Progressive failure mechanism in granular materials subjected to an alternant active and passive trapdoor

Plate and screw anchors provide a significant uplift capacity and have multiple applications in both onshore and offshore geotechnical engineering. Uplift design methods are mostly based on semi-empirical approaches assuming a failure mechanism, a normal and a shear stress distribution at failure and empirical factors back-calculated against experimental data. However, these design methods are shown to under- or overpredict most of the existing larger scale experimental tests. Numerical FE simulations are undertaken to provide new insight into the failure mechanism and stress distribution which should be considered in anchor design in dense sand. Results show that a conical shallow wedge whose inclination to the vertical direction is equal to the dilation angle is a good approximation of the failure mechanism in sand. This shallow mechanism has been observed in each case for relative embedment ratios (depth/diameter) ranging from 1 to 9. However, the stress distribution varies non-linearly with depth, due to the soil deformability and progressive failure. A sharp peak of normal and shear stress can be identified close to the anchor edge, before a gradual decrease with increasing distance along the shear plane. The peak stress magnitude increases almost linearly with embedment depth at larger relative embedment ratios. Although further research is necessary, these results lay the basis for the development of a new generation of design criteria for determining anchor capacity at the ultimate limiting state.

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Study of the Failure Mechanism and Progressive Failure Process of Intact Rock Patches of Rock Slope with Weak Surfaces

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-016-1143-5 ◽

2016 ◽

Vol 50 (4) ◽

pp. 951-966 ◽

Cited By ~ 4

Author(s):

Xiao-Hua Pan ◽

Hong-Yue Sun ◽

Zhi-Jun Wu ◽

Qing Lü

Keyword(s):

Failure Mechanism ◽

Rock Slope ◽

Progressive Failure ◽

Failure Process ◽

Intact Rock

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Upper bound analysis of progressive failure mechanism of tunnel roofs in partly weathered stratified Hoek–Brown rock masses

International Journal of Rock Mechanics and Mining Sciences ◽

10.1016/j.ijrmms.2014.10.002 ◽

2015 ◽

Vol 74 ◽

pp. 157-162 ◽

Cited By ~ 19

Author(s):

C.B. Qin ◽

X.L. Yang ◽

Q.J. Pan ◽

Z.B. Sun ◽

L.L. Wang ◽

...

Keyword(s):

Failure Mechanism ◽

Upper Bound ◽

Progressive Failure ◽

Rock Masses ◽

Upper Bound Analysis ◽

Bound Analysis

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Progressive failures in eastern Canadian and Scandinavian sensitive clays

Canadian Geotechnical Journal ◽

10.1139/t11-059 ◽

2011 ◽

Vol 48 (11) ◽

pp. 1696-1712 ◽

Cited By ~ 73

Author(s):

Ariane Locat ◽

Serge Leroueil ◽

Stig Bernander ◽

Denis Demers ◽

Hans Petter Jostad ◽

...

Keyword(s):

Failure Mechanism ◽

Strain Softening ◽

Progressive Failure ◽

Earth Pressure ◽

Failure Surface ◽

Eastern Canada ◽

Stress Strain ◽

Softening Behaviour ◽

Strain Behaviour

Observations from past events are used to show that the concept of progressive failure may explain translational progressive landslides and spreads — large landslides occurring in sensitive clays. During progressive failure, the strain-softening behaviour of the soil causes unstable forces to propagate a failure surface further in the slope. Translational progressive landslides generally take place in long, gently inclined slopes. Instability in a steeper upslope area is followed by redistribution of stress, which increases earth pressure further downslope. Passive failure may therefore occur in less-inclined ground, heaving the soil. Spreads are usually trigged by erosion of a deposit having a higher angle near the toe. Instability starts near the toe of the slope and propagates into the deposit, reducing earth pressure. This may lead to the formation of an active failure with dislocation of the deposit into horsts and grabens. The failure mechanism of both types of landslides is controlled by the stresses in the slope and the stress–strain behaviour of the soil. The mechanism presented explains the sensitivity of a slope to minor disturbances and the resulting high retrogressions observed for such landslides in Scandinavia and eastern Canada.

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Investigation of Failure Mechanism of Lungchok Landslide, Sikkim (India)

10.20944/preprints201908.0230.v1 ◽

2019 ◽

Author(s):

Neharika Rao Ganta ◽

Neelima Satyam

Keyword(s):

Failure Mechanism ◽

Progressive Failure ◽

Deformation Characteristic ◽

Fem Analysis ◽

Infrastructure Development ◽

Element Analysis ◽

Linear Elastic ◽

Construction Activity ◽

Vehicle Loads ◽

Earthquake Event

Globally 30% of landslides occur in the northeastern part of India [1]. One of the major earthquake events in Sikkim, India occurred on 18th September 2011 (Mw 6.9) led to over 300 landslides and 122 human deaths [2]. These landslides not only controlled by natural disasters but initiated due to human activities. The present study considered Lungchok landslide occurred in south district of Sikkim due to 2011 seismic event. The study focused on the failure mechanism of the landslide based on finite element analysis by adopting eight different cases. The deformation characteristic was investigated for dry and saturated slope conditions under static and dynamic behavior considering vehicle loads using GeoStudio software. The FEM analysis has been carried out using load deformation and linear elastic. The analysis shows that the failure of the slope was not sudden due to the 2011 earthquake event, but progressive failure was observed with time and construction activity. The paper demonstrates that, an increase in infrastructure development including construction by hill cutting increased the initiation of landslide with soil erosion. The cracks developed after 2011 earthquake event led to further deformations during future disasters required effective stabilization measures.

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Prediction of Shear Localisation in Granular Materials based on a Critical State Non-coaxial Model

E3S Web of Conferences ◽

10.1051/e3sconf/20199216006 ◽

2019 ◽

Vol 92 ◽

pp. 16006 ◽

Cited By ~ 1

Author(s):

Hansini Mallikarachchi ◽

Kenichi Soga

Keyword(s):

Granular Materials ◽

Plane Strain ◽

Critical State ◽

Progressive Failure ◽

Shear Bands ◽

State Parameter ◽

Biaxial Compression ◽

Compression Tests ◽

Principal Axes ◽

Shear Localisation

Experimental evidence indicates that the shear localisation acts as a precursor to the failure in biaxial compression tests of granular materials. Once formed they are persistent and lead to progressive failure of most geotechnical structures. It is generally accepted that the primary mode of deformation within these shear bands is simple shear which is accompanied by rotation of principal axes. Hence, the conventional plasticity theories based on the assumption of coaxility is not sufficient to describe the behaviour within those shear bands. This paper highlights the influence of the non-coaxility on the initiation and orientation of shear bands in both drained and undrained sand. The con-coaxial plasticity theory is integrated into a critical state constitutive model enriched with the state parameter concept. The model is capable of taking account of the variation of lode angle under plane strain condition. Numerical plane strain biaxial compression tests are conducted to observe the effect of non-coaxility on shear localisation. Bifurcation criteria based on the acoustic tensor are checked to predict the onset and inclination of the shear band. Predictions from the non-coaxial model are compared with those of coaxial model. The influence of the initial void ratio for the formation of shear bands is explored. Results are compared qualitatively with experimental observations.

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Spectral Analysis of Deteriorated Offshore Structures

Volume 14: Safety Engineering, Risk Analysis and Reliability Methods ◽

10.1115/imece2007-43889 ◽

2007 ◽

Author(s):

H. Karadeniz

Keyword(s):

Failure Mechanism ◽

Stiffness Matrix ◽

Progressive Failure ◽

Offshore Structures ◽

Mode Shapes ◽

Solution Technique ◽

Random Load ◽

Practical Applications ◽

Mass Matrices ◽

Load Vector

In order to present an efficient, practical technique to determine progressive failure mechanism of structures, modelling of member deterioration by using a spring system is outlined. The procedure uses updates of member stiffness and mass matrices as well as the random load vector in incremental forms. In this procedure, the assembly process produces redistributions of the system stiffness and mass matrices, and the load vector. In the calculation of response spectral values, the original forms remain unchanged. Inversion of the stiffness matrix is calculated by using the Neumann expansion solution in which the original stiffness matrix is inverted only once so that a considerable computation time is saved in the whole calculation process. An incremental solution technique is presented for spectral analyses of both static and dynamic sensitive structures. In the case of dynamic analysis, special attention is paid to estimations of modified natural frequencies and mode shapes of deteriorated structures, which may affect response spectral values considerably. The technique, which is presented in the paper, is attractive in practical applications and can be efficiently used in the reliability calculation as well, and also it can be successfully used to determine a progressive failure mechanism of the structure.

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