Barette foundations' distinctive features are the drilling method of construction, and shape of the cast in-situ reinforced members constructed in the subsoil. Drilling is done by the equipments such as hydraulic grab, mechanical grab and / or hydro-fraise. The dimensions of the equipment used governs the section dimensions of barette foundations. A single barette foundation which is constructed with a standard grab size could be typically 60 cm, 80 cm, 100 cm, 120 cm or 150 cm in width and 2.50 m to 2.80 m in length, depending on the equipment used. Depending on the intended load-bearing capacity, as it may be more on the longer edge, plus-shaped, H-shaped or T-shaped barettes can be constructed. The design of barette foundations and measuring methods are the same as standard circular cross-section bored piles.

Barette Foundations are constructed in the following steps respectively;

  • drilling,
  • placing of reinforcement
  • concreting

Drilling is made by using bentonite mud as in conventional diaphragm wall applications. Barette foundations should be positioned in place and guide walls should be used at the elevation of the working platform.

After drilling, bentonite mud is desanded the reinforcement cage is lowered into the drill with the help of a crane and is placed in the specified elevations.

After placing the reinforcement cage barrette foundation is concreted from the bottom to the top by using tremie concreting pipes. Depending on the size of the barette foundation, more than one tremie pipes may be necessary.

The main advantages of barette foundations are;

  • Has more horizontal shear and bending moment capacity compared to the bored pile foundations under the forces acting in the same direction
  • Effective use of capacity and shear through the implementation of one single barrette under each column, as a result of the vertical structural elements and columns provide easy integration
  • As a result of having more peripheral area compared to bored pile foundations, it has more friction capacity
  • Can create an unlimited number of alternative solutions due to extendible dimensions during design

The main quality control during construction is provided by vertical and depth dimension control run by specially developed measuring instruments, positioning of reinforcement, concrete volume and after construction integrity and load tests (static, dynamic, or Oesterberg cell).

The bored piles are constructed by circular cross-section drilling and by placing reinforcement and concrete in the soil.

Bored piles can be constructed by using various capacity and sizes machinery and equipments, depending on factors such as; soil and groundwater conditions, diameter, capacity and the length of the pile. Bored piles are drilled by bentonite mud or casing depending on the ground conditions during the drilling, and length of the piles and the capacity of the equipment.

After drilling, bentonite mud is desanded the reinforcement cage is lowered into the drill with the help of a crane and is placed in the specified elevations.

Bored piles are constructed in the following steps respectively;

  • drilling,
  • placing of reinforcement,
  • concreting.

The placing of the reinforcement is implemented using tremie pipes starting from the bottom of the pile to the surface.

Donatının yerleştirilmesi sonrasında betonlama tremi boruları kullanılarak kazığın alt ucundan yüzeye doğru yapılır.

Typically, the bored pile diameters are drilled by conventional drilling equipments to sizes between 65 cm to 300 cm.

The main quality conctrol during construction is provided by vertical and depth dimension control run by specially developed measuring instruments, positioning of reinforcement, concrete volume and after construction continuity (integrity) and load tests (static, dynamic, or Oesterberg cell).

CFA method is a system used in the construction of bored pile. Pile drilling is done by longer auger drill. The drill should be continuous and should be inserted in the ground all along the pile by turning in the same direction. In this way, some portion of the excavated soil comes out to the surface, while a major part is pushed to be displaced through the walls of the pile in the ground.

After the drilling the pile is filled with concrete up to the surface, and reinforcement cage is placed by using vibro in the concreted section.

Delgi yapılan alan çalışma platformu yüzeyine kadar beton ile doldurulduktan sonra dışarıda önceden hazırlanmış donatı kafesi bir vibro kullanılarak veya kullanılmadan taze beton içerisine yerleştirilir.

CFA piles, different than bored piles constructed by drilling a hollow drill and concreting; are more like semi-displacement piles due to the method of drilling which displaces the subsoil during drilling towards periphery of the pile, consequently improving the surrounding soil.

In appropriate subsoil conditions CFA piling yields rapid construction, therefore preferred.

Driven piles are constructed by the method of placing the structural rigid elements by vibration or pushing, with prespecified section and continuity that can be controlled, for the purpose of carrying the vertical and horizontal loads.

Driven piles made up of steel, can be driven into subsoil typically composed of H-section profiles or using circular section steel pipe (with closed end or open end), either vertically or inclined. Besides steel piles; such as square, round, hexagonal sectioned precast concrete and timber piles can be driven as well. For driven piles commonly constructed by driving steel pipes; either permanent pipe pipes can be used depending on the ground conditions and the purpose of design, or piles are constructed after driving pipes in the subsoil and after the installation reinforcement and concrete the temporary pipes are exctracted by vibration.

Depending on the pile diameter or section, diesel hammers, vibro hammers or hydraulic pressure can be implemented to drive the piles in the subsoil.

Driven piles, different than bored piles constructed by drilling a hollow drill and concreting; are more like semi-displacement piles due to the method of installation which displaces the subsoil during driving.

Sheet piles are composed of steel elements that are constructed by driven piles interlocking, for the purpose of forming a continuous barrier in the soil.

The main application areas can be listed as; to build permanent or temporary shoring structures in limited depths and appropriate ground conditions and to create a barrier.

Different types of cross-sectional steel elements are driven to the ground by vibration method using vibro hammers mounted on a crane or an equipment and can be pulled back again by vibration method after fullfiling its function, if it is temporarily implemented.

Micro piles are relatively small diameter piles. As their lower capacity compared to bored piles considering the ground conditions and functions, they act to be the foundation pile to carry lower vertical loads or vertical element of the shoring systems in deep excavations.

Load tests are the integral parts of the quality controls of the foundations and structures in the foundation engineering applications.

Load tests are carried out to verify the performance of the deep foundations performance, according to the design criteria that are constructed under vertical or horizontal, static or dynamic loads. Load tests are implemented externally on the elements of the deep foundation in stages or by implementing reaction piles and hydrolic jacking systems of the vertical load in stages and duration.

According to the pile capacity desired to be tested, Pile load test can be performed in tension or compression as well as in the horizontal direction. In addition to static loading tests dynamic loading tests can be implemented as well.

Depending on the size and capacity of the equipment used and the load of the pile to be tested, experimental setup is designed and selected and the test is performed accordingly.

Load tests can also be performed by placing a special loading cells and assembly inside the structural members of deep foundations, like piles or barrettes bi-directionally (Oesterberg Cell).

 
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Zetas Zemin Teknolojisi A.S.

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