Focusing the lack of experience regarding surrounding rock deformation characteristics, construction methods and process arrangement for the shallow buried super-large span small clear distance subway station crossing sandstone mudstone interbedded inclined stratum when the of alternating sandstone and mudstone, this study takes the Ciqikou Station project on Chongqing Rail Line 27 as a case study, the different stratum inclination conditions under the influence of the excavation sequence and method of the stability of the station surrounding rock are explored. The preferred construction method of the shallow buried super-large span small clearance subway station crossing sandstone mudstone interbedded stratum is proposed. The results show that: In sandstone inclined interbedded strata, the inclination angle of 40° is the critical threshold of construction sequence, when the inclination angle of the strata is less than 40°, the side chamber passing through the inclined strata should be excavated first; When the inclination angle is more than 40°, excavating the side chamber away from the inclined strata can significantly reduce the deformation of the surrounding rock and settlement, among which, the double sidewall guide pit method as the preferred method can significantly reduce the deformation of the surrounding rock compared to the CRD method, and the CRD method can also significantly reduce the deformation of the surrounding rock. Optimizing the support structure force, which has good applicability under the project conditions.

The stability of the surrounding rock and outburst prevention thickness of karst tunnel are not invariable. Still, it is greatly affected by the size of karst tunnel, and the influence law and mechanism are not clear. Based on FLAC3D numerical simulation method, the three-dimensional calculation model of tunnel karst cave and the surrounding rock energy visualization program are constructed, and the influence of karst cave size on the mechanical response and energy evolution law of tunnel surrounding rock is systematically studied. The results show that: The numerical results are in good agreement with the actual monitoring results, which verifies the reliability of the model; After tunnel excavation, the ratio of karst cave radius to tunnel span (T) has a great influence on the stress of surrounding rock of tunnel, and the degree of tensile stress concentration is positively correlated with the size of karst cave; With the increase of T, the distribution range of displacement is expanded, but the stress is released through the buffer space, resulting in the decrease of the maximum settlement and uplift value; The large karst cave makes the energy release range expand but the intensity decreases, indicating that the stress disturbance is more dispersed; With the increase of T, the minimum outburst prevention layer thickness gradually increases, but the increase amplitude gradually decreases, and gradually tends to saturation. The research results can provide theoretical reference for tunnel stability control in karst area.