At the end of 1955, the Leningrad Mining Institute was involved in the work of the Unipromed Institute to improve the development systems at copper mines in the Urals. The proposed article deals with one of the issues studied by the Institute. The work was carried out by Associate Professor N. N. Polyakov. N. N. Polyakov, Associate Professor E. Y. Makhno and the author of the article under the guidance of Prof. P. I. Gorodetsky. The design of the mobile support and flexible slab was developed jointly by Associate Professor E. Y. Makhno and the author, all laboratory experiments, observations at the mines and calculations were performed by the author of the article.