Slip surfaces in soil mechanics

2005 ◽  
pp. 93-116
Author(s):  
P. Habib
Keyword(s):  
Soil Mechanics ◽  
Slip Surfaces

A Discussion on valley slopes and cliffs in southern England: morphology, mechanics and Quaternary history - The Quaternary history of the Lower Greensand escarpment and Weald Clay vale near Sevenoaks, Kent

1976 ◽  
Vol 283 (1315) ◽  
pp. 493-526 ◽  
Keyword(s):  
Large Scale ◽  
Soil Mechanics ◽  
River Terraces ◽  
Slip Surfaces ◽  
Standing Up ◽  
Clay Matrix ◽  
History Of ◽  
Quaternary History ◽  
Longitudinal Profiles ◽  
Small Channels

In the neighbourhood, of Sevenoaks Weald many of the small hills and ridges standing up to 20 or 30 m above the streams in the clay vale south of the Lower Greensand escarpment are capped by Head deposits consisting of angular chert fragments, and other stones derived from the Greensand, set in a clay matrix. These deposits extend for a distance of at least 2 km from the escarpment, forming dissected remnants of what were originally extensive sheets, inclined at gradients of about 1.5°. The available evidence suggests they are periglacial solifluction deposits of Wol- stonian age. Probably at about the same period large-scale structural disturbances occurred in what are now spurs of the escarpment; massive blocks of the Hythe Beds subsided into the underlying Atherfield and Weald Clays, and the clays were forced up at the foot of the scarp in the form of bulges. Following this stage considerable erosion took place in the vale, accompanied by re­ treat of the escarpment within embayments between the spurs. On the eroded land­ scape solifluction debris moved up to 1 km from the scarp face during the Devensian period. This deposit again consists predominantly of clay with embedded angular chert fragments. It is about 2 m thick, with a minimum gradient of a little more than 2°, and overlies brecciated Weald Clay which typically contains several slip surfaces in its uppermost layers. Landslips in the escarpment within the embay­ ments probably occurred at about the same time. Not long afterwards, in the Late-Devensian Interstadial, around 12000 radiocarbon years b.p., a soil formed of which traces can be found buried beneath a lobate soli­ fluction sheet. The lobes extend over the lower sheet for distances of 300 m from the scarp foot at an average slope of about 7°. In the subsequent Postglacial period only minor changes have taken place; some escarpment landslips have been reactivated and the streams in the vale have eroded small channels or valleys not more than 4 m deep. Based on thaw-consolidation theory, and by using measured properties of the clays, calculations are presented which provide a reasonable explanation, in terms of soil mechanics principles, for solifluction movements of the active layer above perma­ frost on slopes inclined at angles as low as 1.5 or 2°. Under temperate conditions, mass movements are possible only on slopes steeper than about 8°. The paper includes an account of the longitudinal profiles and stratigraphy of the Eden and Medway river terraces.

The growth of slip surfaces in the progressive failure of over-consolidated clay

1973 ◽  
Vol 332 (1591) ◽  
pp. 527-548 ◽  
Keyword(s):  
Shear Stress ◽  
Shear Band ◽  
Slip Surface ◽  
Progressive Failure ◽  
Soil Mechanics ◽  
Propagation Speed ◽  
Viscoelastic Deformation ◽  
Slip Surfaces ◽  
Local Strength ◽  
The Mean

In heavily over-consolidated clays there is a marked peak in the observed relation between shear stress and shear strain. As the strain increases, the stress falls from a peak to a much smaller residual stress. Slopes made from such a clay often fail progressively many years after construction. Sliding occurs on a concentrated slip surface, and it is found that the mean resolved shear stress on that surface is markedly less than the peak shear strength. Concepts from fracture mechanics, and in particular the J -integral, are used to derive conditions for the propagation of a concentrated shear band of this kind. The results indicate the presence of a strong size effect, which has important implications for the use of models in soil mechanics. An elastic analysis makes it possible to determine the size of the end zone in which the shear stress on the shear band falls to its residual value. An attempt is made to assess the possible sources of the time-dependence governing propagation speed of the shear band. They include pore-water diffusion to the dilating tip of the band (which governs the rate at which local strength reductions can occur), viscoelastic deformation of the clay (which allows a gradual build-up of strain concentration at the tip of the band), and the weathering break-down of diagenetic bonds.

Basic set of experiments for determination of mechanical properties of sand

2014 ◽  
Vol 62 (1) ◽  
pp. 129-137
Author(s):  
A. Sawicki ◽  
J. Mierczyński
Keyword(s):  
Mechanical Properties ◽  
Soil Mechanics ◽  
Physical And Mechanical Properties ◽  
Local Strain ◽  
Initial State ◽  
Laboratory Equipment ◽  
Additional Information ◽  
Basic Set ◽  
Initial Anisotropy

Abstract A basic set of experiments for the determination of mechanical properties of sands is described. This includes the determination of basic physical and mechanical properties, as conventionally applied in soil mechanics, as well as some additional experiments, which provide further information on mechanical properties of granular soils. These additional experiments allow for determination of steady state and instability lines, stress-strain relations for isotropic loading and pure shearing, and simple cyclic shearing tests. Unconventional oedometric experiments are also presented. Necessary laboratory equipment is described, which includes a triaxial apparatus equipped with local strain gauges, an oedometer capable of measuring lateral stresses and a simple cyclic shearing apparatus. The above experiments provide additional information on soil’s properties, which is useful in studying the following phenomena: pre-failure deformations of sand including cyclic loading compaction, pore-pressure generation and liquefaction, both static and caused by cyclic loadings, the effect of sand initial anisotropy and various instabilities. An important feature of the experiments described is that they make it possible to determine the initial state of sand, defined as either contractive or dilative. Experimental results for the “Gdynia” model sand are shown.

scholarly journals A process-based method for predicting lateral erosion rates

2021 ◽  
Author(s):  
Myron van Damme
Keyword(s):  
Soil Mechanics ◽  
High Surface ◽  
Shear Stresses ◽  
Empirical Equations ◽  
Predictive Capability ◽  
Surface Shear ◽  
Erosion Rates ◽  
Material Texture ◽  
Empirical Coefficients ◽  
The Impact

AbstractAn accurate means of predicting erosion rates is essential to improve the predictive capability of breach models. During breach growth, erosion rates are often determined with empirical equations. The predictive capability of empirical equations is governed by the range for which they have been validated and the accuracy with which empirical coefficients can be established. Most empirical equations thereby do not account for the impact of material texture, moisture content, and compaction energy on the erosion rates. The method presented in this paper acknowledges the impact of these parameters by accounting for the process of dilation during erosion. The paper shows how, given high surface shear stresses, the erosion rate can be quantified by applying the principles of soil mechanics. Key is thereby to identify that stress balance situation for which the dilatency induced inflow gives a maximum averaged shear resistance. The effectiveness of the model in predicting erosion rates is indicated by means of three validation test cases. A sensitivity analysis of the method is also provided to show that the predictions lie within the range of inaccuracy of the input parameters.

A generalized seismic sliding model of slopes with multiple slip surfaces

2021 ◽  
Author(s):  
Jian Song ◽  
Adrian Rodriguez‐Marek ◽  
Tugen Feng ◽  
Jian Ji
Keyword(s):  
Multiple Slip ◽  
Slip Surfaces
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