| With the continuous development of our country’s economy,the transportation enterprise constantly advancing,the constant improvement of infrastructure,more and more of the tunnel construction in karst area,tunnel construction in karst region after the monsoon rain,unicom’s latent cave around the tunnel and surface water supplement enough,easy to pose a threat to the safety of the tunnel structure.Therefore,it is of great significance to study the influence of latent karst caves on the safety of operating tunnels.Based on the Daping Tunnel Project of the two-lane expressway section from Ziyun to Wangmo,this paper studies the influence of the latent karst cave on the tunnel structure under the condition of heavy precipitation by model experiment and three-dimensional numerical simulation software analysis.The main contents and conclusions are as follows:(1)The causes and characteristics of the pipeline type latent karst caves are summarized,and it is analyzed that the infiltration of heavy rainfall is the main cause of tunnel disasters.(2)According to the similarity theory,the similarity ratio of the surrounding rock material and the secondary lining material in the model test was determined and the similar material was configured.The mechanical parameters of the surrounding rock and the secondary lining material were obtained through the test.The influence of water pressure on the tunnel structure is simulated by model test method when there is a pipeline type latent karst cave in the vault.The results show that with the increase of the water pressure on the vault,the internal force and stress of the vault increase in different degrees.When the external water pressure reaches 1.2MPa,cracks appear in the lining vault,the settlement value of the vault is 5.20 cm,and the inner stress value of the vault is 2.21 MPa.When the water pressure reaches 1.35 MPa,water leakage occurs in the vault,the settlement value of the vault is 6.04 cm,and the stress value of the inside of the vault is 2.35 MPa.(3)A three-dimensional numerical model was established to conduct numerical analysis on the model test conditions.The comparative analysis between the calculated results and the experimental results showed that most errors were within±5%,indicating the validity of the numerical simulation results.Numerical simulation method is used to further model and analyze the situation that the latent karst cave is located in other locations around the tunnel.When the 1.5m karst cave is located in the vault,the lining vault is the damage part and the damage water pressure value is1.2MPa.At this time,the lining safety factor is 0.97,the tensile stress is 2.489 MPa,and the failure occurs when the tensile strength exceeds 2.2MPa.When the 1.5m cave is located at the side wall,the side wall is the failure part,the water pressure value of failure is 1.5MPa,the safety factor is 0.67,and the tensile stress is 2.358 MPa,resulting in tensile failure.When the 1.5m karst cave is located at the bottom of the invert,the invert is the failure part,the failure water pressure value is 1.5MPa,the safety factor is 0.98,and the tensile stress is 2.305 MPa,resulting in tensile failure.With the increase of the size of the cave,the water pressure of the lining decreases gradually.(4)According to the morphological characteristics and relative position of the karst cave in Daping Tunnel,the safety regulation measures to ensure the safe operation of the tunnel are given. |
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