Don Rea, Clay Hill Boring, Inc. from Valdosta , Georgia , excels in tough projects. Recently, he was selected by the general contractor, Spiniello Companies, as the boring sub contractor for a project involving the City of Manassas, VA, and their interceptor rehabilitation project. He was required to do a 72" steel encasement 130' in length, and 24' deep for a water reclamation project to a grade of .96" over 100'.

Don chose to design and build his own shield complete with innovative cutting head, stabilizer plates, fresh air intake, and water system to cool the cutting teeth during the operation.

Don consulted with engineers from McLaughlin, and presented his concept of the unit. After several meetings, together they agreed on the design of the machine. McLaughlin fabricated the unit in-house in Greenville , SC , and Don and McLaughlin personnel observed the building of the unit and made changes as necessary during the fabrication process.

A hydraulic power pack supplied the power to the cutter head through a hydraulic motor to a planetary gear box attached by a solid shaft connected to the cutter head. The shaft was mounted in a bearing carrier, and could advance 2' into the rock face per cycle. Since the rock was extremely hard and abrasive, the 2' void also allowed for the changing of bits as needed by the operator.

Once the 2' cavity was formed, the shield was advanced into the void by a McLaughlin-36/42 boring machine which served as the jacking frame and the conveyance mechanism to remove the spoil from the hole by means of an 18" screw conveyor system.

In order to prevent the shield from rolling from the torque exerted on the rock by the cutting head, hydraulically actuated gripper plates were installed on 120° centers and controlled by three individual valves. These gave the shield additional support and allowed the operator to apply thrust to keep the head into the cut.