A wide column test of crack initiation and propagation through incremental loading.
The Extended Column Test, or ECT, is a wide column test where an incremental load is applied to test both the ease of crack initiation and the propensity for that crack to propagate. The wider column (90 cm wide, 30 cm upslope) makes this test a better judge of propagation and it generally has a lower false-stable rate than small column tests. After the column is isolated on all sides, it is loaded by tapping a shovel blade 10 times from the wrist, 10 from the elbow, and 10 from the shoulder. A fracture that propagates across the entire column (ECTP) is interpreted as an unstable result. Fractures that are discontinuous (ECTN) or tests that don’t fracture (ECTX) are interpreted as stable results, though some recent research shows that ECTNs with fewer than 10 taps are also a sign that caution is warranted. The ECT has limitations assessing very soft storm snow or instabilities where the weak layer is deeper than about 120 cm below the snow surface.