Cuadernos de Investigacion Geografica vol:37 issue:1 pages:94-114
Piping has been observed in natural and anthropogenic landscapes, in different lithologies and climates, and under different types of land uses and vegetation covers. Despite its importance, no standard widely-applied methodology exists to assess susceptibility of soil to piping. The pinhode test, originally developed by Sherard et al. in 1976 is an empirical test based on the qualitative evalution of the dispersibility (colloidal erodibility) of compacted fined-grained soils. This study aims at evaluating the pinhole test for assessing the susceptibility of soils to piping and establishes recommendations to use the pinhole test, and assesses the effects of hydraulic head, water quality and soil moisture content on the hydrological and erosion responses.
Topsoil Ap horizon samples with different moisture contents were taken in Central Belgium. Four hydraulic heads (50, 180, 380 and 1020 mm) and two water qualities (tap and distilled water) were used in the laboratory. The results show: (i) a linear incrase in pipe flow discharge (Qw) and sediment discharge (Qs) with increasing hydraulic head, (ii) a negative trend (not significant) for Qw and Qs with increasing soil moisture content, and (iii) significantly higher Qw and Qs for distilled water than for tap water. This study indicates that the pinhole test is suitable for assessing the susceptibility of soil horizons to piping in a quantitative way (Qw Qs, the time to flow out and the hole size after the test). We recommend the use of : (i) two different and contrasting hydraulic heads (i.e. 180 and 1020 mm), (ii) distilled water, and (iii) different soil moisture contents