• 대한토목학회논문집
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• 제36권4호
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• pp.715-722
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• 2016

국내 대부분의 노선은 자갈도상궤도로 이루어져 있어, 지속적인 유지보수가 요구되고 있다. 따라서, 보다 효과적인 요지보수를 통해 비용 절감을 위해서는 예방보수를 통한 유지보수의 최적화가 필요하다. 여기에는 도상자갈층의 침하 진전모델의 확보가 필수적이다. 그러나, 자갈도상재료는 입자가 큰 조립재료로써 일반 지반재료와는 다른 거동을 보인다. 따라서, 본 연구에서는 자갈재료의 거동에 대한 이해와 침하진전모델의 합리적인 개발을 위해 개별요소해석을 수행하였으며, 입자 형상, 공극률, 하중조합 및 빈도에 따른 침하거동을 비교 분석하였다.

• Structural Engineering and Mechanics
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• 제84권5호
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• pp.699-706
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• 2022

Settlement control techniques are critical for the safety of shield tunnel constructions, especially for facing complex situations. In this study, the shield tunnel structure from Huaita east road station to Heping Road station in Xuzhou metro No.3 line (China) is taken as engineering background, which has various complex problems of the upper-soft and lower-hard composite stratum conditions, twin curve shield tunnels, and underpass the foundation of the piled raft. The deformation characteristics of shield tunnelling passing through buildings are explored. Subsequently, comprehensive research methods of numerical simulation and field measurement are adopted to analyzing the effectiveness of settlement control by using the top grouting technique. The results show that the settlement of the buildings has obvious spatial characteristics, and the hysteresis effect can be obviously observed in soil deformation caused by shield construction. Meanwhile, the two shield constructions can cause repeated disturbances, reducing the soil deformation's hysteresis effect. Moreover, the shield tunnel's differential settlement is too large when a single line passes through, and the shield construction of the outer curve can cause more significant disturbance in the tunnel than the inside curve. Notably, the proposed process control parameters and secondary topgrouting method can effectively control the deformation of the shield tunnel, especially for the long-term deformation.

• 한국농공학회지
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• 제14권1호
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• pp.2503-2519
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• 1972

The studies were carried out to find the cause and the quantitative evaluation of sea dike materials loss which is occured during the period of construction works for the tideland reclamation projects on the west coast of Korea. Major subjects to studies were to establish the typical relationships between the tidal flow and the movement of dike materials, the tidal-flow and the erosion, the dike materials and the ratio of material movement(losses), construction methods and the ratio of materials movement (losses). Based on the above subjects, the studies were made for the purpose of obtain the following informations; (1) Collecting and evaluaing the data of dike material losses due to foundation settlement, from designed existing dikes on the west coast. (2) By the field investigation at A-San Sea Dike, Pyong Taek Project, the Comparison would be made by the relationships between the tide velocity and the movement of dike foundation under the natural conditions and the period of construction so that find out the relationship between the dike materials of foundation situation and settlements. With regard to the dike construction works, it is so difficult to calculate the exact quantity of material losses due to the foundation settlements. The major factors that affect the settlement losses of the dike materials are: (1) Topographical variation (2) Swepting the sectional area of dike by the tide velocity. (3) Dumping riprap to the outerside of dike during the period of construction works. (4) Sectional area losses by the cause of occurence of the new tide channels. (5) material losses by the heavy storms. (6) Consolidation settlement by the foundation weakness. (7) Material losses by the earth materials by tide flow. Most hi호 material losses were occured by the Consolidation settlement due to the foundation weakness, the maximum tide velocities due to decrease the cross sectional area of the gaps and erosion of foundation due to the range of tide, Inner and outerside of dike, or dike material loses due to the tide flow. Final conclusion would be obtained by the continuous measurement of consolidation settlement at the stage of final clusure of the dike. (It is scheduled to close on the end of 1972) However, intermediate conclusion can be introduced as follows: (1) The estimation of material(losses) during the period of construction works for the existing sea-dikes up to date were only empirical. The material losses at the general closure for design was estimated at 10% of the riprap, 20% of the earth materials, and 20% of the riprap, 40% of the earth materials at the final closure of the dike. The final closure estimated double quantity to the general closure, but it is still doubt. (2) The ratio of consolidation settlements was found smaller than the calculated quantity. It can be foreseen that settlement speeds is higher thom the calculated speeds. (3) The movement of dike foundation under the natural conditions were not so depends on the geological conditions of the foundation. (4) When the tide velocities was estimated 100 at the normal tide, it was estimated 125 at the high tide and 55 at the low tide. The tide velocities at the low tide shows apparently lower than the high tide and the higher velocities at the deep water depth.

• 한국지반공학회지:지반
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• 제9권3호
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• pp.77-90
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• 1993

얕은기초의 침하해석에 관련된 토질정수, 하중 및 지층구조는 많은 불확실성을 내포하고 있어 확률적 특성을 고려한 해석이 필요하다. 본 연구는 Monte Carlo Method를 이용하여 독립후팅들로 구성된 얕은기초의 침하에 관한 확률론적 해석을 하였다. 변수의 불확실성을 고려하기 위하여 토질정수와 하중은 정규분포의 확률변수로 가정하여 독립후팅의 침하평균 및 변동계수를 구하고 각 독립후팅의 침하도 정규분포하는 것으로 가정하였다. 또한 지반내에 존재할 수 있는 연약토질 포켓 (soft soil pocket)의 확률을 고려한 각 독립후팅의 침하는 Markov process를 따르는 것으로 하였다. 이와같은 각 변수들의 변화에 따라 최대침하와 부등칭하의 허용한계 초과확률에 대한 민감도분석을 하였으며, 얕은기초의 침하해석은 각 변수의 불확실성과 지반조건을 고려하는 것이 타당하다고 판단된다.

• 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.

• 한국터널지하공간학회 논문집
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• 제20권6호
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• pp.1105-1123
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• 2018

도심지 터널굴착 시 지반침하는 지반조건, 굴착방법, 지하수 상태, 터널 지보방법 등 다양한 조건이 복합적으로 작용하여 발생할 수 있으며 대표적인 위험요인은 크게 터널굴착에 의한 지반침하와 지표면함몰로 나눌 수 있다. 터널굴착에 의한 지반침하를 예측하기 위해서는 대상구간의 현황 및 시공조건 등을 반영하고 응력 및 변위를 고려한 수치해석을 수행하여야 한다. 그러므로 터널 전체 노선 및 인근 지장물 현황을 포함하는 영역에 대해, 터널 심도가 변하는 다양한 조건을 고려해야 하는 수치해석의 복잡한 과정을 단순화하여 터널굴착으로 인한 지표면 및 심도별 지반침하를 간편하게 예측하고 평가할 수 있는 기법이 필요하다. 본 연구에서는 지하안전영향평가 수행 시 주요 평가항목인 터널굴착으로 인한 지반침하를 연구대상으로 선정하고, 지층조건, 지반특성, 토피고(터널심도) 및 터널 중심선으로부터 횡방향 이격거리와 같은 지반침하 영향요소를 고려한 매개변수해석을 수행하여 심도별 지반침하 특성 및 침하 발생경향을 분석하고, 터널굴착으로 인한 지반침하를 간편하게 예측할 수 있는 침하량 평가도표를 도출하였다. 도출된 침하량 평가도표는 수치해석 결과와 비교 분석을 통해 적정성이 검증되었으며 침하량 평가도표를 이용하여 터널굴착 시 지표침하뿐만 아니라 지중 매설물의 위치와 심도에 따른 침하량을 간편하게 예측하고 평가할 수 있다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.574-579
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• 2004

In this study, finite difference method used in order to analyze influence on settlement of shallow foundation as a result of vegetation and environmental changes, On boundary conditions to analyze, divided the foundation to clayey silt, changed the amount of evaportanspiration to consider the influence of vegetation, and assumed that the duration of enviromental changes are 180 days to consider the influence of environmental changes. It is expected that this study will do to predicting settlement of shallow foundation as well as to preventing damage of shallow foundation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.525-532
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• 2001

In this study, performance of reinforced railroad roadbeds with the crushed stones was investigated through the real scale railroad roadbed tests. Several real scale reinforced railroad roadbeds were constructed in the laboratory with different subgrade conditions and were tested with the estimated actual train loads including the impact loading of train. The affecting factors such as settlement, earth pressure and stress change at the surface of reinforced roadbed, subgrade layers as well as surface of rails were measured. It was found through the actual testing that for the roadbed with the same thickness, the settlement and vibration level (velocity) of reinforced roadbed decreases with the increase of reaction modulus of subgrade. The settlement of reinforced roadbed with the same reaction modulus of subgrade also decreases with the increase of thickness of the reinforced roadbed.

• 한국농공학회지
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• 제42권
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• pp.68-77
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• 2000

Analyses, in which load was regarded as instant load and gradual step load, respectively, were performed with data measured on a gradually loaded field, and the results were inspected to find the effect of load conditions, and the final settlements which were predicted by Hyperbolic, Tan's, Asaoka's, and Monden's methods were compared with each other. Settlement curves in which load was regarded as instant load and gradual step load being to coincide at twice the time of duration of embankment. On the ground installed vertical drain, from the results of Hyperbolic, Tan's, Asaoka's, Monden's, Curve fitting I, and Curve fitting II (simple, carrillo) methods it was concluded that Asaoka, Curve fitting I, and Curve fitting II methods are reliable for prediction final settlement with back analysis.

• Geomechanics and Engineering
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• 제5권4호
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• pp.343-362
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• 2013

Simple relationships are proposed in this paper by modifying the Schmertmann's equation for settlement estimations of footings (i.e., $B/L{\approx}1$) carrying vertical loads in saturated and unsaturated sandy soils. The modified method is developed using model plate load tests (PLTs) and cone penetration tests (CPTs) results conducted in saturated and unsaturated sand in a controlled laboratory environment. Seven in-situ large-scale footings tested under both saturated and unsaturated conditions in sands were used to validate the proposed technique. The results of the study are encouraging as they provide reliable estimates of the settlement of shallow footings in both saturated and unsaturated sands using the conventional CPT results.