Abstract: The phenomenon of floor heave is common in highspeed railway tunnels in the argillaceous limestone strata. Hence, a case study is conducted on the ZJY tunnel of the Xi′anChengdu highspeed railway to provide theoretical guidance and data support for floor heave treatment. Briefly, the distribution characteristics of the tunnel floor load and its impact on the tunnel structure are examined by analyzing the tunnel monitoring data, inverted arch filling, track plate structure deformation, floor′s surrounding rock deformation, and inverted arch structure stress. Further, by analyzing the initial and excavation stress fields of the tunnel and based on the identification of the composition and microstructure of the rock mass material and expansion and creep experiments, the physical and mechanical zoning of the surrounding rock layers of the tunnel is proposed; additionally, a layered differential creep model of the tunnel is established using the stress field as a link. The research results of this study are as follows: (1) Tunnel floor heave is caused by rock creep. (2) After tunnel excavation, numerous continuous creeps of microcrystalline calcite occurred within 15 m near the inverted arch in the influence area of stress redistribution at the tunnel floor, resulting in the deformation of the floor heave. (3) The model shows that before tunnel excavation, there existed an uneven initial stress field due to differences in the lithology of strata. After tunnel excavation, multiple bearing zones were formed at different depths below the inverted arch and creep deformation was experienced by rock masses with different lithologies in the deep and shallow bearing zones.(4) The creep phenomenon occurred in the strata before tunnel excavation, and the median of the horizontal differential stress in the same lithological formation was reduced by more than 25% compared with its maximum value. (5) The creep composition of the argillaceous limestone strata after tunnel excavation is up to approximately 80%. The differential stress threshold for creep is approximately 5 MPa(lower limit). (6) The creep test shows that the creep differential stress peak value may be approximately 15 MPa(upper limit); the peak value position is approximately 0.5 m below the tunnel′s inverted arch (equivalent to circle). The peak contact stress of the inverted arch is speculated to be approximately 1 MPa.

Key words: highspeed railway tunnel, creep, floor heave, load, inverted arch, argillaceous limestone