Trenchless Technology

JAN 2019

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Page 46 of 67

gral bell) as the pipe material suited for this project . The pipe can be assembled easily and is not weather-dependent . The RJIB joint has a bell and spigot config- uration with a spline groove available up to 12-in. diameter. Once the joint is engaged, the spline can be inserted through the groove to lock the joint in place. Certa-Lok RJIB cannot be over- belled because the spline will ensure that the pipe is correctly engaged. The spline can be removed and pipe can be disassembled if needed. Once the joint is engaged, no cooling time is needed, and the pipe is ready to be installed right away. Drilling and Reaming Process The bore geometry consisted of an entry angle of 10 degrees and an exit angle of 12 degrees. The total hori- zontal length was 590 ft and the to - tal depth was approximately 28 feet . The bore path crossed other utilities, including the existing 42-in . PCCP and an 8-in . gas line. The technical team from North American Specialty Products reviewed the bore geometry to ensure that the pipe bending ra- dius and pull back forces would meet manufacturer 's installation criteria . The criteria required a maximum allowable tensile load of 60,000-lb force and minimum bending radius of 275 ft . Grava LLC served as the general contractor, with R&A Road Boring , LLC , as the driller. The driller used a Vermeer D24x40 Series II Navigator machine with 24,000 lbs of thrust / pullback . After the pilot hole was drilled, the contractor used a but- terfly cutter head. After two ream- ing passes, the pipe was ready to be pulled in . Another challenge was managing traffic flow as the exit point was just behind the curb of the busy frontage road. The contractor set up a one-lane closure. The pipe joint assembly was done in the far right-hand lane, with wood blocks supporting the pipe and a small excavator lifting and moving each joint with a canvas strap. Pull Back Process To begin the pullback process, ap - proximately 100 ft of pipe joints were pre-assembled and attached to the drill stem with the pulling head. As the driller began pulling the pipe in, the contractor engaged each new joint one-by-one. The challenge with cartridge method is the stop - start- stop process, in which the pipe has a greater risk of getting stuck in the dirt inside the hole. The driller, who had previous experience with this method, designed the slurry to be slippery to reduce the chances of the pipe getting stuck. The forces experienced during the installation were in the range of 20,000-lb force. These conditions test- ed the machine close to its capacity. Despite all this, the pullback process went smoothly. " The operator was very experienced and reamed the hole properly," said W W W.T R E N C H L E S S T EC H N O LO GY.C O M 47

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