A Method for Characterizing Stiffness of a Support System for Excavation Design
Publication: International Journal of Geomechanics
Volume 24, Issue 2
Abstract
This study proposed a method to characterize the effect of support system stiffness in excavation design based on a newly developed stiffness influence factor. Three-dimensional finite-element analyses were performed considering various excavation, support, and soil conditions. Focus was given to the effect of system stiffness in irregular excavation configuration with a re-entrant corner in different soil conditions. Wall deflection and surface settlement within the re-entrant corner zone were smaller due to the corner stiffening effect, yet deeper and wider influence zones of wall deflection and surface settlement were shown. The individual performance of the influence parameters was evaluated and introduced into a unified evaluation model, and the system stiffness influence factor was established. The proposed system stiffness influence factor was sufficiently effective in predicting wall deflection and surface settlement. Case examples showed that the proposed method is valid and effective for excavation design. The sensitivity analysis showed that the wall stiffness contributed most to the performance of the wall, which was applicable to further enhancing and optimizing excavation design.
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Data Availability Statement
All data, models, and codes generated or used during the study appear in the published article.
Acknowledgments
This research was conducted with the support of the “National R&D Project for Smart Construction Technology (No. RS-2020-KA156488)” funded by the Korea Agency for Infrastructure Technology Advancement under the Ministry of Land, Infrastructure and Transport and managed by the Korea Expressway Corporation. It was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (No. 2020R1A2C201196614).
Notation
The following symbols are used in this paper:
- Ai
- excavation influence area;
- As
- strut cross-sectional area;
- B
- width of wall in regular excavation;
- CM
- medium clay;
- Cref
- cohesion intercept;
- CS
- soft clay;
- D
- wall embedment depth;
- dm
- influence zone of sv,m;
- E
- elastic modulus of the wall;
- E50
- secant modulus;
- EA
- axial stiffness of the strut;
- EI
- wall bending stiffness;
- Eoed
- oedometric modulus;
- Es
- soil elastic modulus;
- Eur
- unloading–reloading modulus;
- G0
- shear modulus at small strain;
- H
- height of the wall;
- Hex
- final excavation depth;
- I
- moment of inertia of the wall;
- IF
- system stiffness influence factor;
- IR
- irregular excavation configuration;
- IR-1
- IR with a square corner;
- IR-2
- IR with a rectangular corner;
- K0
- at-rest lateral earth pressure coefficient;
- kz
- proportional coefficient of zm;
- kδ
- proportional coefficient of δw,m;
- L/B
- aspect ratio of regular excavation;
- L
- length of wall in regular excavation;
- m
- stress-dependent stiffness power;
- P1, P2, and P3
- monitoring locations;
- pA
- reference atmospheric pressure;
- R
- regular excavation configuration;
- R-1
- square excavation configuration;
- R-2
- rectangular excavation configuration;
- Rf
- failure ratio;
- Rint
- interface strength reduction factor;
- S
- sand;
- SPh
- strut horizontal spacing;
- SPv
- strut vertical spacing;
- su
- undrained shear strength of soil;
- sv,m
- maximum ground surface settlement;
- sv
- ground surface settlement;
- t
- wall thickness;
- W1–W6
- walls of irregular excavation;
- zm
- depth of maximum wall deflection;
- νur
- unloading–reloading Poisson’s ratio;
- ϕ′
- internal friction angle;
- α
- proportional coefficient of sv,m;
- γ0.7
- shear strain at 0.722G0;
- γs
- unit weight of soil;
- γsat
- saturated soil unit weight; and
- γw
- unit weight of water.
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Published In
International Journal of Geomechanics
Volume 24 • Issue 2 • February 2024
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Dec 7, 2022
Accepted: Aug 8, 2023
Published online: Nov 30, 2023
Published in print: Feb 1, 2024
Discussion open until: Apr 30, 2024
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