**2. The Soil-Steel Bridge**

The considered soil-steel bridge is a new one, built in 2017. It is a single-span arch structure, as shown in Figures 1 and 2. The steel shell is made from UltraCor, 9.5 mm thick, corrugated sheets, produced by ViaCon Polska Ltd. company ([36]) (Rydzyna near Leszno, Poland), which are shown in Figure 3. The corrugated sheets are connected to each other with bolts. S315MC steel was used to produce the shell. The bridge foundations are built of Franki piles. The UltraCor structure is covered by soil compacted in a way that its relative density is not less than 98% of the maximum density determined in the laboratory. In the close vicinity of steel sheets, the compaction is not less than 95%. The steel arc span length is 25.74 m, whereas the total length of the bridge equals 95.70 m. The arc sagitta equals 9.0 m. These basic dimension, characterizing the structure, are depicted in Figure 1.

The bridge carries the national road number 16 and crosses a path for animals and a road built for the purpose of road maintenance (refer to Figure 1).

It is worth to mention that due to the aforesaid dimensions (large total length) it may not be so obvious if this structure should be named as a bridge or a tunnel. Nevertheless, we claim that this is a bridge from the following reasons. The soil-steel structure is made of flexible corrugated sheets and there is no base slab below the service road. Moreover, according to the polish law, appropriate road signs need to be put at the tunnel entrance and its exit. As seen in Figures 1 and 2, there are no such signs. In addition, under the terms of the construction contract the structure was named as a bridge, which meets the definitions provided in the regulations.

**Figure 1.** Soil-steel bridge side-view taken in October 2019.

**Figure 2.** Close up of one of the bridge sides taken in October 2019.

**Figure 3.** The corrugated steel sheets and their bolt connections.
