Lining Diseases Classification And Safety Status Grading Research Of Beijing Subway Tunnels

Beijing subway tunnel has entered into a new period,in which both new constructions and maintenance are executing.The earlier constructions of the tunnel lining has showed a large number of different forms of visible diseases.Based on extensive materials,through field testing,theoretical analysis and numerical calculation,the statistical analysis of the lining quality flaws and the distribution and mechanism have been done.And on the basis of the statistics,the lining structure safety grading is studied.The main research work and conclusions are as follows:(1)For Beijing metro line 1,line 6,line 10 and airport line,and many other lines of 18 intervals,statistics of six kinds of diseases including lining crack,water leakage,lining deterioration,lining void,lining structure aberrance,lining concrete layer peeling off have been done,which involves a total of 18 disease indexes such as the crack length,width,the seepage status,seepage position.And on the basis of these indexes,the overall index system of safety state evaluation has been established.(2)The concept of the main disease has been brought up.A total of 12 intervals of line 1,2,5,6,7,9 and 10 with typical diseases were selected.Based on the domestic and foreign existing specifications and materials on the classification of tunnel lining disease both,"extremely serious diseases" statistics of the 12 intervals were studied.Based on the corresponding analysis model in SPSS,the corresponding relationship between disease indexes and disease range was found,and the main diseases of lining structure are crack,lining infiltration,and lining void.(3)Based on the domestic and foreign existing safety status dividing methods of lining structure,a four-level division method has been brought up.The variation law of lining bending moment and axial force along with the enlargement of void range has been analyzed.Taking the change of concrete safety factor as reference,the position and lateral width of the lining voids are taken as variables to determine the safety level of the lining structure.(4)Based on the less rainy period leakage of the lining,taking the diameter of the steel bar in the water seepage positions and the thickness of the protection layer of the seepage positions as the variables,the change of the main tensile stress of the concrete in the protective layer as the criterion,the safety status of the four-level lining structure related to the seepage disease has been established.(5)Taking the concrete safety factor and the crack tip stability coefficient as criteria,the crack location and the crack depth in the lining as variables,the safety status of the four-level lining structure related to the crack disease has been established.(6)The above safety status grading methods have been successfully applied on the lining structure of Beijing metro line 6 CheGong Zhuang—White Stone Bridge South interval and line 10 ZhiChunLi—ZhiChunLu interval.The final comprehensive evaluation of CheGong Zhuang—White Stone Bridge South interval is in the level of B3,which means extremely serious,and line 10 ZhiChunLi—ZhiChunLu interval is in the level of B2,which means serious,and the corresponding prevention and control measures of different lining safety levels have been brought up.