Surrounding Rock Mass Classification Study On Dawan Tunnel With Wulong-Shuijiang Section In XiangYu Highway

In last ten years, the constructions of roads, railways, hydraulic engineering, gas tunnels, as well as petroleum tunnels had an obviously development in China. Especially in the21th century, highway constructions entered a period of rapid development. With deeply development of Western strategy, highway construction is becoming the first task in a regional developing strategy, following a fast increasing on numbers and lengths with the highway tunnel. With gradually extending to the mountains region of many highways, there has been a series of super long, super large, and super deep tunnel projects associated with expanding of tunnel size and quantities. In process of tunnel construction, there has frequently encountered that wasn’t match the files of exploration on designing of tunnel surrounding rock classification with the actual construction of tunnel surrounding rock, as well as construction changing considerably. It has caused heavy losses to our state with the phenomenon of construction costs continues increasing, which also affecting the progress of projects.It has a great significance on correct classification of tunnel surrounding rock to safety construction, safety operation and construction investment. In recent years, a new expressway from route selection to construction plans delivered only sustained a year or so with the speeding up of expressway construction, and the duration of highway exploration design stage has shortened greatly. The exploration and design units are always using to a single method copied mechanically from norm of tunnel surrounding rock classification for completing a task, and hasn’t comprehensively study using a variety of methods on classification. Based on previous research results, DaWan Tunnel of Wulong-Shuijiang section in XiangYu Highway is proposed as a typical case in this paper, the author has deeply studied the system of tunnel surrounding rock classification, and comprehensively evaluated affecting factors of the classification of tunnel surrounding rock, which can guide design and construction, at the same time also can play the role to guide and help in exploration, design, construction and supervision in the areas of similar geological conditions highway tunnel.(1) Through summarizing and analyzing multiple indicators system method of surrounding rock classification, and inducing out the basic influence factors (such as stratum lithology, domination fault and weathering unloading degree etc.) and secondary influence factors (such as rock hardness, rock mass complete degree, rock mass structural plane characteristics, groundwater state and initial ground stress, etc) of surrounding rock classification.(2) Summarized the main industrial norm in country, the author think that surrounding rock mass classification in projects, tunnel classification in highway, tunnel classification in railway, and tunnel classification in hydraulic power engineering has a good guide function in practice, and can apply well in investigation and design stage. RMR classification and Q system classification, which now populating in the world, have a good guide function in construction stage.(3) For highway tunnel with complicate engineering geological condition in investigation stage, it is suitable to adopt multiple indicators comprehensive classification method. For linear tunnel with complicate engineering geological condition and large size, it is suitable to combine with the tunnel surrounding rock mass classification method in hydraulic power engineering. For linear tunnel with small size, it is suitable to combine with the tunnel surrounding rock mass classification method in railway.(4) Whether quantitative indicators from test or qualitative indicators from in-situ investigation, they can’t match with the practice because of working method, working experience, instrument and equipment,etc, so it is very importance that reasonable and accurate indicators of tunnel surrounding rock mass classification are determined based on comprehensive anlyses. The tunnel surrounding rock mass classification determined in in-site investigation stage can play good guide function in design stage, and reinforcement check and modification in time are necessary in construction stage.