Stone Columns in Extremely Soft Soils in Scandinavia
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Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
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Sammanfattning
Stone columns are a well-established technique for improving the properties of soil
under the foundation of embankments and heavy structures. Stone columns are
inclusions of granular material typically installed using vibratory-displacement or
vibro-replacement methods. A notable advantage of stone columns is that they tend to
have a minimal impact on the properties of the surrounding soil, unlike other ground
improvement methods. The primary outcomes of stone columns in untreated soil
conditions include improved bearing capacity, reduced total and differential
settlements, accelerated consolidation, enhanced stability of embankments and natural
slopes, and decreased liquefaction susceptibility. Stone columns function as inclusions
that provide higher stiffness, shear strength, and permeability than the natural soil. This
enables them to effectively support the structure or embankment without significantly
altering the physical state of the surrounding soil, as well as improve the drainage.
The research aims to examine whether stone columns can be used in the soft clays
typical to Scandinavia, resulting in preliminary design graphs. The numerical
simulations will be carried out using constitutive models such as Creep-SCLAY1S and
Soft Soil under 2D axisymmetric conditions in Plaxis. The simulations will be done as
fully coupled consolidation concerning typical soil characteristics in Scandinavia.
Ultimately, the outcome of this study would include Priebe-type charts suitable for
Scandinavian clay, which can assist designers in constructing stone columns in each
area.
The findings reveal a substantial effect of the chosen constitutive model, the influence
of replacement ratio A/Ac (the ratio of the area of the stone column to the area of the
soil it replaces), and the effective friction angle of the stone column material on the
settlement improvement factor. Furthermore, the results confirm and build upon
previous findings, indicating that creep and increasing lateral earth pressure K increase
the settlement improvement factor. Consequently, the results can be applied in stone
column design for highly soft clay conditions (such as Swedish soil), where using
Priebe’s charts might not be applicable.
Beskrivning
Ämne/nyckelord
creep, extremely soft soil, friction angle, replacement ratio, creep-SCLAYL1S, settlement improvement factor, soft soil, Soft Soil-creep, stone-columns