Earthquake-induced flow liquefaction in fines-containing sands under initial shear stress by lab tests and its implication in case histories

2020 ◽  
Vol 130 ◽  
pp. 105984
Author(s):  
Takaji Kokusho
2020 ◽  
Vol 598 (24) ◽  
pp. 5609-5610
Author(s):  
Andrew Oneglia ◽  
Sauyeh Zamani ◽  
Miles F. Bartlett

2013 ◽  
Vol 14 (1-2) ◽  
pp. 109-115
Author(s):  
Michael Stiehm ◽  
Martin Brede ◽  
Daniel Quosdorf ◽  
Alfred Leder

AbstractThe post-operative situation in a stented vessel is characterised by struts which extend into the vessel lumen. These barriers on the surface provoke a topological change of the blood flow inducing flow deceleration and stagnation zones. Low values of wall shear stress (WSS) especially up- and downstream of the struts are found accordingly. Clinical studies correlate the occurrence of complications like restenosis and thrombosis with the alteration of the spatial WSS distribution. In this study 3D computational models were used to characterise the flow topology of three different stent types. For this purpose steady state simulations of the flow field within a simplified stented coronary artery were performed. The stent types differ in their strut patterns so that the variation of the induced flow structures can be observed. The aim of these investigations is to evaluate the effect of a purposeful flow control by altering the design of the struts. An improved alignment of the struts will be able to guide the flow to benefit the spatial WSS distribution. To compare the performance of the different stent types the size of the area charged with a WSS value below 0.5 Pa is used as a criterion. We will demonstrate that those strut pattern which generate helical flow structures significantly reduce the critical region of low WSS values.


Author(s):  
Peter Robertson

Robertson (2010a) outlined a method to evaluate the susceptibility of soils to undrained strength loss that could result in flow liquefaction as well as a method to estimate the resulting liquefied undrained shear strength of predominately sand-like soils using the CPT. Based on published data and recent case histories this technical note describes a recommended update to the Robertson (2010a) method to estimate the large strain liquefied or remolded undrained shear strength for both sand-like and clay-like soils as well as soils and that transition from sand-like to clay-like. The proposed update acknowledges that soil behavior can vary from sand-like to clay-like and that CPT interpretation to estimate large strain undrained shear strength changes due to the changing drainage conditions during the CPT. The updated method builds upon previously published data combined with recent experience and case histories.


Author(s):  
Jeong-Min Lee ◽  
Yi-Seul Jo ◽  
Sung-Min Kim ◽  
Youn-Jea Kim

In this study, the flow characteristics of the Coandă nozzle were studied with various values of the aspect ratio of induced flow inlet to outlet. Furthermore, four different applied pressure conditions of compressed air were also considered. Numerical analysis was performed using the commercial CFD code, ANSYS CFX with a shear stress transport (SST) turbulent model. The results of total pressure and velocity distributions were graphically depicted with various geometrical configurations and operating conditions.


1967 ◽  
Vol 20 (1) ◽  
pp. 1
Author(s):  
CHJ Johnson

The mean velocity and shear-stress profiles for a wind-induced flow in a closed channel with constant surface slope are first derived using a turbulent viscosity constructed by dimensional arguments. Using a perturbation analysis based on the fact that the surface slope is small, these results are extended to the case where the surface slope, and hence flow conditions generally, are allowed to vary in a downwind direction. Explicit results are obtained for the velocity and shear-stress profiles and also for the surface slope as a function of distance downwind. The results agree quite well with experiment, although better agreement would probably be obtained by using a more elaborate turbulent iscosity_


2020 ◽  
Vol 134 (17) ◽  
pp. 2399-2418
Author(s):  
Yoshito Yamashiro ◽  
Hiromi Yanagisawa

Abstract Blood vessels are constantly exposed to mechanical stimuli such as shear stress due to flow and pulsatile stretch. The extracellular matrix maintains the structural integrity of the vessel wall and coordinates with a dynamic mechanical environment to provide cues to initiate intracellular signaling pathway(s), thereby changing cellular behaviors and functions. However, the precise role of matrix–cell interactions involved in mechanotransduction during vascular homeostasis and disease development remains to be fully determined. In this review, we introduce hemodynamics forces in blood vessels and the initial sensors of mechanical stimuli, including cell–cell junctional molecules, G-protein-coupled receptors (GPCRs), multiple ion channels, and a variety of small GTPases. We then highlight the molecular mechanotransduction events in the vessel wall triggered by laminar shear stress (LSS) and disturbed shear stress (DSS) on vascular endothelial cells (ECs), and cyclic stretch in ECs and vascular smooth muscle cells (SMCs)—both of which activate several key transcription factors. Finally, we provide a recent overview of matrix–cell interactions and mechanotransduction centered on fibronectin in ECs and thrombospondin-1 in SMCs. The results of this review suggest that abnormal mechanical cues or altered responses to mechanical stimuli in EC and SMCs serve as the molecular basis of vascular diseases such as atherosclerosis, hypertension and aortic aneurysms. Collecting evidence and advancing knowledge on the mechanotransduction in the vessel wall can lead to a new direction of therapeutic interventions for vascular diseases.


1958 ◽  
Vol 3 (10) ◽  
pp. 318-319
Author(s):  
ALBERT ELLIS
Keyword(s):  

Sign in / Sign up

Export Citation Format

Share Document