One of the critical factors in preventing failures of structures that consist geosynthetics is
the use of appropriately characterized geosynthetic interface shear friction in the theoretical
design of the structure. The interface shear friction parameters such as the frictional angle
and adhesion must therefore first be determined. The interface friction angle and adhesion
are measured in the laboratory mainly using the direct shear apparatus in accordance with
ASTM-D5321 and ASTM-D6243 standards (Sikwanda et al. 2018). Although these laboratory tests are
standardized the quality of the results can be largely affected by several factors such as
specimen gripping systems shearing rate applied normal stress and the type of geosynthetic
test specimens (Fox & Stark 2004). Among these factors the former is considered to be a major
source of dissimilarities in the results (Fox & Kim 2008). This is because when the
geosynthetic being tested is not sufficiently secured to the shearing blocks by the gripping
system it experiences progressive failure and shear strength that deviates from the actual
field performance (Fox et al. 2004). This could lead to unsafe cost ineffective etc. design
of projects with the respective geosynthetic materials. This research therefore was
undertaken to investigate the effects of the specimen gripping system on shear strength at the
geosynthetic geosynthetic interface using a direct shear device.
