• 한국지반공학회논문집
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• 제32권11호
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• pp.83-96
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• 2016

흙막이 벽체 배후지반의 지표 침하는 인접구조물의 안전성에 많은 영향을 미친다. 그러나 지반굴착에 따른 주변 지반의 침하는 예측하기가 쉽지 않고 굴착면으로부터 이격거리에 따른 침하량을 정량적으로 구하는 것은 더욱 어려운 일이다. 흙막이 벽체의 변형에 의한 지표침하는 수치해석(FEM)이나, 경험적 방법 Peck(1969)등으로 추정하고 있으나 주로 토사층을 대상으로 하고 있다. 본 연구에서는 토사층 하부에 암반층이 위치하는 복합지반을 굴착 할 때 암반층의 깊이와 절리경사에 따른 흙막이 벽체 배후지반의 지표침하를 대형모형실험(규격: $3m{\times}3m{\times}0.5m$)을 수행하여 측정하였다. 모형실험은 축척 1/14.5로 하고 10단계로 굴착을 하였다. 암반층 비율은 35%와 50%로 하였고 암반층의 절리경사를 $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$로 하여 단계굴착하면서 흙막이 벽체 버팀대에 작용하는 토압(Lee 2014)과 흙막이 벽체 배후지반의 지표 침하량을 측정하였다. 암반층비율과 암반층 절리경사가 증가하면 배후지반의 지표침하량도 증가하며 암반층 절리경사 $60^{\circ}$(J60)에서는 수평지반 굴착시에 비해 최대 17배 크게 발생하였다. 흙막이벽체 배후지반에서 최대 지표침하는 경험적 방법과 달리 흙막이 벽체로부터 굴착깊이의 17%~33%만큼 이격된 위치에서 가장 크게 발생하였다. 복합지반의 지표침하는 전반적으로 경험적 추정방법에 의한 지표침하량에 비해 작게 나타났다.

• Geomechanics and Engineering
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• 제15권3호
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• pp.823-831
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• 2018

The most important issue during shield TBM tunneling in soft ground formations is to appropriately control ground surface settlement. Among various operational conditions in shield TBM tunneling, the face pressure and backfill pressure should be the most important and immediate measure to restrain surface settlement during excavation. In this paper, a 3-D hydro-mechanical coupled FE model is developed to numerically simulate the entire process of shield TBM tunneling, which is verified by comparing with real field measurements of ground surface settlement. The effect of permeability and stiffness of ground formations on tunneling-induced surface settlement was discussed in the parametric study. An increase in the face pressure and backfill pressure does not always lead to a decrease in surface settlement, but there are the critical face pressure and backfill pressure. In addition, considering the relatively low permeability of ground formations, the surface settlement consists of two parts, i.e., immediate settlement and consolidation settlement, which shows a distinct settlement behavior to each other.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.469-476
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• 2002

There are many methods to accelerate for consolidation of the soft ground but, in this study, only preloading method was used to improve the soft ground. To measure the settlement of soft ground, surface-settlement plates were installed at several points. To examine settlement behavior of soft ground, back analysis was done using the measured results. In the back analysis, consolidation parameter( $c_{v}$) were obtained and it was compared with test result for undisturbed sample.e.

• Geomechanics and Engineering
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• 제29권3호
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• pp.291-300
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• 2022

Tunnel boring machines combined with the earth pressure balanced shield method (EPB shield TBMs) have been adopted in urban areas as they allow excavation of tunnels with limited ground deformation through continuous and repetitive excavation and support. Nevertheless, the expansion of TBM construction requires much more minor and exquisitely controlled surface settlement to prevent economic loss. Several parametric studies controlling the tunnel's geometry, ground properties, and TBM operational factors assuming ordinary conditions for EPB shield TBM excavation have been conducted, but the impact of excessive excavation on the induced settlement has not been adequately studied. This study conducted a numerical evaluation of surface settlement induced by the ground loss from face imbalance, excessive excavation, and tail void grouting. The numerical model was constructed using FLAC3D and validated by comparing its result with the field data from literature. Then, parametric studies were conducted by controlling the ground stiffness, face pressure, tail void grouting pressure, and additional volume of muck discharge. As a result, the contribution of these operational factors to the surface settlement appeared differently depending on the ground stiffness. Except for the ground stiffness as the dominant factor, the order of variation of surface settlement was investigated, and the volume of additional muck discharge was found to be the largest, followed by the face pressure and tail void grouting pressure. The results from this study are expected to contribute to the development of settlement prediction models and understanding the surface settlement behavior induced by TBM excavation.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.168-171
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• 2001

It is a common practice to extract water from the ground for domestic, agricultural or industrial uses or to lower the groundwater level for construction work. An accurate prediction of ground settlement Is sometimes crucial when groundwater is pumped. This case study have shown that drawdown of the groundwater table may cause ground subsidence. Many settlement gauges was installed in the vicinity of a pumped well to measure the surface settlement. The relationships between the level of groundwater drop and surface settlement is investigated In this research.

• Geomechanics and Engineering
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• 제16권6호
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• pp.635-642
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• 2018

Braced excavation systems are commonly required to ensure stability in construction of basements for shopping malls, underground transportation and other habitation facilities. For excavations in deposits of soft clays or residual soils, stiff retaining wall systems such as diaphragm walls are commonly adopted to restrain the ground movements and wall deflections in order to prevent damage to surrounding buildings and utilities. The ground surface settlement behind the excavation is closely associated with the magnitude of basal heave and the wall deflections and is also greatly influenced by the possible groundwater drawdown caused by potential wall leakage, flow from beneath the wall, flow from perched water and along the wall interface or poor panel connections due to the less satisfactory quality. This paper numerically investigates the influences of excavation geometries, the system stiffness, the soil properties and the groundwater drawdown on ground surface settlement and develops a simplified maximum surface settlement Logarithm Regression model for the maximum ground surface settlement estimation. The settlements estimated by this model compare favorably with a number of published and instrumented records.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.365-370
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• 2007

Foundation settlements(settlements at the embankment surface and ground) has been evaluating to satisfy the strict allowable residual settlement level from the start of the construction of Gyungbu high speed railway. This is because both embankment and ground settlement could be important to minimize the residual settlement after the construction of concrete track. Ground settlement is caused by the increase of effective stress resulting from embankment. The causes of embankment settlement could be come from different sources, for example, the increase of effective stress, rainfall, creep behaviors. Based on the field measured data, this paper analysed the settlement of ground and embankment settlement. The biggest settlement at the embankment surface was 9.7mm during 246days at the STA 000k922.5. The calculated settlement of embankment itself was 8.6mm at the same places. These results conclude that the compressive settlement of embankment could not negligible.

• Smart Structures and Systems
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• 제25권4호
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• pp.433-446
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• 2020

In this paper the effect of confining pressure and tunnel depth on the ground vertical settlement has been investigated using particle flow code (PFC2D). For this perpuse firstly calibration of PFC2D was performed using both of tensile test and triaxial test. Then a model with dimention of 100 m × 100 m was built. A circular tunnel with diameter of 20 m was drillled in the middle of the model. Also, a rectangular tunnel with wide of 10 m and length of 20 m was drilled in the model. The center of tunnel was situated 15 m, 20 m, 25 m, 30 m, 35 m, 40 m, 45 m, 50 m, 55 m and 60 m below the ground surface. these models are under confining pressure of 0.001 GPa, 0.005 GPa, 0.01 GPa, 0.03 GPa, 0.05 GPa and 0.07 GPa. The results show that the volume of colapce zone is constant by increasing the distance between ground surface and tunnel position. Also, the volume of colapce zone was increased by decreasing of confining pressure. The maximum of settlement occurs at the top of the tunnel roof. The maximum of settlement occurs when center of tunnel was situated 15 m below the ground surface. The settlement decreases by increasing the distance between tunnel center line and measuring circles in the ground surface. The minimum of settlement occurs when center of circular tunnel was situated 60 m below the surface ground. Its to be note that the settlement increase by decreasing the confining pressure.

• Geomechanics and Engineering
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• 제33권2호
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• pp.195-202
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• 2023

In this study, the ground settlement in backside of retaining wall and the behavior of the retaining wall were analyzed according to the method of groundwater drawdown due to excavation by using two-dimensional(2D) finite element analysis. Numerical analysis was performed by applying 1) fixed groundwater level, 2) constant groundwater drawdown, and 3) transient groundwater drawdown. In addition, the behavior of the retaining wall according to the initial groundwater level, ground conditions, and surcharge pressure in backside of retaining wall was evaluated. Based on the numerical analysis results, it was confirmed that when the groundwater level is at 0.1H from the ground surface (H: Excavation soil height), the wall displacement and ground settlement are not affected by the method of groundwater drawdown, regardless of soil conditions (dense or loose) and surcharge pressure. On the other hand, when the groundwater level is at 0.5H from the ground surface, the method of groundwater drawdown was found to have a significant effect on wall displacement and ground settlement. In this case, the difference in ground settlement presents by up to 4 times depending on the method of groundwater drawdown, and the surcharge load could increase the ground settlement by up to 1.5 times.

• 한국지반환경공학회 논문집
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• 제16권12호
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• pp.13-22
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• 2015

노후된 하수관의 누수로 인해 발달된 지하공동은 지표침하를 발생시키고 그로 인한 포장재의 취성파괴를 유발시킨다. 이러한 도심지 지반함몰 현상은 최근 5년간 그 빈도수가 꾸준히 증가하고 있는 추세이다. 도심지 지표면은 대부분 아스팔트 또는 콘크리트로 포장이 되어 있어 지하공동의 발생에 따른 지반침하 또는 함몰을 예측하기 어려운 실정이다. 따라서 이 연구는 파손된 하수관의 누수로 인해 발생되는 지하공동의 진행에 따른 지표침하량, 지표면의 영향범위 등 지반거동 및 하수관의 침하를 유한요소해석을 이용하여 분석하였다. 또한 침하 또는 함몰이 발생된 지반을 보강하기 위한 보강재로 가소성유동화토를 사용하였을 때의 보강효과를 수치해석 프로그램을 이용하여 비교 분석하였으며 강도정수 산정을 위해 가소성유동화토의 직접전단시험을 수행하였다.