Cast-in-situ piles are a type of deep foundation used to support structures by transferring loads to deeper soil layers. They are created by drilling a hole into the ground and then filling it with concrete, which hardens to form a strong, stable pile. This method is particularly useful in areas with challenging soil conditions. The construction of cast-in-situ piles allows for flexibility in design and can accommodate various load requirements. They are often used in large construction projects, such as bridges and high-rise buildings, where strong foundations are essential for stability and safety.