A narrow column test that targets fracture quality of deeply buried weak layers.
The Deep Tap Test, or DTT, targets deeply buried weak layers that are too deep to effectively assess with other column tests such as the Compression Test. The objective of the test is to observe the type of fracture that occurs in deep weak layers. The setup for the deep tap test is the same as the Compression Test (a 30 cm by 30 cm isolated column), except that you remove most of the slab from above the weak layer, leaving just 15 cm of snow. Thus, tapping will initiate a fracture for weak layers that are deeper than about a meter and are otherwise too deep to affect from the snow surface. Cleaner and more sudden fractures suggest potential deep slab releases on persisting instabilities.