Mixed-in-place process
The mixed-in-place process (MIP) is a soil mixing process for the production of individual stitches or underground walls in various areas of special civil engineering. The process was patented in 1992 by BAUER Spezialtiefbau GmbH , which is also the owner of the "MIP" community trademark. The MIP process is approved by the German Institute for Building Technology in Berlin.
Procedure
The MIP process can be carried out with single screws or the so-called triple screw. The existing soil and a binding agent suspension are mixed and mortared on the spot. To create walls, the triple auger is drilled while adding suspension . After reaching the final depth, the soil- binding agent mixture is homogenized by alternately turning the individual augers . The result is a solidified, disc-shaped earth concrete body defined by the screw geometry.
In order to ensure a continuous, seamless wall, the individual lamellas are arranged according to the so-called double pilgrim step method .
The quality-relevant manufacturing parameters are recorded and recorded for each stitch.
The earth concrete bodies produced have defined dimensions and a homogeneous quality. The compressive strength that can be achieved depends on the soil material. Sand and gravel soils are best suited. With fine-grained and cohesive soils, the required binder content is higher. Soils with large stones and blocks as well as rock are unsuitable.
The composition of the binder suspension is determined for each individual case by means of suitability tests carried out in advance. For pure sealing walls, MIP walls with lower compressive strength (generally 0.3 to 1 N / mm²) are used. For construction pit sheeting or sealing walls with a static function, compressive strengths of up to approx. 10 N / mm² can be achieved. By installing load-bearing elements, the walls are strengthened in the event of static loads.
Device technology
Currently, the triple auger can produce two different wall diameters (370 mm and 550 mm) with a maximum drilling depth of 24 m.
Mixing plant Different sized batch mixers are used . The systems are largely automated, the suspension pumps are controlled remotely by the drill operator.
If the MIP process is carried out with the triple screw, i. d. R. Augers with continuous helix are used. By varying the direction of rotation of the three screws, the soil-suspension mixture is transported vertically. This makes it possible to ensure a constant material quality over the entire height of the slot even in changing soil layers .
Applications
The wall elements manufactured in the MIP process are used in different ways:
- Sealing walls with and without a static function in dams / dykes
- Construction pit protection
- Foundation elements / soil improvements
- In-situ immobilization of pollutants
advantages
In the MIP process, the existing soil is used as an aggregate for the earth concrete element to be created. The built-in binder suspension fills i. d. Usually only the naturally existing pore spaces. As a result, with the MIP process, the transport costs, both for the delivery of the building materials and for the removal of the cuttings, are significantly reduced.
Thanks to the low-vibration production and the high flexibility of the MIP drilling rigs, MIP walls can also be designed preferably in urban areas. MIP walls are usually cheaper than conventional special civil engineering systems such as diaphragm walls or bored pile walls .
Triple auger
The triple auger is a special drilling tool that is used to create mixed-in-place walls (MIP). The triple auger can be attached to the leader across or lengthways . The direction of rotation and speed of the screws can be varied individually.
Double pilgrimage
The double pilgrim step process is an implementation method for the wet-on-wet production of walls using the MIP process. It is characterized in that the overlapping area of the primary stitch and the secondary stitch is processed again. The process is patented by BAUER Spezialtiefbau GmbH .
Web links
- Exemplary embodiment: Foundation of the high-speed line Hamburg - Berlin (PDF file; 3.08 MB)