Surface Heave Mechanisms in Horizontal Directional Drilling

Damage resulting from directionally drilled crossings has become a concern for municipalities and contractors due to the increased popularity of this trenchless installation method. Surface heave is one mechanism through which directionally drilled installations may damage existing surface structures such as pavements and foundations. Several factors contribute to the development of surface heave including backream rate, borehole pressure, downhole tooling, depth of cover, annular space size, and geotechnical properties. This paper presents and discusses results of a detailed field experiment which monitored surface heave under various installation characteristics. Four borepaths were designed to implement a full factorial examination to determine the interaction of backream rate, depth of cover, drill mud flow, and reamer type have on the development of surface heave. With greater understanding of how drilling practices affect the development of surface heave, practitioners of this technology may better plan installations to minimize the impact of their operation.