At first glance, it seems that the pile length calculated in the design should always be sufficient. But in practice, things are a little different. Soil is a capricious material: in one place it's dense loam, while two meters away it's quicksand or peat. Therefore, when driving the pile, you have to adapt to the actual situation. The main reasons for extending piles are: 1. Not reaching the solid soil layer. When driving, the operator feels that the pile still moves easily, indicating that there is no supporting layer yet. If left untreated, the foundation may "wander" or settle. 2. Elevation differences on the site. On slopes, lower piles must be longer to ensure the foundation pad is level. 3. Drilling or calculation errors. Sometimes the designer failed to take into account soil characteristics, or site conditions have changed due to rain, backfill, or machinery use...