mode 34 or belt conveyor 44 in the 34 open mode 34 without the need for interchanging screw conveyor hopper 49 and belt conveyor hopper 51 belt conveyor 44 need only be retracted or extended and bulkhead 45 added or removed for tunnel boring machine 10 to operate in the 34 open mode 34 and the 34 closed mode 34 respectively specifically swinging chute 55 is pivoted by swing cylinders known in the art not shown such that swinging chute 55 is in position a to channel tunneled material into screw conveyor 42 in the 34 closed mode 34 swinging chute 55 is oriented in position b to channel tunneled material into belt conveyor 44 in the 34 open mode 34 note that fig3 c shows the 34 open mode 34 of operation because belt conveyor 44 is present referring specifically to fig1 and 7 secondary conveyor 48 is located at the end of belt conveyor 44 remote from cutterhead 12 for removal of rock from the tunnel in the 34 open mode 34 secondary conveyor 48 is also oriented such that it communicates with dewatering screw 50 located in the watering tank 52 for removal of solids on secondary conveyor 48 in the 34 closed mode 34 the following elements all pertain to both of the 34 closed mode 34 modes of operation of tunneling machine 10 diagrammatically shown in fig6 and 7 connecting dewatering tank 52 to screw conveyor 42 is pressure lock 46.