• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.27-50
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• 2009

This paper describes an adaptive management approach for predicting, monitoring, and controlling ground movements associated with excavations in urban areas. Successful use of monitoring data to update performance predictions of supported excavations depends equally on reasonable numerical simulations of performance, the type of monitoring data used as observations, and the optimization techniques used to minimize the difference between predictions and observed performance. This paper summarizes each of these factors and emphasizes their inter-dependence. Numerical considerations are described, including the initial stress and boundary conditions, the importance of reasonable representation of the construction process, and factors affecting the selection of the constitutive model. Monitoring data that can be used in conjunction with current numerical capabilities are discussed, including laser scanning and webcams for developing an accurate record of construction activities, and automated and remote instrumentations to measure movements. Self-updating numerical models that have been successfully used to compute anticipated ground movements, update predictions of field observations and to learn from field observations are summarized. Applications of these techniques from case studies are presented to illustrate the capabilities of this approach.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1990년도 PROCEEDINGS OF THE FIRST KOREA-JAPAN JOINT GEOTECHNICAL SEMINAR ON EXCAVATION and TUNNELING IN URBAN AREAS
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• pp.145-162
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• 1990

• Geomechanics and Engineering
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• 제32권4호
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• pp.427-443
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• 2023

Across the globe, rapid urbanization demands the construction of basements for car parking and sub way station within the vicinity of high-rise buildings supported on piled raft foundations. As a consequence, ground movements caused by such excavations could interfere with the serviceability of the building and the piled raft as well. Hence, the prediction of the building responses to the adjacent excavations is of utmost importance. This study used three-dimensional numerical modelling to capture the effects of twin excavations (final depth of each excavation, H_e=24 m) on a 20-storey building resting on (4×4) piled raft. Because the considered structure, pile foundation, and soil deposit are three-dimensional in nature, the adopted three-dimensional numerical modelling can provide a more realistic simulation to capture responses of the system. The hypoplastic constitutive model was used to capture soil behaviour. The concrete damaged plasticity (CDP) model was used to capture the cracking behaviour in the concrete beams, columns and piles. The computed results revealed that the first excavation- induced substantial differential settlement (i.e., tilting) in the adjacent high-rise building while second excavation caused the building tilt back with smaller rate. As a result, the building remains tilted towards the first excavation with final value of tilting of 0.28%. Consequently, the most severe tensile cracking damage at the bottom of two middle columns. At the end of twin excavations, the building load resisted by the raft reduced to half of that the load before the excavations. The reduced load transferred to the piles resulting in increment of the axial load along the entire length of piles.

• 대한토목학회논문집
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• 제31권2C호
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• pp.65-74
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• 2011

본 논문에서는 대구경 소일-시멘트 교반체를 보강재로 적용한 토류벽의 굴착 시 거동을 현장 시험시공 결과를 통해 분석하였다. 먼저 대구경 소일-시멘트 교반체 공법에 대한 설명 및 기본 설계개념을 기술하였다. 공법을 9.8 m 굴착 현장에 적용하면서 굴착 단계별 벽체의 거동을 수평변위 및 하중 계측자료를 바탕으로 분석하였으며, 굴착에 의해 발생한 인접지반의 변위를 침하 계측 및 수치해석을 통해 평가하였다. 분석 결과, 대구경 소일-시멘트 교반체로 보강된 벽체는 보강재 길이가 0.45 H (H:벽체 높이) 이상인 경우 변위 및 토압 발생 거동이 소일 네일링과 같은 기존 공법으로 지지된 토류벽과 유사한 것으로 나타났다.

• Geomechanics and Engineering
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• 제37권1호
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• pp.31-48
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• 2024

To stabilize the excavations in urban area, soil anchorage is among the very common methods in geotechnical engineering. A more efficient deformation analysis can potentially lead to cost-effective and safer designs. To this end, a total of 116 three-dimensional (3D) finite element (FE) models of a deep excavation supported by tie-back wall system were analyzed in this study. An initial validation was conducted through examination of the results against the Texas A&M excavation cases. After the validation step, an extensive parametric study was carried out to cover significant design parameters of tie-back wall system in deep excavations. The numerical results indicated that the maximum horizontal displacement values of the wall (δ_hm) and maximum surface settlement (δ_vm) increase by an increase in the value of ground anchors inclination relative to the horizon. Additionally, a change in the wall embedment depth was found to be contributing more to δ_vm than to δ_hm. Based on the 3D FE analysis results, two simple equations are proposed to estimate excavation deformations for different scenarios in which the geometric configuration parameters are taken into account. The model proposed in this study can help the engineers to have a better understanding of the behavior of such systems.

• Geomechanics and Engineering
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• 제14권4호
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• pp.315-324
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• 2018

With rapid economic growth, numerous deep excavation projects for high-rise buildings and subway transportation networks have been constructed in the past two decades. Deep excavations particularly in thick deposits of soft clay may cause excessive ground movements and thus result in potential damage to adjacent buildings and supporting utilities. Extensive plane strain finite element analyses considering small strain effect have been carried out to examine the wall deflections for excavations in soft clay deposits supported by diaphragm walls and bracings. The excavation geometrical parameters, soil strength and stiffness properties, soil unit weight, the strut stiffness and wall stiffness were varied to study the wall deflection behaviour. Based on these results, a multivariate adaptive regression splines model was developed for estimating the maximum wall deflection. Parametric analyses were also performed to investigate the influence of the various design variables on wall deflections.

• 한국지반공학회논문집
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• 제31권5호
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• pp.35-46
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• 2015

본 연구에서는 최근 국내에서 사용이 증가하고 있는 2열 자립식 흙막이 공법에 있어서 안정성에 영향을 미치는 주요 설계인자들을 분석하고 설계기준을 제안하기 위하여 현장적용 결과의 분석 및 3차원 유한차분 해석을 수행하였다. 지반특성에 따른 본 공법의 거동을 분석하기 위하여 사질토가 지배적인 현장과 점성토가 지배적인 2개의 현장에 적용을 수행하였으며, 굴착에 따른 흙막이 벽체의 수평변위 및 휨모멘트를 분석하였다. 3차원 유한차분 모델링 기법의 타당성을 검증하기 위하여 현장적용 결과와 비교 분석을 수행한 결과, 본 연구의 수치해석 모델링 기법은 본 공법의 굴착에 따른 거동을 합리적으로 모사하는 것으로 나타났다. 또한 흙막이 벽체를 구성하는 전열말뚝(엄지말뚝) 및 후열말뚝(억지말뚝)의 간격(S), 전열말뚝과 후열말뚝간의 거리(D), 굴착심도(H) 및 말뚝의 근입깊이(Z) 등, 본 공법의 주요 설계인자들의 영향 정도를 분석하기 위하여 다양한 경우의 3차원 유한차분 모델링 및 해석을 수행하였다. 그 결과, 굴착에 따라 발생하는 흙막이 벽체의 최대 수평변위는 전열말뚝 및 후열말뚝의 간격의 감소, 전열말뚝과 후열말뚝간의 거리의 증가 및 말뚝 근입심도의 증가에 따라 감소하였으며, 이러한 특징은 점성토 조건의 지반보다는 사질토 조건의 지반에서 보다 명확하게 나타나는 것을 확인할 수 있었다.

• Geomechanics and Engineering
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• 제13권5호
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• pp.715-742
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• 2017

Earth berms are often left in place to support retaining walls or piles in order to eliminate horizontal struts in excavations of soft soil areas. However, if the excavation depth is relatively large, an earth berm-supported retaining system may not be applicable and could be replaced by a multi-bench retaining system. However, studies on multi-bench retaining systems are limited. The goal of this investigation is to study the deformation characteristics, internal forces and interaction mechanisms of the retaining structures in a multi-bench retaining system and the failure modes of this retaining system. Therefore, a series of model tests of a two-bench retaining system was designed and conducted, and corresponding finite difference simulations were developed to back-analyze the model tests and for further analysis. The tests and numerical results show that the distance between the two rows of retaining piles (bench width) and their embedded lengths can significantly influence the relative movement between the piles; this relative movement determines the horizontal stress distribution in the soil between the two rows of piles (i.e., the bench zone) and thus determines the bending moments in the retaining piles. As the bench width increases, the deformations and bending moments in the retaining piles decrease, while the excavation stability increases. If the second retaining piles are longer than a certain length, they will experience a larger bending moment than the first retaining piles and become the primary retaining structure. In addition, for varying bench widths, the slip surface formation differs, and the failure modes of two-bench retained excavations can be divided into three types: integrated failure, interactive failure and disconnected failure.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1251-1258
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• 2008

The purpose of this research is to introduce the new temporary earth retaining wall system using landslide stabilizing piles. This system is a self-supported retaining wall(SSR) without installing supports such as tiebacks, struts and rakers. The SSR is a kind of gravity structures consisting of twin parallel lines of piles driven below dredge level, tied together at head of soldier piles and landslide stabilizing piles by beams. There are three types of excavation wall structures: standard method for medium retained heights(<8.0m), internal excavation method and slope excavation method for deep-excavation applications(>8.0m). In the present study, the measured data from seven different sites which the SSR was used for excavation were collected and analyzed to investigate the characteristic behavior lateral wall movements associated with urban excavations in Korea.

• 한국지반공학회논문집
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• 제25권1호
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• pp.41-54
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• 2009

본 연구는 터파기 형태의 건설공사에서 레이커나 지반앵커 등의 추가적인 버팀이 필요 없는 2열 H-파일을 이용한 자립식 흙막이(SSR) 공법에 대한 것이다. SSR 공법은 사면파괴 방지용 억지말뚝의 역할을 하는 후열말뚝으로 1차적인 토압을 감소시켜 흙막이 벽체의 토압을 분담하고 억지말뚝과 흙막이 벽체의 일체화를 통해 흙막이 벽체의 강성을 증대시킴으로써 레이커나 지반앵커 등의 지보재가 필요 없이 지반굴착을 수행할 수 있는 자립식 흙막이 공법이다. 본 연구에서는 SSR 공법에 대한 실내모형실험 결과를 통하여 굴착에 따른 지반 및 흙막이 구조체의 변협과 토압특성을 분석하였으며, 여러 현장적용 사례와 계측결과를 통하여 굴착방법에 따른 흙막이 가시설의 실제 변형 특성 및 공법의 적용성을 평가하였다. 평가결과, 발생변위가 모두 계측 허용치 이내에서 만족하였다.