Steerable boring systems have found wide acceptance over the past few years for the underground installation of gas and water pipes, and for the laying of Cable TV, telephone and electricity cables. Most systems operate by injecting a water/Bentonite slurry into the ground, combined with hydraulic thrust from an angled bore rig. The main problems faced with the usage of steerable bores are when soil types with stone inclusions or very hard ground are encountered into which a typical JET head cannot penetrate or steer. For these types of ground conditions, boring units with greater forces (often being more bulky, more expensive) have to be used. However, the returns on investment from prices chargeable per metre of pipes or cables installed often do not justify the use of higher capital cost boring rigs. A combined hydraulic/dynamic steerable boring system, designed in different classes for installing PE pipes up to 355mm diameter over lengths up to more than 300m and bore depths down to 10 - 15m - making it ideal for under river, rail and major highway crossings (smaller diameter bores over longer distances are possible). While normal Bentonite-assisted, hydraulic thrust boring systems may come to a stand-still in hard, densely compacted grounds with stone inclusions or - as in many western European countries - encountering back-filled material, the bore head of a hydro-dynamic system will make steerable forward progress due to its hammer action produced from the rear of the drill stems. With a variable impact rate of up to 1,000 strokes per minute, the hammer action can drive the drill stems into ground types that were up until now a natural obstruction and which had prevented steerable boring progress.
Pratical experiences in Europe with hydro dynamic horizontal directional drilling systems
Praktische Erfahrungen in Europa mit hydrodynamischen Waagerechtbohrsystemen
International NO-DIG, 14 ; 351-365
1997
12 Seiten, 11 Bilder
Aufsatz (Konferenz)
Englisch
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