The construction process of the piles depends on several very important aspects such as, a well-implemented soil study, the use of the appropriate equipment to drill the ground, a suitable design of the foundation design, obtaining the appropriate steel for the foundation and finally that the concrete has the necessary resistance, we will see all these aspects in more detail in this article.
1. What is the soil study and why is it the first step in building piles?
Soil studies or also known as geotechnical study , is a process that has several activities and is useful when it comes to having information about the characteristics of the land where a construction is to be carried out, this work is carried out by experts who have their due accreditation and those who are in charge of issuing a final report in which recommendations are given on the type of foundation to be used for each project, taking into account what the soil study has produced, this means that it is a great information value to design and execute any type of construction project.
2. Drilling options for foundations
For the construction process of the piles, the study of soils and the design of the foundation are taken into account, once these two important aspects are known, we proceed to choose the equipment that best suits to drill the ground and achieve the necessary specifications. There are different types of equipment for drilling these we will see below.
Manual type piles
Manual type piles are characterized by the fact that in their production procedure a tripod is used, a drill with a pipe that is installed manually, two people who rotate the pipe and the drill bit using pipe wrenches. In this procedure, drilling with diameters 0.30, 0.40 and up to 0.50 can be made on several occasions with a maximum drilling of up to 25 linear meters, these specifications can be obtained depending on the type of soil that the land has.
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Micropiles are being the best option for projects that do not have enough space or that their land simply does not support the weight of a heavier machine, these machines are characterized by being very fast when drilling, their drilling specifications are 0.07M, 0.10M, 0.20M, 0.30M, 0.40M and 0.50M in diameter with a drilling capacity of up to 30 linear meters, in this case it also depends on the characteristics of the terrain and the power of the micropiling machine.
Continuous screw piling machine
Continuous screw piling machines work thanks to the use of a Dredge Shovel where the hydraulic drilling equipment is installed, this type of piling machine reaches a maximum drilling of 25 linear meters with an excavation diameter of 600 mm, they are characterized by having a concrete pump that makes it easy to fill the gaps while the rig is being removed.
Propeller type pile driver
This type of machine to make piles is characterized by being hydraulic, it is designed to carry out piloting works with a continuous propeller, its process is carried out thanks to the fact that it works inside a steel jacket where both the propeller and the sleeve have rotaries independent thanks to this, the soil is continually being extracted until it reaches the necessary depth. It is characterized by being able to excavate to a depth of 50 linear meters with a maximum excavation diameter of 1500 mm.
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Kelly Type Pile
This drilling machine to make piles is characterized by starting the drilling of the well using a cover that has a reinforced bit, the bit is responsible for drilling the soil in order to reach the estimated depth, the casing is inserted at a depth of 1 , 5 to 2 meters to fill it, then it is removed to clean it and inserted again until the proper depth is reached. The excavation depth is up to 50 meters with a maximum diameter of 1200 mm.
For the pile driving process, two methods are used which are percussion driving and pressure driving, in both systems precast concrete piles or steel piles are used, this means that the dimensions and material of the piles depend strictly from the conditions of the foundation designs.
3. Drilling or drilling in the pile construction process
This is the next step that you must carry out taking into account the topographic stakeout to be able to locate the pile driver in the center of the pile location, then the excavation is carried out to the necessary depth, in many cases thanks to the fact that the walls of the hole present instability due to the presence of the water table or other ground conditions, it is advisable to use stabilizing polymers such as bentonite.
What is bentonite and its use in civil engineering
The use of activated sodium or calcium bentonite in civil engineering are the ones that perform best in the different tasks in this area. They are generally used to cement rock crevices and fissures, to protect pipes, in order to prevent subsidence, waterproof barriers in the ground, in piling to support the ground of drilled wells, to stabilize the construction of tunnels, among others .
4. Making the baskets or pile armor
The baskets or pile armor are elements that are manufactured with corrugated bar steel that are characterized by having a great resistance of circular section, these baskets are usually made in the same place of the project, on several occasions the iron comes in the form Spiral or piloting companies have equipment to give them the shape and size necessary for your project.
Read: Slab Foundation Pros and Cons
In what situations is the use of baskets recommended
Depending on the geotechnical characteristics of the soil, the use of pile cages is suitable taking into account the following conditions.
- At the moment it is necessary to distribute the load transmitted by a structure in a shallow foundation.
- When the soils of your project have low-quality soils at the surface level, but with a great bearing capacity at a certain depth.
- At the time that the ground is subjected to considerable temperature variations due to shrinkage and swelling produced by expansive clays.
- When structures are located on the water or have a water table close to ground level.
- At the moment the foundations must be subjected to great tensile stresses.
Advantages of baskets or trusses in the construction process of piles
For the construction of piles “in situ” the use of baskets is very frequent in order to give a greater reinforcement to the pile, but they can also have the following advantages:
- It is in charge of guaranteeing the concentricity or shape of the pile and the excavation.
- If it is assembled properly as indicated in the plans, it guarantees better stability and rigidity.
- The baskets are responsible for distributing the steel in the best way throughout the pile.
- They optimize the costs that a project can have.
- It is in charge of optimizing the foundation time
5. Inserting the basket into the drilled well
After finishing the drilling of the well, an auxiliary crane is used, or in other cases it can be introduced with the same drilling equipment or depending on the dimensions manually. It is important that the basket is located at the correct level, taking into account the depth of the drilling and the final level in order to carry out the offset of the plate.
Tip of the basket for axial loads
When you need to perform axial loads, it is important that the pile cages have steel between 0.5% and 1% of their nominal area. If needed, rods can be used to serve as pokers to give it greater rigidity and ease the installation maneuver.
Read: How to Calculate Cubic Meter of Concrete
6. Ready-mix concrete is poured into the well
This is the last step in the construction process of piles and is carried out after having introduced the basket, for this it is important to use tremie pipe to the bottom of the excavation so that the concrete is introduced from the bottom to the beginning of the well raising and removing the pipe as it fills, at the same time displacing the polymer with a pump. Finally, it is important to remove the initial 30 centimeters of the concrete from the pile, because it is considered poor, it is important that it be removed using the overflow or settling technique.
These are the general aspects that you should know about the construction process of piles, so do not forget them so that your piles are well made, keep in mind that Cortequipos is a piling company that operates in Bogotá and all of Colombia and we are also trained to carry out this task.