Sduty On Stability Of Tunnel Surrounding Rock Based On Analysis Of Monitoring Data

The stability of tunnel surrounding rock has always been an important issue concerned by domestic and international engineering circles, Many experts and scholars have done lots of useful exploration and research on the stability of tunnel surrounding rock from theory to practice, and now we have achieved more significant results. However, due to the complexity of the tunnel project and the existing theory and identification method of the stability of tunnel surrounding rock is still not yet mature. At present, the theory and practice of the stability of tunnel surrounding rock are not disjointed in engineering practice, which mainly depends on the previous engineering experience and the feedback from the field monitoring measurement. Therefore, how to judge the stability of tunnel surrounding rock based on the field monitoring data and its standard that widely recognized is still an important subject today in the field of geotechnical engineering.In this paper, based on the Guantong Tunnel of Shitian Highway, with significant amounts of information of Argillaceous slate as the engineering background, and on the basis of collecting large number of field data and combining different construction methods, through monitoring of the surrounding rock deformation and combining with previous research experience, to systematically analysis and summary the deformation law of Guantong Tunnel and the relationship between the deformation of surrounding rock and construction conditions,and to put forward the control standard of the stability of Guantong Tunnel surrounding rock by using these laws. Besides, deformation characteristics and advantages and disadvantages of different construction methods are summarized, and technical points and deformation control measures in the construction of bench method are put forward. Finnally, by summarizing the common problems in the construction of the lower steps of the bench method, to discuss step excavation method and skip excavation method for the lower step of construction. The main research results are as follows:(1)The monitoring data of a large number of conventional deformation section and special working conditions are analyzed in lignt of the engineering geological condition and construction condition of the Guantong Tunnel, and the relationship between the deformation law of the surrounding rock and construction condition is summarized. The results of analysis indicate that the stability of tunnel surrounding rock is affected by the construction method and the progress of the construction.and the control standard of the stability of Guantong Tunnel surrounding rock is established which is suitable for the construction status of the tunnel.(2)According to combining with different construction methods and the stability of tunnel surrounding rock, the deformation characteristics of tunnel surrounding rock of different construction methods are analyzed. And by summing up the reasons of large deformation in three-bench method construction, deformation control measures in different situation and construction countermeasures are put forward.(3)The construction of the lower steps is an important step in the construction process of the bench method, by analysising the relationship between the deformation of the surrounding rock and excavation process indicate that the amount of deformation caused by excavation of the lower steps is an extremely important part(up to about 40% of the total deformation) of the total deformation of surrounding rock, and the construction of lower steps directly affects the safety of the tunnel construction and the closure time of the retaining structure and the construction speed of the tunnel. To solve this problem the construction method of the lower step is discussed combining with tunnel site construction, the step excavation method and skip excavation method is discussed which is suitable for lower bench excavation.