Over-break/shortbreak Control Technology for and Cost Analysis on Rock Tunnels Constructed by Drilling and Blasting Method:Case Study on Tunnels on Jiujiang-Ruichang Highway

The state-of-art of overbreak/shortbreak in tunneling is presented,the causes for overbreak/shortbreak are analyzed,and the influences of overbreak/shortbreak on the tunneling cost are described,so as to reduce the cost induced by overbreak/shortbreak of rock tunnels constructed by drilling and blasting method and to improve the qualification rate of tunnel excavation.Effective overbreak/shortbreak control technologies are determined on basis of investigations and trials.After these technologies are applied,the average qualification rate in tunnel excavation has been raised from 67.4% to 83.9%,and the economic efficiency has been improved by 49.9%,which demonstrates that the technologies applied are effective.The paper can provide reference for similar projects in the future.