Method for enlarging hole in building-ground, involves rotating outer fitting opposite to rotating direction of inner fitting, where front drilling pipe is shortened and rear drilling pipe is extended according to drilling advancement

摘要

The method involves connecting a drilling device with a front drilling pipe (4) over an inner sleeve fitting (2), and connecting the device with a rear drilling pipe (5) over an outer sleeve fitting (3). The device is pulled through a pilot hole (12) by the front pipe such that the hole expands to an expand hole (13) with large diameter. The inner fitting is rotated by the front pipe in clockwise direction, and the outer fitting is rotated opposite to the rotating direction of the inner fitting. The front pipe is shortened and the rear pipe is extended according to the drilling advancement. An independent claim is also included for a drilling device.