Abstract: In order to test the effect of fire prevention measures in the middle joint area of the actual tunnel, and further optimize the configuration, a cable tunnel to be put into operation was used to conduct physical fire test. The ignition device and data acquisition system were designed and applied in this paper. The fire development in the intermediate joint area was analyzed by monitoring images and data. Then the fire prevention and extinguishment effects under different configurations were tested and analyzed. The results show that the combustion of the simulated intermediate joint under the breakdown and fracture fault has high temperature and is easy to produce dripping melt. Under the existing protective measures, the cables around the faulty connector may still be damaged. The optimized configuration measures are as follows: The upper and lower layers of the intermediate joint area shall be equipped with fire barriers; A 4 kg superfine dry powder fire extinguishing device shall be installed at the top support where the intermediate connector is located and 1 m from both sides of the cable connector centerline; Wrap the cable within 4 meters on both sides of the cable intermediate joint with fireproof tape, which can effectively prevent the fire in the intermediate joint area.

Key words: cable tunnel fire, intermediate joint failure, physical fire test, fire prevention effect