Since the inception of Horizontal Directional Drilling in the 70’s there have been amazing advances in technology and equipment. The equipment in the early 80’s was still basic, not designed specifically for Horizontal Directional Drilling, unsafe with their cable winches, and not particularly reliable. Crossings were executed mostly in “sand, silt or clay” formations.
However, in the mid 80’s things changed rapidly under the influence of HDD contractors such as HDI, who introduced end of 1984 the rack and pinion concept that has now become standard on all modern HDD rigs. In the early 90’s, major manufacturers who had previously concentrated on the vertical drilling industry realized there was an untapped new market for Rigs, High Pressure Pumps, Drill Pipes, Down Hole Tools and Steering Equipment, and started to produce equipment dedicated to Horizontal Directional Drilling. This lead to bigger, better Rigs, Pull loads up to 500 tons, high torque capability, large diameter drill pipes and solid hole opening equipment, specially designed for the Horizontal Directional Drilling system and suitable for most types of subsoil formations. In the mid-90’s, mobile Mud Recycling units were added to the HDD spreads and mud systems started to receive way more attention.
Rock crossings were tackled as soon as the early 90’s, and with the advent of well-engineered and manufactured bits and rock hole openers, drilled rock strengths of 400 MPA are now achieved.
With the arrival of large diameter Drill Pipes, 48” and 56” pipelines have become common, installed with pipeline buoyancy control systems in holes reamed with buoyant reaming tools for the larger diameter passes.
Technology has produced more accurate magnetic and gyroscopic steering tools. During the last 10 years steering engineers have mastered the Intercept method, enabling two Rigs facing each other to drill and meet face to face in the middle of the crossing, allowing far greater lengths to be drilled successfully.
This changed the face of Horizontal Directional Drilling, whereas in the mid 80’s a 16” diameter 1,450m drilled crossing was a considerable achievement, it now palls into relative insignificance. Lengths in excess of 5,000m have recently been achieved, and 48” pipelines have been installed in holes of more than 1,500m.
Applications have also been diversified. Previously restricted to river, road and railway crossings essentially for Oil and Gas pipelines, HDD is now routinely used for outfalls, landfalls, soil stabilization, shipwreck removal, Electricity or Water networks and many other areas totally unthought-of 35 years ago.
The recent arrival of fully electric HDD spreads, providing noise reduction and lower energy consumption, is another reason for the constantly renewed interest for the HDD crossing method.
The last 10 years have also seen the development of the Direct Pipe® method, where the steel conduit is directly pushed in the ground behind a Tunnel Boring Machine, allowing precise installation of large diameter pipelines along a profile similar to HDD over distances now in excess of 1500m. Direct Pipe® is rapidly becoming a preferred method for large diameter crossings in tricky soil conditions, at shallow depth when necessary.