Seismic Design of Tunnels - Parsons Brinckerhoff
Seismic Design of Tunnels - Parsons Brinckerhoff
Seismic Design of Tunnels - Parsons Brinckerhoff
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3.3 Free-Field Axial and Curvature Deformations 31<br />
Background 31<br />
A Practical Approach to Describing Ground Behavior 31<br />
Simplified Equations for Axial Strains and Curvature 33<br />
3.4 <strong>Design</strong> Conforming to Free-Field Axial and Curvature Deformations 35<br />
Background and Assumptions 35<br />
<strong>Design</strong> Example 1: The Los Angeles Metro 35<br />
Applicability <strong>of</strong> the Free-Field Deformation Approach 37<br />
3.5 Tunnel-Ground Interaction 37<br />
Simplified Interaction Equations 38<br />
<strong>Design</strong> Example 2: A Linear Tunnel in S<strong>of</strong>t Ground 43<br />
3.6 Special Considerations 48<br />
Unstable Ground 48<br />
Faulting 48<br />
Abrupt Changes in Structural Stiffness or Ground Conditions 49<br />
4.0 Ovaling Effect on Circular <strong>Tunnels</strong> 53<br />
4.1 Ovaling Effect 55<br />
4.2 Free-Field Shear Deformations 55<br />
Simplified Equation for Shear Deformations 56<br />
4.3 Lining Conforming to Free-Field Shear Deformations 58<br />
4.4 Importance <strong>of</strong> Lining Stiffness 60<br />
Compressibility and Flexibility Ratios 60<br />
Example 1 61<br />
Example 2 62<br />
Summary and Conclusions 63<br />
4.5 Lining-Ground Interaction 64<br />
Closed Form Solutions 64<br />
Numerical Analysis 76<br />
Results and Recommendations 76<br />
5.0 Racking Effect on Rectangular <strong>Tunnels</strong> 83<br />
5.1 General 85<br />
5.2 Racking Effect 86<br />
5.3 Dynamic Earth Pressure Methods 87<br />
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