Installation of bored piles
To install a pile you should drill a borehole of a specified diameter and depth. Next the borehole should be filled by fine-aggregated concrete and reinforced with a metal frame of a required cut. So, the bored piles are installed and concreted directly on a site. The diameter varies up to 1500mm and depth - up to 10m or 30 m and more. To increase bearing capacity the piles should be installed with a widening at the bottom of the borehole (a foot of pile). Mostly such types of bored piles are used in situations when there are heavy loads to a foundation and the few compressible soils are deep-seated.The installation of bored piles is free of dynamic effects to soils and foundations of existing buildings. This main advantage of bored piles is more appreciable during a construction within the urban zone. Moreover this type of foundations allows installing of a pile in any soil; even there are construction waste, remains from the previous structures and boulder and cobble deposits.
Quality control is very important during installation of bored piles. All rigs are equipped with a special computer system to control a pile concreting process. The monitoring piles’ parameters are depth, pressure of concrete mix, concrete volume and shape of piles.
CFA technology (diameter 600mm/450mm, depth up to 28m)
The bored piles installed by the CFA technology (CFA – Continuous Flight Auger) have become the most commonly used because of theirs high efficiency, bearing capacity, technological effectiveness and reliability. This method is the best to install piles on a site with the irregular bedding of soils including sand and clay interlayers. The core of this technology is using of the continuous flight auger. The auger column is driven up to the target depth. After this along the inner tube of the auger a concrete pump conveys concrete up to the place. During the concreting it is necessary to remove the auger column from the borehole. Having the borehole full of concrete it is required to put a space frame specified by a project into this borehole with the help of a vibrator.
Advantages of the CFA technology:
High productiveness.
High quality of a borehole’s concreting as concrete is delivered under pressure.
Pile drilling in dense sand layers.
No ground fluctuations.
The CFA method is very useful in narrow urban conditions.
Using of this method allows working very closely to the existing buildings.
To save time during a borehole drilling it is not necessary to change an operating tool.
Specifics of the technology:
It is quite possible that there will be higher consumption of concrete on a site with soft ground.
Driving of a reinforced frame is required using of a vibrator.
Full displacement piles (FDP) without soils excavation (diameter 410mm, depth up to 20m)
This technology implies drilling of a borehole by a specific boring head that can compact all ground up to the design depth. The borehole concreting is performed through a hole in the boring head with the help of a concrete pump. Next using a vibrator or a special crane a reinforced frame should be immersed into the borehole up to the design depth.
This technology of bored piles installation allows drilling of a borehole without soils excavation.
Advantages and specifics of the technology:
High productiveness and high pile capacity.
High quality of a borehole’s concreting as concrete is delivered under pressure.
Exact location of a pile according to a project and adherence to a vertical position of a pile (testing by an on-board computer).
Pile drilling in dense sand layers (a specific boring head properly mounted on a drilling body).
No muck and drilling cuttings on a site.
Driving of a reinforced frame is required using of a vibrator.
Installation of bored piles by a kelly-bar with or without a casing pipe (diameter 620mm, depth up to 31m)
Using of casing pipes is applied for drilling through unstable grounds to prevent caving of walls of a borehole.
Immersion of casing pipes should be done during a borehole drilling by means of a rotor and a rig. The rotor provides a column by swinging movement.
The rotor and the rig spin a casing pipe into the ground using the weight of the rig and a powerful winch.
Pulling of these casing pipes is made by means of a power applied by the winch through a system of polyspasts.
For a pile installation is required to use concrete with strength no less than class B15, W4-12. Concrete mix should be agile and has a cone slump 16-20cm at the fraction of applied chip 5-20mm.
Piles can be reinforced by a space frame made from armatures of periodic profiles (die-rolled section) not less than class AIII and if it’s required by rigid reinforcement. Pile reinforcing is made according to additional calculation.
This technology of bored piles installation by a kelly-bar with or without a casing pipe enables to install the following constructions:
single piles;
pile clusters;
“slurry-type walls” structures from tangent and contiguous bored piles.
“Slurry-type walls” structure is a frame filling and bearing structure, which enables to build underground structures close to existing buildings, as well as inside of operating premises.
Casing pipe enables the following:
block horizons of running soils;
provide security of piling works;
control parameters of a borehole;
guarantee high quality of a hole concreting.
Advantages of the technology:
High reliability enables to control a drilling process with achieving of a base layer.
No dynamic and vibration impacts to soils.
Enables drilling and extracting of boulders encountered at the depth.
Having a reinforced frame in a borehole, it enables to fill it through a concrete pipe. If the technology is observed there is no necking.
Verification of the real engineering and geological conditions to the project requirements is fulfilled while drilling.
Possibility to install a widening at the bottom of a pile (a foot of pile) enables to use a pile’s bearing capacity in full.
Specifics of the technology:
In some cases it is required to find another design decisions that allows using of a pile bearing capacity in a full.
To prevent boiling (pile heave) while drilling water saturated soils it is required to make a big ground plug or return pressure by water or mud solution.
This technology implies drilling of a borehole by a specific boring head that can compact all ground up to the design depth. The borehole concreting is performed through a hole in the boring head with the help of a concrete pump. Next using a vibrator or a special crane a reinforced frame should be immersed into the borehole up to the design depth. This technology of bored piles installation allows drilling of a borehole without soils excavation.
Advantages and specifics of the technology:
High productiveness and high pile capacity.
High quality of a borehole’s concreting as concrete is delivered under pressure.
Exact location of a pile according to a project and adherence to a vertical position of a pile (testing by an on-board computer).
Pile drilling in dense sand layers (a specific boring head properly mounted on a drilling body).
No muck and drilling cuttings on a site.
Driving of a reinforced frame is required using of a vibrator.
Installation of bored piles by a kelly-bar with or without a casing pipe (diameter 620mm, depth up to 31m)
Using of casing pipes is applied for drilling through unstable grounds to prevent caving of walls of a borehole.Immersion of casing pipes should be done during a borehole drilling by means of a rotor and a rig. The rotor provides a column by swinging movement.
The rotor and the rig spin a casing pipe into the ground using the weight of the rig and a powerful winch.
Pulling of these casing pipes is made by means of a power applied by the winch through a system of polyspasts.
For a pile installation is required to use concrete with strength no less than class B15, W4-12. Concrete mix should be agile and has a cone slump 16-20cm at the fraction of applied chip 5-20mm.
Piles can be reinforced by a space frame made from armatures of periodic profiles (die-rolled section) not less than class AIII and if it’s required by rigid reinforcement. Pile reinforcing is made according to additional calculation.
This technology of bored piles installation by a kelly-bar with or without a casing pipe enables to install the following constructions:
single piles;
pile clusters;
“slurry-type walls” structures from tangent and contiguous bored piles.
“Slurry-type walls” structure is a frame filling and bearing structure, which enables to build underground structures close to existing buildings, as well as inside of operating premises.
Casing pipe enables the following:
block horizons of running soils;
provide security of piling works;
control parameters of a borehole;
guarantee high quality of a hole concreting.
Advantages of the technology:
High reliability enables to control a drilling process with achieving of a base layer.
No dynamic and vibration impacts to soils.
Enables drilling and extracting of boulders encountered at the depth.
Having a reinforced frame in a borehole, it enables to fill it through a concrete pipe. If the technology is observed there is no necking.
Verification of the real engineering and geological conditions to the project requirements is fulfilled while drilling.
Possibility to install a widening at the bottom of a pile (a foot of pile) enables to use a pile’s bearing capacity in full.
Specifics of the technology:
In some cases it is required to find another design decisions that allows using of a pile bearing capacity in a full.
To prevent boiling (pile heave) while drilling water saturated soils it is required to make a big ground plug or return pressure by water or mud solution.
No comments:
Post a Comment