Study On Soil Deformation Induced By Double-O-Tube Shield Tunneling

With the rapid development of urbanization and modernization,urban underground space is less and less.Therefore,how to make more effective use of underground space has gradually become a very important issue.Compared with single-circular tunnel construction,the construction of Double-O-Tube shield tunnel has many advantages,such as high construction efficiency,saving underground space and little influence on the surroundings.In this paper,the construction technology of Double-O-Tube shield tunnel is introduced from the aspects of construction principle,shield machine structure,lining structure and assembly,and several typical projects are introduced as well.Then,the calculation methods of soil deformation induced by Double-O-Tube shield tunneling are introduced,including the equivalent area method,the superposition method,the stochastic medium theory method and the elastic theory method,and the prediction results and analysis are carried out by several examples.Then,the influence of Double-O-Tube shield rolling on soil deformation is taken into consideration,and the calculation methods of soil deformation under the rolling condition are introduced,including the stochastic medium theory method and the elastic theory method.The influence of shield rolling on soil deformation is carefully calculated and analyzed by examples.The main work and the results of this paper are summarized as follows:(1)The construction principle of Double-O-Tube shield tunneling is similar to that of single-circular shield tunneling.The main difference is that the cross section of the Double-O-Tube shield is made up of two incomplete circular sections,which results in differences in the aspects of the shield machine,lining segment and assembly,etc.The more the control equipment is,the more difficult the control will be.(2)Without considering the Double-O-Tube shield rolling,the equivalent area method,the superposition method,the stochastic medium theory method and the elastic theory method can be used to calculate the soil deformation caused by the soil loss in the construction of the Double-O-Tube shield tunnel.But different method has different prediction results and scope.The equivalent area method and the superposition method can only be used to calculate the surface settlement.The prediction results of the two methods are very close,but both of them deviate greatly from the measured values,for the predicted maximum surface settlement value is too large.The stochastic medium theory can be used to calculate the settlement and horizontal deformation of the soil above the tunnel excavation area,but it cannot calculate the deformation of the soil on both sides of the tunnel excavation area and below the tunnel,and its prediction results are too small.The elastic theory method can be used to calculate the deformation of any soil,and the results are close to the measured value,which is the best of the four methods.(3)Shield rolling is a key construction controlling point in the Double-O-Tube shield tunneling,which not only affects the common utilization and service life of the tunnel,but also causes the additional soil deformation.Therefore,the impact of shield rolling should be considered in the prediction of soil deformation in the construction of the Double-O-Tube shield tunnel.The rolling angle of ± 0.6° is usually used in practical constructions,but this is only an empirical value.(4)The stochastic medium theory method and the elastic theory method can be used to calculate the soil deformation caused by the Double-O-Tube shield tunneling under the rolling condition.According to the examples,the influence magnitudes of the shield rolling on the soil deformation are different in different cases,which is mainly due to different geological conditions and construction conditions in actual tunnel engineering.