The trenchless technique for horizontal-directional drilling: soil-related risks and risk mitigation

摘要

The horizontal-directional drilling technique is very popular nowadays. While the majority of the cables and pipelines installed with this technique succeed, in several cases the technique still lacks sufficient control of the risks arising from the subsurface conditions. Therefore, a soil related-risk analysis for the prevention of unwanted events during the drilling stages or after the installation activities is recommended. The identification of the risks is the most important stage in the risk analysis, and requires sufficient knowledge of the processes during the drilling stages. Once all the risks are qualitatively identified, their importance can be determined. Very often, calculations are necessary to classify the risk in a quantitative or semi-quantitative way. After classifying the risks, mitigation measures can be established for the significant risks. Since an overview of all possible risks in horizontal-directional drilling would be extensive, this paper focuses on the most-often-occurring soil-related risks: high pulling forces or incomplete pull-back caused by local bore instability; high pulling forces or incomplete pull-back caused by frictional forces in the bore; and seepage through the bore to the surface.