Abstract:
The undrained shear strength (Su) and cohesion
(Cu) of cohesive soils are frequently determined using an
unconfined compression test. However, the test results
are heavily dependent on specimen size. This causes
uncertainty in geotechnical analyses, constitutive models,
and designs by overestimating or underestimating the
shear strength of cohesive soils. Therefore, the study aims
to assess the effect of the height-to-diameter ratio on the
unconfined compressive strength (UCS) of cohesive soil.
The soil specimen was tested on a compacted cylindrical
specimen at the maximum dry density and optimum
moisture content with a height to diameter (H/D) ratio of
1–3 for 38, 50, and 100 mm specimen diameters. Disturbed
sample specimens were considered for the laboratory
program. Accordingly, the standard Proctor compaction
test determines soil classification and compaction
characteristics. The unconfined compression test was
performed for undisturbed and compacted remolded
states of various diameters of cohesive soil specimens
to investigate the strength variation with the specimen
variation in H/D ratio. The laboratory test results revealed
that cohesive soil’s unconfined compression strength
value drops rapidly with height-to-diameter ratios and
the soil specimens’ diameter increases. However, the
UCS value was stable at H/D ratio from 1.75 to 2.25. As
the specimens’ diameter and H/D ratio increased, the
peak UCS value axial strain decreased. Similarly, the
gap between the axial strains of peak UCS value for the
smallest and the most significant H/D ratio decreased
with increase in the specimens’ diameter.
