Pile driving method, involves sinking bush having a helical blade and spiral drill bit at different rotary speeds and then filling borehole with concrete as bush and bit are lifted out of ground

摘要

A non-soil compacting pile with a helical shape is sunk by driving a bush (2) which has a diameter of 30-60 cm and which is provided with a helical blade (3) having a constant thickness (S) and a width (B) of at least 50 mm with respect to the bush. The bush is sunk using a spiral drill (1) having an auger bit (6) whose pitch is opposite to that of the blade. The drill is housed inside a tube. A lifting device is used to move the bush and bit in a downward direction at the same time whilst two independent drill tables are used to rotate the bush and bit in opposite directions, in order to sink the pile by moving the bush and bit in a downward direction at a rotary speed approximately equal to one blade step per revolution. The rotary speed of the bit is 1-2 times that of the bush. The spiral drill is removed by pulling on the bush and bit at the same time, at the same rotary speed and in the same rotation direction, but in the opposite direction to the rotation direction used when sinking the pile. The speed at which the bush and bit are lifted is approximately equal to one blade step per revolution. The borehole is filled with concrete at the same time as the bush and bit are removed.