Abstract
At the collapse zone, the effects of the thickness of the consolidation grouting layer and the water pressure on the steel lining are vital to the stability of steel-lined pressure diversion tunnels. In this paper, a joint element and the load-sharing ratio of the consolidation layer are introduced to investigate the joint load-bearing characteristics of the steel lining and the consolidation layer and to determine a suitable consolidation layer thickness; a coupling method for simulating the hydromechanical interaction of the reinforced concrete lining is adopted to investigate the effect of internal water exosmosis on the seepage field at the collapse zone and to determine the external water pressure on the steel lining. In the case of a steel-lined pressure diversion tunnel, a numerical simulation is implemented to analyse the effect of the thickness of the consolidation layer and the distribution of the seepage field under the influence of internal water exosmosis. The results show that a 10 m thick consolidation layer and the adopted antiseepage measures ensure the stability of the steel lining at the collapse zone under internal and external water pressure. These research results provide a reference for the design of treatment measures for large-scale collapses in steel-lined pressure tunnels.
Highlights
During the excavation of large-section hydraulic tunnels under complex geological conditions, collapses are relatively common geological disasters that have relatively significant detrimental impacts on tunnel construction and operation
The goal of a collapse treatment is to ensure the safe operation of the tunnel at the collapse zone under the effect of the internal and external water pressure during the operating period in addition to ensuring the stability of the surrounding rocks at the collapse zone during the construction period
The consolidation layer, in comparison with the surrounding grouted rocks, has a relatively low strength and a low inherent bearing capacity; this study focuses on the crown and the consolidation layer above the tunnel at the collapse zone
Summary
During the excavation of large-section hydraulic tunnels under complex geological conditions, collapses are relatively common geological disasters that have relatively significant detrimental impacts on tunnel construction and operation. (2) The stability of the steel lining at the collapse zone under the external water pressure during the operating period: the presence of a collapse cavity alters the thickness and continuity of the cover layer above the tunnel. To address the aforementioned two problems, a joint element and a coupling method for simulating the hydromechanical interaction of the reinforced concrete lining are adopted, which consider the effects of the joint load-bearing characteristics of the steel lining and the consolidation layer and the internal water exosmosis on the stability of the steel lining at the collapse zone. A numerical simulation is implemented to study the joint load-bearing characteristics of the steel lining and the consolidation layer and the distribution characteristics of the seepage field at the collapse zone and to determine the thickness of the consolidation layer and the external water pressure on the steel lining
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