• Geomechanics and Engineering
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• 제2권1호
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• pp.57-69
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• 2010

A major consideration in the design of tunnels in urban areas is the prediction of the ground movements and surface settlements associated with the tunneling operations. Excessive ground movements can damage adjacent building and utilities. In this paper, a neural network model is used to predict the maximum surface settlement, based on instrumented results from three separate EPB tunneling projects in Singapore. This paper demonstrates that by coupling the trained neural network model to a spreadsheet optimization technique, the reliability assessment of the settlement serviceability limit state can be carried out using the first-order reliability method. With this method, it is possible to carry out sensitivity studies to examine the effect of the level of uncertainty of each parameter uncertainty on the probability that the serviceability limit state has been exceeded.

• 지질공학
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• 제12권1호
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• pp.1-21
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• 2002

최근 고도의 경제성장으로 인한 도시화와 바른 산업발달은 지하공간의 확장 뿐만 아니라 이용 및 최적화를 필요로 한다. 지하시설물이나 근접구조물의 피해 및 침하와 같은 많은 문제점을 일으키는 흙막이구조물을 위한 버팀굴착의 지역에서 넓고 깊은 기초가 건설되고 있다. 본 연구는 5개의 굴착 공사현장으로부터 얻어진 측정결과에 근거한 침하량과 침하의 영향거리에 관하여 고 하였다. 굴착깊이를 이용한 최대지표침하량(0.28∼0.3)(%)H는 계측값 및 Clough방법에 의한 값과 유사성을 갖으며 Clough 방법에 의한 침하량 및 침하영향거리의 산정이 가장 합리적임을 알 수 있다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.363-372
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• 2007

The residual settlement due to difference between predicted and observed settlement is one of the social problems during reclaiming construction in the soft ground having a deep depth such as Busan and Gwangyang province. Prediction error for the secondary compression settlement makes the construction much harder. To examine characteristics of the secondary compression settlement, the secondary compression index is the most important factor. In this study, various empirical methods for determining the secondary compression index are evaluated. And errors applied to the design case practically are also explained. The pre loading method is the only way to reduce the secondary compression settlement and reduction ratio of the secondary compression should be investigated correctly. Hence, research results on the reduction ratio of the secondary compression are analyzed in this paper. Moreover, decrement of the secondary compression index due to over consolidation ratio is examined closely by laboratory consolidation test using clay in the Gwangyang area.

• 한국지반환경공학회 논문집
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• 제13권4호
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• pp.61-69
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• 2012

본 연구에서는 부지 내 절토부에서 발생하는 암버력을 층당 7m씩 총 9층으로 단계별 동다짐 성토하여 조성된 최대 63m 고성토(高盛土) 암버력 지반의 거동특성을 파악하기 위해, 각 층 성토 완료 시 지중침하계를 설치하여 성토 중 침하량을 분석하였다. 또한, 암버력을 성토 단계별로 동다짐할 경우 하부 성토지반의 구속압 증가로 인하여 지반의 변형특성이 초기 상태와 차이가 발생할 것으로 예상됨에 따라 시공이력을 반영한 수치해석을 실시하여 지중침하계로부터 계측한 성토 단계별 침하량과 비교하였다. 한편, 최종 성토완료 후 선행재하 시 계측한 침하량을 분석하여, 본 연구대상 현장의 2차 크리프 침하량을 예측하였다.

• Geomechanics and Engineering
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• 제15권3호
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• pp.851-859
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• 2018

There are two primary causes of the ground movement due to tunnelling in urban areas; firstly the lost ground and secondly the groundwater depression during construction. The groundwater depression was usually not considered as a cause of settlement in previous research works. The main purpose of this study is to analyze the combined effect of these two phenomena on the transverse settlement trough. Centrifuge model tests and numerical analysis were primarily selected as the methodology. The characteristics of settlement trough were analyzed by performing centrifuge model tests where acceleration reached up to 80g condition. Two different types of tunnel models of 180 mm diameter were prepared in order to match the prototype of a large tunnel of 14.4 m diameter. A volume loss model was made to simulate the excavation procedure at different volume loss and a drainage tunnel model was made to simulate the reduction in pore pressure distribution. Numerical analysis was performed using FLAC 2D program in order to analyze the effects of various groundwater depression values on the settlement trough. Unconfined fluid flow condition was selected to develop the phreatic surface and groundwater level on the surface. The settlement troughs obtained in the results were investigated according to the combined effect of excavation and groundwater depression. Subsequently, a new curve is suggested to consider elastic settlement in the modified Gaussian curve. The results show that the effects of groundwater depression are considerable as the settlement trough gets deeper and wider compared to the trough obtained only due to excavation. The relationships of maximum settlement and infection point with the reduced pore pressure at tunnel centerline are also suggested.

• 한국지반공학회지:지반
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• 제13권2호
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• pp.137-154
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• 1997

한계상태설계법상에서 말뚝기초는 상부구조물의 안정성과 공용성에 근거하여 지지력과 침하 량을 만족하도록 설계되어야한다. 본 논문에서는 공용성을 검토하기위해 과압밀된 점토지반에 위치한 9본의 군말뚝과 2본의 단말뚝에 대하여 실무에서 많이 이용되고 있는 예측식과 현장에서 수행한 피조콘 자료를 이용하여 침하량을 산정했다. 지반에 따라 공간적으로 변화하는 탄성계수가 침하예측에 미치는 영향을 간략히 조사했다. 예측방법으로는 단순탄성론적 예측식 인 베직법 (Vesic's method)과 풀러스법 (Poulos'B method)을 이용했으며 산정된 침하량을 실지 말뚝재하실험을 통해서 계측한 것과 비교한 결과 대부분 과다하게 예측했고 지반의 탄성계수를 직선적으로 가정한 같파는 침하계산에 큰 영향은 미치지 않는 것으로 판단되었다.

• Geomechanics and Engineering
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• 제21권6호
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• pp.583-598
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• 2020

This study is attempted to propose a new hybrid artificial intelligence model called integrative genetic algorithm with multivariate adaptive regression splines (GA-MARS) for settlement prediction of shallow foundations on sandy soils. In this hybrid model, the evolution algorithm - Genetic Algorithm (GA) was used to search and optimize the hyperparameters of multivariate adaptive regression splines (MARS). For this purpose, a total of 180 experimental data were collected and analyzed from available researches with five-input variables including the bread of foundation (B), length to width (L/B), embedment ratio (D_f/B), foundation net applied pressure (q_net), and average SPT blow count (N_SPT). In further analysis, a new explicit formulation was derived from MARS and its accuracy was compared with four available formulae. The attained results indicated that the proposed GA-MARS model exhibited a more robust and better performance than the available methods.

• 한국지반신소재학회논문집
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• 제23권2호
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• pp.9-17
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• 2024

연약지반의 성토나 구조물 축조할 때, 지반의 침하와 안전에 대한 관리가 중요하다. 하지만 실제 지반의 거동과 설계 계획과는 현저한 차이를 보일때가 많다. 본 연구에서는 연약지반 설계시 이론식에 의해 추정되는 설계침하량과 시공시 게측되는 계측침하량의 차이를 통한 침하량 예측을 통하여 그 결과를 비교,분석하고자 하였다. 집중공 18개소에 대한 침하량 분석결과, 역해석 침하량은 계측침하량과 유사한 결괏값을 확인하였으나, 설계침하량의 경우 계측침하량 대비 높은 침하량 값을 확인하였다. 설계침하량의 경우 계측값을 통해 도출된 역해석 침하량과 실내침하량 보다 1.2~1.4배 이상 높은 값을 보였다. RMSE 분석결과, 설계침하량의 경우 0.6212m, 역해석침하량의 경우 0.1697m로 확인되었다. 역해석침하량과 계측침하량의 차이가 설계침하량과 계측침하량의 차이보다 70%이상 낮은 결과를 보였으며, 이는 역해석침하량 값이 설계침하량보다 더 낮은 오차율을 보인다는 것을 확인할 수 있다.

• 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.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.725-730
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• 2002

The areas around the Nam-Hae are mostly covered in thick soft clay deposits(50∼60.0m). In order to improve the ground in these areas verticals trains have been partially penetrated up to the depth of about 25.0m. However, since the predicted values of settlement have often been changed at some predicted time. Finite element analysis was performed to investigate the consolidation behaviour for it. The results from FEM was compared with various observational methods.