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Structural Capacity of Custom Shape Tunnels in DeepEX

Model Simulation, 2D Finite Element Analysis – Structural Capacities


A. INTRODUCTION

Determining the moment and shear capacity of custom shape tunnel sections presents a formidable challenge. This article demonstrates the seamless process of drawing and generating custom tunnel section shapes within DeepEX – Shoring and Tunnel Design section. DeepEX, a robust software suite, empowers engineers to design and analyze deep excavations and tunnels effortlessly. With its interactive interface and implemented Finite Element Analysis engine, DeepEX enables detailed simulation of all objects within the soil mass, facilitating comprehensive analysis of stresses, moments, shears, displacements, settlements, and more, while considering full soil-structure interaction.


Tunnel lining moments graph and settlement shadings in DeepEX

Figure 1: DeepEX 2D FEM analysis - Tunnel lining moments graph and settlement shadings


B. CUSTOM SHAPE SEM TUNNEL SIMULATION IN DEEPEX

In the subsequent sections, we showcase the simulation of a custom shape tunnel with shotcrete lining using DeepEX software. This simulation encompasses all intermediate construction stages for tunnel construction, including partial soil deactivation, final excavation, and activation of the shotcrete lining. Table 1 provides the soil properties and stratigraphy assumed in this example, offering a comprehensive basis for analysis.


Table 1: Assumed soil properties and stratigraphy

Soil

Top El.

Description

Unit Weight

Friction Angle

C’ or Su

Soil Behavior

Eload

exp

(-)

(m)

(-)

(KN/m3)

(deg)

(kPa)

(-)

(kPa)

(-)

F

0

Fill - Sand

19.6

30

0

Exponential

15000

0.5

C

-2

Undrained Clay

20

0

150

Exponential

20000

1

R

-6

Rock

27

30

60

Exponential

500000

0.5

 

 

STEP 1: Define soil properties and stratigraphy

In DeepEX, engineers can conveniently define soil properties using a user-friendly dialog. This dialog allows for direct specification of the soil name, type, and general properties, including soil behavior properties such as constitutive law, modulus of elasticity, and exponent. Users have the flexibility to input these parameters manually or utilize the implemented soil estimation tools for expedited input. Furthermore, DeepEX facilitates the generation of stratigraphy by enabling engineers to define the top elevation and soil type for each soil layer, ensuring accurate representation of subsurface conditions in the model.


Editing the soil properties and stratigraphy in DeepEX

Figure 2: Editing the soil properties and stratigraphy in DeepEX


STEP 2: Add a tunnel in the DeepEX 2D model area

Within DeepEX, engineers can easily access the "Draw Supports" drop-down menu located in the general tab of the software. From this menu, users can select the "Draw a tunnel" tool to initiate the tunnel creation process. By clicking on the desired position within the model area, engineers can designate the center of the tunnel. A dialog will then appear, providing options to adjust the precise tunnel center position, edit the tunnel's structural section, and implement features such as partial deactivation of the tunnel in specific construction stages. This intuitive interface empowers engineers to customize tunnel designs with precision and efficiency, ensuring optimal performance within the simulation.


Adding a tunnel in a DeepEX model

Figure 3: Adding a tunnel in a DeepEX model


Tunnel properties dialog in DeepEX - Define the tunnel position and section

Figure 4: Tunnel properties dialog in DeepEX - Define the tunnel position and section

 

STEP 3: Draw a custom tunnel shape and edit point coordinates

DeepEX includes a CAD tool equipped with basic drawing functions, enabling engineers to create any tunnel shape effortlessly. By simply clicking on points within the CAD area, users can generate the desired tunnel shape. Subsequently, engineers have the capability to define the exact coordinates for each point along the perimeter of the tunnel shape, ensuring precise customization to meet project requirements. This intuitive feature empowers engineers to design tunnels with intricate geometries and tailored specifications, enhancing flexibility and accuracy within the simulation environment.


Drawing a custom tunnel shape in DeepEX

Figure 5: Drawing a custom tunnel shape in DeepEX


STEP 4: Define the structural section for the tunnel lining

Within DeepEX, engineers can swiftly select the desired tunnel structural section type from a range of options, including reinforced concrete, precast concrete, steel plates, steel ribs, corrugated sheeting, and more. Once selected, engineers can directly define the section properties, tailoring them to project specifications. This includes specifying structural materials, lining thickness, rebar size, positions, and other relevant parameters. By providing this comprehensive range of options and customization capabilities, DeepEX empowers engineers to efficiently design tunnel structures that meet performance requirements and project constraints with precision.


Tunnel lining structural section properties in DeepEX

Figure 6: Tunnel lining structural section properties in DeepEX


C. FEM ANALYSIS RESULTS & TUNNEL STRUCTURAL CAPACITIES

The generated tunnel model underwent analysis using the DeepEX Finite Element Analysis engine. DeepEX presents all results on the model area comprehensively, enabling engineers to swiftly evaluate them and identify potential issues. Figures 7 through 10 illustrate the calculated soil mass displacement shadings, tunnel lining stress results and capacities, as well as the moment-axial interaction diagram for the shotcrete lining section.


DeepEX FEM analysis - Soil mass shading settlements

Figure 7: DeepEX FEM analysis - Soil mass shading settlements


Tunnel lining moment diagram and moment capacity

Figure 8: Tunnel lining moment diagram and moment capacity


Tunnel lining shear diagram

Figure 9: Tunnel lining shear diagram


Tunnel lining moment axial interaction diagram

Figure 10: Tunnel lining moment axial interaction diagram


D. CONCLUSION

In conclusion, DeepEX emerges as an indispensable tool for engineers grappling with the complex task of designing and analyzing custom shape tunnels. By providing a user-friendly interface, advanced FEM analysis capabilities, and comprehensive results visualization, DeepEX streamlines the design process and enhances precision. We invite all tunnel engineers to harness the power of DeepEX and elevate their tunnel design endeavors to new heights of efficiency and accuracy.


 


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