Continuous Flight Auger Pile CFA

TECHNICAL EXECUTION OF THE CONTINUOUS FLIGHT AUGER PILE

In the foundation works made by monitored mini continuous flight auger (Mini CFA), we highlight three distinct steps of the technical execution process, which are:

DRILLING

The monitored continuous flight auger pile is drilled with a spiral auger and is driven into the ground by rotation. The spiral augers are filled with the ground, and at the bottom of the auger there are knives to facilitate the cutting of high-resistance grounds, which can cut through 30 to 60 *SPT soil layers depending on the type of material.

Examples of soil types: silt, clay, sand, etc.

The machine achieves the required depth in each project with high productivity, which varies between 250 and 600 meters per day, depending on the diameter of the propeller, the foundation depth of the pile and the type of ground.

CONCRETING

At the end of the drilling process, the concreting of the pile is started. In the spiral auger there is a hollow central pipe through which the concrete is pumped and as the auger is extracted from the ground, it is simultaneously filled with pressurized pumped concrete (being controlled by the drill operator), so that no failures or bubbles occur in the *stem.

A specific concrete type is used that follows the requirements of the Brazilian Association of Technical Standards (ABNT) NBR 6122: 2010 (Item F.9) that are:

- Cement consumption of not less than 400 kg/m³;
- *Slump test equal to 22±3, according to ABNT NBR NM 67;
- Water–cement ratio ≤ 0,6;
- Agglomerate: sand and gravel (Gravel 0);
- % of mortar mass ≥ 55%;
- Pumped type mixture;
- *Fck ≥ 20 *MPa at 28 days, according to ABNT NBR 6118, ABNT NBR 5738 and ABNT NBR 5739.

ARMOR

At the end of the concreting phase, the cage frame is placed and manually inserted into the pile or with the aid of a machine.

Long cages should be built with thick bars and spiral stirrups, while the tips should be tapered so that they do not screw into the drill wall.

Technical References:

*SPT: The standard penetration test (SPT) is an in-situ dynamic penetration test designed to provide information on the geotechnical engineering properties of soil.
*Stem: It is the base of the pile.
*FCK: It is a characteristic resistance of the concrete to compression.
*MPa: A megapascal is a measure of the compressive strength of concrete. (strength on the surface area).

ADVANTAGES OF THE MINI CONTINUOUS FLIGHT AUGER

- Low noise and vibration level.

- High productivity and load capacity of the piles.

- Great ground drilling power.

- Fast execution of the construction works.

- Cleaning in the area where the work is carried out.

- Low mobilization cost.

- Execution of drilling in small-sized grounds.

- Easy access to restricted urban areas.

- Execution of the pile in preexisting constructions.

- Retaining wall.

CONTINUOUS FLIGHT AUGER (CFA) AND TECHNOLOGY

COMPUTER MONITORING

Rei Helice Continua's mini drills count with a computer monitoring that generates accurate, real-time data (via satellite) of the drilling and also the foundation concreting.

The monitoring screen viewed by the operator is the same screen monitored and supervised by the engineering team, providing all support, control and quality for the foundation works of the clients.

The monitoring is done through electronic sensors, which feed the monitored computer and are divided into two steps:

DRILLING

A) TORQUE:
It is responsible for measuring the average ground drilling force in (* bars) that the machine makes to cut the ground.

B) ROTATION:
Indicates the speed the auger rotates about its own axis (* rpm).

C) DRILLING SPEED:
It is the speed of drilling / ground penetration (* cm/s).

*BARS: it is a metric unit of pressure.
*RPM: Revolutions per minute.
*(cm/s): Centimeters per second.

CONCRETING

D) CONCRETE PRESSURE:
It detects pressure measured in bars when the concrete passes through the central tube of the spiral auger, helping the machine operator, so that the pressure is always positive, avoiding possible failures in the concreting.

E) EXTRACTION SPEED:
It is the sensor that indicates the speed of the auger extraction in the ground (*cm/s).

F) PILE PROFILE:
It is the estimate of how the stem was performed.

G) SLOPE:
Shows the slope of the auger positioning, helping the operator to shape the pile plumb on the "X" and "Y" axes.

GRAPHIC REPORTS

Rei Rei offers quality and state-of-the-art technology and its concern focuses on sending exclusive graphical monitoring reports via email to its clients, engineers, architects and all those involved in the construction works.

Additionally, graphical reports of the foundation works performed are provided, containing identification with the details of the work and of each pile dug, such as:

Customer name, date of work execution, commencement time of drilling, concreting start time, diameter executed, length, contract number, concrete volume, overconsumption and the graph of drilling and concreting.

Continuous Flight Auger Pile CFA