Small variation of annual temperature in deep tunnel can produce annual variation in tilt and strain

In this paper, finite element method (FEM) of axisymmetric linear elastic model has been used to calculate the tilt and strain induced by small annual temperature variations in a deep tunnel. The results show that even if the amplitude of the annual variation meets the construction standard of seismic station issued by China Earthquake Administration (the annual temperature variation amplitude in the tunnel is no more than 0.5 °C), a small annual temperature variation of amplitude just 0.2 °C in the tunnel would produce 10⁻⁷ rad changes in tilt and 10⁻⁷ changes in strain. Especially, at the end and the corner of the tunnel, changes of tilt and strain can be even larger. Therefore, in the future, it is an important task to reduce the annual temperature variation in the tunnel as far as possible. Within the tunnel, for both baseline instrument and pendulum instrument, the modeling suggests ways of construction of the tunnel and installation of the instrument to decrease the influence of the annual temperature variation. Foundation item: China Earthquake Administration Sector Fund (2008419077) and Knowledge Innovation Program of the Chinese Academy of Sciences (kzcx2-yw-123).