• 한국터널공학회:학술대회논문집
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• 한국터널공학회 2005년도 학술발표회 논문집
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• pp.77-86
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• 2005

In urban areas, new tunnel construction work is often taking place adjacent to existing piled foundations. In this case, careful assessment for the pile-soil-tunnel interaction is required. However, research on this topic has not been much reported, and currently only limited information is available. In this study, the complex pile-soil-tunnel interaction is investigated using the upper and lower bound methods based on kinematically possible failure mechanism and statically admissible stress field respectively. It is believed that the limit theorem is useful in understanding the complicated interaction behaviour mechanism and applicable to the pile-soil-tunnel interaction problem. The results are compared with numerical analysis. The material deformation patterns and strain data from the FE output are shown to compare well with the equivalent physical model tests. Admissible stress fields and the failure mechanisms are presented and used to develop upper and lower bound solutions to assess minimum support pressures within the tunnel.

• 산업기술연구
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• 제15권
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• pp.147-152
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• 1995

The purpose of this paper is to analyze the bearing capacity, settlement and pile action of pile groups in cohesionless soil, based on a wide range of model test in laboratory. Model test were conducted with changing the variables affecting the behavior of group pile; Number of pile, Diameters, Spacings between piles and Arrangement of piles. Effects of these variables on group efficiency were investigated by analyzing test results. Test results were also compared with the existing analytical method and data obtained in-situ tests.

• Computers and Concrete
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• 제32권2호
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• pp.217-232
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• 2023

Numerous studies have been performed on the behavior of pile foundations in cold regions. This study first attempted to employ artificial neural networks (ANN) to predict pile-bearing capacity focusing on pile data recorded primarily on cold regions. As the ANN technique has disadvantages such as finding global minima or slower convergence rates, this study in the second phase deals with the development of an ANN-based predictive model improved with an Elephant herding optimizer (EHO), Dragonfly Algorithm (DA), Genetic Algorithm (GA), and Evolution Strategy (ES) methods for predicting the piles' bearing capacity. The network inputs included the pile geometrical features, pile area (m²), pile length (m), internal friction angle along the pile body and pile tip (Ø°), and effective vertical stress. The MLP model pile's output was the ultimate bearing capacity. A sensitivity analysis was performed to determine the optimum parameters to select the best predictive model. A trial-and-error technique was also used to find the optimum network architecture and the number of hidden nodes. According to the results, there is a good consistency between the pile-bearing DA-MLP-predicted capacities and the measured bearing capacities. Based on the R2 and determination coefficient as 0.90364 and 0.8643 for testing and training datasets, respectively, it is suggested that the DA-MLP model can be effectively implemented with higher reliability, efficiency, and practicability to predict the bearing capacity of piles.

• 한국지반공학회논문집
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• 제35권9호
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• pp.15-28
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• 2019

PHC말뚝을 생산하는 17개 중소산업체의 품질 성능 검사 자료, 17개 중소산업체 및 6개 대기업 산업체의 장기허용압축하중 제원 표를 분석하였다. 현 단계의 국내 설계에서는 PHC말뚝의 장기허용압축하중의 평균 약 70% 수준을 반영하고 있고 품질이 우수함에도 불구하고 PHC말뚝의 장기허용압축하중에는 안전율 4.0을 적용하고 있다. 대부분의 품질 검사 기준은 KS F 4306에 명시되어 있다. 그러나 원심력으로 다져진 콘크리트 압축강도시험 기준은 KS F 2454에 명시되어 있다. 각 제조사의 품질 시험 자료를 분석한 결과 모든 항목에서 기준값 보다 높은 성능을 보였다. 따라서 PHC말뚝 설계 시 PHC말뚝의 지지력을 PHC말뚝의 허용연직압축하중의 최대값까지 사용할 수 있을 것으로 판단되었다.

• Geomechanics and Engineering
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• 제11권4호
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• pp.587-605
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• 2016

This study aimed to develop upper and lower bounds to predict the tunnel support pressure under the pile tip during the circular tunnel excavation. Most previous studies on the upper and lower bound methods were carried out for the single ground structures, e.g., retaining wall, foundation, ground anchor and tunnel, in the homogeneous ground conditions, since the pile-soil-tunnel interaction problem is very complicated and sophisticated to solve using those bound methods. Therefore, in the lower bound approach two appropriate stress fields were proposed for single pile and tunnel respectively, and then they were superimposed. In addition, based on the superimposition several failure mechanisms were proposed for the upper bound solution. Finally, these upper bound mechanisms were examined by shear strain data from the laboratory model test and numerical analysis using finite element method.

• Geomechanics and Engineering
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• 제36권3호
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• pp.259-276
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• 2024

The undrained shear strength is widely acknowledged as a fundamental mechanical property of soil and is considered a critical engineering parameter. In recent years, researchers have employed various methodologies to evaluate the shear strength of soil under undrained conditions. These methods encompass both numerical analyses and empirical techniques, such as the cone penetration test (CPT), to gain insights into the properties and behavior of soil. However, several of these methods rely on correlation assumptions, which can lead to inconsistent accuracy and precision. The study involved the development of innovative methods using extreme gradient boosting (XGB) to predict the pile set-up component "A" based on two distinct data sets. The first data set includes average modified cone point bearing capacity (q_t), average wall friction (f_s), and effective vertical stress (σ_vo), while the second data set comprises plasticity index (PI), soil undrained shear cohesion (S_u), and the over consolidation ratio (OCR). These data sets were utilized to develop XGBoost-based methods for predicting the pile set-up component "A". To optimize the internal hyperparameters of the XGBoost model, four optimization algorithms were employed: Particle Swarm Optimization (PSO), Social Spider Optimization (SSO), Arithmetic Optimization Algorithm (AOA), and Sine Cosine Optimization Algorithm (SCOA). The results from the first data set indicate that the XGBoost model optimized using the Arithmetic Optimization Algorithm (XGB - AOA) achieved the highest accuracy, with R2 values of 0.9962 for the training part and 0.9807 for the testing part. The performance of the developed models was further evaluated using the RMSE, MAE, and VAF indices. The results revealed that the XGBoost model optimized using XGBoost - AOA outperformed other models in terms of accuracy, with RMSE, MAE, and VAF values of 0.0078, 0.0015, and 99.6189 for the training part and 0.0141, 0.0112, and 98.0394 for the testing part, respectively. These findings suggest that XGBoost - AOA is the most accurate model for predicting the pile set-up component.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.545-553
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• 2009

A lot of long-span marine bridge, which connects land to island or island to island, are being designed and constructed lately in south-west coast in South Korea. In the past, caisson foundations in marine were mainly adopted in construction and stability aspect, however, nowadays with development of pile construction technology, drilled shaft foundations are mainly adopted. As the long span cable stayed bridge and suspension bridge applied with lots of loads are being designed, the scale of pile foundations are getting larger. As the construction cost of substructure including foundation in marine bridges is too high, the appropriate evaluation of the axial bearing capacity of pile becomes a core factor to decide the construction cost of foundation if the drilled shaft is adopted as foundation type of bridge. The evaluation values of skin friction and end bearing capacity of drilled shaft in weathered rock suggested in south Korea are only to introduce the foreign specifications, and most of them are designed in a kind of hard soil layer. Also the allowable load of pile section is less than the expected bearing capacity of pile in the soil condition since the allowable capacity of pile is undervalued. Recently in order to improve this factor the bi-axial hydraulic load test of pile was taken, the data of load transfer analysis of pile, unit of skin friction and end bearing capacity are accumulated. In our country, the design of piles are made with ASD, however, LRFD considering service, strength and extreme state was adopted in Incheon Grand Bridge implemented with BTL, and the research to systematize the resistance coefficient appropriate at home country are being progressed.

• 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.

• 한국산학기술학회논문지
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• 제12권7호
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• pp.3287-3295
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• 2011

현재 건설현장에서 매입말뚝공법인 SIP(Soil-cement Injected Precast pile)공법이 널리 활용되고 있다. 그러나 SIP공법 시공시 문제점 발생 요인들로 말뚝의 품질이 저하되거나 부실시공이 빈번히 발생하고 있다. 본 연구에서는 이 문제를 줄이는 방법으로 SIP공법을 중심으로 시공할 때 문제점 발생 요인 종류별로 현장 기술자들을 대상으로 설문조사를 수행하였다. 그리고 설문 분석 결과를 토대로 문제점 종류별로 자주 발생되는 문제점 요인을 분석함으로써 대응 방안을 제시하였다. 본 연구에서 제시한 문제점 요인별 대책은 향후 건설현장에서 SIP공법으로 시공할 때, 문제점을 최소화할 수 있는 효과적인 자료가 될 것으로 사료된다.

• 한국터널지하공간학회 논문집
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• 제24권2호
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• pp.129-151
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• 2022

본 연구에서는 기초판으로 연결된 군말뚝 형태의 기초 하부를 터널이 근접 통과할 경우 이로 인해 발생하는 말뚝의 거동을 파악하기 위하여 3차원 유한요소해석을 수행하였다. 이때 터널과 말뚝기초 사이의 지반보강을 조건별로 고려하여 수치해석을 수행함으로써 결과를 분석하였다. 수치해석에서는 터널 굴착으로 발생하는 말뚝의 침하, 축력, 전단응력 및 상대변위를 고찰하였으며, 추가적으로 IoT 플랫폼 예비 설계 가이드라인을 제시하였다. 지반보강을 고려하지 않으며 터널로부터 이격거리가 가장 가까운 말뚝은 지반보강을 가장 크게 고려하고 터널로부터 이격거리가 가장 멀리 존재한 말뚝에 비해 말뚝두부의 침하가 약 70% 크게 발생하였다. 또한, 말뚝 품질관리 요소 데이터는 수집 및 정제과정을 통해 다양한 형태의 API (Application Programming Interface)로 제공되었으며, 각 데이터 플로우 프로세스를 정의하여 데이터가 생성되는 시점에 따라 적합한 API를 제공하는 것이 중요한 것으로 분석되었다. 본 연구를 통하여 기초판으로 연결된 군말뚝의 거동에 영향을 미치는 주요 인자를 보강조건에 따라 심도 있게 고찰하고, 말뚝의 품질관리 IoT 플랫폼을 제시하였다.