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| Influence of model boundary on ground settlement caused by excavation of a circular tunnel |
| FANG Qian, DU Jianming, WANG Gan, YANG Xiaoxu
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| Tunnel and Underground Engineering Research Center of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China |
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Abstract To explicate the size of model boundary required for the analysis of ground settlement caused by circular tunnel excavation, the influences of the sizes of bottom boundary and horizontal boundary of the model on the ground settlement caused by a circular tunnel excavation were studied by the theoretical analysis and the numerical simulation. The Bobet, Park and Verruijt methods were adopted in the process of the theoretical analysis. The elastic and elastoplastic constitutive models were adopted in the process of the numerical simulation. The results of research showed that the mapping point of the circular tunnel vault on the ground surface gradually changed from settlement to uplift as the size of the model bottom boundary increased. When the model bottom was a half-space infinite body, the mapping point of the circular tunnel vault on the ground surface bulged infinitely. This phenomenon was obviously contrary to engineering reality. When there was an underlying hard layer at the model bottom boundary, if the elastic modulus of the underlying hard layer was 5 times that of the overlying soil, the underlying hard layer could be used as the bottom boundary condition of the model. The size of the model horizontal boundary was closely related to the size of the model bottom boundary and the tunnel radius. The size of the model horizontal boundary increased approximately linearly with the increased of the size of the model bottom boundary and the tunnel radius.
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Received: 08 July 2021
Published: 20 March 2022
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