Bore designs for Horizontal Directional Drilling (HDD) have significant constraints that need to be determined in order to dictate the validity of design prior to construction. The length of the proposed bore is determined once the design radius of curvature has been established. Factors that need to be considered when designing a bore include:
- Depth of cover with respect to the natural surface level – in conjunction with ground conditions this is a serious issue so as to reduce the likelihood of frac out.
- Depth of existing services located along the bore path and required clearance.
- The intended use of the bore – either gravity or pressure mains.
- Entry and exit inclination angle.
- The bend radius of the product pipe and drill rods.