For both types of soil, a larger cyclic gradient amplitude corresponds to a stronger post-erosion contractive shearing behaviour and a smaller critical friction angle. Nevertheless, the internally stable soil experienced a small amount of particle loss, even under large cyclic gradients. For the internally unstable soil, the eroded soil mass and hydraulic conductivity increased significantly with increasing cyclic gradient amplitude. The cyclic seepage promotes the loss of fine particles and leads to larger hydraulic conductivity. Results show that the erosion development is significantly influenced by both the initial grain size distribution and the pattern of imposed cyclic hydraulic gradient.
Hydraulic gradient full#
For circular pipes flowing full this can be taken as the pipe diameter divided by 4. The effects of mean hydraulic gradient and cyclic gradient amplitude were investigated in detail. This is the area of flow divided by the length of the water-pipe interface. Representative internally stable and unstable soils were tested. A Dictionary of Earth Sciences More From 196. in the direction of the maximum hydraulic gradient. Maximum flow will normally be in the direction of the maximum fall in head per unit of horizontal distance, i.e. In this study, preliminary laboratory tests have been conducted to investigate the development of internal erosion and changes in hydraulic conductivity under one-way cyclic seepage, and the post-erosion stress–strain behaviour. hydraulic gradient A measure of the change in groundwater head over a given distance. Under such complex cyclic hydraulic conditions, the soil erodibility, hydraulic conductivity and subsequent stress–strain behaviour may differ from those under the monotonic seepage condition, and are still poorly understood. Four different increase velocities of hydraulic gradient were used to simulate the different load histories of hydraulic gradient. At a time of global climate change, rapid pore-water pressure changes in soil masses are frequently induced by extreme rainfall, storm surges, waves, flash floods and so on. To validate the effectiveness of the measures and to evaluate earth canal functions, hydraulic gradients (surface water gradients) have to be measured. Numerous incidents and failures of earth slopes, dykes, levees and embankment dams are caused by internal erosion.
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