The 2nd Hanrahan Lecture: Geotechnical properties of Irish compressible soils

2020 ◽  
Vol 53 (4) ◽  
pp. 475-522
Author(s):  
Michael Long
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Geotechnical Properties ◽  
Rapid Rate ◽  
Soft Soils ◽  
Micro Scale ◽  
Ground Investigation ◽  
The Future ◽  
Work Done ◽  
Undrained Shear

The objectives of this paper are to provide an update on work done and the development of knowledge on Irish compressible soils since Eamon Hanrahan's book on the topic. Eamon subdivided these soils into three categories; namely, alluvial, estuarine and lake-bed deposits, and he termed them ‘troublesome soils’. A brief background geology will initially be presented. The complexity of the deposits both on a macro- and micro-scale will be highlighted. Sites that have been well studied will be summarized and the engineering solutions used to construct on these sites will be reviewed. Although work on these sites presents a significant engineering achievement, some important lessons were learned. The remainder of the paper deals with how these lessons might be addressed in the future; for example, how to use modern ground investigation techniques to best characterize these complex deposits and what are the best techniques for examining important detailed aspects of 1D consolidation behaviour such as the identification of the apparent preconsolidation stress, the sometimes rapid rate of consolidation and creep, and also how to characterize the undrained shear strength of the soils. The work will be benchmarked against experience of the behaviour of Scandinavian soft soils.

scholarly journals Some Geotechnical Properties of Plastic Soil Enhanced with Cement Dust

2021 ◽  
Vol 27 (10) ◽  
pp. 20-33
Author(s):  
Abeer F. Hussein ◽  
Ahmed S. Ali ◽  
Abbas J. Al-Taie
Keyword(s):  
Shear Strength ◽  
Dry Weight ◽  
Undrained Shear Strength ◽  
Geotechnical Properties ◽  
Cement Kiln ◽  
Compression Tests ◽  
Cement Dust ◽  
Engineering Structures ◽  
Soil Cement ◽  
Undrained Shear

Plastic soil exhibits unfavorited geotechnical properties (when saturation), which causes negative defects to engineering structures. Different attempts (included various materials) were conducted to proffer solutions to such defects by experimenting in practical ways. On one hand, these attempts aimed to improve the engineering characteristics of plastic soil, and on the other hand, to use problematic waste materials as a stabilizer, like cement kiln dust, and to reduce environmental hazards. This paper explored the shrinkage, plasticity, and strength behavior of plastic soil enhanced with cement dust. The cement dust contents were 0%, 5%, 10%, 15% and 20% by dry weight of soil. An experimental series of shrinkage and plasticity tests and unconfined compression tests were carried out to explore the effects of cement dust on the quantitative amount of shrinkage, plasticity characteristics, and shear strength experienced by plastic soil. The effects of curing on soil strength were also investigated. The finding of this paper showed that the critical behavior and plasticity of plastic soil could be reduced by mixing the soil with 15% or 20% of cement dust. The undrained shear strength, cu, of plastic soil-cement dust mixtures increased with the increasing dust content up to 20%. In fact, this strength was affected by the curing period. The best enhancement was attained when the content of cement dust was 20%, and the undrained shear strength was increased more than three times at this content.

Undrained Shear Strength of K0 Consolidated Soft Soils

2008 ◽  
Vol 8 (2) ◽  
pp. 105-113 ◽  
Author(s):  
Li-Zhong Wang ◽  
Kai-lun Shen ◽  
Sheng-Hua Ye
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Soft Soils ◽  
Undrained Shear

Geotechnical properties of soft clays from the Witch Ground Basin, central North Sea

1991 ◽  
Vol 7 (1) ◽  
pp. 151-156 ◽  
Author(s):  
M. A. Paul ◽  
L. M. Jobson
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Geotechnical Properties ◽  
Seismic Surveys ◽  
Soft Clays ◽  
Fine Grained ◽  
Acoustic Signatures ◽  
The Witch ◽  
Central North Sea ◽  
Undrained Shear

AbstractThe Witch Ground Basin to the northeast of Peterhead is occupied by Late to Postglacial clays which reach a maximum thickness of over forty metres. High resolution seismic surveys have shown that the Sediments can be divided into two stratigraphic units on the basis of their acoustic signatures: the upper Witch Ground Formation shows in its lower part a finely detailed pattern of laterally continuous multiple reflectors, whereas the lower Swatchway and Coal Pit Formations present a disorganised signature in which few reflectors are continuous.Profiles of bulk density, water content and undrained shear strength have been obtained from two continuously sampled, adjacent boreholes which penetrated the sediments to a depth of forty metres. These show that the deposits of the Witch Ground Basin comprise a single geotechnical unit with the properties expected of a fine grained sediment of glaciomarine origin. The principal geotechnical properties change gradationally as a result of changes in composition and from selfweight compression. The different seismic signatures on which the basin stratigraphy is based are not reflected by major geotechnical changes within the sediment, but may well result from secondary features of the geotechnical profile.

scholarly journals Slope Stability of Embankments on Soft Soil Improved with Vertical Drains

2020 ◽  
Vol 6 (1) ◽  
pp. 164-173 ◽  
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.

scholarly journals Improving geotechnical properties of clayey soil using polymer material

2018 ◽  
Vol 162 ◽  
pp. 01002 ◽  
Author(s):  
Hussein Karim ◽  
Kawther Al-Soudany
Keyword(s):  
Shear Strength ◽  
Polymer Material ◽  
Clayey Soil ◽  
Undrained Shear Strength ◽  
Geotechnical Properties ◽  
Fiber Content ◽  
Strength Parameter ◽  
Polymer Content ◽  
Polymer Fiber ◽  
Undrained Shear

This study illustrates the application of polymer material for clayey soil stabilization. The article will focus on studying the strength behavior of the clayey soils reinforced with homogenously polymer fiber. In the current research, “polypropylene” was selected as polymer material to reinforce the natural clay soil. This polymer fiber was added to the clayey soil with four different percentages of (0, 1.5, 3, and 5%) by weight of soil. Various tests with different polymer contents were performed to study the effect of using such a polymer as a stabilizing agent on geotechnical properties of clay. As the fiber content increases, the optimum moisture content (OMC) is increased while the specific gravity decreases. For Atterberg’s limits, the results indicated increasing liquid limit and plasticity index while decreasing plastic limit with increase in polymer content. The outcomes of the tests also reflected a considerable improvement in the unconfined compressive strength with noticeable improvement in the shear strength parameter (undrained shear strength, cu) of the treated soils. The undrained shear strength obtained from treated soil with 5% polymer addition is more than three times that of the untreated soil. With an increase in polymer content, the consolidation parameters (Compression index Cc and recompression index Cr) decreases. Finally, the benefit of the reinforcement is increased with increasing polymer fiber content.

A Study on the Effect of a Dyke Reinforced by Geotextile-Encased Sand Columns

2014 ◽  
Vol 919-921 ◽  
pp. 7-9
Author(s):  
Fang Ouyang ◽  
Jun Wei Bi ◽  
Jian Wei Han ◽  
Wei Ming Liao
Keyword(s):  
Shear Strength ◽  
Soft Soil ◽  
Undrained Shear Strength ◽  
Settlement Rate ◽  
Soft Soils ◽  
Three Stages ◽  
Undrained Shear

A dyke construction was dealed with geotextile-encased sand columns. The dyke was used to enclose a polder in Hamburg-Finkenwerder, Germany. With the help of geotextile, the columns can be used in very soft soils , even undrained shear strength cu < 15 kN/m2, without excessive bulging. After the system is installed, the dike can be filled immediately. To analysis observed data of the long-term settlements in the dyke, three stages can be gotten i.e. "Primary settlements" - "Secondary settlements" - "Creep settlements". Most settlements occurred during the primary filling, while, only little settlements appeared after that construction was accomplished. The settlement rate decreases from the first settlement stage to the last one. No jump takes place when unloading soft soil. Furthermore, the method shorten time and saved a lot of money.

scholarly journals Parameter variability of undrained shear strength and strain using a database of reconstituted soil tests

2020 ◽  
Vol 57 (8) ◽  
pp. 1247-1255 ◽  
Author(s):  
Mair E.W. Beesley ◽  
Paul J. Vardanega
Keyword(s):  
Shear Strength ◽  
Shear Strain ◽  
Triaxial Compression ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Shear Mode ◽  
Soil Failure ◽  
Ground Investigation ◽  
Reconstituted Soil ◽  
Undrained Shear

During construction, the mobilization of undrained shear strength must be limited to avoid soil failure. Soil strains must be controlled to avoid compromising structural serviceability. To assess foundation performance by strength mobilization, an understanding of soil strains at various levels of strength mobilization is required. In practice, ground investigation data are often limited, and assessment of the expected variation of stress–strain and undrained shear strength is improved with empirical correlations calibrated with a database. The new database RFG/TXCU-278 contains data of 278 consolidated–undrained triaxial tests on reconstituted fine-grained soil samples compiled from the literature. Analysis of the database to evaluate the variability of undrained strength ratio (cu/[Formula: see text]) and a reference shear strain with shear mode is undertaken in this paper. The new database provides evidence that shear strain (like undrained shear strength) is sensitive to the consolidation (isotropic or K0) and shear mode (triaxial compression or extension) applied in the test. For the materials included in the database, the strength mobilization parameters obtained from a triaxial compression test can be used to predict the corresponding triaxial extension parameters to a reasonable accuracy.

On the retrogression of landslides in sensitive muddy sediments

1977 ◽  
Vol 14 (4) ◽  
pp. 582-602 ◽  
Author(s):  
M. A. Carson
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Micro Scale ◽  
Soft Sediments ◽  
Retrogressive Landslide ◽  
Muddy Sediments ◽  
Short Time ◽  
Undrained Shear ◽  
Landslide Retrogression

The literature dealing with extensive retrogression of landslides in sensitive sediments is reviewed and found to be inadequate in several respects. One obvious deficiency is in the link between supposed retrogressive mechanisms and the morphology of the resultant ‘earthflow’ cavity. Detailed attention is focussed on the origin of linear clay ridges that protrude from the floors of fresh earthflows, and persist for only a short time before being degraded to micro-scale features. The theory of landslide retrogression proposed by Odenstad, after the Sköttorp landslide in Sweden, is discussed, and developed into a model for the prediction of landslide retrogression, and for the explanation of 'flowbowl' morphology. The model, essentially an undrained retrogressive spreading failure, is tested against selected retrogressive landslide sites for which all the necessary information is available; the agreement between nature and theory is good. Some speculation is made regarding the origin of bottlenecked flowbowls, which are viewed as the exception rather than the rule in the sensitive muds of the St. Lawrence Lowlands. Emphasis is directed at the importance of the undrained shear strength of sensitive sediments, and less significance is attached to the actual magnitude of sensitivity of such deposits. Finally, the limitations of the model in very soft sediments, such as found in parts of Norway, are briefly pointed out.

scholarly journals Determination of bearing capacity of bored pile using SPT number N and undrained shear strength Su

2014 ◽  
Vol 17 (3) ◽  
pp. 86-93
Author(s):  
Nhat Dai Vo
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Skin Friction ◽  
Undrained Shear Strength ◽  
Soft Soils ◽  
Bored Pile ◽  
Undrained Shear

In this paper, the determination of bearing capacity of bored pile using the SPT number and undrained shear strength is presented. The advantages of this method are simple and always feasible, especially for bridge and pier designing in case of expressway projects constructed on soft soils. The 22TCN 272-05 standard is used to calculate bearing capacity of bored pile including skin friction and end bearing capacities. An applicable form for calculating the bearing capacity of bored pile is made. An example is presented and the applied result is shown.

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