Research On The Physical Model Test On Non-uniform Settlement Of Shield Tunnel

With the development of the city,the further development of underground space,metro underground commercial streets,large shopping malls,office buildings,etc.are more and more concentrated.The existing tunnels are affected by the complex surrounding environment,and the structure will inevitably produce uneven settlement,which will have certain impact on the safety of the tunnel structure and the railway train operation safety.The local loading of the ground is an important factor causing the settlement of existing tunnels.Based on this background,a similar model test is carried out for the longitudinal uneven settlement of the tunnel.The main research contents are as follows:(1)The reason of uneven settlement caused by tunnels is analyzed.With Shanghai Metro and Beijing Metro Airport Line as examples.(2)Based on the three similarity theorems,the similarity relations of physical quantities in this model test are deduced.The tube piece concrete is simulated by the mixed material of water:gypsum:diatomite=1:1.5:0.1,and the hoop joint adopts the principle of equivalent rotational stiffness,which is simulated by the outer slotting,the longitudinal joint adopts the principle of equivalent bending stiffness and equivalent tensile stiffness,which is simulated by 8 iron welding wires(J50).(3)Taking the urban single-hole shield tunnel as the prototype,the transverse and longitudinal structure tests under the concentrated force load were carried out by means of the staggered splicing method.Obtained the effective range of transverse and longitudinal flexural rigidity of shield tunnel based on the test method in this paper.(4)The model test of sand-tunnel structure interaction was carried out.The30-ring staggered joint tunnel was used to simulate different working conditions,such as local static load,uneven underlying soil layer,tunnel buried depth and load location.The influence of these factors on tunnel settlement and bending moment was analyzed.The longitudinal settlement law of the tunnel is obtained,and the corresponding countermeasures are put forward.(5)The relationship between the ground heaped load and the radius of curvature at the maximum settlement of the tunnel is analyzed.Find that the relationship between heaped load and the radius of curvature can be described byy=a?x~b.For the same level of load,the radius of curvature of a soft soil tunnel is much larger than that of a homogeneous soil tunnel.