Theoretical research on shield tunnels with different diameters crossing through existing tunnels in saturated soil area
With the diversified development of spatial sections of urban subway tunnel,existing tunnels inevitably face the huge risk of shield tunnel crossing with different diameters.Based on the initial value solution of semi-infinite saturated soil,considering the diameter and type of shield machine,the corrected calculation methods for the additional thrust on the shield excavation face,the friction of shield shell,the grouting pressure of the shield tail and other construction factors were given.The calculation formula of the vertical deformation of the existing tunnel caused by shield tunnel crossing with different diameters in saturated soft soil area was deduced.The results show that compared with previous calculation methods in the literature,the proposed calculation method is more advantageous in predicting the deformation of the existing tunnel caused by the crossing of the large-diameter shield in saturated soil.When the shield tunnel obliquely passes through the existing tunnel,the longitudinal settlement tank will be skewed,and the deformation of the existing tunnel tends to be stable after the shield leaves the tunnel axis by 4.5 times the length of shield machine.The difference in the stability principle of the excavation face of different types of shield machines is the key factor affecting the calculation results.The additional thrust on the shield excavation face considering the mud weight distribution is more sensitive to the change of the shield diameter than that in the consideration of squeezing effect.
shield tunnelsaturated soilshield crossinglarge diametersexcavation face
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