| In the tunnel construction,it usually runs into such a situation in which the tunnel is in a steady state at the initial stage,but collapses later due to the lack of timely support,suggesting that the deformation and the stress of surrounding rocks and supporting structure is closely related to the time.In this paper,the deformation law of surrounding rocks,the stress of surrounding rocks and mechanical characteristics of the supporting structure in the tunnel construction under the interaction of space effect and time effect are mainly studied,by relying on the Liantang Tunnel and combining the theoretical derivation,experimental analysis and numerical simulation.Meanwhile,influence analysis is carried out for such construction parameters as the excavation footage,arch spacing and second lining supporting opportunity in the tunnel construction of different qualities of surrounding rocks.The main research work and contents are as follows:(1)The information about rock creep tests is sorted out,the constitutive model of rock creep is determined,and the transformational relation of creep parameters of surrounding rocks in one-dimension state and three-dimension state is deduced.The curve fitting and parameter transformation is carried out according to rock creep laws,and the value range of creep parameters of surrounding rocks in different qualities is confirmed,and creep calculation parameters of surrounding rocks are determined with the displacement back analysis method by combining the practical monitoring data.(2)Numerical simulation is carried out for the tunnel construction with the creep constitutive model of surrounding rock,to study the impact of combined action of space effect and time effect on the tunnel deformation law,surrounding rock stress and mechanics characteristic of supporting structure,including the calculation of initial deformation that cannot be monitored due to the construction disturbance,change rules of crown settlement and crown settlement rate,stress change rules of the crown and side-wall surrounding rocks,stress change rules of primary support and second lining.Moreover,the mechanical behavior in the process of tunnel construction under the combined action of space effect and time effect is analyzed systematically.(3)Based on the above stated numerical model,the influence law of construction parameters like the excavation footage,arching spacing and second lining supporting opportunity on the stress and deformation of surrounding rocks and stress of supporting structure is further studied,and safe excavation footage of class III and class IV surrounding rock tunnel is confirmed according to the stress of surrounding rocks in different excavation footages.Besides,safe arch spacing of class IV surrounding rock tunnel is confirmed according to the stress rules of arch in different arch spacing.The above study can help to correctly understand the impact of the combined action of space effect and time effect on the deformation and the stress of the tunnel during the construction,and in the meantime,it can provide references for saving the cost and accelerating the project progress in tunnel construction. |
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