Construction machine for special civil engineering

A construction machine comprising:

• (a) a leader;
• (b) an advancing carriage guided on the leader and comprising a holder for a work device;
• (c) a first advancing cable and a second advancing cable for moving the advancing carriage along the leader;
• (d) a drive winch or a drive cylinder connected with the first advancing cable and the second advancing cable for displacing the advancing carriage using the first advancing cable and the second advancing cable;
• wherein at least one of the first advancing cable and the second advancing cable is attached to a first fixed point on the leader or to the advancing carriage or to both the leader and the advancing carriage;
• wherein a second fixed point is formed by a cable tensioner attached to the leader or the advancing carriage;
• wherein the cable tensioner comprises a tensioning drum and an end-side section of the first advancing cable or the second advancing cable is attached on the tensioning drum with a plurality of cable windings of the first advancing cable or the second advancing cable;
• and
• wherein the cable tensioner has a lock configured to lock the tensioning drum in at least one position of rotation.