Discussion on Stability Analysis and Classification Method Improvement of Soft Red-Bed Rock Mass
Taking the first phase of the Tingzikou irrigation project(Section Ⅳ)as an engineering example,typical engineering geological conditions of small-diameter tunnel is selected.The engineering geological classification method,RMR method,and Q-system rock mass classification method are used to classify the stability of the surrounding rock of soft red-bed rock tunnel.This approach helps to avoid systematic bias caused by a single method,providing a more systematic understanding of the surrounding rock of the tunnel in this project.The applicability of each method is evaluated,and the classification indicators and problems emphasized during the classification process of each method are pointed out.It provides valuable technical references and ideas for improving engineering geological classification methods and establishing a specialized surrounding rock classification method for this project:(1)For small-diameter tunnel,the weight of intact soft rock strength indicators can be appropriately reduced;(2)For surrounding rocks without structural plane development,the deduction item of the structural plane occurrence and tunnel direction combination relationship can be appropriately reduced;(3)For the soft rock in this project that are sensitive to hydraulic properties,there is a significant difference in engineering properties between the dry state and the water-bearing state,and the engineering geological classification method underestimates the deterioration effect of soft rock after water-bearing,so the weight of groundwater indicators can be appropriately increased.(4)The influence of tunnel diameter can be incorporated into the scoring system,with a certain standard tunnel diameter as the zero-score item,and scores are added or deducted when exceeding this tunnel diameter range.Improving the engineering geological classification according to the above ideas will also be of high value for revising the specifications.
soft red-bed rockrock mass classificationrock mass stabilityindicator weight
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