At present, jet-grouted horizontal waterproof curtain reinforcement has become an essential method for deep foundation pit groundwater control. However, there is still a lack of an effective theoretical calculation method for horizontal waterproof curtain reinforcement, and there is little research on the seepage laws of foundation pits under different horizontal waterproof curtain conditions. Based on Darcy’s seepage theory, theoretical analysis models of deep foundation pit seepage were established considering the effect of a horizontal curtain in a highly permeable formation. Through the established models, the calculation method of the water inflow and the water pressure under the condition of a horizontal curtain was derived. Then through indoor tests, the reliability of the theoretical calculation method was verified. Furthermore, the established theoretical calculation method is used to analyze the influence of various factors on the water inflow and the water pressure, such as the ratio of hydraulic conductivity of the horizontal curtain to surrounding soil, thickness, and reinforcement position of the horizontal curtain. It is found that the hydraulic conductivity ratio has the most significant influence on the seepage characteristics of the foundation pit. Finally, the design method was applied to an example of the horizontal waterproof curtain of the foundation pit, which is located at Juyuanzhou Station in Fuzhou (China). The water inflow per unit area is 0.36 m³/d in the foundation pit, and this implies that the design method of the horizontal waterproof curtain applied for the excavation case is good and meets the requirements of design and safety.

The lining of operating high-speed-railway tunnels suffers from cracks, the peeling of material, and other deteriorations and defects, all of which seriously affect driving safety. However, the trajectory of a falling block from the tunnel lining in a tunnel train wind environment and its impact on driving safety are unknown. To study the movement of falling blocks under a coupling effect of tunnel train wind and the local flow field of the falling blocks, a three-dimensional gas–solid-coupling numerical calculation model of spalling blocks–train–tunnel–air was established using FLUENT software The aerodynamic evolution mechanism governing the spalling blocks of the lining was analyzed, and we found that the falling process of a spalling block is affected by the coupling of its own characteristics and transient train wind. Train wind directly induced the horizontal motion of falling blocks, generated curves and eddy currents, and changed the motion state of spalled blocks. Furthermore, by comprehensively considering the motion trajectories of flaky and blocky blocks at different positions, the impact of spalling blocks on driving safety was obtained. The dangerous area of spalling blocks was approximately 5.5 m above the ground, which must be paid attention to. Our results provide guidance for the operation and maintenance of high-speed-railway tunnels.

To address water leakage in tunnels with high water pressure, a new waterproof drainage system was proposed. The system uses a spray-applied material with double-adhesive properties as a waterproof layer, significantly reducing leakages, and incorporates a unique bottom drainage system to reduce water pressure. In order to check the effectiveness of the new drainage system and to analyze the effects of various structural measures on pressure reduction, a numerical seepage analysis was carried out under the conditions of a water head of 160 m and a surrounding rock permeability of 1 × 10⁻⁶ m/s. The results show that the maximum water pressure on the secondary lining is 0.6 MPa, which is about 60% reduction compared to a fully enclosed waterproof system and shows a significant pressure reduction. The spacing of the circumferential drainage pipe and the width of the drainage sheet significantly affect the drainage performance, while the arrangement of the drainage system and the size of the bottom drainage pipe have minimal impact. With full consideration of pressure reduction, cost efficiency and construction feasibility, it is recommended to use the following drainage scheme for iterative calculations during the design stage: “1” shaped arrangement, blind pipe diameter of 10 cm, width of drainage sheets of 0.8 m, and drainage spacing of 6 m. By combining the experimentally determined hydrostatic peel-off strength of 1.4 MPa for spray-applied membrane, the applicable scope of the new drainage system was acquired. The research results can provide valuable insights into the application of spray-applied waterproofing membrane in drainage tunnels with high water pressure.