Rock mass classification method in highway tunnel based on fuzzy analytic hierarchy process

A method of rock mass classification in highway tunnel based on fuzzy analytic hierarchy process(AHP) was established. AHP method was used to construct the hierarchy relationship with factors of rock mass and their hierrarchy structures was set up. The weight of every factor was computed based on the positive reciprocal matrix using fuzzy sets method. The evaluation criteria of every factor and rock mass classification were constituted. After all grades were acquired by means of geological investigations and mechanical experiment,the rating of rock mass was calculated according to grading synthetically by iterative logical arithmetic. The arithmetic flow of the method was put forward,and the proposed method was applied to Guankouya tunneling(44 sections) along with Changde—Zhangjiajie Highway in Hunan province. The results show that the determined results are in a good agreement with those of the actual rock mass. 43 sections by the proposed method are accorded with actual sections,but only 36 sections by RMR. The proposed method can overcome the limitation of fixed factors and fixed mode of grading existing in traditional methods,acquire the effect factors dynamically,minimize judgmental bias,provide a quantitative measure of rock mass,and make the result more acceptable to the engineering fact,which offers a new thought to the research of rock mass classification method in such engineering fields as highway tunnelling,slope and underground project.