changes, with the finest pond material reaching a unique NCL earliest. The preparation method was found not to have a large effect on the behaviour for these tailings. Unique CSLs could be clearly identified for all the three tailings, but with different shapes, giving rise to a changing susceptibility to liquefaction. This susceptibility tends to increase from the pond to the upper beach.

The asymptotic behaviour of extinction probability in the Smith–Wilkinson branching process

1993 ◽  
Vol 25 (02) ◽  
pp. 263-289
Author(s):  
D. R. Grey ◽  
Lu Zhunwei
Keyword(s):  
Asymptotic Behaviour ◽  
Rate Of Convergence ◽  
Population Size ◽  
Random Environment ◽  
Critical State ◽  
Branching Process ◽  
Extinction Probability ◽  
Subcritical State ◽  
Regularity Conditions

Under some regularity conditions, in the supercritical Smith–Wilkinson branching process it is shown that as k, the starting population size, tends to infinity, the rate of convergence of qk, the corresponding extinction probability, to zero is similar to that of: k–θ, if there exists at least one subcritical state in the random environment space; xkk–α , if there exist only supercritical states in the random environment space; exp , if there exists at least one critical state and the others are supercritical in the random environment space. Here θ, x, α and c are positive constants determined by the process.

scholarly journals The mechanics of subglacial sediment: an example of new “transitional” behaviour

2010 ◽  
Vol 47 (7) ◽  
pp. 775-790 ◽  
Author(s):  
Fatin Altuhafi ◽  
Béatrice A. Baudet ◽  
Peter Sammonds
Keyword(s):  
Critical State ◽  
Triaxial Compression ◽  
Interesting Case ◽  
Strain History ◽  
Compression Tests ◽  
Specimen Density ◽  
The Difference ◽  
Triaxial Compression Tests ◽  
Normal Compression

A series of isotropic compression tests and drained and undrained triaxial compression tests have been performed on glacial sediment from Iceland. Langjökull sediment, which is well graded, is thought to have reached a critical grading during deposition and transportation. Multiple parallel normal compression lines (NCLs) were found, but a unique critical state line (CSL) could be identified. This is unlike other so-called “transitional” soils, whose grading varies between reasonably well graded to gap graded, which tend to have distinct NCLs and critical state lines depending on the specimen density. It is thought that in the case of the Langjökull sediment studied, its particular strain history that involved incessant shearing during deposition accounts for the difference in behaviour. This provides the interesting case of a soil that has been crushed to a critical grading in situ, which depends on the mineralogy of the grains, which was then sampled and tested. Despite the unique grading, samples with a range of different void ratios can be prepared and the combination of grading and density seems to set a fabric that cannot be changed by compression, resulting in multiple parallel NCLs. At the critical state, however, the fabric has been destroyed and the CSL is unique.

The asymptotic behaviour of extinction probability in the Smith–Wilkinson branching process

1993 ◽  
Vol 25 (2) ◽  
pp. 263-289 ◽  
Author(s):  
D. R. Grey ◽  
Lu Zhunwei
Keyword(s):  
Asymptotic Behaviour ◽  
Rate Of Convergence ◽  
Population Size ◽  
Random Environment ◽  
Critical State ◽  
Branching Process ◽  
Extinction Probability ◽  
Subcritical State ◽  
Regularity Conditions

Under some regularity conditions, in the supercritical Smith–Wilkinson branching process it is shown that as k, the starting population size, tends to infinity, the rate of convergence of qk, the corresponding extinction probability, to zero is similar to that of:k–θ, if there exists at least one subcritical state in the random environment space; xkk–α, if there exist only supercritical states in the random environment space; exp , if there exists at least one critical state and the others are supercritical in the random environment space.Here θ, x, α and c are positive constants determined by the process.

Some aspects of the compressibility behaviour of a clayey sand

2001 ◽  
Vol 38 (6) ◽  
pp. 1177-1186 ◽  
Author(s):  
Flavia Burmeister Martins ◽  
Luiz Antônio Bressani ◽  
Matthew Richard Coop ◽  
Adriano Virgilio Damiani Bica
Keyword(s):  
Published Data ◽  
Clayey Sand ◽  
One Dimensional ◽  
Sand Mixture ◽  
Oedometer Tests ◽  
Compression Line ◽  
Normal Compression

The intrinsic behaviour of a residual clayey sand derived from sandstone was investigated in one-dimensional compression. The data show some interesting differences when compared with other published data, in that no unique normal compression line can be identified. Although the compressibility on first loading is similar to that for many sandy materials at states on their normal compression lines, the locations of the compression curves were found to be a function of the initial voids ratio, and there was no convergence at higher stresses. Tests on a model clay-sand mixture indicated that this behaviour is common to gap-graded clayey sands.Key words: sands, compressibility, oedometer tests.

scholarly journals Magneto-Transport Properties of Co–Cu Thin Films Obtained by Co-Sputtering and Sputter Gas Aggregation

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 134
Author(s):  
Ricardo López Antón ◽  
Juan Pedro Andrés ◽  
Mihail Ipatov ◽  
Juan Antonio González ◽  
Julián González ◽  
...  
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Preparation Method ◽  
Magnetic Measurements ◽  
Hysteresis Loops ◽  
Ferromagnetic Behavior ◽  
Fabrication Method ◽  
Different Shapes ◽  
The Magnetic Field

Cu100−xCox thin films have been obtained by sputtering (x = 3, 9) and sputter gas aggregation (x = 2.5, 7.5) and subsequent annealing at 400 °C for 1 h. We have studied their structural, magnetic, and magnetotransport properties, both for the as-deposited and annealed samples, confirming the important role of the fabrication method in the properties. The magnetic measurements and the fitting of the hysteresis loops evidence that as-deposited samples consist of superparamagnetic (SPM) and/or ferromagnetic clusters, but in the samples obtained by gas aggregation the clusters are greater (with ferromagnetic behavior at room temperature) whereas in the samples obtained by sputtering, the clusters are smaller and there are also diluted Co atoms in the Cu matrix. The annealing affects negligibly the samples obtained by gas aggregation, but the ones obtained by sputtering are more affected, appearing greater clusters. This behavior is also reflected in the magnetoresistance (MR) measurements of the samples, with different shapes of the MR curves depending on the preparation method: more lineal in the whole range for sputtering, saturation at low fields (about 10 kOe) for gas aggregation. Finally, a Kondo-like minimum in the resistance versus temperature is found in the samples obtained by sputtering, affected by the magnetic field and the annealing. The observed Kondo-like behavior and the influence of annealing on a Kondo-like minimum in sputtered thin films have been attributed to the presence of diluted Co atoms in the Cu matrix and the Co precipitations from the Co–Cu solid solution upon annealing respectively.

scholarly journals An elastic-viscous-plastic structured UH model

2021 ◽  
Vol 248 ◽  
pp. 01033
Author(s):  
Zhu Enyang ◽  
Wang Yihe
Keyword(s):  
Test Data ◽  
Soil Structure ◽  
Model Simulation ◽  
Time Effect ◽  
Plastic Strains ◽  
Time Effects ◽  
Hardening Model ◽  
Combined Actions ◽  
Compression Line ◽  
Normal Compression

On the basis of the structured unified hardening model (structured UH model) considering soil structured collapse, the time effect is take into account, and an elastic-viscous-plastic structured UH model is extended. In the presented model, the moving normal compression line (MNCL) is extended to a moving instant normal compression line (MINCL) for simulating both soil structure effect and time effect. Then the instance plastic strains irrespective of time effect are calculated by referring the MINCL, and the plastic strains due to time effect are calculated by referring the traditional instant normal compression line. Comparisons between test data and model simulation indicate that the presented elastic-viscous-plastic structured UH model is qualified to simulate the combined actions of soil structure and time effects both in compression and in shearing.

scholarly journals Proposal for a Mechanical Model of Mobile Shales

2021 ◽  
Author(s):  
Juan Soto ◽  
Mahdi Heidari ◽  
Michael Hudec
Keyword(s):  
Mechanical Behaviour ◽  
Critical State ◽  
Mechanical Model ◽  
Structural Systems ◽  
Continental Margins ◽  
Subsurface Structure ◽  
Mud Volcanoes ◽  
The Poor ◽  
Poor Understanding

Abstract Structural systems involving mobile shale represent one of the most difficult challenges for geoscientists dedicated to exploring the subsurface structure of continental margins. Mobile-shale structures range from surficial mud volcanoes to deeply buried shale diapirs and shale-cored folds. Where mobile shales occur, seismic imaging is typically poor, drilling is hazardous, and established principles to guide interpretation are few. The central problem leading to these issues is the poor understanding of the mechanical behaviour of mobile shales. Here we propose that mobile shales are at critical state, and discuss how this proposition can explain key observations associated with mobile shales. The critical-state model can explain the occurrence of both fluidized shales (e.g., in mud volcanoes) and more viscous shales flowing with grain-to-grain contact (e.g., in mud diapirs), mobilization of cemented or compacted materials, and the role of overpressure in shale mobility. Our model offers new avenues for understanding complex and fascinating mobile-shale structures.

Outcomes for critical conditions in newborns depending on the time of interhospital transportation

2013 ◽  
Vol 4 (3) ◽  
pp. 15-23 ◽  
Author(s):  
Yuriy Stanislavovich Aleksandrovich ◽  
Konstantin Viktorovich Pshenisnov ◽  
Vadim Vladimirovich Andreyev ◽  
Yevgeniy Vladimirovich Parshin ◽  
Roman Ivanovich Cherevatenko ◽  
...  
Keyword(s):  
Intensive Care Unit ◽  
Intensive Care ◽  
High Risk ◽  
Critically Ill ◽  
Bronchopulmonary Dysplasia ◽  
Critical State ◽  
Neonatal Period ◽  
Critical Conditions ◽  
Optimal Time ◽  
Neonatal Icu

This article analyzes the influence of interhospital transportation duration of newborns in critical state on the close outcome. The features of intensive care measures, the frequency of seizures, bronchopulmonary dysplasia and open arterial duct were studied regarding the age at which an infant was admitted to a neonatal ICU in a hospital of III level. It was found that transportation of critically ill infants at the age of one day or three days of life was associated with high risk of complications in the neonatal period. It was shown that the optimal time for interhospital transportation of a newborn baby to an intensive care unit of a hospital of III level is the second day after birth.

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