Abstract:

To elucidate the reason behind failure of a karst tunnel structure after heavy rainfall, a geological survey, surface investigation, and water connectivity test is conducted for the Dabaoshan tunnel. The geological information and hydraulic connectivity characteristics are analyzed. A combination of an unmanned aerial vehicle flight and threedimensional(3D) geological modeling is introduced to construct a refined 3D simulation model based on topography, tunnel structure, and geological information. Furthermore, the law of structural internal force and deformation response during the sudden rise of the groundwater level after heavy rainfall is investigated. The results reveal the following: (1) The development of karst provides a good hydraulic channel for the downward runoff of rainwater, and the resulting rise in the groundwater level and sudden increase in the external water pressure after the rainstorm is the direct cause of the structural collapse. (2) The initial stress state of the tunnel in the left and right lines is different under the influence of the topography, and with the rise in the ground water level, the asymmetric increase in the external water pressure and internal force makes the difference in the tunnel stress more obvious. (3) The structural risk of overlimited compressive stress and low safety appears at the sidewall and arch foot of the high mountain side of the left tunnel when the groundwater level rises by 60 m, and it coincides with the actual disease characteristics, which verifies the feasibility and effectiveness of the simulation method.

Key words:  , highway tunnel, karst, lining failure, heavy rainfall, water connectivity test, threedimensional numerical simulation