Study On Surrounding Rock Classification System Of Karst Tunnel

With the western development strategy,more and more tunnel be builded in karst area.However,the classification of surrounding rock is the basis of tunnel design and construction,It has very important position in tunnel project.But,the current surrounding rock classification method can't satisfy the need of tunnel surrounding rock classification in the karst area. Therefore it's very nesscessary to build the classification of karst tunnel surrounding rock system.This paper take the building Xunlingguan tunnel on the expressway from naxi to guizhou as the example,based on the previous reasearch results, by using the method of field geological investigation,math-physical and numerical simulation,analyze the traits of karst development.moreover,considering the effect of karst to the surrounding and supporting structure,using combination of qualitative index and quantitative index,select classifying index scientific and eatablish a set of systematic.This systematic aim at the surrounding rock classification and guiding construction karst tunnel.The main contents of this paper are as follow:①By Invested the engineering geological condition of tunnel area, analyze the main factors of karst development scale and shape,we find the characteristics of karst development.what's more,Summarize and analyze the karst development law of tunnel area.②By Summarized and compared the advantages and disadvantages of four methods Q-system,RMR-system, HC-system and BQ-system, that are commonly used by domestic and foreign scholar to the surrounding rock classification.,combined with the characteristics of specific project, determine the system of karst surrounding rock classification,put forward the index system of karst tunnel surrounding rock.③Study on the karstification level index. Based on the research of the karst development law of tunnel area,epurate the index that effect the karstification level and determine the weight of index by used analytics hierarchy process.④By Summarized research results of domestic and foreign scholar about the effect of karst to surrounding rock stability, considered the feature that most of cave are lateral and vertical cave,using Hoek-Brown strength emprical criterion, simulate the tunnel three-dimensional dynamic construction mechanics,analyze the effect of different distance lateral cave to the surrounding rock stability, Furthermore, determine the index that effect the surrounding rock stability. ⑤Study on the system of surrounding rock classification.based on the resrarch of the index of surrounding rock classification, easablish the quantitative table and mathematical model of the classification of karst tunnel surrounding rock system.And with the entrance region of Xunlingguan tunnel as a example,check the rationality and accuracy of the classification system.The system of karst tunnel surrounding rock not only be used to surrounding rock classification on karst area,but also referenced by other tunnels surrounding rock classification have special geological condition.