Abstract: In view of the force-deformation incoordination problems of traditional anchor and cable in largely deformed roadway roof support system, a new type of lengthened bolt is invented. After a tensile test and mechanical analysis of traditional anchor, cable and new lengthened bolt and an analysis of the deformation and failure characteristics of surrounding rock in large deformation roadway roof, ,a support system for large deformation roadway roof called lengthened bolt coupling support system is devised. The constitutive models of lengthened bolt coupling support system and cable coupling support system are established and analyzed. The research result shows that when the roof deformation exceeds the maximum elongation of cable, the cable in the coupling support system reaches the elongation equilibrium and is broken earlier than the traditional bolt due to the low elongation, but lengthened and traditional bolt could coordinately support the surrounding rock of roof both in deformation and force aspects. Lengthened bolt could improve the self-loading performances of surrounding rock, and not only has a large amount of elongation, but ensures a strong supporting force. Lengthened bolt coupling support system has been successfully applied to the test area of 11031 in Zhaogu Mine. The deformation of new support program is 20% less than that of the ordinary program. Besides, time-cost decreases 33% from roadway excavation to a stable roof rock, and the subsidence speed turns to be much slower than that of an ordinary program.

Key words: lengthened bolt, support system, large deformation roadway, constitutive model