Conclusion
Anti-permeability strength as the critical triggering condition
of soil failure caused by water seepage in subsidence is
an applicable parameter that can be tested for and used to
determine the probability of forming subsidence sinkholes.
Fifteen samples with different thicknesses were tested and
a thickness of 2.0 cm was chosen as the standard size to
test the anti-permeability strength in this paper. The testing,
applied to natural Quaternary clay beneath the research
site, has a low susceptibility to the formation of subsidence
sinkholes under current conditions because the anti-permeability
strength of 40.8 kPa is higher than the groundwater
seepage pressure of 19.6–38.3 kPa. This low
susceptibility determination is consistent with a field
investigation that revealed an absence of subsidence sinkholes
within 3 km of the site.