How does a material dilation angle influence the behavior of soils reinforced with stone columns?
Please see the following reference:
Analytical Method for the Analysis of Stone-Columns According to the Rowe Dilatancy Theory. Pulko, B and Majes, B. 2006, Acta Geotechnica Slovenica, pp. 37-45.
M. Gunaratne
University of South Florida
I would suggest another more recent paper by the same authors.
https://www.researchgate.net/publication/251543769_Geosynthetic-encased_stone_columns_Analytical_calculation_model
There is a calculation spreadsheet. For normal stone columns you just need to set the geotextile stiffness to 0.
Regards,
Jorge
Article Geosynthetic-encased stone columns: Analytical calculation model
Thank you so much mr. Jorge, but i have another question in the same subject, so how can we define a value of the dilatation angle of the stone column or the sand column and the surrounding soft soil?
soft soil -> zero dilation angle
stone column -> 5-10º
Sand column a bit less -> 0-5º
A common expression is friction angle minus 30º
You may have a look the following paper of our group, which was implemented in AFENA, (UNSW@ADFA modifed version)
Lo, S.R., Zhang, R., and Mak, J. 2010. Geosynthetic-encased stone columns in soft clay: A numerical study. Geotextiles and Geomembranes 28(3): 292-302. doi: 10.1016/j.geotexmem.2009.09.015.
Thank you very much Mohammad,
But i can't download this paper.
Can you send me it please .
Thank you.
Dear Tabchouche Seifeddine
At the moment there is no scientific means of determining the influence of
material dilation angle on the behavior of soils reinforced with stone columns. This can only be done using properly instrumented laboratory test. You can make it your research focus for publication in a high impact journal.
However, it is necessary to understand the principles involved. Let sai =dilation angle. phi_p = peak friction angle; phi_c = critical friction angle.
sai = phi_p - phi_c
The deviator stress versus axial strain diagram for dense granular material (gravel) will rise to a peak at a certain material dependent strain and thereafter diminishes until it approaches the critical friction angle for the material.
Stone columns are provided beneath columns to increase the bearing capacity of soft soil.
The question in the design is what friction angle do you ascribe to the granular material in order to design the combined system under the superstructure load-Phi_p or phi_c or some intermediate value. This depends on how much the stone column-surrounded by the soft soil- strains horizontally under the applied foundation load. Intuitively this strain will depend on the relative stiffnesses of the stone column and the insitu soft soil.
With the above you can plan your laboratory tests to capture the parameters that influence the friction angle of the stone column as it interacts with the surrounding soft soil under loading.
I wish you luck!
Hello Tabchouche Seifeddine
You can also carry out your investigation via a numerical elastoplastic 3D finite element analysis of the soil/stone-column aggregate using a Mohr-Coulomb yield criterion with various dilation angle and ratios of stone-column/soil stiffnesses. This will then provide results from which the influence of the various parameters can be deduced. The system demand of such a 3D analysis can be quite heavy and a micro computer may be needed. Nevertheless, there is no substitute for a well organized laboratory investigation.
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