Bore Planning Method of Single-Sided Directional Drilling for Pipeline Crossing Loess Gully

Some long-distance pipelines are planned and laid in loess plateau which is a typical kind of landform particularly in China. Complex geological condition in loess area makes great difficulties to pipeline construction using traditional trenched method especially to large gully crossing. In past decades, manual inclined shaft has been widely used for gully crossing, but it is inefficient and danger in construction. Recently, single-sided directional drilling (SDD) has been employed as a new method for loess gully crossing. Different from Horizontal Directional Drilling (HDD), SDD drills a bore hole through the gully from top to bottom and pipeline is installed by slipping along the hole. For its high efficiency, SDD has been regarded as the best selection for large loess crossing. But it is still limited in engineering because bore planning for SDD is almost determined by experiences which could induce unforeseeable questions or accidents in construction. This paper introduces the method for bore planning of SDD crossing including: 1) bore planning with linear drill path for loess gully with gentle slope and 2) bore planning with curve drill path for gully with steep slopes or unstable soil covering. Equations of main parameters for bore planning are derived and the application step is proposed as well. Finally, two typical cases of pipeline crossing loess gully in Yulin-Jinan gas pipeline are analyzed and bore planning design for each case is determined and conducted. Proposed method gives a reliable guideline for pipeline crossing loess gully with SDD and effectively increases construction quality and safety. © 2011 ASCE.