1. Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China 2. Tunnel and Underground Engineering Research Center of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China 3. School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
The interaction model between the shield and the soil was simplified into the elastic half-space hole problem in order to analyze the contact stress between shield shell and soil during shield tunneling. The shield tunneling was simplified into radial, vertical and horizontal displacement boundary modes. Then a method of the additional contact stress between the shield shell and soil was proposed by using the complex variable function method, and the method was verified by three-dimensional numerical simulation. The sensitivity analysis of relevant parameters was conducted by using the method. Results show that the additional contact stress appears a number of gradually increasing stress peaks with the increase of the relative displacement of the machine and soil, and the corresponding peak stresses are approximately the same when the displacements in different modes are the same. When the displacement boundary condition is the same, the smaller Poisson's ratio and the larger elastic modulus of soil are, the greater the additional contact stress at the extreme point is, while the burial depth has little effect on the mechanical - soil additional contact stress. The distribution function of additional stress coefficient around the shield shell was defined, and the balance equations of force and moment increment of the shield were established. The calculations show that the horizontal posture adjustment load, vertical posture adjustment load, yaw moment of the shield machine are proportional to the change of attitude angle, and the longitudinal posture adjustment load is less affected by the change of attitude angle.
Fig.1Relative displacement of machine-soil under different driving attitude
Fig.2Contact relationship between shield and soil during excavation
Fig.3Elastic half-space model with holes
Fig.4Conformal mapping area
Fig.5Displacement boundary conditions due to shield migration
Fig.6Three-dimensional numerical model of machine-soil contact
Es /MPa
μ
γ /（kN·m?3）
K0
3.01
0.491
17.7
0.55
Tab.1Formation parameters
s /m
r1 /m
R /m
u0 /m
Δv /m
Δu /m
0
3.14
3.115
0.025
0
0
2
3.14
3.117
0.023
0.006
0.006
4
3.14
3.119
0.021
0.012
0.012
6
3.14
3.121
0.019
0.018
0.018
8
3.14
3.123
0.017
0.024
0.024
10
3.14
3.125
0.015
0.030
0.030
Tab.2Relative displacements of machine and soil in each section
Fig.7Theoretical and numerical value of contact stress
Fig.8Longitudinal distribution of stress peak
Fig.9Additional contact stress between shield machine and soil under different relative displacements
Fig.10Additional contact stress between machine and soil under different burial depths
Fig.11Additional contact stress between machine and soil with different Poisson’s ratios
Fig.12Additional contact stress between machine and soil with different soil elastic module
Fig.13Stress coefficient distribution function
Fig.14Shield tunneling movement
Fig.15Horizontal and vertical posture adjustment load curves
Fig.16Torque curve
Fig.17Longitudinal thrust curve
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