Size Effect of Deep Circular Working Shaft Excavation for Rail Transit Construction
To address issues related to the size effect of deep circular shaft excavation for rail transit,this study analyzes the stress and deformation characteristics of a circular excavation enclosure structure using the foundation pit project of the Shenzhen-Daya Bay Intercity circular working shaft as a case study.The load-structure method is employed to systematically examine these characteristics under various diameter conditions.The study compares the calculation results from both a 3D spatial structure model and a 2D elastic foundation beam model,discussing the impact of excavation size on the performance of the circular enclosure structure.The findings reveal that the circular diaphragm wall behaves as a quasi-circular structure,generating a vertical bending moment due to soil and water pressure,which indicates a multidirectional stress state.It is feasible to utilize a simplified 2D equivalent model for designing a circular-foundation pit-retaining structure,as its calculation results are more conservative than those of the 3D model.Furthermore,the spatial dimension significantly influences the performance of the circular enclosure structure,with noticeable circumferential effects observed when the diameter of the deep circular working shaft is less than 30 m.
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