Evaluation of the Shear Punching Test - A comparative analysis with fall-cone and direct simple shear test
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Type
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Model builders
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Abstract
Between the years 2019 and 2023, SGI developed a new method to assess the
undrained shear strength in cohesive soils. The new test, named the shear punching
test, is developed to possibly replace or compliment existing test methods, particularly
the fall-cone test. The fall-cone test, which is an index test for evaluating the
shear strength of soil, is based on empirical analyses. This makes it challenging to
derive mathematically and often underestimates the results. A method similar to
the shear punching test was devised by Bror Fellenius 1935. Although the results
were considered promising at the time, the method came to nothing.
This thesis aims to investigate the potential of the shear punching test to become a
standardized test in geotechnical investigations by analyzing the correlation between
the shear punching test, fall-cone test and direct simple shear test (DSS). This is
achieved by conducting a literature review and analyzing results from soil samples
where all relevant methods have been performed. Furthermore a numerical model
of the shear punching apparatus is developed using Plaxis 2D, and an in depth stability
analysis is conducted on a section from Gamleby Harbor in Västervik using
Geostudio SLOPE/W.
The results show that the shear strength that is calibrated to the DSS test aligns reasonably
well with empiricism and naturally in relation to the shear strength obtained
from DSS tests. The normalized shear strength however, shows a wide spreading
within 2 standard deviations as well as a few outliers. Numerical modeling in Plaxis
can to some extent recreate results from the laboratory tests. During evaluation of
the shear strength trend for the use in stability analysis, the shear punching test
leads to an increase in cases where the DSS test is excluded.
In conclusion, the shear punching test cannot be considered a complete replacement
for the fall-cone test as an index test, as the sensitivity of the soil cannot be determined.
However, it can be used as a complement to other tests for the evaluation of
the undrained shear strength in cohesive soils. Due to the scatter in the normalized
shear strength, no specific range for certain parameters can be observed where shear
punching is relevant or not. It can be concluded that it is possible to recreate the
shear punching numerically and obtain results that reasonably align with laboratory
results. Including results from the shear punching test in the evaluation of the shear
strength trend will only have an effect if more reliable test methods are not included.
Description
Keywords
Shear punching test, slope stability, data analysis, Numerical FE modelling, shear strength