| 摘要 |
The invention provides apparatus for drilling trenches in the ground, the apparatus comprising a frame and a drilling assembly having a horizontal support plate connected to the bottom end of the frame, said plate supporting drilling tools disposed beneath said plate, said trench being filled with a drilling mud. The periphery of said plate has resilient sealing means for co-operating with the walls of the trench so as to provide at least partial sealing between said plate and the walls of the trench, and means for adjusting drilling mud flow rates from the portion of the trench situated above said plate to the portion of the trench situated beneath said plate, and also in the opposite direction.
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