Geological mapping is relatively simple; however, in rock tunnels and underground caverns it is often an issue, essentially because of a limited time frame in industrial projects as well as difficult working conditions (humidity, dust, low lighting, accessibility, height). Because of such conditions, geological maps of the face or walls performed immediately the blast sequence may become totally useless for tunnel construction, especially in fractured rock masses. Nevertheless, a reliable mapping of the discontinuities is essential for stability and permeability/grouting purpose. The objective is the workshop is twofold: i) to demonstrate the interest of structural geology for the performing of quick and reliable mapping, adapted to fractured rock masses and ii) to provide simple but efficient structural tools to do so, that can be easily applied in industrial projects. Several examples from tunnels and caverns in China, Japan, India will be used all along the workshop.