Research On Sub-classification Method Of Weak Surrounding Rock In Hydraulic Tunnel And Its Engineering Applicatio

Based on the engineering geological classification of surrounding rock in ’ Code for engineering geological investigation of water conservancy and hydropower ’(GB50487-2008),this paper studies the sub-classification method and sub-classification of weak surrounding rock in hydraulic tunnel,in which the surrounding rock types are mainly for Class III,IV and V surrounding rock.Based on the preliminary classification and detailed classification of surrounding rock by HC method,the indexes of sub-classification of surrounding rock are studied,and the sub-classification indexes of preliminary classification and detailed classification of surrounding rock are established.Among them,three sub-classification indexes of preliminary classification are determined,which are rock type,rock mass structure type and others.On the basis of the five indexes of detailed classification of surrounding rock,the over-limit correction index is added according to the limited conditions,which constitutes six sub-classification indexes of detailed classification of surrounding rock,which are rock strength,rock mass integrity,structural plane state,groundwater state,main structural plane occurrence and over-limit correction index.Based on the sub-classification index,the sub-classification method of surrounding rock classification is studied.Because the classification indexes of the preliminary classification are all qualitative indexes,the discriminant function and the sub-classification standard of the prelimin ary classification of III,IV and V surrounding rock are established by using the quantitative theory II and Kmeans clustering analysis.The III surrounding rock is divided into three sub-categories,namely III1,III2 and III3.Class IV surrounding rock is divided into three sub-categories,namely IV1,IV2,IV3;the type V surrounding rock is divided into two sub-categories,namely V1 and V2.Based on the CRITIC weight method and Kmeans clustering algorithm,a CRITIC-multi-cycle Kmeans + +discriminant classification method for sub-classification of detailed classification of surrounding rock is proposed.Using the results of sub-classification of preliminary classification,the clustering analysis is carried out by optimizing the initial center,eliminatin g the influence of different initial centers on the clustering results,and taking the contour coefficient as the evaluation index.The boundary of sub-classification of III,IV and V types of surrounding rock is optimized by the lowest misjudgment rate method,and the influence of ground stress on surrounding rock is considered.