| Our country is very broad, aboat 70% of the land is mountain, the geography geology's condition is very complicated, and is the most wide area where the karst distribute exists in the word. In resent years along with the fast fierce development of science and techlology progress and the social productivity, our country's tunnel solution cavity dissolved to settle a technique to also get a homologous development. The solution cavity to influence a mian performance to the engineering of tunnel's deformation or bucking, usually cause the tunnel open to dig medium of the part collapse to fall, drop a piece, rockslide. Karst disaster is often encountered in tunnel construction in mountain area. This geological phenomenon existence has creatted serious threaten to the tunnel construction and operation. Today there is lack a profound and system study on the karst tunnel. Therefore, the systematic study of the impact of construction on the tunnel cave to explore the discipline to ensure the safety of tunnel construction in karst areas, improve predictability and karst tunnel work efficiency, reduce lava tunnel geological hazards is necessary.Relied on the Bai Zhi mountain tunnel, the paper summarized the domestic and foreign predecessor's research results, passing thorough research the solution cavity to the country rock's stability of tunnel, making sure regularities of distribution and of running about the stress field and the Tunnel Cave stability conditions, and obtained some useful conclusions.Comparing the results of stress fields by numerical Analysis, the main results obtained are as follows:â‘ The karst cave distributed around the location of the tunnel, the rock stability will decreased by the distance increased with the tunnel cave. Numerical calculations showed that when the cave at the top or left side of the tunnel, the spacing to 2 to 3 times of the cavity size, cavity effects on the stability of surrounding rock can be neglected.â‘¡The karst cave at or near the top of the tunnel have an influence to the vault and the rock near the vault.There is a negative correlation between the size of the karst cave and the sinking displacement, the larger the size of caves, the smaller sinking displacement. The distance increases have a little impact on the surrounding rock of the tunnel, when the karst cave at the left or the bottom of the main tunnel. The larger the radius of the karst cave wicth between the two tunnels is, the greater the impact on the surrounding rock.â‘¢The karst cave at the top of the tunnel have a little affect to the tunnel wall, and have a greater impact on the vault; The left side of the main tunnel cave and tunnel between the two tunnels on the tunnel cave major impact of the vertical tunnel in easily lead to bias phenomenon.Cave at the bottom of the tunnel, loaded easily lead to the bottom of the tunnel collapse, it should be the bottom of the cave Bearing Capacity.â‘£Paper application software to establish simulation model of MIDAS, Karst whole section of tunneling under the mechanical behavior of the construction.The results show:The construction method is both reasonable and feasible,during the construction of underground structure and the surrounding environment is not security risks.This project provides the basis for the smooth implementation and guidance for similar projects. |
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