| An in-depth study of the safety of subway shield tunnels through shield cable tunnels is conducted through numerical simulation,as if the construction distance between external works and the underground cable tunnel is too close,it can intensify the disturbance to the tunnel,potentially leading to more serious disease issues in urban underground spaces.This thesis examines the impact of stacking angle and clear distance on the deformation and mechanical response of the cable tunnel,thereby determining the safety protection distance.The results of this research can be used to provide theoretical guidance for engineering issues and have both theoretical and practical implications.The main work and conclusions of this thesis are as follows:(1)Using the two-stage method to analyze the impact of the new shield tunnel spanning down through the existing shield cable tunnel,it was found that:(1)The maximum settlement value of the existing cable tunnel decreases as the net distance between the two tunnels increases;(2)The maximum deformation curvature of the existing cable tunnel tends to decrease as the net distance increases;(3)The maximum settlement value of the existing cable tunnel also decreases as the stacking angle increases;(4)The impact range of the shield subway tunnel construction on the existing cable tunnel gradually decreases as the stacking angle increases,and increases as the net distance increases.(2)A local refinement model of the existing cable tunnel was established using the shell-spring model to accurately simulate the mechanical behavior of the tube sheet joints,and the impact of the new shield tunnel construction on the existing cable tunnel lining tube sheet was simulated by applying forced displacements on the local refinement model,the findings of which are as follows:(1)In the upper span and lower crossing condition,with the increase of the superposition angle of the two tunnels,the internal force value of the existing cable tunnel decreases,and the new metro shield tunnel construction has less disturbance to the existing cable tunnel;(2)As the net distance between the two tunnels continues to increase,the internal force value of the existing cable tunnel continues to decrease,and the less the new metro shield tunnel construction disturbs the existing cable tunnel;(3)In the upper span condition,the joints of the tube sheet at the bottom and vault of the existing cable tunnel are subject to negative bending moment,and the joints of the tube sheet at the top and bottom of the vault are subject to positive bending moment;in the lower span condition,the joints of the tube sheet at the bottom and vault of the existing cable tunnel are subject to positive bending moment,and the joints of the tube sheet at the top and bottom of the vault are subject to negative bending moment;(4)When an underpass tunnel crosses an existing tunnel,the maximum axial force occurs at the head spring between the rings of the tube sheet arrangement.(3)The existing cable tunnel safety impact law: as the distance between the two tunnels gets closer,the smaller the minimum safety coefficient of the existing structure,according to which,the relationship between the safety coefficient of the subway shield tunnel construction on the neighboring existing shield cable tunnel lining tube piece and distance is proposed,and the safety protection distance under the relevant calculation conditions is developed. |
