Classic drilled piles

Technology of drilled reinforced concrete piles

BASIC CONDITIONS FOR SELECTION AND APPLICATION OF PILLARS:

Classically drilled piles without hoses are used in cases when the terrain is built of coherent materials (wood, clay, marl, marly clay, etc.) in category III land and larger categories. It is also important to know what the inflow of groundwater is, if it is insignificant and does not affect the well itself during the process of making the pile from a time interval of 1h to 2h.

Preparatory works:

Preparatory works include appropriate works on the construction site and works on the selection, delivery and installation of appropriate equipment and installation of the same, all in accordance with the specific projected field and construction conditions.

  • Preparatory works on the construction site include construction of a working plateau and access roads, and according to the needs and conditions for movement and manipulation of machinery for drilling piles, removal of extracted material from the pit, delivery of reinforcement baskets to the construction site and within reach of drilling equipment and the very approach of auto-mixers to the very pile of contractors.

    The spatial position, quality and dimensions of the working plateau, as well as the road, should correspond to the technical conditions of the machine and the equipment that will be engaged during the production of piles. The working plateau where the piles are made must be packed and flat in the width of 7-8 m, the ground must be packed with 30-35 MPa, as well as the ramps for lowering the machinery to the working plateau. It is not desirable that the ramp, like the working plateau itself, has a large slope due to the weight of the machinery, which weighs 65-70 tons. The machine that performs drilling only is MAIT HR 130, MAIT HR 180 and MAIT HR 30.

    The working plateau and access roads should be filled with dirty gravel or 63 mm shreds 20 cm thick. The substrate itself should be charged 30MPa to 35 MPa due to the movement of machinery.

  • Preparatory works on the choice of mechanization depend on the geomechanical testing and the characteristics of the soil, it also depends on the characteristics of the piles, which are the dimensions and depth.

    Depending on the geotechnical conditions and soil characteristics, clogging is not necessary, and the stability of the well can be ensured by a fluid support, it is necessary to prepare and install equipment and installations in accordance with the appropriate system for preparation and recycling of bentonite suspension.

Specific tools are used for drilling:

The tools used during the drilling itself (drill, cutter, bucket) mounted on a telescopic rotary system (keli) mechanization used is MAIT HR 130 and MAIT HR 180.

At the end of the excavation, the machine itself accepts the reinforcing basket with an auxiliary cable and inserts it into the pile pit. bottom of the spike. The diameter of the pipes themselves is Ø110mm in segments of 1m and 2m, which is

conditioned by the rheological properties of fresh concrete mass for plastic concrete, which are used in this technology.


Drilling with fluid support

Fluid backing or bentonite suspension is used for the same purposes as sealing to protect the well from collapsing if necessary. Accordingly, a bentonite suspension of appropriate bulk density and viscosity is used. The suspension is made in a slurry and poured directly into the well during the operation of the machine so that it is half a meter lower than the level of the working plateau. The drilling tool for bentonite suspension is the same.

To apply the suspension, it is necessary to install a plant for the preparation and recycling of a certain suspension before starting drilling work. A temporary recipient is being made to dispose of the bentonite suspension, which is later used to make the next piles.


Drilling without support

This drilling can be reported in terrains built of coherent materials without or with a slight presence of water, so that the walls of the wells are stable in the technologically necessary time and without upgrades (clay, wood, marl, etc.).

In such conditions, drilling is performed with the same plant and tools (MAIT HR 180, MAIT HR 130) but without a plant for making bentonite suspension, which allows much simpler, cleaner and more efficient operation.

The drilling set is placed in the working position and leveled above the axis of the pile, when the machine is leveled and placed exactly in the position, it starts drilling. Drilling is performed from the elevation of the working plateau to the projected elevation of the bottom of the pile.


Pile reinforcement

Reinforcing baskets for drilled reinforced concrete piles are similar to reinforcing baskets used in other piles. The basic structural elements (positions) for the manufacture of reinforcement baskets are:

Inner ring that is installed at a distance of 1-1.5 m and over which vertical bearing rods are arranged and welded. Welding is practically performed on 50% of joints.

Vertical rods of appropriate length, including the length of piles and anchors for the overhead structure, welded to the inner ring (50% of the joints) as in the previous paragraph.

Spiral of stirrups wound around vertical rods (approx. 50% of joints are welded)

Centralizers - bumpers for centering the reinforcement basket in the axis of the pile, made of sheet metal or reinforcement welded to vertical rods at the appropriate distance and arrangement. Bumpers come out of the dimensions of the reinforcing basket for the thickness of the protective layer of concrete in accordance with regulations.

The armature basket is installed in the pile by hanging for the auxiliary cable from the machine, excavator or car crane. The reinforcement basket is placed exactly above the hole of the pile and lowered into the pit. The reinforcement basket is fixed at the projected elevation of the pile depth.

Concreting panes

Contractor pipes are lowered to 0.20 m above the bottom of the well (approx. 1D of contractor pipes), and during concreting the contractor pipes are pulled in accordance with raising the level of concrete in the pile, so that the contractor pipes should remain immersed in concrete for at least 2-3 m.

Standard contractor pipes with a minimum inner diameter Dmin = 200mm with extensions 2.20m 1.00m and couplings on the cable are used.

The introductory funnel is mounted with the help of cables for contractor pipes and its volume (Vmin = 100L) and position is fixed at the top of the well. The auto-mixer approaches the hopper of the contractor pipes or with the help of a self-pump that places the outlet branch in the position above the hopper.

After the concreting of the pile is finished, the mechanization is placed above the next marked pile and the process of making the pile begins.

Geomechanical team

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