School of Civil, Environmental and Mining Engineering

Postgraduate research

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Current and completed research by our postgraduate students.

Contact

Neyamat Ullah

Phone: (+61 8) 6488 3141
Fax: (+61 8) 6488 1044


Start date

Aug 2011

Submission date

Aug 2014

Neyamat Ullah

Neyamat Ullah profile photo

Thesis

Penetration of Spudcan Foundations into Offshore Multi-Layered Soils

Summary

The research work to be performed here will investigate the load-penetration behaviour of spudcan foundations in layered soils, identifying the penetration mechanisms and the consequent load-penetration profiles. Since field tests are impractical due to time and environmental conditions, scaled model tests using a geotechnical centrifuge will be conducted, supported by large-deformation finite element analyses. The centrifuge modelling approach effectively scales up the model foundation to the prototype dimensions to obtain test results under the correct stress conditions and using well-controlled soil conditions. The failure mechanisms will be identified through a series of test using half spudcan models penetrating against a transparent window. The spudcan and soil movement will be recorded by high-resolution digital camera and analysed utilizing the PIV (Particle Image Velocimetry) technique (White et al., 2003). Different spudcan sizes will be tested for each soil layered profiles to investigate the foundation size effect. The research aims of this project are to:

i) Study the responses of spudcan deep penetration resistance on multilayered soils using full spudcan models in centrifuge testing. From the measured spudcan penetration responses, the punch-though failure potentials can be identified. The spudcan peak-resistance and punch-through failure depth can be gathered for the test cases preformed.

ii) Identify soil failure mechanisms involved during spudcan penetration in multilayered soils through half-spudcan model tests in centrifuge using PIV analysis. The soil failure mechanisms identified with the soil layered profiles tested will allow for analysis and predictions of spudcan penetration responses established for any layered soil profiles.

iii) Perform large-deformation finite element analyses to support the activities described above; to replicate the failure mechanisms observed by PIV, to replicate the measured load-penetration profiles, and to perform additional cases as required – for example, to assess the influence of the boundaries of the experimental chamber.

iv) Develop design guidelines for predicting the spudcan foundation load-penetration response on multilayered soils, where a set of formulas and design charts will be compiled for peak-resistance and potential punch-through depth with any given spudcan size and soil conditions. The different spudcan sizes tested can provide guidelines for the necessary spudcan size to avoid punch-through failure under given soil layered profiles.

Why my research is important

The research is significant in terms of accurate load-penetration response predictions of complex multi layer offshore stratigraphy involving sand and clay. As current analytical models are inefficient in predicting collapse loads of spudcan foundation new analytical models will be developed which caters for the strength-dilitancy relationships for sand. The minimum dimensions of the centrifuge container to avoid the boundary effects will be researched which will help to identify the possible interaction of the soil with the boundary. Possible choice of the approprate boundary condition in physical model tests will be emphasized.


 

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