Slaking of solid clays and claystones under hydraulic and mechanical action

In tunnel drives with slurry-supported face in semi-solid to solid clay and claystone, hydraulic and mechanical actions can lead to the slaking of the excavated soil aggregates. Heavy slaking can lead to laborious separation associated with high cost. For investigations as preparation for a project, two test rigs were developed at the Zentrum Geotechnik of the TU München. These can be used to investigate slaking both phenomenologically in series tests and also on a large scale. Investigations on solid clays and claystones showed that varied soil properties influence the slaking. High plasticity indices and high lime contents tend to reduce slaking. Bentonite suspensions can approximately halve slaking compared to water and suitable polymer suspensions can largely prevent slaking.