A Classification Method Of Surrounding Rock Mass Quality For Tunnel Excavated By Roadheader Based On Fuzzy Theory

Surrounding rock quality grading is an important basis for adaptability evaluation of the tunnel milling excavation method.The adaptability of this construction method is very important for the construction method selection,equipment selection,construction schedule and construction cost of tunnel excavation with roadheader.Therefore,it is necessary to consider the adaptability of the tunnel milling excavation method to study the quality classification of surrounding rock,as well as it has important theoretical and practical significance.For this reason,based on discussing the influencing factors of the tunnel milling excavation method,the fuzzy theory will be used to study the quality classification of tunnel surrounding rock from the perspective of accuracy and practicality.Firstly,selecting the instantaneous cutting rate as the quantitative index of surrounding rock grading standard based on the instantaneous cutting rate,which can comprehensively reflect the influence of engineering geological condition and mechanical equipment affecting factors to the tunnel excavation with roadheader.Then,considering the fuzzy uncertainty of its influence,a fuzzy c-means clustering analysis method is used to classify a large number of measured values of instantaneous cutting rate.Based on this,the surrounding rock grading standard for tunnel milling excavation method was established.Secondly,the influence factors of tunnel milling excavation method,their fuzzy and hierarchical characteristics to the classification result of surrounding rock quality were discussed.Then,a three-stage fuzzy synthetic judgment model to classify surrounding rock quality for tunnel excavation with roadheader was suggested.Meanwhile,the methods to determine the membership degrees and weight vectors of continuous and discrete evaluation indexes were proposed.And the corresponding strategies were also submitted to reduce the subjectivity when determining the membership degrees and weight vectors.This model considers factors comprehensively,and minimizes subjective interference as much as possible to ensure that the model has good operability.Thirdly,the uniaxial compressive strength of rock,the quality index of rock mass,and the cutting power of roadheader are selected as the grading indicators,which are the most important factors of both rock lithological conditions and construction equipments,as well as they can be obtained through routine testing methods.Thus,it make the surrounding rock quality grading model more practical.Then,considering the fuzzy uncertainties of the grading indicators,a fuzzy inference method that can reflect the nonlinear relationship between grading indicators and surrounding rock quality grades is introduced.Meanwhile,a classification model for surrounding rock quality was proposed.The parameters of this model are simple and easy to obtain,and make maximum use of existing engineering measured data or engineering experience to ensure that the model has good practicality and rationality.Finally,through the analysis of two engineering examples,it shows that the two models of surrounding rock quality established in this paper all have certain rationality and feasibility.