| Karst is one of the common geological disasters in tunnel construction in anhui mountain area,which seriously threatens the safety of tunnel construction and operation.At present,although a series of research achievements have been made on the influence of karst on mountain tunnels at home and abroad,few researches have been carried out on the hydrology and engineering geology characteristics of karst tunnels in anhui mountains.Therefore,the research of this paper has important theoretical significance and application value to solve the hidden danger of anhui mountain tunnel safetyPapers in anhui province with weeds huang high-speed fog ridge,head of the engineering background of highway tunnel,the numerical simulation and field measurement,the method of combining analysis of karst cave of big section highway tunnel surrounding rock stability,the influence of karst cave and safe distance between tunnel,based on the measured deformation law of surrounding rock of the tunnel are studied,obtained the main research results in the paper are as follows:(1)Based on the actual working conditions,the deformation of tunnel surrounding rock is numerically analyzed.The results show that the cave is located 20m above the tunnel,the final settlement value of the tunnel vault is 4.6mm,the final uplift value of the invert bottom is 5.5mm,the deformation of the left and right sides of the tunnel arch waist is symmetrically distributed,and the maximum horizontal displacement is 2.3mm.The calculated results are verified by in-situ monitoring results of surrounding rock deformation。(2)Numerical analysis shows that the larger the span of the top cavern is,the closer it is to the tunnel,the more obvious the unloading effect of the cavern is,and the smaller the deformation of surrounding rock is;The existence of cavern will cause the stress concentration of surrounding rock near the cavern.The larger the cavern span is,the closer it is to the tunnel,the more obvious the stress growth is.When the value exceeds the compressive strength of concrete,the lining of the side will be damaged.The existence of cave will promote the development of plastic zone between cave and tunnel.The larger the cave span is,the closer it is to the tunnel,the more significant the plastic zone develops.When the cave span is greater than 6m and the distance from the tunnel is less than 4m,the plastic zone is connected.(3)Based on the research method combining numerical simulation and orthogonal experiment,the safe distance between cave and tunnel is obtained,and the influence degree of cave span,height-span ratio,lateral pressure coefficient and surrounding rock level on tunnel excavation is analyzed by factor analysis.The results show that the span of karst cave has the most obvious effect on the stability of surrounding rock,and the ratio of height to span has the weakest effect.Finally,the empirical formula of the safe thickness of karst cave from the tunnel in the upper,lower and side directions is fitted.(4)The comparative analysis shows that the effect of karst caves in different directions on the stability of surrounding rock is basically the same as that of overlying karst caves,and the effect order is lateral karst caves>lower karst caves>top karst caves.(5)By measuring the surrounding rock measurement points after the construction of Wulingtou highway tunnel,the settlement of the vault and the convergence deformation of the arch waist after the excavation of the surrounding rock are revealed,and combined with the field conditions,the optimal construction time of the secondary lining is determined.Figure 69 table 25 reference 64... |
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