• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.513-520
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• 2003

A numerical comparison or predictions by limit equilibrium analysis and 3n analysis is presented for slope/pile system. Special attention is given to the coupled analysis based on the explicit-finite-difference code, FLAC. To this end, an internal routine (FISH) was developed to calculate a factor of safety for a pile-reinforced slope according to shear strength reduction technique. The case of coupled analyses was performed for stabilizing piles in slope in which the pile response and slope stability are considered simultaneously and subsequently the factors of safety are compared to uncoupled analysis (limit equilibrium analysis) solution for a homogeneous slope. Based on a limited parametric study, it is shown that in the free-head condition the factor of safety in slope is more conservative for a coupled analysis than for an uncoupled analysis and a definitely larger value represents when piles are installed in the middle of the slopes and are restrained in the pile head.

• Geomechanics and Engineering
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• 제32권5호
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• pp.523-540
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• 2023

The failure of slope can cause remarkable damage to either human life or infrastructures. Stabilizing piles are widely utilized to reinforce slope as a slip-resistance structure. The workability of pile-stabilized slopes is affected by various parameters. In this study, the performance of earth slope reinforced with piles and the behavior of piles under static load, by shear reduction strength method using the finite difference software (FLAC^3D) has been investigated. Parametric studies were conducted to investigate the role of pile length (L), different pile distances from each other (S/D), pile head conditions (free and fixed head condition), the effect of sand density (loose, medium, and high-density soil) on the pile behavior, and the performance of pile-stabilized slopes. The performance of the stabilized slopes was analyzed by evaluating the factor of safety, lateral displacement and bending moment of piles, and critical slip mechanism. The results depict that as L increased and S/D reduced, the performance of slopes stabilized with pile gets better by raising the soil density. The greater the amount of bending moment at the shallow depths of the pile in the fixed pile head indicates the effect of the inertial force due to the structure on the pile performance.

• 한국지반공학회논문집
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• 제19권5호
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• pp.163-173
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• 2003

본 연구에서는 억지말뚝으로 보강된 사면에서 한계평형 해석법과 3차원 해석 결과를 비교 분석하였다. 특히, 유한차분법을 이용한 FLAC 3D를 바탕으로 하는 커플링 해석에 주안점을 두었으며, FLAC을 이용하여 전단강도감소기법에 따른 보강사면의 안전율을 계산하기 위해 FLAC의 내장언어인 FISH를 이용하여 작성하였다. 커플링 해석에서 억지말뚝에 의한 안정화된 사면을 해석하기 위해 말뚝의 거동과 사면안정을 동시에 고려하였다. 따라서 본 연구에서는 이 두 방법을 적용하여 일렬 억지말뚝이 사면선단, 중앙부, 정부에 위치할 경우에 있어서 각각의 활동 파괴면 및 안전율을 비교 분석하였으며 강도정수 감소법을 적용한 해석기법의 적용성과 타당성에 대한 분석을 수행하였다.

• Geomechanics and Engineering
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• 제21권6호
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• pp.513-525
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• 2020

Slopes stabilised with piles are seldom analysed considering uncertainties in the parameters of the pile-slope system. Reliability analysis of the pile-slope system quantifies the degree of uncertainties and evaluates the safety of the system. In the present study, the reliability analysis of a slope stabilised with piles is performed using the first-order reliability method (FORM) based on Hasofer-Lind approach. The implicit performance function associated with the factor of safety (FS) of the slope is approximated using the response surface method. The analyses are carried out considering the design matrices formulated based on both the 2^k factorial design augmented with a centre run (2^k fact-centred design) and face-centered cube design (FCD). The finite element method is used as the deterministic model to compute the FS of the pile-slope system. Results are compared with the results of the Monte Carlo simulation. It is observed that the optimum location of the row of piles is at the middle of the slope to achieve the maximum FS. The results show that the reliability of the system is not uniform for different pile configurations, even if the system deterministically satisfies the target factor of safety (FS_t) criterion. The FS_t should be selected judiciously as it is observed that the reliability of the system changes drastically with the FS_t level. The results of the 2^k fact-centred design and FCD are in good agreement with each other. The procedure of the FCD is computationally costly and hence the use of 2^k fact-centred design is recommended, provided the response of the system is sufficiently linear over the factorial space.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 사면안정학술발표회
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• pp.65-81
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• 2003

During the last few decades in Korea, the development of hillside or mountain areas has rapidly increased for infrastructure construction such as railroads, highways and housing. Many landslides have occurred during these constructions. Also, the amount and scale of damage caused by landslides have increased every year. In the case of Far East Asia including Korea, the damage of landslides is consequently reported during the wet season. In this paper, the effect of stabilizing piles on slope stability is checked and the behavior of slope soil and piles are observed throughout the year by field measurements in the large-scale cut slopes. In particular a large-scale cut slope situated on the construction site for the express highway in Donghae, Korea. First of all, The behavior of the slope soil was measured by inclinometers during slope modification. Landslides occurred in this area due to the soil cutting for slope modification. The horizontal deformations of slope soil gradually increased and rapidly decreased at depth of sliding surface indicating that the depth of sliding surface below the ground surface can be predicted. On the basis of being able to predict the depth of the sliding surface, stabilizing piles were designed and constructed in this slope. To ensure the stability of the reinforced slope using stabilizing piles, an instrumentation system was installed. The maximum deflection of piles is measured at the pile head and it is noted that the piles deform like deflection on a cantilever beam. The maximum bending stress of piles is measured at the soil layer. The pile above the soil layer is subjected to lateral earth pressure due to driving force of the slope, while pile below soil layer is subjected to subgrade reaction against pile deflection. As a result of research, the effect and applicability of stabilizing piles in large-scale cut slopes could be confirmed sufficiently.

• 한국재난관리표준학회지
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• 제1권2호
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• pp.67-72
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• 2008

본 논문에서는 도로확장공사 현장의 절토사면 안정검토를 위해서 몇가지 조사 및 분석을 수행하였다. 압성토 및 억지말뚝으로 보강된 절토사면의 추가 보강사례를 그 연구대상으로 하며, 절토사면에 보강된 안정화파일의 효과를 분석하기위한 시험장비 또한 설계 및 설치하였다. 결론적으로, 추가보강방법으로써 억지말뚝공법과 Earth Anchor공법을 검토한 결과, 억지말뚝공법과 Earth Anchor공법 모두 안정성은 확보하였으나 기존 보강공법의 연계성과 경제성을 고려하여 억지말뚝공법을 추가보강공법으로 선정하였다.

• 한국지반공학회논문집
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• 제33권7호
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• pp.17-28
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• 2017

본 연구에서는 건조사질토 지반에 근입된 말뚝의 동적 거동을 분석하기 위해 1g 진동대 실험을 수행하였다. 지반-말뚝 시스템의 고유 진동수를 측정한 후 고유 진동수를 기반으로 하중 진동수를 산정하고 이에 대한 거동을 분석하였다. 또한, 추가적으로 말뚝의 동적 거동에 영향을 미치는 인자를 분석하기 위하여 입력 가속도, 상부하중, 말뚝 두부 구속 조건에 따른 거동을 분석하였다. 분석결과, 하중 진동수가 지반-말뚝 시스템의 고유 진동수보다 큰 경우 상대적으로 말뚝 두부변위와 휨모멘트가 크게 발생하고 동적 p-y 곡선의 기울기가 작게 나타났다. 또한, 동적 p-y 곡선의 영향인자를 분석한 결과, 말뚝 두부구속조건은 동적 p-y 곡선의 기울기에 영향을 적게 끼침을 확인하였고, 입력가속도, 상부하중 등의 의한 관성력, 지반-말뚝 시스템의 고유 진동수와 입력 진동수의 관계 그리고 지반조건이 동적 p-y 곡선의 기울기에 큰 영향을 끼치는 것으로 확인되었다.

• Smart Structures and Systems
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• 제9권5호
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• pp.393-410
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• 2012

Conventional geotechnical instrumentation techniques available for monitoring of slopes, especially soil-nailed slopes have limitations such as electromagnetic interference, low accuracy, poor longterm reliability and difficulty in mounting a series of strain sensors on a soil nail bar with a small-diameter. This paper presents a slope monitoring system based on fibre Bragg grating (FBG) sensing technology. This monitoring system is designed to perform long-term monitoring of slope movements, strains along soil nails, and other slope reinforcement elements. All these FBG sensors are fabricated and calibrated in laboratory and a trial of this monitoring system has been successfully conducted on a roadside slope in Hong Kong. As part of the slope stability improvement works, soil nails and a toe support soldier-pile wall were constructed. During the slope works, more than 100 FBG sensors were installed on a soil nail, a soldier pile, and an in- place inclinometer. The paper presents the layout and arrangement of the instruments as well as the installation procedures adopted. Monitoring data have been collected since March 2008. This trial has demonstrated the great potential of the optical fibre monitoring system for long-term monitoring of slope performance. The advantages of the slope monitoring system and experience gained in the field implementation are also discussed in the paper.

• 지질공학
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• 제19권2호
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• pp.191-203
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• 2009

본 연구에서는 대규모 절개사면에서 억지말뚝의 효과를 확인하고, 사면과 억지말뚝의 거동을 조사하였다. 먼저, 사면의 절토공사시 경사계를 이용하여 사면지반의 거동을 조사하였다. 계측결과 사면지반의 수평변위는 점차적으로 증가하고, 사면활동면의 발생위치에서 급격히 감소하는 것으로 나타났다. 이를 통하여 사면활동깊이의 예측이 가능하였다. 사면활동면의 예측을 통하여 억지말뚝의 설계와 시공이 수행되었다. 그리고 억지말뚝으로 보강된 절개사면에 대하여 각종 계측시스템을 적용하여 억지말뚝의 거동을 조사하였다. 계측결과 억지말뚝의 수평변위는 켄틸레버보의 변형형상과 유사하게 발생되었으며, 말뚝두부의 철근콘크리트보의 설치로 인하여 두부의 수평변위 억제효과를 확인할 수 있다. 억지말뚝의 최대휨응력이 발생되는 깊이는 대상지반의 상부토사층이 존재하는 깊이와 유사한 것으로 나타났다. 또한, 쏘일네일링 시공을 위한 억지말뚝 전면부 사면굴착시 억지말뚝의 수평변위가 증가함을 알 수 있다. 본 연구를 통하여 대규모 절개사면에 대하여 억지말뚝의 적용성 및 효과를 확인할 수 있다.

• 한국지진공학회논문집
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• 제21권5호
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• pp.255-264
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• 2017

Dynamic numerical simulation of pile-supported slab track system embedded in a soft soil and embankment was performed. 3D model was formulated in a time domain to consider the non-linearity of soil by utilizing FLAC 3D, which is a finite difference method program. Soil non-linearity was simulated by adopting the hysteric damping model and liner elements, which could consider soil-pile interface. The long period seismic loads, Hachinohe type strong motions, were applied for estimating seismic respose of the system, Parametric study was carried out by changing subsoil layer profile, embankment height and seismic loading conditions. The most of horizontal permanent displacement was initiated by slope failure. Increase of the embedded height and thickness of the soft soil layer leads increase of member forces of PHC piles; bending moment, and axial force. Finally, basic guidelines for designing pile-supported slab track system under seismic loading are recommended based on the analysis results.