Soil friction along HDD's - the influence of a refined model on expansion

In the article the aspects influencing the built up of soil friction along HDD's are introduced. Based on these aspects a proposal is done how to deal with soil friction modeling along HDD sections in a day to day engineering practice. After definition of this approach a quantitative assessment on the proposed model itself and its impact on longitudinal elongation (expansion) along the HDD section are presented. This is done for three typical HDD sizes: DN100, DN600 and DN1200. The assessment shows that applying soil friction significantly influences the expansion built up along the HDD and in the end leads to a reduction of stress in the upper bends. By applying soil friction, the need of taking mitigating measures to divert expansion (e.g. expansion cushions, expansion loops) is lower for some cases.