What equipment design allows the bucket to push up from below the excavation?

The power shovel is designed to push up from below the excavation due to its specific mechanism and operational capabilities. It typically features a bucket attached to a boom that moves in an upward direction to lift material out of the excavation site. When the bucket is positioned below the ground level, the power shovel can engage the material and then lift and swing it to deposit it elsewhere, making it particularly effective for deep excavations and heavy lifting tasks.

This design is particularly advantageous for moving bulk material and for operations that require a significant lifting capacity, as the power shovel can operate continuously in a manner that utilizes gravity and mechanical advantage to effectively engage materials below the surface.

In contrast, the other equipment types mentioned operate based on different mechanics and principles. The backhoe digs and lifts soil primarily using a bucket that scoops and pulls material toward itself rather than pushing from below. The dragline is also designed for excavating from a distance, operating with a bucket that is dragged horizontally before being lifted, while the earth auger is primarily a drilling device designed to bore into the ground rather than push material upwards. Thus, the power shovel is distinct in its ability to push up from beneath the excavation site, making it the correct answer for this question.