| In the reconstruction of the old city municipal pipeline,the researches on the influence of vehicle loads on the urban utility tunnel constructed with the shield method of shallow buried depth and small diameter and its surrounding rock are relatively few.Aiming at the problem that how to establish effective simplified models of vehicle loads and consider the influence of the additional dynamic vehicles load,this paper adopts stratum structure method and loading structure method to study the response rules of the branch utility tunnel in old urban district under vehicle loads,this paper provides an important theoretical basis for the improved design of the urban utility tunnel under vehicle loads.Aiming at the problem that how to consider the change of rupture angle under dynamic vehicle loads when the standard method is introduced to calculate the value of rupture angle,according to coulomb pressure theory,the rupture body weight is calculated,and the equilibrium relation of the rupture is combined.the rupture angle is calculated by using extreme principle,and the improved equivalent substitution of soil layer method is obtained to simplify vehicle loads,providing theoretical basis to analyze the effect of vehicle load on the urban utility tunnel.Aiming at the problem that how to effectively reflect the force and deformation of the urban utility tunnel under vehicle loads,considering the interaction between the structure of the tunnel and the soil.the effective simplified models are built when considering the additional dynamic load effect of vehicle.The influence of vehicle loads on the force and deformation of the tunnel and the surface subsidence are analyzed.the maximum tensile of the branch utility tunnel with the improved method increase about 6% and 13% than that with the conventional method and the conventional method,and the pressure stress increase about1.5% and 5%,the maximum vertical displacement increase 0.391 mm and 0.766 mm.The increases of the value of vehicle loads and its load coefficient will strengthen the influence of the urban utility tunnel under vehicle loads to a certain extent when using the improved method,but the increases of the stress and vertical displacement on the segment as well as the ground settlement are limited.In design and construction of the branch utility tunnel project in the reconstruction of old city municipal pipeline,the improved method can be more effective and reasonable to reflect the effects of vehicle loads.Aiming at the problem that the connecting modes of segment ring and the different location can induce the increases of the force and deformation of the urban utility tunnel,Considering the the form of staggered and stitching of the segment ring,the load of vehicle load and the pressure of surrounding rock are calculated.Combining with the relative position of vehicle load and tunnel and the characteristics of load distribution,the response regularities of internal forces and displacement of the segment lining under vehicle loads and the connecting modes of segment ring are studied.After considering the effect of vehicle loads,the maximum bending moment and maximum axial force of the segment ring with the form of staggered and stitching is increased by about 2.2 kN m and 10 kN respectively,while the overall displacement increases by about 0.17 mm.When the tunnel is buried less than 7 m,the impact of vehicle load on the internal forces and displacement of the segment lining are more obvious,when the tunnel is buried more than 7 m,the impact of vehicle load is weak.When the buried deep of branch utility tunnel is same,with the distance between the utility tunnel and the vehicles increasing,the effect of vehicle loads on the branch utility tunnel is gradually decreasing.The buried depth of utility tunnel outsides the scope of 7 m and the distance between the utility tunnel and the vehicles beyond the range of 4 m are appropriate in the area of the location of branch utility tunnel project. |
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