The BYS tunnel was established over a coal mine, and some parts extend through the mine’s old goaf. Chongqing Bayueshan (BYS) tunnel is an important length of highway engineering from Chongqing to Sichuan, China. Anasys,, UDEC, and 3DEC are mostly used numerical simulation software. Numerical simulation is currently the method that is used mostly in tunnel damage analysis. The elastic-plastic medium theory is often based on a hypothesis and simplified model, but it cannot reflect the actual geological and mining conditions, and its results are often significantly different from actual ones. The stochastic medium method is a semiempirical influence function, and it can be used to obtain reliable subsidence results with the parameters of field observation, but it lacks a reasonable explanation of deformation mechanisms. The first is based on the model of stochastic medium theory, the second on the theory of the elastic-plastic medium theory, and the third and most used is numerical simulation. There are mainly three major methods used to predict coal-mine subsidence of tunnels. In China, with rapid econiomic development in recent decades, numerous highways and railways have been established in which tunnels must pass through a coal-mining area or over old goafs. Mining-induced subsidence will cause deformation of the construction above a goaf or destruction. Underground mining can change rock’s original stress condition, and the rock mass will move to achieve a new balance. Several engineering suggestions for ways to maintain the tunnels are given in this paper, and the research provides a reference for safety evaluation for tunnels crossing over an old goaf. Poor geological conditions, water, and vehicle dynamic loads were also important factors that induced damage. The simulations further show that uneven horizontal displacement and subsidence were the major factors in inducing tunnel construction defects. The excavation led to increase in the tunnels’ stress concentration. The maximum subsidence of the left tunnel was 505 mm and that of the right tunnel was 512 mm.
The simulation results show that the subsidence of the ground surface increased annually. To evaluate the reasons for the damage, fast Lagrangian analysis of continua in three dimensions ( ) was used to simulate the underground coal-mine excavation yearly from 2012 to 2015. The tunnels have been damaged three times between 20. The tunnels were established crossing over the old goafs of a coal mine. The Bayueshan (BYS) tunnels are adjacent tunnels which comprise key engineering structures important for Yurong highway from Chongqing to Sichuan, China.
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