• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.45-65
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• 2022

In this paper, a diaphragm wall that supports soils and rock was modeled using FLAC, a finite difference analysis program, to evaluate the seismic behavior of temporary retaining structures in a deep excavation. The appropriateness of the numerical model was verified by comparing its results with those of the centrifuge test performed in a similar condition. The bending moment distribution along the diaphragm wall shows a very similar tendency, and the maximum acceleration obtained at the backfill and top of the wall shows a difference within 5%. Based on the developed model, a parametric study was conducted in various input earthquake, ground, and excavation conditions. The maximum structural forces and bending moment under earthquake loading were compared with the maximum values during excavation, from which the critical condition that requires a seismic design was roughly sorted out. The maximum bending moment of a wall that retains soil layers increased 17%. Particularly, the axial force of struts located in loose soils increased 32% under 100 years return period of an earthquake event, which strongly is estimated to require seismic design for structural safety.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1089-1095
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• 2014

In this study, we compared and analyzed the displacement of final excavation with measured value through an inverse analysis method used in urban excavation construction. We maximized the effectiveness of the inverse analysis method, and plan to achieve cost-effective and practical construction management in the field with identical conditions. As the first stage, we suggest an example of a field which has the inverse analysis method. We applied the inverse analysis method to three different fields on which construction and measuring were finished. Of these three fields, two fields showed a very satisfactory result. However, in one field, there were significant differences between the analysis and measured value. The result of our analysis indicated that, we should unite the conditions of the inverse analysis method and field construction. We need to thoughtfully reconsider the RANKINE earth pressure application in a triangle type. This is because the uniformity of earth pressure is made by its arching effect, in the condition of the displacement of lower underground occurring widely, which is differentiated with the earth pressure conditions of RANKINE, even if the slurry wall has stiffness. Also, when recalculating the soil parameter, we should emphasize the adhesion of the weathering zone, and give experimental consideration to ground water level.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.276-285
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• 2006

Application of anchored or strutted wall system for the earth retention of excavation works in a populated urban area or a poor soil deposit can be limited due to various restrictions. Since the strut becomes longer in a wide excavation site, the stability of an earth retaining wall is decreased, the wall deformation is increased, and the ground settlement is also increased due to an increased buckling or bending deformation of struts. Especially, in a populated urban area, the installation of anchors can be problematic due to the property line of adjacent structures or facilities. Thus, a new concept of earth retaining system like Self-Supported diaphragm Wall can solve several problems expected to occur during excavation in the urban area. In this study, Numerical analyses of counterfort diaphragm wall was introduced and the monitored data from the site was compared with the original results of numerical analyses. Also, in the case of the deep excavation applied the counterfort diaphragm wall, numerical analyses was performed to predict the wall deformation and the reinforcement to reduce the wall deformation was suggested.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.775-782
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• 2004

Recently, the cases which are constructed close by neighboring structure or underground structure are on the increase to get the utmost out of the land exploitation of underground space in the downtown area. As the building becomes larger, the excavation depth is getting deep, and the excavation area is getting, wide too. These are frequent occasions that the application of Strut or Anchor method is difficult, because of site boundary, civil application and the ground condition. Therefore, to solve these problem, we analyze and compare design with measuring data, change the design factor and show the improvement of course through the application of self-supported diaphragm wall using counterfort technique which is a new method. It is expected to be a contribution to the suitable exploitation method of construction.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.605-613
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• 2008

Application of anchored or strutted wall system for the earth retention of excavation works in a populated urban area or a poor soil deposit can be limited due to various restrictions. Since the strut becomes longer in a wide excavation site, the stability of an earth retaining wall is decreased, the wall deformation is increased, and the ground settlement is also increased due to an increased buckling or bending deformation of struts. Especially, in a populated urban area, the installation of anchors can be problematic due to the property line of adjacent structures or facilities. Thus, a new concept of earth retaining system like Self-Supported diaphragm Wall can solve several problems expected to occur during excavation in the urban area. Application of self-supported counterfort diaphragm wall was verified in this paper though comparing the design of self-supported counterfort diaphragm wall with the data monitored during excavation in Singapore.

• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.77-88
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• 2006

A series of model tests were performed to investigate the ground deformation during trench excavation for diaphragm walls. An apparatus was manufactured to observe the failure pattern of a slurry-supported trench in sandy ground. Ground deformations including settlement and lateral displacement of the surrounding ground adjacent to the trench were carefully monitored during excavation. Experimental observations indicated that the settlement of the adjacent ground increased with closing to the trench. Especially, the considerable settlement occurred at the distance which was equal to 40% of the excavation depth. And, the higher settlement was obtained when the relative density of ground was looser and the ground water table was higher. Also, the lateral wall face of excavated trench was bulged with lowering the slurry level In stages and then the upper part of trench failed finally. The envelope of ground surface settlement could be represented as a hyperbolic line and the measured settlement was smaller than those predicted by Clough and O'Rourke (1990).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.920-926
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• 2014

In this study, we applieorithmd the inverse analysis alg to the prediction of displacement shape in the example construction and verified the feasibility of suggested algorithm. For this purpose, as information processing knowledge in the field of IT is required and the need for convergence with the major is emerged, it is intended to try to apply the algorithm to the construction sector. Prediction of displacement shape is very important since it is related to the earth pressure of slurry wall and effecting on the safety of slurry wall after anchor removal. 3 levels of inverse analysis were applied to the slurry walls in 3 sites and compared the measured displacement shape with predicted displacement shape of the last excavation construction. As the predicted displacement shape was matched well with the measured one, the applied analysis algorithm in this study can be applied to the excavation construction.

• Journal of Korean Association for Spatial Structures
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• v.11 no.2
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• pp.129-138
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• 2011

Construction methods for underground structure are classified as bottom-up, up-up, and top-down methods depending on the procedure of construction related to a superstructure. In top-down construction methods, building's main structure is built from the ground level downwards by sequentially alternating ground excavation and structure construction. In the mean time, the main structure is also used as supporting structure for earth-retaining wall, which results in the increased stability of the earth-retaining wall due to the minimized deformation in adjacent structures and surrounding grounds. In addition, the method makes it easy to secure a field for construction work in the downtown area by using each floor slabs as working spaces. However top-down construction method is often avoided since an excavation under the slab has low efficiency and difficult environment for work, and high cost compared with earth anchor method. This paper proposes a combined construction method where semi-open cut is selected as excavation work, slurry as earth -retaining wall and CWS as top-down construction method. In the case study targeted for an actual construction project, the proposed method is compared with existing top-down construction method in terms of economic feasibility, construction period and work efficiency. The proposed construction method results in increased work efficiency in the transportation of earth and sand, and steel frame erection, better quality management in PHD construction, and reduced construction period.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.119-135
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• 2022

This paper used dynamic centrifuge tests to examine the seismic response for a deep temporary retaining wall with four input motions of 100, 1,000, and 2,400 years of return periods. The centrifuge model was designed based on an actual deep excavation design with a 50 m maximum excavation depth. The model backfill was prepared with dry silica sand at a relative density of 55%, and the retaining wall was modeled as a 24.8 m height diaphragm wall supported by struts. Acceleration response was amplified at the backfill surface, top of the wall, and near bedrock. However, in the middle of the model, input motion was de-amplified. The member forces of the wall and strut induced by the seismic load, which excited, were compared with the member force at rest condition. The wall's maximum negative and positive moments were increased to 36% and 10% compared to the maximum moment at rest. The maximum axial force increases to 70% of the at rest axial force on the bottom strut. The equivalent static analysis using Mononobe-Okabe (M-O) and Seed-Whitman (S-W) seismic earth pressures were compared to the centrifuge results. Considering the bending moment, the analysis results with the M-O theory underestimates but that with the S-W theory overestimates.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.87-95
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• 2023

Recently, redevelopment of the original downtown area is underway, the necessity of construction in adjacent location is increasing. However, excavations in dense urban areas are prone to ground problems due to various causes, so it is necessary to use materials and methods that can minimize such problems. As a general earth retaining method, various methods such as diaphragm wall and CIP method are applied using cement. However, since a large amount of cement is used for the installation of earth retaining method, it is necessary to conduct research on the development of new cement substitute materials to significantly reduce greenhouse gas emissions. In this study, we utilized the hardening reaction of blast furnace slag powder, desulfurized gypsum and high calcium fly ash by alkali activation and applied it to the SCW method. As a result, it was analyzed that the compressive strength of solidified soil using development solidification material was 96.2 ~ 106.3% of OPC at 28 days of curing. In addition, the strength increment ratio was 2.06 for sandy soil and 2.41 for clayey soil, which was higher than 1.85 of OPC. It seems an advantageous in terms of long-term strength. In addition, from the environmental point of view, it was analyzed that there is no elution of heavy metals and that greenhouse gas emissions can be dramatically reduced. Therefore, if further studies are conducted, it can be applied to the SCW method.