| With the gradual advancement of my country’s transportation modernization,the urban rail transit network has gradually become denser,and more and more new tunnels have penetrated existing structures.Due to regional differences,the stratigraphic conditions,existing structural projects,and construction methods of new tunnels in various cities in my country are different,and the existing structural responses in the crossing construction reflect different characteristics.In the subway underpassing project,the ground and structure have complex dynamic interactions,and the existing structure response law is mainly affected by factors such as structural rigidity and the characteristics of interlayer soil between the new and old structures.Based on the stiffness analysis method,the study of the construction impact of subway underpassing existing structures has important theoretical and practical significance for the safety prediction and control of urban crossing projects.Based on the statistical analysis of the new subway underpassing the existing tunnel,this paper proposes to study the stratum-structure interaction in the underpassing project from the perspective of stiffness.Through theoretical analysis and numerical simulation,the existing structure stiffness,interlayer soil stiffness,and soil-structure interface are analyzed.The effect of stiffness and deformation joint position on the deformation of the existing structure was studied,and the following main results were obtained:(1)A statistical analysis of 82 cases of new metro underpassing existing tunnels in cities across the country,analysis from three aspects of engineering structure and construction method information,geological conditions,and existing structural deformation,and summarizing the geological conditions,The general laws of the buried depth of the new and old structures,the thickness of interlayer soil,the maximum settlement of the existing structure,etc.,are mainly classified according to the geomechanical characteristics of the stratum.(2)Based on the principle of the current layer method,the Peck empirical formula,the Sagaseta theoretical formula and the Loganathan-Poulos theoretical formula are revised,and the existing structure deformation prediction model that can consider the rigidity of the existing structure and the relative position relationship between the new and the old structure is proposed.Based on actual engineering,the validity and applicability of the model is verified,and the sensitivity analysis of the main parameters is carried out.The results show that the existence of the existing tunnel has a restrictive effect on the stratum and hinders the upward expansion of stratum deformation;when the existing structure stiffness is taken into account by the current layer method,the accuracy of predicting the deformation of the under-passing existing tunnel is higher;it affects the structure The order of sensitivity of the four parameters of settlement deformation is:structural stiffness>sandwich soil stiffness>structure buried depth>sandwich soil thickness.(3)Through numerical simulation,the influence of the thickness of the interlayer soil and the main mechanical parameters on the structural deformation is analyzed.The results show that under the same engineering conditions,the influence of soil elastic modulus and Poisson’s ratio on the deformation of the existing structure is in inverse proportion.(4)Based on the analysis of the mechanical characteristics of the soil-structure contact surface,the contact surface element is selected to numerically simulate the soilstructure contact surface and the deformation joints of the existing structure.The effect of the stiffness of the contact surface and the position of the deformation joint on the deformation of the existing structure is studied.influences.The results show that the existing structure with deformation joints presents the characteristics of flexible deformation as a whole,and the pipe joints between the deformation joints rotate rigidly. |
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