Abstract
It is possible to pass through a collapsible loess stratum during metro tunneling. When the surrounding potential water sources with pressure are induced by external influences, the tunnel structure will be influenced in the affected area of loess collapsibility. To deal with the water inrush disaster of the tunnel in a collapsible loess stratum, the mechanism of grouting diffusion in the loess stratum is analyzed. It is found that the main influencing factors of the grouting effect are the radius of the grouting ring and the permeability coefficient of the grouting ring. Then, based on the water inrush section of a metro tunnel in Xi’an city, China, the treatment effect of the project is compared and analyzed through field tests, field monitoring, and finite element simulation. The results show that the water pressure at the measuring point of the tunnel vault is reduced by 4 MPa; the maximum and the minimum principal stresses at the top of the segment lining increased by 34.9 kPa and 8.8 kPa, respectively, which is less than the increase without grouting; and the maximum displacement of the surrounding rock is reduced by 19 mm. The plastic area produced by local water source infiltration is about 62% of that before grouting. The treatment measures of grouting in the tunnel are safe and effective. This study is of valuable meaning for the treatment of water inrush disaster of a loess tunnel under the water environment.
Highlights
Loess is mainly distributed in the arid and semiarid areas in the northern hemisphere and South America and New Zealand in the southern hemisphere, and it is most widely distributed in Asia [1]
If the potential confined water around the subway tunnel leaks due to external influence, water pressure will act on the surrounding rock, and the surrounding rock in some areas will be immersed in water, which makes the surrounding rock saturated
The water pressure directly acts on the tunnel structure; on the other hand, it permeates through the surrounding rock of the tunnel, which leads to the increase of the sliding force of the soil around the tunnel and the failure of the soil structure under the action of the seepage pressure and induces the displacement of the tunnel structure
Summary
Loess is mainly distributed in the arid and semiarid areas in the northern hemisphere and South America and New Zealand in the southern hemisphere, and it is most widely distributed in Asia [1]. If the potential confined water around the subway tunnel leaks due to external influence, water pressure will act on the surrounding rock, and the surrounding rock in some areas will be immersed in water, which makes the surrounding rock saturated. The leakage of urban pipelines will lead to large-scale collapsibility of the loess strata and water inrush accidents [11,12,13]. The theory and technology of disaster prevention and control cannot use the existing theory and technology, so it is necessary to study the treatment mechanism and reinforcement effect of surrounding rock under instantaneous external water pressure in the collapsible loess area. According to the water inrush section of a metro tunnel in Xi’an, China, through field monitoring and finite element simulation, the effect of grouting reinforcement is analyzed. It is expected to provide theoretical support and safety guidance for metro safety construction and maintenance under the influence of the water environment in the future
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