Random analysis method for longitudinal deformation of existing shield tunnels induced by new tunnelling underpass considering geological uncertainty
The strata variation along the longitudinal direction of shield tunnel is inevitable.Most of the existing analytical models for calculating the longitudinal deformation of existing shield tunnels treat the soil underneath the tunnel as a homogeneous foundation due to new tunnel construction,ignoring the variability of the stratum.In this paper,to address the longitudinal deformation of existing shield tunnels caused by new tunnel construction,an analytical model of longitudinal mechanics of shield tunnels considering the stratum variability was constructed.Based on the random field theory and Monte Carlo simulation strategy,a random analysis method for the longitudinal deformation of existing shield tunnel caused by tunnel undercrossing was proposed.Based on a project case and the established stochastic analysis method of the longitudinal deformation of shield tunnel,the stochastic analysis of longitudinal deformation of existing shield tunnel under the influence of new tunnel undercrossing construction was made,and the results were compared with the measured results.Finally,the influence of the variation coefficient of stratum stiffness and horizontal fluctuation distance on the longitudinal deformation of the existing shield tunnel was analyzed.The results show that the influence of stratum rariability on the longitudinal deformation of shield tunnel cannot be ignored,the coefficient of variation of stratum stiffness is more sensitive to the mean value and dispersion degree of the longitudinal displacement of existing tunnels,and the coefficient of variation of stratum stiffness has more significant effect on the reliability index.
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