Improved Surrounding Rock Classification Method for the Middle Rock Pillar of a Small Clear-Distance Tunnel

In tunnel design and construction, proper accurate classification of rock surrounding tunnels is needed to ensure construction safety, guarantee quality, reduce project costs. With rapid urbanization, numerous small clear-distance have been constructed in dense urban road networks. Compared with ordinarily separated tunnels, the scale difficulty are greater, requirements for accordingly higher. A an super large complex underground interchange hub Xiamen Haicang Evacuation Channel was selected as background, method middle pillar a presented based on general standard rocks. Based geometric, physical, mechanical factors pillar, six indices affecting stability quality were selected, index system established from two dimensions basic auxiliary indices. The scored using scoring method, different grades divided according scores. applied assessment which provided basis on-site proved accuracy superiority improved standard. newly can provide reference selecting correct supporting structure type tunnels.