| 摘要 |
An overburden drilling device includes a drill bit body, a percussion element for applying impacts to the body, and a casing attached to the body. The casing is connected to the drill bit body by a casing shoe. The casing shoe and the drill bit body are interconnected by radially overlapping walls so that the drill bit body pulls the casing along during a drilling operation while rotating relative thereto. A wedge-shaped member is provided around the casing close to a rear end of the casing shoe so as to facilitate removal of the drilling equipment from a bore.
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