Horizontal directional drilling is short for HDD. The development of domestic horizontal drilling machine is in middle or small scale development level. No matter the requirements of foreign marketing or state environmental protection policy, the market prospect of HDD is very good.
Foreign horizontal directional drill rig is developing toward to large-scale, microminiaturization, mechanical automation, hard stratum working, exceed length and depth oriented monitoring drilling.
In exceed length horizontal directional, when pilot hole drill to a certain distance, the drilling stem is too long and form “s” bending lead to the drill rig is difficult to deliver pushing ahead and appear the track of drill bit is difficult to control. The construction technology of traditional horizontal directional drilling and equipment machines tools can’t meet the requirement of drilling, so solving exceed distance horizontal directional drilling is the emphasis development trend of HDD equipment and tools.
In exceed distance through process, using the counter through technology process is advanced. Using two sets drilling rig drill the pilot hole from distinguish designing import and export soil point, jointing in middle reasonable location can solve the traditional technology’s risk and malpractice. When traditional technology produce exceed distance through, the pilot hole is difficult to control, sometimes it needs repeatedly adjust and the mud pressure is high occur the accident of risk mud.
In counter trough technology, the most difficult and important is the butt joint of pilot hole. The advantages of butt joint of pilot hole for through.
The distance of through is long; especially the through distance is within 2000m and difficult single direction through process; the precision of through is high; there don’t have error of importer and exporter soil point.
The principle of counter through is the main drill rig drilling bit find the auxiliary process drill rig drilling bit, in the drilled holes follow auxiliary construct drilling bit, it avoids the long distance stress bending and easily breakage of single through drilling stem to improve the construction safety factor.
Compared with developed country, domestic popularization and application of trenchless technology can’t reach the proper level.