Study on the effect of creep of surrounding rock on the basement uplift of high-speed railway tunnel in diatomite stratum

The objective of this study is to investigate the long-term stability of high-speed rail tunnel basements in diatomite stratum. A series of experiments that included scanning electron microscopy, X-ray diffraction, and creep tests of diatomite were carried out to investigate its microscopic mechanism, chemical composition, and mineral composition. The Burgers model was employed to reveal and describe the creep and deformation characteristics of diatomite. Additionally, the deformation characteristics of the tunnel basement in diatomite stratum under different conditions were investigated using FLAC3D finite-difference software. The results show that different diatomites contain a large number of disc-shaped diatomites and cylindrical diatomites, which are composed of complete diatomites, diatomite fragments, and clay minerals. Under the same load, the creep deformation of white diatomite and blue diatomite with increasing saturation shows the trend of decreasing and then increasing. The deformation of tunnel basement uplift in diatomite stratum with the increase of time under different conditions exhibits a law of change characterized by a rapid rise, attenuation, and subsequent tendency towards stability. The long-term deformation of the stratum 1 m under the tunnel basement and below the center of the tunnel basement (up to the model boundary) is in the order of high saturation > low saturation > saturation, white diatomite > blue diatomite, and full coverage > semi-full coverage > under coverage. The research results can be an important reference for the geotechnical stability research of diatomite affected by the creep effect.