Construction Methods

 

Diaphragm walls have a static and / or sealing function and can serve as cut-off walls for dams or excavation pits, as foundations or as enclosures / exterior wall of structures.

They are executed as concrete or steel-reinforced concrete walls, built from ground level. Made of plastic concrete cut-off walls, they are adequately ductile to provide required flexibility in earthen embankments of dams. As structural concrete walls, they are considered very resistant to deformation and virtually water-impermeable. They are excavated in sections or elements / panels (primary and secondary) by crawler cranes using suitable diaphragm wall grabs or cutters, with the aid of a stabilizing fluid, between previously fabricated guide walls, which serve primarily to guide the excavator, allow fluctuations in level of the stabilizing fluid and carry temporary loads from the reinforcement or stop end elements if required for structural walls. When the final depth is reached, the stabilizing fluid is desanded and the bottom of the excavated element / panel is appropriately cleaned. Then the concreting by tremie-method is carried out.

 

 

Applications


Diaphragm Wall (grabbed) Details


Diaphragm Wall (cut) Details


 "BAUER Trench Cutter Systems" brochure

 

 

 

 

 

"Pile walls for use in positive cut-off construction consist of a series of overlapping/secant bored piles. The (great) advantage of this construction method is that the installation of the piles can be accomplished in almost any type of ground, especially in rock, such as karstic limestone. Thus it can be assured that the bottom of the wall is socketed into a firm base without leaving a gap between wall and the pervious ground."

Source: ICOLD

 

Construction process

Secant pile walls are formed by constructing intersecting concrete piles. Alternate primary piles (initial) are installed first with secondary piles (closure) constructed in between primary piles once the latter gain sufficient strength. Pile overlap is typically chosen to form a continuous wall with the specified minimum thickness.
Piles can be filled with either structural or lean concrete.

The main advantages of secant pile walls are:

  • Increased construction alignment flexibility
  • Simplified site setup
  • Relatively smaller working platform required
  • Can be installed in challenging ground (cobbles/boulders)


Care has to be taken

  • to achieve specified verticality tolerances for deep piles
  • to properly form the larger number of joints
  • to consider the limited depth of the technique during design stage already

 

Bored cast-in-place concrete piles brochure

 

Why haul away soil and bring in new materials when the soil can be used for construction? The Mixed-in-Place(MIP)- and Cutter-Soil-Mixing(CSM)-methods developed by the BAUER Group avoid the need for labour-intensive transport coordination, cut costs, reduce emissions and so relieve the strain on residents in the neighbourhood. Both methods offer efficient, cost-effective and environmentally friendly alternatives in the appropriate ground.

 

 

Mixed-in-Place Details

 

Cutter-Soil-Mixing Details

 

"Mixed-in-Place" Brochure

 

Dike inner seals without a structural funktion

 

Inner seals are introduced in order to reduce or prevent flow and thus increase the stability of the dikes. These walls are generally constructed starting from the crest along the dike axis.

 

They are either embedded into layers of low groundwater mermeability or serve as an extension ot the seepage path. the hardened cut-off wall materials must be able to withstand erosion and the dikes must be prtected against burrowing animals.


 

 MIP_ohne_statische_Funktion_Skizze

 

 

Dike inner seals with a structural funktion

 

If inner seals are exposed to static load due to a dismantling of the slope shoulder on one side, the Mixed-in-Place cut-off wall is to be measured for this load case.

 

Any absorption of a shearing force or moment load resulting from earth and water pressures will be protected against by the installation of reinforcement cages or girders. The size and distance of the lead-bearing elements as well as the compression strength required of the Mixed-in-Place materials are specified in the static calculations.

 

 

  MIP_mit_statischer_Funktion_Skizze        MIP_mit-statischer-Funktion1_Skizze

 

Grouting - or injection - is a procedure to improve the strength properties of the subsoil or to diminish its permeability. Open voids in porous soils or in jointed rocks often impair the strength and/or the impermeability of the underground which cannot be stressed as required.

On account of the essentially different nature of the voids in soils from those in rocks, grouting techniques have been adapted to meet specific requirements.

 

Grouting for DAM PROJECTS can be subdivided into different methods:
Permeation grouting, compaction grouting, rock grouting, jet grouting and gravity grouting.

 

Grouting

 

 

 

Continually rising real estate prices mean that even ground with less than adequate load-bearing capacity is becoming ever more attractive to developers. Soil improvement can be achieved by the highly productive methods of vibro-compaction-, vibro-displacement densification, vibro-cast-in-place- or soil stabilization columns. Selection of the most suitable method depends primarily on the ground at the site and on the loads to be carried.

 

Vibro-Compaction Densification (VCD) Details

 

Vibro-Displacement Densification (VDD) Details

 

Soil Improvement brochure