Abstract:
Critical hydraulic gradient is an essential parameter
for determining the factor of safety against piping
failure of earthen dams, excavations, etc.
Theoretically, the critical hydraulic gradient of a soil
is taken as a function of the saturated unit weight of
soil. The occurrence and development of piping is a
very complex process due to complicated
interactions between water and soil. It was observed
that fines content and plasticity characteristics of soil
affect the initiation of piping of soils. In addition, the
above properties affect the roof supporting
capabilities of soil, which is an essential criterion for
propagation of piping. This paper is based on a study
of the effect of fines content of soil on the initiation
of piping at optimum moisture content.
Soil with particle size of 0.075 to 2 mm and fine sand
with particle size of less than 0.075 mm were mixed
at different mass percentages. By performing the
proctor compaction test optimum moisture content
was found. Sample was prepared at the optimum
moisture content and placed in mould and immersed
into stable water slowly to get saturated sample.
Series of permeability tests were performed to
measure the critical hydraulic gradient. The critical
hydraulic gradient was greater than the theoretical
critical hydraulic gradient and increased with the
increment of fine percentage.
