Pile is in demand as the deep footing for various structures. For the bridge, we generally cast the bridge pier above the pile foundation. It supports the load by skin friction and the end bearing resistance. Different types of piles are categorized based on the material, loading type, and resistance type. In this post, we are going to discuss cast-in-situ concrete construction. There are the following stages of concrete pile construction,
- Inserting the casing
- Drilling of bore
- Clearing the bottom
- Inserting the reinforcement cage
- Chipping off
- Reinforcement for pile-cap
- Pire reinforcement
- concreting of pile-cap
Also read: design of pile, quality test of concrete
First of all, we try to align the bore machine over the center mark. After the alignment, we generally check level by spirit level. This process maintains the hole straight.
Inserting the casing
After marking the point, we first insert the casing. This casing supports the bore wall. Now, after this process, we can start the drilling of the bore.
Drilling of bore
We use rotary drill for drilling the bore, generally of 1.2 m dia in the case of the bridge pier. In this process, we keep flowing the bentonite solution. This solution keeps the wall stuck in a place and prevents it from falling. Before drilling, we generally perform the density test for bentonite, which should come around 1.
Clearing of bottom
After drilling process we perform the cleaning of bore hole. This process make concrete more effective.
Inserting the reinforcement of pile
We have to insert the reinforcement cage vertically into the bore hole. This is a very critical operation. As the weight of the reinforcement cage is higher and we have to maintain the proper spacing between reinforcement and the wall of the borehole.
Concreting of pile
Concreting is done through the tremie pipe method. Tremie pipe is shown in fig. Concreting is done from the bottom of the hole. As concrete is heavier than the water in concrete, it settles down. As concreting proceeds, impure water starts rising and finally comes out from the top of the bore hole. The minimum grade of concrete is M25, and the slump is about 110 to 140 mm.
After concreting, we allow it to cure for 28 days. After the sufficient curing period, the concrete pile is ready up to ground level. Now we excavate up to the cutoff level. We generally chip off all the concrete above this level. We call this process chipping of concrete. All concrete above the cut-off level has been chipped; only reinforcement remains there.
After chipping of concrete up to the cutoff level we generally level the surface. After leveling of surface we generally provide plain cement concrete. Above this, we cast the PCC concrete.
Reinforcement of pile-cap
As mentioned in the above point, reinforcement for pile-cap is being laid on the PCC. All top, bottom, side reinforcement according to the drawing is provided.
After the reinforcement of pile-cap we generally find out the center of pile-cap and make the reinforcement of pier of the bridge.
Concreting of pile-cap
After this process, we cast the pile-cap. After concreting we allow it to cure properly. Then start casting the pier of the bridge.
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