scholarly journals Failure Criteria of Gas-Infiltrated Sandy Shale Based on the Effective Stress Principle

Energies ◽  
2016 ◽  
Vol 9 (11) ◽  
pp. 972 ◽  
Author(s):  
Wenpu Li ◽  
Dongming Zhang ◽  
Minghui Li
Keyword(s):  
Effective Stress ◽  
Failure Criteria ◽  
Sandy Shale

scholarly journals Cracking behaviour of fine-grained soils: from laboratory testing to numerical modelling

2019 ◽  
Vol 92 ◽  
pp. 16004
Author(s):  
Pierre Gerard ◽  
Ian Murray ◽  
Alessandro Tarantino
Keyword(s):  
Effective Stress ◽  
Failure Criterion ◽  
Shear Failure ◽  
Digital Camera ◽  
Failure Criteria ◽  
Fine Grained ◽  
Fine Grained Soil ◽  
Desiccation Cracking ◽  
Stress States ◽  
Stress Dependent

Many experimental evidences suggest that desiccation cracks in clay initiate as a result of the mobilization of soil tensile strength. However this mechanical approach disregards the cohesionless and effective stress-dependent behaviour of fine-grained soil. On the other hand recent findings in the literature suggest that effective stress-dependent shear failure criteria would be appropriate to explain the mechanisms of desiccation cracking for tensile total stress states. This work aims at assessing the validity of a shear failure criterion to predict the onset of cracking in clay forms exposed to air drying. Clay forms of various geometries were experimentally subjected to non-uniform hydraulic and mechanical boundary conditions. Time and location for crack initiation are monitored using a digital camera. Cracking experiments are then modelled in a hydro-mechanical framework using an effective-stress shear failure criterion. The comparison of simulations with experimental results for both the time and the location of cracking allows assuming that cracking occurs due to failure in shearing.

scholarly journals Interpretation of vane shear tests for geotechnical stability calculations

2017 ◽  
Vol 54 (12) ◽  
pp. 1775-1780 ◽  
Author(s):  
George Kouretzis ◽  
Jubert Pineda ◽  
Kristian Krabbenhøft ◽  
Lachlan Wilson
Keyword(s):  
Effective Stress ◽  
Slip Surface ◽  
Failure Criteria ◽  
Shear Tests ◽  
Vane Shear Test ◽  
Rate Effects ◽  
Undrained Strength ◽  
Geotechnical Stability ◽  
The Given ◽  
Theoretical Considerations

In this note we consider the problem of calibrating failure criteria for short-term stability calculations based on the results of vane shear tests. Numerical and theoretical considerations supported by experimental data provide evidence that we can use the vane shear test to obtain the undrained strength of a sample tested under simple shear conditions at a normal stress equal to the horizontal effective stress at the given depth. Consequently, it is argued that there is no need to correct the field vane undrained strength to obtain the mobilized strength for embankment stability calculations, provided that soil strength is normalized to the normal effective stress acting on the slip surface and rate effects are properly considered. We further show that the standard Tresca failure criterion, albeit simplistic, will provide reasonable estimates of the mobilized strength if properly calibrated against field vane tests.

Experts' opinion on 2nd-line treatments failure criteria for patients with multiple sclerosis

2018 ◽  
Author(s):  
JEROME DE SEZE ◽  
Françoise Durand-Dubief ◽  
Elisabeth Maillart ◽  
Elisabeth ['MEKIES'] ◽  
Elisabeth ['papeix'] ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Failure Criteria

A comparative study on methods for determining the hydraulic properties of a clay shale

2020 ◽  
Vol 224 (3) ◽  
pp. 1523-1539
Author(s):  
Lisa Winhausen ◽  
Alexandra Amann-Hildenbrand ◽  
Reinhard Fink ◽  
Mohammadreza Jalali ◽  
Kavan Khaledi ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Ion Beam ◽  
Applied Pressure ◽  
Pressure Oscillation ◽  
Stress Conditions ◽  
Data Set ◽  
Clay Shale ◽  
Permeability Coefficients ◽  
Effective Stresses

SUMMARY A comprehensive characterization of clay shale behavior requires quantifying both geomechanical and hydromechanical characteristics. This paper presents a comparative laboratory study of different methods to determine the water permeability of saturated Opalinus Clay: (i) pore pressure oscillation, (ii) pressure pulse decay and (iii) pore pressure equilibration. Based on a comprehensive data set obtained on one sample under well-defined temperature and isostatic effective stress conditions, we discuss the sensitivity of permeability and storativity on the experimental boundary conditions (oscillation frequency, pore pressure amplitudes and effective stress). The results show that permeability coefficients obtained by all three methods differ less than 15 per cent at a constant effective stress of 24 MPa (kmean = 6.6E-21 to 7.5E-21 m2). The pore pressure transmission technique tends towards lower permeability coefficients, whereas the pulse decay and pressure oscillation techniques result in slightly higher values. The discrepancies are considered minor and experimental times of the techniques are similar in the range of 1–2 d for this sample. We found that permeability coefficients determined by the pore pressure oscillation technique increase with higher frequencies, that is oscillation periods shorter than 2 hr. No dependence is found for the applied pressure amplitudes (5, 10 and 25 per cent of the mean pore pressure). By means of experimental handling and data density, the pore pressure oscillation technique appears to be the most efficient. Data can be recorded continuously over a user-defined period of time and yield information on both, permeability and storativity. Furthermore, effective stress conditions can be held constant during the test and pressure equilibration prior to testing is not necessary. Electron microscopic imaging of ion-beam polished surfaces before and after testing suggests that testing at effective stresses higher than in situ did not lead to pore significant collapse or other irreversible damage in the samples. The study also shows that unloading during the experiment did not result in a permeability increase, which is associated to the persistent closure of microcracks at effective stresses between 24 and 6 MPa.

scholarly journals Trial of aerosolised surfactant for preterm infants with respiratory distress syndrome

2021 ◽  
pp. fetalneonatal-2021-321645
Author(s):  
Luke Jardine ◽  
Kei Lui ◽  
Helen G Liley ◽  
Timothy Schindler ◽  
James Fink ◽  
...  
Keyword(s):  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Preterm Infants ◽  
Distress Syndrome ◽  
Failure Criteria ◽  
Open Label ◽  
Dose Escalation Study ◽  
Safety Issues ◽  
Label Dose ◽  
Historical Controls

ObjectiveTo evaluate the safety of an aerosolised surfactant, SF-RI 1, administered via nasal continuous positive airway pressure (nCPAP) and a prototype breath synchronisation device (AeroFact), to preterm infants with respiratory distress syndrome (RDS).DesignMulticentre, open-label, dose-escalation study with historical controls.SettingNewborn intensive care units at Mater Mothers’ Hospital, Brisbane, and Royal Hospital for Women, Sydney, Australia.PatientsInfants 26 weeks through 30 weeks gestation who required nCPAP 6–8 cmH2O and fraction of inspired oxygen (FiO2) <0.30 at <2 hours of age.InterventionsIn part 1, infants received a single dose of 216 mg/kg of aerosolised surfactant. In part 2, infants could receive up to four doses of aerosolised surfactant. Three historical control infants were matched for each enrolled infant.Main outcome measuresTreatment failure was defined as Respiratory Severity Score (FiO2×cmH2O nCPAP) >2.4, nCPAP >8 cmH2O, arterial carbon dioxide >65 mm Hg, pH <7.20 or three severe apnoeas within 6 hours during the first 72 hours of life. Other outcomes included tolerance of the AeroFact treatment and complications of prematurity.Results10 infants were enrolled in part 1 and 21 in part 2 and were compared with 93 historical controls. No safety issues were identified. In part 2, 6 of 21 (29%) AeroFact-treated infants compared with 30 of 63 (48%) control infants met failure criteria. Kaplan-Meier analysis of patients in part 2 showed a trend towards decreased rate of study failure in the AeroFact-treated infants compared with historical controls (p=0.10).ConclusionThe AeroFact system can safely deliver aerosolised surfactant to preterm infants with RDS who are on nCPAP.Trial registration numberACTRN12617001458325.

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