| Abstract | Light-weight vibracoring is a well-established technique used to collect a continuous core of saturated, loose sand and silt deposits. It uses a resonating core barrel that liquefies contacting sediment
and sinks into and around the underlying sediment column. GSC-NC equipment consists of a 2.5 hp Honda motor that powers a 5.1 cm (2 in) diameter vibrator head via a 10.7 m long flexible steel shaft. Core sediments are collected in 7.6 cm (3 in) O.D.
aluminum irrigation pipe cut into 2.3-2.4 m (7.5-8 ft) lengths. The pipes are joined with couplers, as necessary, to create a continuous length of core barrel of up to 12.1 m (40 ft) long. A core catcher at the mouth of the core barrel helps retain
penetrated sediment. After vibrating a core barrel into the ground, it is extracted using a one ton hoist mounted on a JAWS 'A' frame ladder. Shallow cores (less than 2m deep), however, have been recovered manually. The retrieved core barrel is cut
up into 1 to 1.5 m lengths, capped, sealed with tape, and transported to the laboratory for analysis. In the laboratory, the core barrel sidewalls are cut longitudinally with a circular saw and the enclosed deposits split, logged and sub-sampled.
Core recovery is variable, depending on deposit grain size and sorting, but can exceed 90%. The vibracoring equipment requires a crew of two and can be transported by a pickup truck, ATV and/or snowmobiles. Vibracoring has been used to collect cores
up to 5.5 m long from lacustrine deposits in the French River and North Bay areas and, most recently, from small wetlands on Leda clay earthflows in the Ottawa area. |