Image Number 3 for United States Patent #4084386.
A drive shield of a tunnelling apparatus has elongate drive members supported and guided for longitudinal movement in a manner known per se. The drive members are connected to rear members or tails forming a rear shield and fluid concrete is introduced into a reception space within the rear shield to create a permanent lining for the tunnel. The rear members are shaped or profiled to provide recesses which are closed-off over a certain zone with the aid of covers. Reinforcing bars or the like can be inserted into the recesses to become cast into the concrete lining and means for delimiting the front end of the concrete reception space, such as a ring component, engages on the covers which form a smooth continuous bearing surface therefor.