| 摘要 |
A tunneling alignment device and method to provide azimuth .and grade of a tunnel are provided, which incorporates the use of the invention and a string that joins two surveyed points on opposite sides of a tunnel wall. The self leveling device is attached to the string and projects a light beam parallel to the planned azimuth and grade of the tunnel and provides a means to adjust: the grade of the light beam as required for tunnels of different grades.
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