Abstract: Abstract: The combustion properties of the sheath layer materials of fire-resistant cables and common cables were analyzed via oxygen index （LOI） tester, vertical combustion tester and radiation cone. Combined with cable tunnel model test, the influence of the quantity of cables and laying spacing on the combustion properties of two kinds of cables were investigated. The results show that the LOI value of the sheath layer materials of common cables is 25.5%, and it passes the vertical combustion V-0 rating, and there is obvious shrinkage curl phenomenon during the combustion process, it can not effectively protect the internal core material. The LOI of fire-resistant cable is 34.5%, and it can form a dense expanded carbon layer to protect the internal core structure effectively during the burning process. Cable burning test shows that the fire hazard of cables increases gradually with the increase of cable laying quantity and decreases gradually with the increase of cable laying spacing, among which the fire hazard of cables is the lowest when the cable laying spacing is 2 times of the cable diameter. Compared to the tight arrangement, the average mass loss of fire-resistant cables and common cables are reduced by 87.1% and 97.6% respectively, and the average char length was reduced by 92.6% and 92.9%, respectively. In addition, compared with fire-resistant cables, the fire hazard of common cables is more influenced by the quantity and spacing of cable laying.

Key words: Key words: fire-resistant cable, common cable, laying quantity, laying spacing, combustion properties