scholarly journals Constitutive modelling approach for evaluating the triggering of flow slides

2012 ◽  
Vol 49 (5) ◽  
pp. 499-511 ◽  
Author(s):  
Giuseppe Buscarnera ◽  
Andrew J. Whittle
Keyword(s):  
Stress State ◽  
Slope Angle ◽  
Constitutive Modelling ◽  
Published Data ◽  
Shear Stresses ◽  
Initial Stress State ◽  
Hydraulic Fill ◽  
Static Liquefaction ◽  
Flow Slides

The paper presents a methodology to evaluate flow slide susceptibility in potentially liquefiable sandy slopes. The proposed approach accounts for both contractive and dilative volumetric behaviour during shearing using the MIT-S1 constitutive model. As a result, it is possible to distinguish among different types of undrained response induced by a rapid shear perturbation. The first part of the paper describes the general methodology for infinite slopes, providing an index of stability for incipient static liquefaction in shallow deposits. The methodology accounts for the anisotropy due to the initial stress state and uses simple shear simulations to assess instability conditions as a function of slope angle, stress state, and density of the soil. The resulting stability charts define the margin of safety against static liquefaction and the depths likely to be affected by the propagation of an instability. The second part of the paper applies the methodology to the well-known series of flow failures in a berm at the Nerlerk site. The MIT-S1 model is calibrated using published data on Nerlerk sands and in situ cone penetration test (CPT) data. The analyses show that in situ slope angles α = 10°–13° are less than the critical slope angle needed for incipient instability. Liquefaction and flow failures were therefore promoted by small perturbations in shear stresses that could be generated by rapid deposition of hydraulic fill.

EFFECT OF MANUFACTURING ON THE TRANSVERSE RESPONSE OF THERMOSET COMPOSITES

2021 ◽  
Author(s):  
SAGAR P. SHAH ◽  
MARIANNA MAIARU
Keyword(s):  
Stress State ◽  
Initial Stress ◽  
Process Modeling ◽  
Computational Models ◽  
Test Procedure ◽  
Initial Stress State ◽  
Virtual Test ◽  
Matrix Properties ◽  
Composite Response

This study presents a finite element (FE) based virtual test procedure to investigate the effect of the manufacturing process on the transverse composite response. Computational models of the composite microstructures are generated and analyzed in commercial FE solver Abaqus supplemented by user-written subroutines. Several realizations of the composite microstructure with random fiber arrangement are analyzed assuming appropriate initial stress state and material definitions. The virtual test procedure is established to define the evolution of process-induced in-situ matrix properties through direct and inverse process modeling approaches. Subsequently, the composite microstructures are virtually tested in transverse tension to predict the transverse composite properties by implementing progressive damage models. In order to quantify the effect of manufacturing on the transverse composite response, predictions from the two approaches are compared to a third case which assumes an initial stress-free state and neglects the effect of processing conditions on the in-situ matrix properties. Variations of ±5% in average strength and 18% in standard deviations are observed with respect to ideally cured RVEs. It is established that process modeling in necessary to optimize the residual stress state and improve composite performance.

Collapse of dry sand

1994 ◽  
Vol 31 (6) ◽  
pp. 1008-1014 ◽  
Author(s):  
Peter Skopek ◽  
N.R. Morgenstern ◽  
P.K. Robertson ◽  
D.C. Sego
Keyword(s):  
Stress Path ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
Pore Pressures ◽  
Static Liquefaction ◽  
Triaxial Cell ◽  
Flow Slides ◽  
Dry Sand ◽  
Stress States ◽  
Undrained Loading

Loose cohesionless saturated materials have proved responsible for a number of serious or catastrophic flow slides. Liquefaction failures with no obvious triggering mechanism have also been recorded. This phenomenon of sudden liquefaction without a presence of cyclic shear stresses is often referred to as spontaneous or static liquefaction. Results from previously published studies suggest that liquefaction is triggered not by the undrained loading and generation of pore pressures but by the collapse of the metastàble sand structure, which in turn generates the driving pore pressures in a saturated material. Hence, the collapse is a characteristic response of a material to certain stress states rather than a result of some enforced undrained loading. This theory is evaluated on very loose dry Ottawa sand. It is shown that the very loose dry sand when subjected to a constant deviatoric stress path significantly changes its behavior at a certain discreet stress state, increases compressibility, and becomes increasingly unstable. This results in collapse – vigorous contraction of the specimen. This structural collapse appears to be equivalent to the pore-pressure generation in collapsing, very loose saturated sand. Key words : dry sand, collapse, liquefaction, stress path, triaxial cell.

Influence of soil nail orientations on stabilizing mechanisms of loose fill slopes

2013 ◽  
Vol 50 (12) ◽  
pp. 1236-1249 ◽  
Author(s):  
C.Y. Cheuk ◽  
K.K.S. Ho ◽  
A.Y.T. Lam
Keyword(s):  
Earth Pressure ◽  
Slope Movement ◽  
Numerical Analyses ◽  
Soil Nails ◽  
Soil Nail ◽  
Static Liquefaction ◽  
Liquefaction Failure ◽  
Loose Fill ◽  
Typical Design

Soil nailing has been used to upgrade substandard loose fill slopes in Hong Kong. Due to the possibility of static liquefaction failure, a typical design arrangement comprises a structural slope facing anchored by a grid of soil nails bonded into the in situ ground. Numerical analyses have been conducted to examine the influence of soil nail orientations on the behaviour of the ground nail–facing system. The results suggest that the use of steeply inclined nails throughout the entire slope could avoid global instability, but could lead to significant slope movement especially when sliding failure prevails, for instance, due to interface liquefaction. The numerical analyses also demonstrate that if only subhorizontal nails are used, the earth pressure exerted on the slope facing may cause uplift failure of the slope cover. To overcome the shortcomings of using soil nails at a single orientation, a hybrid nail arrangement comprising nails at two different orientations is proposed. The numerical analyses illustrate that the hybrid nail arrangement would limit slope movement and enhance the robustness of the system.

scholarly journals In situ stress state from walkaround VSP anisotropy in the Kumano basin southeast of the Kii Peninsula, Japan

2011 ◽  
Vol 12 (9) ◽  
pp. n/a-n/a ◽  
Author(s):  
Takeshi Tsuji ◽  
Ryota Hino ◽  
Yoshinori Sanada ◽  
Kiyohiko Yamamoto ◽  
Jin-Oh Park ◽  
...  
Keyword(s):  
Stress State ◽  
In Situ Stress ◽  
Kii Peninsula ◽  
Kumano Basin

Back Analysis Methods in Geotechnical Engineering

2014 ◽  
Vol 1020 ◽  
pp. 423-428 ◽  
Author(s):  
Eva Hrubesova ◽  
Marek Mohyla
Keyword(s):  
Rock Mass ◽  
Geotechnical Engineering ◽  
Back Analysis ◽  
Rheological Parameters ◽  
Analysis Method ◽  
Direct Optimization ◽  
Initial Stress State ◽  
Analytical Functions ◽  
Is Evaluation

The paper deals with the back analysis method in geotechnical engineering, that goal is evaluation the more objective and reliable parameters of the rock mass on the basis of in-situ measurements. Stress, deformational, strength and rheological parameters of the rock mass are usually determined by some inaccuracies and errors arising from the complexity and variability of the rock mass. This higher or lower degree of imprecision is reflected in the reliability of the mathematical modelling results. The paper presents the utilization of direct optimization back analysis method, based on the theory of analytical functions of complex variable and Kolosov-Muschelischvili relations, to the evaluation of initial stress state inside the rock massif.

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