• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.265-272
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• 2001

Excavation in a big city is different from excavation in a local area because construction methods and stability are directly connected in a loss of life. Especially, estimate of rock mass slope stability is excuted by more detail and safty work. In this study, we are made reserches in rock mass slope stability and safety method that the slope is closed by elementary school in a big city. The result of many field study and numerical analysis is shown up direct reinforcement used to anchor.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.225-235
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• 2005

The stability of innovative prestressed wale system applied in urban excavation was investigated. The IPS is a wale system prestressed by tension of steel wires. The IPS consists of steel wires, H-beam support and wale. The IPS provides a high flexural stiffness to resist the bending moment caused by earth pressures. And the IPS transmits earth pressures due to excavation to corner struts. The IPS provides a larger spacing of support, economical benefit, construction easiness, good performance and safety control. This paper explains basic concept and mechanism of the IPS and presents the measured performances of the IPS applied in urban excavation. In order to investigate applicability and stability of the IPS in urban excavation, observations and measurements in site were performed. The IPS applied in urban excavation was performed successfully. The results of the field instrumentation were presented. The measured performances of the IPS were investigated. And behavior of the wall and corner struts was investigated.

• Geomechanics and Engineering
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• v.34 no.3
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• pp.329-339
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• 2023

The objective of this study is to develop a Stability Evaluation System for retaining walls to assess their safety in real-time during excavation. A ground investigation is typically conducted before construction to gather information about the soil properties and predict wall stability. However, these properties may not accurately reflect the actual ground being excavated. To address this issue, the study employed a differential evolution algorithm to estimate the soil parameters of the actual ground. The estimated results were then used as input for an artificial neural network to evaluate the stability of the retaining walls. The study achieved an average accuracy of over 90% in predicting differential settlement, wall displacement, anchor force, and structural stability of the retaining walls. If implemented at actual excavation sites, this approach would enable real-time prediction of wall stability and facilitate effective safety management. Overall, the developed Stability Evaluation System offers a promising solution for ensuring the stability of retaining walls during construction. By incorporating real-time soil parameter analysis, it enhances the accuracy of stability predictions and contributes to proactive safety management in excavation projects.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.87-92
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• 2000

In excavation of tunnels especially located in shallow depth, it is not rare to meet geological change in excavation progress worse than expected in the initial design stage. This paper present a case study on the re-design of excavation and support system of a shallow tunnel under construction where it meets the unexpected bad geological condition during excavation. The detailed geological investigation shows that the rock mass is heavily weathered and fractured with RMR value less than 20. Considering this geological condition, the design concept is focused on the reinforcement of the ground preceding the excavation of tunnel. Two design patterns, LW-grouting & forepoling with pilot tunnelling method and the steel pipe reinforced grouting method, are suggested. Numerical analysis by FLAC shows that these two patterns give the tunnel and roof ground stable in excavation process while the original design causes severe failure zone around the tunnel and floor heaving. In point of the mechanical stability and the degree of construction, the steel pipe reinforced grouting technique proved to be good for the reinforcement of heavily fractured rock mass in tunnelling. This assessment and design process would be a guide in the construction of tunnels in heavily weathered and fractured rock mass situation.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.

• Journal of Industrial Technology
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• v.33 no.A
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• pp.73-80
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• 2013

This paper is results of numerical analysis on the behavior of colluvium slope with combinations of soil nails and earth anchors during excavation. In order to maintain the stability of the colluvium cut, being composed of gravel and boulder and thus local in stability being expected during slope cut, temporary reinforcing method of soil nailing with shotcrete might be used. Subsequent method of cast-in-place facing with earth anchors can be used to maintain cut slope stable permanently. For the cut slope where these methods had been applied, the numerical techniques were applied to their behaviors and investigate the stability of the slope. Limit equilibrium methods were used to confirm to maintain the slope stability during and after excavation and application of those reinforcing methods. Another numerical technique of FEM was also used to find the stress and strain as well as deformation distribution in reinforcing materials and slope ground during excavation.

• Geomechanics and Engineering
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• v.17 no.6
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• pp.573-581
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• 2019

Excavation of underground cavern and shaft was proposed for the construction of a ventilation facility in an urban area. A shaft connects the street-level air plenum to an underground cavern, which extends down approximately 46 m below the street surface. At the project site, the rock mass was relatively strong and well-defined joint sets were present. A kinematic block stability analysis was first performed to estimate the required reinforcement system. Then a 3-D discontinuum numerical analysis was conducted to evaluate the capacity of the initial support and the overall stability of the required excavation, followed by a 3-D continuum numerical analysis to complement the calculated result. This paper illustrates the application of detailed numerical analyses to the design of the required initial support system for the stability of underground hard rock mining at a relatively shallow depth.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.123-132
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• 1991

The GEOKST program was used to solve the tunnel example problem. The package can solve such geotechnical problem as excavation, embankment, foundations, etc., in which the soil can be modeled by various elastoplastic geomaterial models. The main objective was to consider the effects of excavation depth to the face of the tunnel on the stability of the ground and support system. Depended on the strength of the ground materials, the limit excavation depth without any support system could be established by analyzing three-dimensional excavation problem. In this given example problem, the strengths of the ground materials were enough for the stability of the tunnel without any support system up to fairly deep excavation and the maximum tunnel section displacement was stabilized as the excavation proceed. The asymptotic value was approximately the same as that of the plane strain analysis. Thus, assuming the plain strain condition and simulation the actual excavation procedure, the maximum tunnel section displacement was caculated after final step. The maximum calculated displacement occured at the top section of the tunnel geometry and was about 8mm.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.49-83
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• 2005

ESCP Project showed an urban excavation case and introduced design method for case of Soil-Structure behavior in urban excavation. In this case, a retaining structures design to analysis the behavior of retaining wall and adjacent structures in urban excavations was applied by using a Elasto-plastic beam and limit Equilibrium analysis and soil-structure interaction analysis. Reliable design of earth retaining structures and the ground adjacent to braced wall in urban excavation are often difficult due to many variable factors. The ground settlement and the damage of adjacent structures in urban excavation has been an imprtant issue. Therefore, the stability of the adjacent structures must be secured with the excavation support and research on the protection of adjacent structure is necessary.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.191-201
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• 2000

In this study, the earth retaining structure using a row of piles considering plastic flow of the ground is suggested for shallow excavation works instead of conventional anchored sheet-pile wall method in the marine clays with high groundwater level. The behavior of the earth retaining structure using a row of piles is precisely observed during excavation by inclinometer and piezometer installed in opposite to the excavation side. As a result of field measurement, it was found that the behaviors of the piles and the soil were influenced mainly by slope of excavation face, interval ratio of piles, fixity condition of pile head, and stability number, etc. The earth retaining structure using a row of piles is ascertained for workability, stability, and economical construction on the soft ground having no adjacent structures.