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| Design method of combined support of prestressed bolt and cable for super large span tunnel |
| WANG Hao
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| China Railway 15th Bureau Group Co., Ltd., Shanghai 200070, China |
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Abstract In order to address the design problem of the combined support of prestressed bolts and prestressed cables in super-large span tunnels, based on the theory of the perimeter rock pressure arch, the combined effect of prestressed bolts and prestressed cables, along with the anchoring parameters, was analyzed. The support effect was evaluated in the large span transition section of Badaling Great Wall Station. It was found that the optimal arch axis of a pressure arch followed an elliptical shape, with the semi-axes were determined by the in-situ stress and the cross-sectional geometry. The axial force of the pressure arch was determined by the coincidence of the short axis direction and long axis direction of the pressure arch ellipse with the excavation section. Prestressed bolts were observed to interact with shallow surrounding rock to form pressure arches with bearing capacity, and the anchoring parameters were found to determine the shape and compressive strength of the pressure arches. Prestressed cables were utilized to fully exploit the bearing capacity of deep, stable surrounding rock, with the anchoring parameters determining their ultimate bearing capacity. The supporting effect of the combined support of prestressed bolts and prestressed cables was analyzed through the settlement of the vault. The maximum settlement of the vault was measured at 36.9 mm, indicating that the combined support system of prestressed bolts and prestressed cables effectively controls the deformation of surrounding rock.
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Published: 28 March 2025
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