Quantitative Classification Method Of Surrounding Rockand Applied Research Of Upper Soft And Lower Hard Stratum Tunnel

Tunnel section is located in upper-soft lower-hard strata and structural plane between hard and soft strata,easy to cause surface subsidence,instability of surrounding rock and supporting damage,etc.Currently lack this kind of design method of tunnel,theoretical research seriously lagging behind the need of engineering practice,surrounding rock classification method is theoretical basis of this kind of tunnel design,construction and operation safety.The project relies on project supported by National Natural Science Foundation of China,applying the comprehensive research methods of combination of relevant basic theory,numerical simulation and engineering practice,combined closely with upper-soft lower-hard strata characteristics and construction progress,to put forward quantitative classification indexes of surrounding rock of upper-soft lower-hard strata tunnel based on Safety factor indicators.For upper-soft lower-hard strata tunnel design,construction,maintenance,and disaster prevention and control to provide theoretical foundation and scientific method,to enrich and develop the theory on tunnel engineering in China has very important scientific significance and practical significance.The primary coverage and the achievement obtained studied in this text have the following points:(1)This article makes a statistical analysis of surrounding rock classification method and classification index used commonly in homogeneous formation at home and abroad presently,and points out the existing deficiency when traditional classification method and classification index are used in the the special kind of upper soft and lower hard stratum,then on this base,to put forward quantitative classification index of surrounding rock of upper soft and lower hard stratum tunnel can be considered that with not only sundry geological factor and engineering factor but Strict theoretical significance and practical significance —— minimum stable safety factor at surrounding rock without supporting.(2)Using MIDAS/GTS finite element software,to study and put forward surrounding rock classification standard of homogeneous formation tunnel based on the safety factor by means of finite element numerical analysis theory and strength reduction method,and some research and analysis are carried out on tunnel damage evolution law of homogeneous formation and upper soft and lower hard stratum targetedly,to find two kinds of stratum have similar laws: stability of surrounding rock becomes worse when the buried depth is larger in shallow buried tunne,self-stabilization capacity of surrounding rock has little relationship with buried depth in deep buried tunne.(3)The self-stabilization of surrounding rock with different strata combination tunnel has been studied when soft and hard stratum interface position changes,to find that safety factor is also different when tunnel excavation site is different,self-stabilization curve of surrounding rock presents five stages of change,the influence of the interface on the stability of surrounding rock is only related to the tunnel span,not related to buried depth,thus to obtain that theoretical standard for surrounding rock quantitative classification of upper soft and lower hard stratum tunnel.(4)Aiming at the combination of upper soft stratum,interface position,lower hard stratum,to establish quantitative classification method of surrounding rock of upper soft and lower hard stratum tunnel,and the research results are applied to the case study in the mine tunnel of Fuzhou Metro Line 1.Verified by engineering example,to show that reliability and practicability of quantitative classification method of surrounding rock of upper soft and lower hard stratum tunnel that the text puts forward.