BEHAVIOUR OF POLYETHYLENE PIPES INSTALLED USING A MIDI HORIZONTAL DIRECTIONAL DRILL

摘要

Between 1997 and April 2001 four instrumented 200mm high-density polyethylene pipes (DR-17) and tworn150mm medium-density polyethylene pipes (DR-11) were installed under controlled conditions at thernUniversity of Waterloo field test site using a midi directional drill. Pipe installation lengths of 55, 90 and 180mrnwere investigated. Instrumentation was installed on the drill rig and pipe to monitor their performance duringrnboring and pipe installation. Instrumentation was used to monitor drill rig hydraulic pressures, pipe strain andrnload, and slurry pressure adjacent to the pipe. Two of the six pipe installations were exhumed 8 and 12rnmonths following installation to determine the condition of the drilling fluid in the bore, bore and pipe ovality,rnpipe rotation along the bore axis, and “as built” pipe vertical and horizontal profiles.rnThe paper summarizes the University of Waterloo field instrumentation program from 1997 to 2001 and itsrnmain findings: 1) There appears to be an excellent correlation between measured pipe strain, load and drillrnrig differential hydraulic fluid pressures; 2) pipe load vs. pipe installation length appears to be linear when thernpipe installation is 55m; 3) When the pipe installation is 90m or greater the measured pipe load vs.rninstallation length appears to be non-linear. 4) Pipe loads also appear to decrease when the pipe isrnapproximately 2/3 installed; 5) Pre-reaming the entire bore path prior to pipe insertion appears to reducernbore slurry pressure; 6) Drill slurry pressures appear to decrease after the installation is approximately 2/3rncomplete; 7) Field measured pipe profile during the pilot bore agrees well with the actual insitu profile; and 8)rnSlurry surrounding the pipe can consolidate to densities similar to the surrounding native soil within 8 monthsrnwhen the pipe installation occurs above the groundwater table and the native soils are predominately silt.