Ground Displacement Monitoring During Horizontal Directional Drilling & Other Trenchless Installations

Horizontal directional drilling (HDD) methods involve steerable tunneling systems for both small and large diameter lines. HDD is a two-stage process. The first stage consists of drilling a small diameter pilot hole along the desired centerline of a proposed line. The second stage consists of enlarging the pilot hole to the desired diameter to accommodate the utility line and pulling the utility line through the enlarged hole. The HDD methods have the ability to track the location of the drill bit and steer it during the drilling process. The result is a greater degree of precision in placing the utilities. HDD has traditionally been used for cable and pressure pipeline installations. In recent years, there have been innovative applications for HDD, such as, gravity pipe installations, pipe removal, pavement stabilization and environmental applications such as horizontal wells and gas extraction applications in sanitary landfills. Ground displacements and borehole stability are always of prime concern during HDD installations under pavements, in close proximity to existing buried utilities and structures. Stable boreholes also relate to successful completion of the projects. The Trenchless Research and Development Center (TRDC) at University of Missouri — Columbia, is conducting research concerning ground displacement monitoring and borehole stability in cooperation with Missouri Department of Transportation (MoDOT) and several industry participants. The objective of this research is to study the cavity expansion within the soil caused by the HDD process and to study the displacements of the soil in the vicinity of the cutterhead, reamer and at the ground surface.