【Haichuan Civil Engineering Issue】What is this for? Is it to infuse liquid into the foundation?

No, this is actually pretty much the same as intravenous infusion

With the large-scale development of high-rise buildings in our country and the increasing demands for urban environmental protection, more and more construction projects are adopting bored cast-in-place piles as engineering piles. Bored cast-in-place piles have advantages such as suitability for various geological conditions, a wide range of pile diameters and lengths, as well as low noise and vibration levels. However, due to factors such as sediment at the bottom of the pile, mud layer on the side of the pile, relaxation of the soil around the pile, and rebound of the soil layer at the pile tip, the quality of these piles can vary significantly; their bearing capacity is not very stable, and the cost of constructing pile foundations is high. To improve the bearing capacity of single piles, reduce construction costs, and minimize variations in pile quality, the post-grouting technique for cast-in-place piles has been gradually adopted and promoted. Its effectiveness in enhancing the bearing capacity of drilled cast-in-place piles and reducing pile foundation settlement has been widely recognized.