Journal ArticleDOI
Driven piles in clay - the effects of installation and subsequent consolidation
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TLDR
In this article, the effects of installing a driven pile on the strength of the soil were investigated using a work-hardening elasto-plastic soil model, which has the unique feature of allowing the strength to change as the water content changes, thus it is possible to calculate the new intrinsic soil strength at any stage during consolidation.Abstract:
This paper describes the results of numerical analysis of the effects of installing a driven pile. The geometry of the problem has been simplified by the assumption of plane strain conditions in addition to axial symmetry. Pile installation has been modelled as the undrained expansion of a cylindrical cavity. The excess pore pressures generated in this process have subsequently been assumed to dissipate by means of outward radial flow of pore water. The consolidation of the soil has been studied using a work-hardening elasto–plastic soil model which has the unique feature of allowing the strength of the soil to change as the water content changes. Thus it is possible to calculate the new intrinsic soil strength at any stage during consolidation. In particular the long-term shaft capacity of a driven pile may be estimated from the final effective stress state and intrinsic strength of the soil adjacent to the pile. A parametric study has been made of the effect of the past consolidation history of the soil...read more
Citations
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Book ChapterDOI
Elastic-plastic model for soil
TL;DR: In this paper, a simple elastic-plastic model of soil behavior is presented, based on the experimental observation of the existence of yield loci that was discussed in Chapter 3.
Book ChapterDOI
Elastoplastic solution to spherical cavity expansion and calculation of penetration resistance for the miniature penetrometer test.
TL;DR: In this article, the elastoplastic solution to spherical cavity expansion for stress distribution in saturated clay is studied using the cavity expansion theory in combination with the modified Cambridge clay (MCC) model.
Journal ArticleDOI
Influence Analysis of Large-area PHC Pipe Pile Construction on the Surrounding Environment in Deep Silt Site
TL;DR: In this paper, the impact of large-area pile group construction on the surrounding environment is discussed, and it is shown that the load imposed on the pile top and the pile sinking depth during the construction of the foundation pile increase according to an exponential function.
Journal ArticleDOI
Elastoplastic analysis of cylindrical cavity expansion responses in anisotropic unsaturated soils under plane stress condition
TL;DR: In this article , an anisotropic critical state model for saturated soils was extended to unsaturated conditions by introducing suction into its yield function, which can reflect the soil-water retention behavior during cavity expansion.
Dissertation
On long term behaviour of overlapping pile foundations
Abstract: Piles are used world wide as foundation or as a soil strengthening method. The purpose of this thesis is to analyse how a system of overlapping piles, as a foundation technique, behaves over a design life of 100 years. Commonly piles are installed as either floating or end bearing which both have their advantages and drawbacks. In the early sixties a new technique was introduced which combined the two traditional methods in order to cope with the disadvantages from using one method alone. Overlapping piles have been used widely in Mexico City but in Sweden this piling system has only been used in a handful of projects, all constructed within the last decades. The idea of analysing overlapping pile systems with traditional pile systems was brought alive with the project of Regionens Hus located in the center of Gothenburg. The analysis is carried out with the finite element software Plaxis 2D together with the soil model Creep-SCLAY1S in order to capture long term behaviour of the clay. Soil model parameters are derived from the soil, CRS and triaxial tests conducted at Regionens hus. Several models, of both overlapping piles and more common floating pile systems, are created and compared in order to study the differences in terms of forces, settlements and soil response. As long term behaviour is dependent on soil loading history, the installation effects from pile driving are considered. It is shown that the most suitable way of modelling overlapping piles in Plaxis 2D is with the use of plate elements in a plane strain environment. With these it is possible to capture some installation effects as well as settlements, force distribution and load transmission. However, when using plate elements in 2D plane strain analysis Plaxis will consider piles as rigid walls. This wall effect will create a soil response that in some cases are not realistic. To capture the installation effects, without compromising the result, it is shown that a suitable method is to replace a volume of soil around the pile with remodelled soil. It is also shown that if overlapping piles are used it is possible to either shorten the floating piles about 50 % or increase the spacing between them about seven times compared to a system with floating piles only. This thesis indicates that there might be something to the idea of overlapping piles in terms of capacity and suitability, but more studies have to be conducted in order to confirm it, for example a study of economics as the price in most cases govern what foundation technique is going to be used. Additionally, the results from this thesis should ideally be verified and compared to real measurements and more advanced models.
References
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On the generalized stress-strain behavior of wet clay
TL;DR: The theory of the three-dimensional stress-strain behavior of WET CLAYs was introduced by BURLAND as discussed by the authors, who showed that WETCLAYs are subject to three dimensions of stress and strain.
Journal ArticleDOI
Skin Friction between Various Soils and Construction Materials
TL;DR: In this article, the authors used several hundred experiments to determine the magnitude of skin friction, in which the following variables were considered: (1) Various construction materials: steel, wood, concrete; (2) For each material two surface conditions were used: smooth and rough; which are described in such a way that they may be reproduced by anyone with a reasonable degree of accuracy.
Journal ArticleDOI
The Sensitivity of Clays
A. W. Skemption,R. D. Northey +1 more
TL;DR: The sensitivity of clays is defined as the ratio of their undisturbed and remoulded strengths, and varies from about 1·O for heavily overconsolidated clays to values of over 100 for the so-called extrasensitive or quick clays.
Journal Article
Bearing capacity and settlement of pile foundations
TL;DR: In this paper, the authors point out further aspects of limit point bearing capacity of piles in sand as well as the overlayered stratum and critical depth, and propose a relationship between the critical depth D sub c and p sub c, or 1 sub 1.