Study On The Safety And Environmental Protection Of The Construction Of Super Shallow Buried Arch Tunnel Under The Great Wall In Tourist Area

During the construction of the super shallow buried double-arch tunnel in the tourist area,the noise produced by the tunnel excavation,the "three wastes" and the formation deformation will inevitably have a certain degree of influence on the surrounding environment.Because of the complexity of the tourist area environment,the tunnel construction often inevitably passes through the existing buildings in the tourist area,and the formation deformation may threaten the safety of the existing buildings.Therefore,it is of great practical significance to study the influence of super shallow buried double-arch tunnel construction on the surrounding environment and buildings.On the basis of extensive research on domestic and foreign literature,based on theoretical analysis,on-site monitoring and numerical simulation,the influence of super shallow buried double-arch tunnel construction on the surrounding environment,the optimal selection of tunnel construction scheme and the influence of the Lao Longtou tunnel through the ancient Great Wall site on the stability of the Great Wall are studied systematically.Specific research and results are as follows:(1)The environmental assessment index system of the scenic area was established by selecting five indexes of noise pollution,dust pollution,solid waste pollution,waste water pollution and human landscape architecture in view of the characteristics of the impact on the surrounding environment of the super shallow buried double-arch tunnel in the tourist area.Using the game theory combination weighting method to empower the evaluation index,and correcting the shortcomings of the traditional Nemerow index method in the environmental assessment of scenic area,a model of environmental impact assessment of tunnel construction in tourist area is constructed.(2)In order to study the scientific and effective method of selecting the construction scheme of super shallow buried double-arch tunnel in tourist area,seven evaluation indexes,such as support strength,project schedule,project cost,operationcost and maximum surface settlement,are selected,and the evaluation index system of tunnel construction scheme selection is established.By using Mahalanobis distance and grey relational analysis to improve the TOPSIS,the optimal model of construction scheme for super shallow buried double-arch tunnel in tourist area is constructed.(3)Combining with the engineering practice of the ancient Great Wall under the Lao Longtou tunnel,Putting forward the Lao Longtou Great Wall deformation control standard,and adopting the field monitoring and numerical simulation method to reveal the variation law of the Great Wall settlement and inclination rate under the influence of tunnel construction.The results show that in the construction stage of Lao Longtou tunnel,the original support scheme can not guarantee the ancient Great Wall within the standard of safe deformation control,so it is necessary to add temporary inverted arch support and effective auxiliary strengthening measures.The final state of tunnel construction is not the maximum deformation state of the Great Wall.The excavation of different parts has different influence on the deformation of the Great Wall and the surface settlement,among which the excavation of parts 4 and8 is the key sequence of the largest deformation of the Lao Longtou Great Wall during the excavation process.The settlement of the left hole after the excavation is larger than that of the first right hole.