New measurement and control technology in tunnelling - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 254

Figure 6-9 Hose levelling
instrument based on pres-
sure measurement, from
H.-J. Collins [39].

6.2.6 Inclinometer
Inclinometers can show, for example, the inclination of a tunnelling machine or ground
deformation. They are normally constructed with a pendulum rotating about an axis and
held in position by an electrical control circuit. The current necessary to compensate the
torque resulting from an inclination is proportional to the angle of inclination and deliv-
ers the measured signal. Two inclinometers arranged at 90° to each other can deliver the
complete deviation of a machine against the vertical.

6.3 Control in drill and blast tunnelling

The drilling rig, drilling booms and drilling process in drill and blast tunnelling were all orig-
inally manually controlled. Attempts were then made to display the arrangement of holes
and the blasting pattern on the face with an aligned projector, but this process did not become
established. Since the overbreak, extra concrete and the geometry of the support layer essen-
tially depend on the precision of the holes set out by the drillers, the trend for some years has
increasingly been the development of drilling jumbos with computer control and computer
assistance. The most significant innovation is the determination of the position of the drilling
boom and the automation of the drilling process. The developments extend from the automa-
tion of individual working steps through full automation with repositioning of the drilling
boom to fully automatic drilling during the entire round cycle. In order to achieve this, the
machine only has to be aligned once with the tunnel laser and thereafter the drilling of the
entire face only has to be watched by the operator. Computer-assistance and -control of the
drilling jumbo are thus a significant aid for quality assurance in tunnel driving.

6.3.1 Drilling jumbo navigation
In order to determine the starting position in drill and blast tunnelling, firstly the location is
determined. The drill jumbo is levelled on jacks. Then two sighting targets are mounted on
one of the drill feeds. This feed is then aligned so the beam from the directional laser passes
through both sighting targets (Fig. 6-10). The exact position is determined from the line of the
laser beam and the tunnel chainage of the jumbo and the drilling of the next round can begin.