Loads on Braced Excavations in Soft Clay

Karlsrud, Kjell; Andresen, Lars

doi:10.1061/(asce)1532-3641(2005)5:2(107)

Cited by 33 publications

(14 citation statements)

References 3 publications

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“…Emergency shoring systems more closely resemble braced excavations, thereby requiring shoring design to use a "reasonable" earth thrust pressure distribution [5][6][7][8][9][20][21][22][23][24]. e actual stress distribution for braced excavations varies significantly compared to that of Coulomb theory and between shallow (less than 6.1 m) and deep (greater than 6.1 m) excavations [24,25].…”

Section: Derivation Of Simplified Earth Pressures (T-l Method)mentioning

confidence: 99%

“…e actual stress distribution for braced excavations varies significantly compared to that of Coulomb theory and between shallow (less than 6.1 m) and deep (greater than 6.1 m) excavations [24,25]. e majority of the research into braced excavation, i.e., Terzaghi and Peck [8], Peck [6], Tschebotarioff [9], Wang [22], Karlsrud and Andresen [21], Blackburn and Finno [20], is limited to deep excavation sites and are not necessarily applicable in emergency trench rescue operations [24,25]. Yokel [23], LaBaw [25], and LaBaw and Aggour [24] are the only research efforts, known to the authors, on shallow braced excavations.…”

Section: Derivation Of Simplified Earth Pressures (T-l Method)mentioning

confidence: 99%

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Emergency Trench Shoring and Rescue: A Simplified Method for Calculating Lateral Earth Pressures

Taylor

LaBaw

2018

Advances in Civil Engineering

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Emergency trench shoring design for rescue operations has no reliable standard to determine lateral earth pressures. As a result, the first responder community is forced either to rely predominantly on either “rule-of-thumb” methods or similarly to assume the OSHA 29 CFR for Type C soil to determine a “worst-case scenario.” However, the use of generalized methods, i.e., the C-80, is not officially supported by OSHA standards, which are overly conservative and do not reflect the observations of actual trench surface failures. Additionally, the shoring system requirements can be unnecessarily prohibitive in short-term emergency operations. The current “rule-of-thumb” method used by first responders underestimates braced earth pressures for weak sandy soils and is not recommended for continued use. Therefore, a simplified soil mechanics-based lateral earth pressure framework, the “T-L method,” that accurately represents actual earth pressures based on the in situ soil failure conditions, is presented. The T-L method is validated against Coulomb earth pressure theories and braced excavation thrust pressures for Type C soils. The results indicate a significant reduction in estimated lateral earth pressures which are typically required for a standard construction shoring system design, while providing an adequate and safe emergency rescue shoring standard for first responders.

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Section: Derivation Of Simplified Earth Pressures (T-l Method)mentioning

confidence: 99%

Section: Derivation Of Simplified Earth Pressures (T-l Method)mentioning

confidence: 99%

Emergency Trench Shoring and Rescue: A Simplified Method for Calculating Lateral Earth Pressures

Taylor

LaBaw

2018

Advances in Civil Engineering

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“…Over the past decades, various analytical studies have been carried out to improve our understanding of the behavior of braced excavation protection systems [1]. As a protection system, the trench box shield is different from other braced systems because, instead of shoring up or otherwise supporting the trench face, it primarily aims to protect workers from cave-ins or similar incidents.…”

Section: Introductionmentioning

confidence: 99%

“…Their analyses also revealed the development of an arching effect in the ground in contact with the shoring. Karlsrud and Andresen [1] concluded that the development of earth pressure on supporting structures set up in sensitive clays is a complex function that depends on the flexibility of the support, the anisotropy property, the thickness of the clay layer in the trench bottom, and deformations in the clay layer. Lam [8] showed that a mobilized strength design database can be used to investigate the relationship between structural response ratio and soil-structure stiffness ratio and to capture the range of wall stiffnesses between sheet piles and thick diaphragm walls.…”

Section: Introductionmentioning

confidence: 99%

Flexible Temporary Shield in Soft and Sensitive Clay: 3D FE Modelling of Experimental Field Test

Alam

Chaallal

Galy

2021

Modelling and Simulation in Engineering

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A finite-element (FE) numerical study using PLAXIS-3D software was carried out to reproduce and validate a full-scale experimental in situ test and to investigate the earth pressure on a flexible temporary trench box shield in soft and sensitive clay soil. The excavation trench model was 6 m (20 ft) deep and was considered as nonlinear and anisotropic clay. A 45 kPa (0.94 ksf) surface overload on top of the soil near the trench box was also simulated to produce a maximum load case on the flexible wall of the shield. Both Mohr-Coulomb (MC) and hardening soil (HS) constitutive soil models were considered for FE analysis. Different values of the modulus reduction factor (MRF) and the coefficient of earth pressure at rest ( K 0 ) were considered to validate the model. For a specific shear strength profile, FE analysis with a linear elastoplastic soil model showed relatively small differences in soil pressure with the field test results along the depth of the trench. Results were also compared with the predictions of well-established analytical formulae.

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“…The FEM has been used to study earth pressures, strut loads, bending moments, and horizontal deflection for a strutted sheet pile and ground settlement pattern (Ng and Lings 1995;Vaziri 1996;Ng. et al 1998;Karlsrud and Andresen 2005;Zdravkovic et al 2005;Costa et al 2007;Kung et al 2009;Kung 2009;Chungsik and Dongyeob 2008). With the help of the FEM, a parametric study of a 13.6-m-deep braced excavation was carried out by Bose and Som (1998), who found that the width of the excavation influences the soil-wall deformations and that prestressing the struts has a marked effect on the performance of such a braced cut.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Design Parameters for Braced Excavation: Numerical Study

2013

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This paper discusses the development of a numerical model for a braced excavation to estimate the various design parameters that significantly influence the excavation's behavior. The results of the numerical model were compared with those of a reported case study of a braced excavation in sand, and close agreement between the results was observed. The developed model is used for parametric study to show the influence of different design parameters, such as strut stiffness, wall thickness, strut arrangement and the embedded depth of the wall on strut force, maximum moment developed in the wall, maximum lateral displacement of the wall, and maximum vertical displacement of ground surface. It was found that, among all the combinations studied, a particular type of strut arrangement for a particular ratio of embedded depth and excavation depth produces the best possible result. A design guideline is also presented based on the results of this numerical study.

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Loads on Braced Excavations in Soft Clay

Cited by 33 publications

References 3 publications

Emergency Trench Shoring and Rescue: A Simplified Method for Calculating Lateral Earth Pressures

Emergency Trench Shoring and Rescue: A Simplified Method for Calculating Lateral Earth Pressures

Flexible Temporary Shield in Soft and Sensitive Clay: 3D FE Modelling of Experimental Field Test

Estimation of Design Parameters for Braced Excavation: Numerical Study

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