Discussion of “
            Undrained Shear Strength of Liquefied Sands for Stability Analysis
            ” by Timothy D. Stark and Gholamreza Mesri (November, 1992, Vol. 118, No. 11)

With the increase in offshore wind farms, the demands for umbilicals and power cables have increased. The on-bottom stability of umbilicals and power cables under the combined wave and current loading is the most challenging design issue, due to their light weight and the complex fluid–cable–soil interaction. In the present study, the methodology for dynamic lateral stability analysis is first discussed; and the reliable hydrodynamic load model and cable–soil interaction model based on large experimental test data are described in detail. The requirement of the submerged weight of a cable w s to obtain on-bottom stability is investigated for three types of soil (clay, sand and rock), using the finite element program PONDUS, and the results are w s , r o c k > w s , c l a y > w s , s a n d under the same load conditions. Several different aspects related to optimization design of the on-bottom stability are explored and addressed. There is a significant benefit for the on-bottom stability analysis to consider the reduction factors, due to penetration for clay and sand soil. The on-bottom stability is very sensitive to the relative initial embedment z 0 / D for clay and sand soil, due to the small diameter of the cables, and therefore, reliable prediction of initial embedment is required. In the energy-based cable–soil interaction model, the friction coefficient μ and the development of penetration affect each other and the total effect of friction force F f and passive resistance F r is complicated. The effect of the friction coefficient μ on the on-bottom stability is different from engineering judgement based on the Coulomb friction model. The undrained shear strength of clay is an important parameter for the on-bottom stability of umbilicals and cables. The higher the undrained shear strength of the clay, the larger the lateral displacement. Meanwhile, the submerged weight of sand has a minor effect on the lateral displacement of cables. The method used in the present study significantly improves the reliability of the on-bottom stability analysis of umbilicals and power cables for offshore wind application.

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Stochastic stability analysis of a test excavation involving spatially variable subsoil

Canadian Geotechnical Journal ◽

10.1139/t06-062 ◽

2006 ◽

Vol 43 (10) ◽

pp. 1074-1087 ◽

Cited By ~ 7

Author(s):

Yu-Jie Wang ◽

Paul Chiasson

Keyword(s):

Shear Strength ◽

Stability Analysis ◽

Slope Stability ◽

Spatial Variability ◽

Progressive Failure ◽

Soft Clay ◽

Stochastic Modelling ◽

Undrained Shear Strength ◽

Slope Stability Analysis ◽

Undrained Shear

A stochastic slope stability analysis method is proposed to investigate the short-term stability of unsupported excavation works in a soft clay deposit having spatially variable properties. Spatial variability of undrained shear strength is modelled by a stochastic model that is the sum of a trend component and a fluctuation component. The undrained shear strength trend, which is also spatially variable, is modelled by kriging or a random function. Slope stability analyses are performed on the stochastic soft clay model to investigate the contribution of spatial variability of undrained shear strength to a disagreement among high factors of safety computed from deterministic methods for slopes that have failed. Probabilities of failure as computed from the stochastic analyses give a better assessment of failure potential. Probability of failure values also correlate with time delay before failure. This phenomenon may be related to progressive failure or creep and to pore pressure dissipation with time.Key words: slope stability analysis, failure probability, spatial variability, stochastic modelling, geostatistics, vane tests, sensitive clay.

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Slope Stability of Embankments on Soft Soil Improved with Vertical Drains

Civil Engineering Journal ◽

10.28991/cej-2020-03091461 ◽

2020 ◽

Vol 6 (1) ◽

pp. 164-173 ◽

Cited By ~ 5

Author(s):

F. Kassou ◽

J. Ben Bouziyane ◽

A. Ghafiri ◽

A. Sabihi

Keyword(s):

Shear Strength ◽

Stability Analysis ◽

Slope Stability ◽

Factor Of Safety ◽

Field Measurements ◽

Undrained Shear Strength ◽

Slope Stability Analysis ◽

Soft Ground ◽

Soft Soils ◽

Undrained Shear

The overloads of structures or embankments built on clayey soft ground are generally applied gradually, respecting a specific phasing. This phasing on construction allows the undrained shear strength of clay increasing over consolidation in order to avoid the risk of collapse during loading. In this work, the undrained shear strength of clay over the consolidation was estimated following SHANSEP method of which parameters proposed by eight researchers have been employed, as well as the slope stability analysis of embankments on soft soils during staged construction. Assessment of factor of safety for slope stability was conducted basing on the Bishop method. Additionally, the variations of undrained shear strength and factor of safety were presented. In order to validate the methods discussed in this study, slope stability analysis of five embankments constructed on clayey soft soils improved by the vertical drain technique in a high-speed railway construction project in Morocco was performed. For these embankments, field measurements about lateral displacement are presented. It was found that some of the adopted methods is in a good agreement with field measurements. Hence, generalization of these methods to many soft ground cases can be proposed.

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