Computer dynamic simulation analysis of the setting mode of buffer layer in tunnel

In recent years, earthquakes happened frequently throughout the world resulting in serious damage to a large number of tunnels and underground structures, which brings great significance to the study of aseismatic technology. Setting a buffer layer on tunnel structures is an effective method to reduce the dynamic response of lining structure. However, the buffer layer is impacted by some factors, such as setting mode, design parameters and construction conditions, so it is seldom used. Aiming at exploring its damping mechanism and efficiency of the buffer layer in tunnels with different setting modes, the computer aided simulations of earthquake dynamics was presented in this paper. On the basis of computation and analysis, a new setting mode of buffer layer, namely ‘rock - primary support - buffer layer - the second lining’ mode, is put forward then. And the in-depth studies on its damping effect, material selection, and thickness design and application scope were also carried out by using the three-dimensional dynamics finite difference technique. The results show that the new buffer layer mode can significantly reduce the seismic dynamic response of the second lining, especially when the thickness of the buffer layer of soft latex is 10 ~ 20cm, the peak dynamic stress of the second lining will be reduced up to 50% ~ 80%, and that the stress state is also efficiently improved, which can reduce or avoid severe earthquake damages to the second lining. As compared with the conventional ‘rock - buffer layer - primary support - second lining’ mode, the new mode is more suitable for NATM used in tunnel construction projects, and its construction is convenient and its cost is lower. Meanwhile, this paper provides a scientific basis for the design and construction of anti-shock and shock absorption tunnels or underground engineering in high-intensity earthquake areas.