Tunnelling shield

Abstract

Tunnel Boring Machines (TBMs) are known that comprise a large metal cylindrical shield fronted by a rotating cutting wheel and containing a chamber where the excavated soil is deposited (and optionally mixed with slurry for extraction, depending on the type of geological/soil conditions). However, TBMs have various disadvantages including the stop-start nature of their tunnelling, and that a single TBM cannot easily transition between different rock/soil types (especially heavily fractured and sheared rock layers). The invention provides a tunnelling shield provided with jet grouting tools arranged to project from a leading edge thereof. In this way, the quality of the geological material into which the tunnel is being excavated may be improved dynamically as part of the excavation process.

1 . A tunnelling shield, comprising:
 a movable protective structure for use during excavation of a tunnel, the movable protective structure configured to protect an interior region thereof from collapse of the tunnel;   at least one guiding probe arranged to project from a leading edge of the movable protective structure into geology into which the tunnel is to be excavated, the at least one guiding probe configured to guide the shield into position; and   a jet grouting tool located on the at least one guiding probe, the jet grouting tool configured to inject grout into the geology to improve its quality.   
     
     
         2 . The tunnelling shield of  claim 1 , configured to deposit a reinforcing component into material that has been injected during jet-grouting. 
     
     
         3 . The tunnelling shield of  claim 1 , wherein the at least one guiding probe comprises a plurality of guiding probes, each guiding probe provided with a jet grouting tool thereon, wherein the jet grouting tools are configured to be activated simultaneously. 
     
     
         4 . The tunnelling shield of  claim 1 , wherein the at least one guiding probe comprises a plurality of guiding probes, each guiding probe provided with a jet grouting tool thereon, wherein the jet grouting tools are configured to be activated independently. 
     
     
         5 . A method of constructing a tunnel, the method comprising the steps of:
 providing a tunnelling shield according to  claim 1 ;   moving the protective structure within a tunnel to be excavated to protect an interior region thereof from collapse;   project at least one guiding probe from a leading edge of the movable protective structure into geology into which the tunnel is to be excavated;   guiding the shield into position using the at least one guiding probe; and   injecting grout into the geology to improve its quality by using the jet grouting tool.