The SCM-DH in action.
Bauer’s mixing tool works on the double
In response to market demand, Bauer has developed a soil mixing tool that enhances the proven single column tools with two sets of counter-rotating mixing paddles, which are effective in various types of soils.
01 October 2012
BAUER Maschinen, together with its subsidiary RTG Rammtechnik, has responded to a growing number of enquiries from various customers with regard to mixing tools for soil mixing columns with ever-increasing diameters.
The newly developed SCM-DH (Single Column Mixing-Double Head) soil mixing tool represents a significant improvement of the single column mixing tools that have proved themselves over many years and established themselves worldwide.
A company official says: “Different soil mixing techniques have been in operation for many years. However, when mixing cement slurry into loose or soft, non-load-bearing subsoil, the load-bearing capacity of the subsoil increases and the settlement is reduced.
“For this purpose, Bauer Group offers several types of equipment and processes which are also suitable for the construction of cut-off and load-bearing retaining walls.”
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In the SCM-DH, two interlinked sets of mixing paddles are driven in opposite directions by two coaxial casing tubes. These two counter-rotating mixing tool components are capable of achieving intensive levels of mixing and homogenisation of the soil with the slurry. “The tool can be employed not only in sandy and silty soils, but due to its intensive mixing capability, it is also suitable for the construction of soil mixing columns in cohesive soils,” says the spokesman.
The unit is driven either by a double-head rotary drive (DKS 100/200-02 or DKS 50/100) or a KDK rotary drive of the Bauer BG rotary drilling rigs in combination with a BTM torque multiplier.
The outer set of mixing paddles is driven with high torque by the outer casing tube, which is connected to the lower rotary drive – its primary task being to loosen the soil. The inner counter-rotating mixing paddle is driven at a higher rotational speed by the inner casing tube, which is connected to the upper rotary drive, and facilitates exceptionally intensive levels of mixing between the loosened soil and the slurry.
Based on their extremely sturdy design, the mixing tools are currently available for column diameters of 1,800 mm and 2,400 mm.
Both the RG machines of RTG Rammtechnik and the rotary drilling rigs of the Bauer BG Series can be used for this technique. Due to the high level of hydraulic power output produced by the RG rigs, these machines are particularly suitable for this soil mixing process.
Bauer’s spokesman says the SCM-DH was tested successfully in a large-scale field trial last August. “For the purpose, the mixing tool was attached to an RG 25S fixed leader rig and driven by the latest double rotary drive DKS 100/200-02. The installed engine power of 570 kW proved particularly beneficial in maintaining a high rotational speed throughout the mixing process, despite an increase in soil resistance. The maximum mixing depth attainable with an RG 25S machine is approximately 23.5 m.”
In-house expo
Early this year, Bauer showcased several new additions to its drilling and tunnelling range at its in-house exhibition, which was attended by more than 2,000 visitors from 72 countries.
Here, Bauer presented for the first time two new product line sub-divisions of its rotary drilling rig series: the Value Line and the Premium Line. Both product lines incorporate the fundamental design principles which are characteristic of Bauer’s BG series.
The Value Line is a product line optimised for kelly drilling applications with its features including long mast for large drilling depths, extended drill axis clearance for larger drilling diameters, high winch lifting capacity, high torque capability and an economical diesel engine.
The Premium Line, meanwhile, combines all multi-functional rigs for the many different applications in specialist foundation engineering. These include techniques such as kelly drilling with or without casing oscillator, drilling with the continuous flight auger (CFA) system and the full displacement pile system. Premium Line machines can also be converted to the cutter soil mixing (CSM) or the cased continuous flight auger (CCFA) technique. The attachment of depth vibrators or BC diaphragm wall cutters is also possible.
Also on show at the Bauer exhibition grounds was the small diameter drilling technology of Klemm Bohrtechnik with its drilling rigs of the KR series, while Prakla Bohrtechnik showcased an RB 15 universal water well drilling rig mounted on a crawler base as specified by a customer. Hausherr, a specialist in blast hole drill rigs, exhibited its HSB 3000 model.
