The Analysis of Two Slope Failures in Cemented Champlain Clays

1974 ◽  
Vol 11 (1) ◽  
pp. 89-108 ◽  
Author(s):  
G. Lefebvre ◽  
P. La Rochelle
Keyword(s):  
Strain Softening ◽  
Progressive Failure ◽  
Residual Value ◽  
Strength Parameters ◽  
Brittle Behavior ◽  
Clay Deposits ◽  
Softening Material ◽  
The Stability ◽  
Peak Value ◽  
Natural Slopes

Detailed investigations have been made on the sites of two landslides which occurred in the sensitive Champlain clay deposits of the Saint-Laurent Lowlands. Laboratory tests made on specimens cut from block samples have led to a better understanding and evaluation of the brittle behavior of these cemented clays. The results have shown that very little strain is required for the strength to decrease from a well defined peak value to a residual value; this brittle behavior is evident only when tests are made at sufficiently low stress level such that the cementation bonds are preserved during consolidation.The analyses of the slides have shown that the use of the peak strength parameters led to a gross overestimate of the factors of safety; the residual strength parameters, however, give a fairly accurate assessment of the stability, the calculated factors of safety being close to unity. That behavior may be explained by the fact that the cemented clay is extremely brittle and, like any other strain softening material, is subjected to the mechanism of progressive failure. This study leads to a very efficient practical approach to the analysis of the stability of natural slopes.

scholarly journals Factor of Safety Reduction Factors for Accounting for Progressive Failure for Earthen Levees with Underlying Thin Layers of Sensitive Soils

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Adam J. Lobbestael ◽  
Adda Athanasopoulos-Zekkos ◽  
Josh Colley
Keyword(s):  
Finite Element ◽  
Strain Softening ◽  
Progressive Failure ◽  
Limit Equilibrium ◽  
Thin Layers ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Limit Equilibrium Methods ◽  
The Stability ◽  
Reduction Factors

The effects of progressive failure on flood embankments with underlying thin layers of soft, sensitive soils are investigated. Finite element analysis allows for investigation of strain-softening effects and progressive failure in soft and sensitive soils. However, limit equilibrium methods for slope stability analysis, widely used in industry, cannot capture these effects and may result in unconservative factors of safety. A parametric analysis was conducted to investigate the effect of thin layers of soft sensitive soils on the stability of flood embankments. A flood embankment was modeled using both the limit equilibrium method and the finite element method. The foundation profile was altered to determine the extent to which varying soft and sensitive soils affected the stability of the embankment, with respect to progressive failure. The results from the two methods were compared to determine reduction factors that can be applied towards factors of safety computed using limit equilibrium methods, in order to capture progressive failure.

Analysis of progressive deformation of the Edmonton Convention Centre excavation

1987 ◽  
Vol 24 (3) ◽  
pp. 430-440 ◽  
Author(s):  
D. H. Chan ◽  
N. R. Morgenstern
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Strain Softening ◽  
Progressive Failure ◽  
Field Measurements ◽  
Shear Zones ◽  
Element Model ◽  
Progressive Deformation ◽  
Element Analysis ◽  
The Stability

A finite element analysis was performed of the deformations observed during the excavation of the Edmonton Convention Centre. Local geology in the Edmonton area consists of layers of shale with weak bentonite seams overlain by glacial deposits. The presence of the bentonite seams, which possess strain-softening characteristics, controls the stability of the excavation, which is located in a valley wall. To simulate the influence of the bentonite seams a strain-softening finite element model is used to estimate the amount of deformation in the foundation of the excavation. Field measurements indicated that localized progressive straining had occurred during the excavation process, and substantial heave of the foundation floor was observed. The finite element results show progressive deformation of the excavation and propagation of shear zones. Good agreement between the finite element results and the field observations is obtained. Key words: progressive failure, strain softening, finite element analysis, shear band, excavation stability.

Study on Post-Failure Deformation and Residual Strength of Rock Mass Based on Hoek-Brown Criterion

2012 ◽  
Vol 170-173 ◽  
pp. 121-124
Author(s):  
Jian Xin Han ◽  
Xing Hua Tong ◽  
Lei Wang ◽  
Guo Fu Sun
Keyword(s):  
Rock Mass ◽  
Residual Strength ◽  
Strain Softening ◽  
Strain Curve ◽  
Strength Criterion ◽  
Stress Strain Curve ◽  
Strength Parameters ◽  
Softening Parameter ◽  
Residual Values ◽  
The Stability

In order to predict the stability of surrounding rock mass in geotechnical engineering, it is important to study the post-failure deformation property and residual strength of rock mass. Based on evolutional behavior of strength parameters, aiming at generalized Hoek-Brown strength criterion, selecting major principal strain as strain softening parameter, this paper presents the method of solving post-failure stress-strain curve . In numerical case, the effect of evolutional law of strength parameters ， and to deformation and residual strength is discussed and we can draw the following conclusions: the greater the residual values of ， are and the smaller the residual value of is, the post-failure strain softening curve falls more gently and the greater the residual strength is.

scholarly journals Fracture Mechanical Models of Dry Slab Avalanche Release

1980 ◽  
Vol 26 (94) ◽  
pp. 517
Author(s):  
David M. McClung
Keyword(s):  
Strain Softening ◽  
Slip Surface ◽  
Shear Crack ◽  
Progressive Failure ◽  
Shear Instability ◽  
Fracture Geometry ◽  
Weak Layer ◽  
Mechanical Models ◽  
Softening Material ◽  
Propagating Shear

Abstract Experimental evidence shows that snow is a pressure-sensitive, dilatant, strain-softening material in slow, constant-rate shear deformation. When strain-softening initiates in a weak layer underneath a snow slab, avalanche release is hypothesized to be possible with or without loading. Specifically, two cases are discussed : (i) a shear-crack-like disturbance can initiate by formation of a slip surface in the weak layer and traverse the layer by a self-propagating progressive failure with or perhaps without loading; (ii) a self- propagating shear instability can develop when a region of the weak layer is driven past peak shear strength by loading. These cases represent the extremes in weak-layer deformations under which strain-softening failures might precipitate avalanche release. For these cases the associated fracture sequences, fracture geometry, time scale of release, and temperature- related effects are consistent with the known facts of dry-slab avalanche release.

scholarly journals Numerical Simulation of Bedrock Sagging Sinkholes in Strain-Softening Rock Induced by Embankment Construction

2019 ◽  
Vol 2019 ◽  
pp. 1-19
Author(s):  
Zhen Zhang ◽  
Zhongda Chen
Keyword(s):  
Failure Mode ◽  
Strain Softening ◽  
Bending Moment ◽  
In Situ Stress ◽  
Jiangxi Province ◽  
Strength Parameters ◽  
Softening Behaviour ◽  
Karst Caves ◽  
The Stability

A bedrock sagging sinkhole occurred in Jiangxi Province of China when constructing the Changli freeway above shallow karst caves. It was chosen as a case to investigate the failure mechanism and potential evolution. The in situ stress of the study area was measured and numerically reproduced. The Hoek–Brown strength parameters were obtained by laboratory tests. A strain-softening constitutive model was established according to the strain-softening behaviour exhibited by the specimens in the triaxial test. The stress-strain curves of the specimens were reproduced by numerical methods. Then, bedrock sagging sinkholes in strain-softening rock induced by embankment construction were simulated. The occurrence of the strain-softening zone and its transition to the residual zone were observed and classified into four stages. The stress paths of the four stages were analysed. Interestingly, in this case, the supports at both ends of the bedrock began to yield from the top and extended downward, while the midspan position began to yield from the bottom and extended upward, and the reasons for yielding were related to tension. Further analysis found that the failure mode was basically consistent with the size and direction of the bending moment. In fact, this failure mode was quite similar to a fixed supported beam. Then, the feasibility of calculating the stability of karst caves based on beam assumptions was discussed. Finally, potential evolution of the bedrock sagging sinkhole was discussed.

scholarly journals Fracture Mechanical Models of Dry Slab Avalanche Release

1980 ◽  
Vol 26 (94) ◽  
pp. 517-517
Author(s):  
David M. McClung
Keyword(s):  
Strain Softening ◽  
Slip Surface ◽  
Shear Crack ◽  
Progressive Failure ◽  
Shear Instability ◽  
Fracture Geometry ◽  
Weak Layer ◽  
Mechanical Models ◽  
Softening Material ◽  
Propagating Shear

AbstractExperimental evidence shows that snow is a pressure-sensitive, dilatant, strain-softening material in slow, constant-rate shear deformation. When strain-softening initiates in a weak layer underneath a snow slab, avalanche release is hypothesized to be possible with or without loading. Specifically, two cases are discussed : (i) a shear-crack-like disturbance can initiate by formation of a slip surface in the weak layer and traverse the layer by a self-propagating progressive failure with or perhaps without loading; (ii) a self- propagating shear instability can develop when a region of the weak layer is driven past peak shear strength by loading. These cases represent the extremes in weak-layer deformations under which strain-softening failures might precipitate avalanche release. For these cases the associated fracture sequences, fracture geometry, time scale of release, and temperature- related effects are consistent with the known facts of dry-slab avalanche release.

scholarly journals Stability of non-localized responses for damaging materials

2008 ◽  
Vol 30 (4) ◽  
Author(s):  
K. Pham ◽  
J. J. Marigo
Keyword(s):  
Strain Softening ◽  
Damage Model ◽  
Damage Threshold ◽  
Tensile Loading ◽  
Local Model ◽  
Local Damage ◽  
Damage Models ◽  
Damage States ◽  
Softening Material ◽  
The Stability

This work is devoted to the analysis of the stability of the homogeneous states of a bar made of a brittle strain softening material submitted to a tensile loading. We distinguish two types of damage models: local damage models and gradient damage models. We show that a local damage model necessarily leads to the unstability of the homogeneous response once the first damage threshold is reached. On the contrary, in the case of a gradient damage model, viewed as a regularization of the underlying local model, the homogeneous damage states of “sufficiently small" bars are stable.

scholarly journals Effect of Strength Anisotropy on the Stability of Natural Slopes

2021 ◽  
Vol 710 (1) ◽  
pp. 012025
Author(s):  
Magnus T Aamodt ◽  
Gustav Grimstad ◽  
Steinar Nordal
Keyword(s):  
Strength Anisotropy ◽  
The Stability ◽  
Natural Slopes

The Experimental Analysis on the Regularity of Heating Load in Buildings Using Heat Meters with On-Off Time and Area Method in Shijiazhuang Area

2014 ◽  
Vol 694 ◽  
pp. 272-275
Author(s):  
Chao Wang ◽  
Chun Hua Sun ◽  
Cheng Ying Qi ◽  
Feng Yun Jin ◽  
Bo Shao
Keyword(s):  
Load Distribution ◽  
Distribution Curve ◽  
Heating System ◽  
Measuring Method ◽  
Heating Period ◽  
Heating Load ◽  
The Stability ◽  
Heating Loads ◽  
Off Time ◽  
Peak Value

Based on the heating load experiment adopting on-off time and area measuring method of typical heat users located in different places of different buildings in Shijiazhuang, the heating loads of the heat users which are summarized as two typical heat using modes are studied in this paper and the heating loads in the whole winter heating season of the building is estimated. The results shows that with the user’s heat adopting ratio in these two modes increases, the corresponding heating load is lower, the heating load distribution curve gets smoothly in the whole heating period and the peak value of the system heating loads reduces. This regularity of heating load distribution is beneficial for enhancing the stability of heating system and the thermal efficiency of the heat source.

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