Technical description

Vertical core sampler. 1 = cap; 2 = head; 3 = pin; 4 = handle; 5 = protuberance; 6 = pin hole; 7 = tube; 7-1 = furrow; 7-2 = thread; 8 = cutting point; 9 = compactor; 10 = jaws; 10-1 = notch; 11 = jack; 12 = base

The soil core sampler is composed of a polished stainless steel tube (diagram part 7), hardened stainless steel cutting point (8), and a head (2) adapted with replaceable aluminum caps (1) and handles (4). It also has a compactor rod (9).

The tube can be 40-80 cm long and has a 32-mm inner diameter and a 300-700 (depending on the size of the tube) x 10-mm open furrow (diagram 7-1) with depth markers engraved every 50 mm. The cutting point is a modification of the Veihmeyer design of 1929. It is screwed onto the tube by 38™1-mm threads, offset by 2 mm from the end of the tube to protect the threads. The cutting point is shaped to form a soil core without shoving the soil ahead of the cutting edge and without compacting the core inside the tube. The inner diameter of the cutting point widens from 27 mm at the distal end to 32 mm at the other end of the cutting point, an essential feature designed to reduce friction on the inner wall of the tube, minimizing compression of the core and preventing the core from falling out after the tube is removed from the ground.

The outer diameter of the head is 50 mm (2). Its inner diameter varies throughout the head. At the top it is 33 mm wide to accommodate the samplerís cap, and tapering down to 32 mm over a distance of 40 mm. The diameter then increases to 38 mm in two graduations for distributing the force from the hammer. The head can be screwed or welded to the tube. We adopted the welded option to increase rigidity of the sampler.

Two trough-shaped shoulders (5) were welded to opposite sides of the head and two 20-cm removable handles (4) are connected to them by stainless steel pins (3 and 6). The shoulder attachment allows clockwise turning only to prevent unscrewing of the clockwise-screwed cutting point, which would then remain in the deep hole. A protuberance (5-1) on the lower surface of each shoulder was designed to fit into a small notch (10-1) in the jaws of the puller (described below). Finally, the sampler was equipped with several soft aluminum replaceable caps (1) to protect the head from hammer blows. The total weight of the sampler is 2.5-3.5 kg (depending on length).

A 6-kg hammer is used; a lighter one is useful in sandy soil; a heavier one (10-15 kg) is burdensome to operate and required a strong and fit operator if many samples are retrieved.

The soil sampler is removed from the hole with a puller because it is impossible to lift by hand except in sand dunes. The puller is a mechanical car tire jack (2-t lift with high clearance capacity, 11), that is mounted on a 10-mm-thick steel base (300™300 mm). An opening larger than the diameter of the sampler tube was cut in the base (12). The lifting arm of the jack is equipped with U-shaped steel jaws (10) set 51 mm apart. Each jaw was engraved with a notch to accommodate the protuberance on the sampler shoulder to prevent separation of the puller from the sampler during lifting. The weight of the puller is 3-5 kg and a relatively small effort was needed to retrieve the sampler from the ground.

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