With the development of the offshore natural gas and wind industry, the demand for the construction of transfer pipeline and cables has also increased. HDD is a technique used to drill a subsea tunnel or under other designated area with the goal to pull a pipe or other facility through the drilled underground tunnel. This article presents the horizontal directional drilling (HDD) as one of the most suitable technique used to reduce the impact on the environment during the submarine pipe and cable installation process, especially in the coastal area and shallow waters. In the developed countries, it's the most common method used to surrogate the open-cut method for water supply installations in areas where the latter is not desirable or not acceptable (Najafi & Gokhale. According to Harbuck (2000), horizontal directional drilling (HDD) is preferred in many urban areas of the world due to three basic reasons: (1) the costs of restoring the surface in the case of open-cut are high, (2) the municipal authorities find it very inconvenient to perform open-cut in the congested areas and business districts, (3) the right-of-way is not accessible due to other structures that have been developed over the years. The pilot hole is drilled with a surface-launched rig with an inclined carriage, typically adjusted at an angle between 5 and 15 degrees with the ground for entrance and between 5 and 12 degrees for exit angle (Iseley & Gokhale, 1997). In a few instances, some mini-HDD systems utilize dry bore systems (with compressed air) in hard, dry soils and calcified or soft rock formations. Most systems adopt either fluid-assisted drilling or a high pressure fluid jetting methods during the pilot hole and back reaming stages. However, for large diameter pipes, the back reaming and pipe pullback operations are performed separately. The product pipe (connected to the back end of the reamer by swivel) is pulled through the enlarged hole. In most cases, HDD is a two-stage process: (1) drilling a pilot hole approximately 75 to 200mm (3 to 8 in) in diameter along the proposed design path and (2) enlarging the pilot hole to the desired diameter to accommodate the pipeline using a back reamer. consists of a rig that creates a pilot hole by pushing a rotating and steerable drilling head that is tracked from the surface as shown in Figure 1.
#Horizontal directional drilling diagram manual#
The pipe was high-density polyethylene (HDPE) pipe 300mm (12 inch) in diameter SDR 11 to be able to withstand the required pressure rating of 160 psi according to the Kenya water design manual (MOW.
#Horizontal directional drilling diagram install#
Two pre-reams would be carried out to enlarge to pilot hole to 450mm (18 inch) in diameter and to install the waterline. The pilot hole was assumed to be launched from the surface at an angle of 7 o to the horizontal and transitions to the horizontal at the target installation depth of 1.8m (6 LF). The HDD operation was divided into 10 installation segments of 100m (328 LF) each with a set- back distance of 15m (50 LF) on each side. The road reserve was not paved, and therefore, pavement restoration is needed only at crossing roads. A typical street in Nairobi, Kenya is assumed to encompass two lanes of paved surfaces and a 7-meter stretch of "Road Reserve" taken from the curb to the edge of the private propriety as shown in Figures 1 and 2. This water line is 1.8m (6 feet) deep underneath a typical Nairobi City street with all the existing underground utilities. scope of the study was to compare the construction cost of one kilometer (3280 LF) of 300mm (12 inch) in diameter water main based on two methods of construction: open cut and HDD.