• Title/Summary/Keyword: pile-slope system

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Stability Analysis of Pile/Slope Systems Considering Pile-slope Interaction (억지말뚝-사면의 상호작용을 고려한 사면안전율 분석)

  • 김병철;유광호;정상섬
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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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.

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Comprehensive evaluating the stability of slope reinforced with free and fixed head piles

  • Xixi Xiong;Ying Fan;Jinzhe Wang;Pooya Heydari
    • Geomechanics and Engineering
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    • v.32 no.5
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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 (FLAC3D) 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.

Coupled Effect of Pile/Slope Systems (억지말뚝-사면의 상호작용 효과)

  • 정상섬;유광호;이선근
    • Journal of the Korean Geotechnical Society
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    • v.19 no.5
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    • pp.163-173
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    • 2003
  • In this paper, a numerical comparison of predictions by limit equilibrium analysis and 3D analysis is presented for slope/pile system. Special attention is given to the coupled analysis based on the explicit finite difference code, FLAC 3D. To this end, an internal routine (FISH) was developed to calculate a factor of safety for a file 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. In this study, by using these methods, the failure surfaces and factors of safety were compared and analyzed in several cases, such as toe, middle and top of the slope, respectively. Furthermore, the coupled method based on shear strength reduction technique was verified by the comparison with other analysis results.

Reliability analysis of slopes stabilised with piles using response surface method

  • Saseendran, Ramanandan;Dodagoudar, G.R.
    • Geomechanics and Engineering
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    • v.21 no.6
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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 2k factorial design augmented with a centre run (2k 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 (FSt) criterion. The FSt should be selected judiciously as it is observed that the reliability of the system changes drastically with the FSt level. The results of the 2k 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 2k fact-centred design is recommended, provided the response of the system is sufficiently linear over the factorial space.

Reinforcement Effect of Stabilizing Piles in Large-scale Cut Slops (대절토사면에 보강된 억지말뚝의 활동억지효과에 관한 연구)

  • 홍원표;한중근;송영석;신도순
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.06a
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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.

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A Case Study of Extra Reinforcement by Road Extension work on Existing Cut Slope Reinforced with Counterweight Fill and Stabilizing Piles (압성토 및 억지말뚝으로 보강된 도로의 확장공사로 인한 추가 보강사례 연구)

  • Park, Jeong-Yong;Kim, Woo-Seong;Kim, Jae-Kyoung;Yang, Tae-Sun;Na, Kyung-Joon
    • Journal of Korean Society of societal Security
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    • v.1 no.2
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    • pp.67-72
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    • 2008
  • To confirm the stability of a cut slope in the road extension construction site, several investigations were carried out and countermeasures of slope was studied. This paper describes a study of design case of extra reinforcement on existing cut slope reinforced by preloading and piles in roads. To investigate the effect of stabilizing piles installed in a cut slope, an instrumentation system also designed, was. As a result that the stabilizing file and earth anchor are considered as the extra reinforcement, both stabilizing pile and earth anchor guarantee the stability of cut slope. However, stabilizing pile is selected in aspects of economy and continuity to the existing cut slop reinforcement including counterweight fill and stabilizing piles.

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Analysis of Dynamic Behavior of a Single Pile in Dry Sand by 1g Shaking Table Tests (1g 진동대 실험을 통한 건조사질토에 근입된 단독말뚝의 동적 거동 분석)

  • Lim, Hyun-Sung;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.33 no.7
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    • pp.17-28
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    • 2017
  • This paper presents the investigation of dynamic behavior of a single pile in dry sand based on 1g shaking table tests. The natural frequency of soil-pile system was measured, and then a range of loading frequency was determined based on the natural frequency. Additionally, the studies were performed by controlling loading accelerations, pile head mass and connectivity conditions between pile and cap. Based on the results obtained, relatively larger pile head displacement and bending moment occur when the loading frequency is larger than the natural frequency of soil-pile system. However, the slope of the p-y curve is smaller in the similar loading frequency. Also, it was found that inertia force like input acceleration and pile head mass, and relation of the natural frequency of soil-pile system and input frequency have a great influence on the slope of dynamic p-y curve, while pile head conditions don't.

An optical fibre monitoring system for evaluating the performance of a soil nailed slope

  • Zhu, Hong-Hu;Ho, Albert N.L.;Yin, Jian-Hua;Sun, H.W.;Pei, Hua-Fu;Hong, Cheng-Yu
    • Smart Structures and Systems
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    • v.9 no.5
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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.

The Behavior of Stabilizing Piles installed in a Large-Scale Cut Slope (대규모 절개사면에 설치된 억지말뚝의 거동)

  • Song, Young-Suk;Hong, Won-Pyo
    • The Journal of Engineering Geology
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    • v.19 no.2
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    • pp.191-203
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    • 2009
  • The effect of stabilizing piles on cut slopes is checked and the behavior of slope soil and piles are observed throughout the year by field measurements on the large-scale cut slopes. 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 are gradually increased and rapidly decreased at depth of sliding surface. As the result of measuring deformation, the depth of sliding surface below the ground surface can be known. Based on the measuring the depth of the sliding surface, some earth retention system including stabilizing piles were designed and constructed in this slope. To check the stability of the reinforced slope using stabilizing piles, an instrumentation system was installed. As the result of instrumentation, the maximum deflection of piles is measured at the pile head. 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. The deflection of piles is increased during cutting slope in front of piles for the construction of soil nailing. As a result of research, the effect and applicability of stabilizing piles in large-scale cut slopes could be confirmed sufficiently.

Evaluation of Dynamic Behavior for Pile-Supported Slab Track System by 3D Numerical Analysis (3차원 수치해석을 통한 궤도지지말뚝의 동적거동 평가)

  • Yoo, Mintaek;Back, Mincheol;Lee, Ilhwa;Lee, Jinsun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.21 no.5
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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.