underground tunnel segment 3d model

Create a clean, modular 3D model of a straight Berlin U8 underground tunnel segment. Geometry: - Straight tunnel segment, exactly 10 meters long - Rectangular box-shaped tunnel cross-section - Minimum interior width: 20 meters - Enough open interior space for two parallel railway tracks - No railway tracks, no rails, no sleepers - Flat concrete floor - Flat vertical side walls - Flat concrete ceiling - Open at both ends - Constant rectangular cross-section along the full 10 meter length - No curves - No stations or platforms - No pillars in the interior Style: - Berlin underground / U-Bahn infrastructure - Functional reinforced-concrete tunnel construction - Raw grey concrete surfaces - Slight realistic concrete roughness and subtle construction seams - No decorative elements 3D requirements: - Real-world metric scale - Modular tunnel element designed to connect seamlessly to identical tunnel pieces - Perfectly straight and symmetrical - Clean topology - Simple geometry - Waterti