Oatley &gt; Sydney &gt; Contracted in.

Here two vacuum Micro tunnelling attempts were made. The first was with a smaller machine boring a 305mm bore for just under 100m. A rock roller was used on the initial bore. Then when the drill head came out in the receiving pit a pull-back reamer was fitted with PCD cutters. This was then pulled back reaming the bore out to 520mm. This exercise was slow and wear and tear on the machine made this attempt uneconomical.
The second attempt was another bore in sandstone , but this time 600mm in diameter. Week's of preparation was put into the exercise with attention being given to the drill head , PCD cutters ,power pack and not to mention a complete set of new drill rods ,100m of them. The larger cutting surface and the sandstone where every exacting and the boring machine proved no match for the task. As can be seen in one of the pictures the drive-shaft actually began to twist because of the high rotational torque required. Due to the time shedule required by the contractor and with respect for his project it became apparent that we would not finish this bore on time. Humbly we ceded to machine and mother earth and went home. We were reminded by this Chinese proverb “Better go home and make a net, rather than dive for fish at random.”
Poorer in the pocket. Richer in experience.