Rock Refinement Classification Research And Application Of Qingdao Subway Tunnel Construction Phase

With the continuous development of the national economy and city urbanization, metro is becoming the best choice to solve the problem of traffic jams. Qingdao metro tunnel is excavated with shallow excavation method. It’s confronted with complicated engineering geological conditions that base rock surface has sharp ups and downs, rotten rock has a wide range of engineering behavior, layer where the subway tunnel passes through is made up of soil and rock, and so on. Correct classification of rock is the most important key to underground engineering design or to develop a reasonable construction program. It is an important parameter for evaluating the stability of surrounding rock, and also the important basis for chamber support program design and construction process to determine. To guide metro construction well, the paper will try to set up subdividing surrounding rock classification systems that is applied to metro tunnel of construction stage, basing on the background of Qingdao metro project. The research progress will adopt theoretical analysis, numerical computation and site test, basing on the individual geological environment of soft rocks in Qingdao. The core research contents and conclusions are as follow:(1) Study of the tunnel surrounding rock classification refinement criteria of the construction phase. Through simulation experiment which aiming at buried depth of self-sustaining of surrounding rock, the paper does some numerical experiments by taking different combinations between the level of rock completeness and the hardness degree of rock, finding the different level of self-sustaining of surrounding rock in different buried depth and different combinations. According to that research results, three, four and five level of surrounding rocks are divided into two, three and three subclasses accordingly.(2) Selecting rock hardness, rock integrity and groundwater status, the surrounding rock sub-grade level of the coefficient of determination and the determination value equation are calculated by using number theory, and the system of the tunnel surrounding rock sub-level segmentation of the construction phase is established.(3) Surrounding rock classification systems, aiming at construction stage, has been successfully applied to Qingdao metro. Through this systems and information construction, the construction period of relevant projects are shorten and deformation is controlled.