• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.466-470
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• 2000

Recently, the calculation of horizontal bearing capacity of piles foundation has been considered very important for earthquake or wind resistant design in Korea. This study deals with the lateral resistance of PHC pile instead of vertical capacity for earthquake resistant design as well as wind. As case study, the prediction values were compared with measured ones based on ASTM. During this research, Matlock & Reese, Davisson & Gill, Broms and Chang's methods were selected in calculating prediction of lateral resistance of PHC piles. In decomposed granite and clayey soils, The result showed that prediction values proposed by Matlock & Reese(Davisson & Gill), Chang and Broms were smaller values than real values. four proposed methods by Matlock & Reese(Davisson & Gill) and Chang based on lateral deflection and Broms by ultimate lateral resistance turned out valid in view of engineering practice.

• Geomechanics and Engineering
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• 제15권5호
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• pp.1101-1111
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• 2018

This study aims to present accurate soil modeling and validation of a single roadside guardrail post as well as a single concrete pile installed near cut slopes or compacted sloping embankment. The conventional Winkler's elastic spring model and p-y curve approach for horizontal ground cannot directly be applied to sloping ground where ultimate soil resistance is significantly dependent on ground inclination. In this study, both grid-based 3-D FE model and particle-based SPH (smoothed particle hydrodynamics) model available in LS-DYNA have been adopted to predict the static behavior of a laterally loaded guardrail post. The SPH model has potential to eliminate any artificial soil stiffness due to the deterioration of the node-connected Lagrangian soil mesh. For this purpose, this study comprises two parts. Firstly, only 3-D FE modeling has been tested to show the numerical validity for a single concrete pile in sloping ground using Mohr-Coulomb material. However, this material option cannot be implemented for SPH elements. Nevertheless, Mohr-Coulomb model has been used since this material model requires six input soil data that can be obtained from the comparative papers in literatures. Secondly, this work is extended to compute the lateral resistance of a guardrail post located near the slope using the hybrid approach that combines Lagrange FE elements and SPH elements by the suitable node-merging option provided by LS-DYNA. For this analysis, the FHWA soil material developed for application to road-base soils has been used and also allows the application of SPH element.

• 한국지반공학회논문집
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• 제36권11호
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• pp.107-117
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• 2020

개단 강관말뚝의 경우 일반적으로 말뚝에 작용하는 외부 주면 마찰력뿐만 아니라 설치과정에서 폐색된 흙이 강관 내부에 작용하는 내부 마찰저항이 존재한다. 내·외부 저항에 따라 극한하중의 변화가 예상되며, 말뚝이 시공된 지반이 점성토일 경우 지반 침하로 유발되는 부주면 마찰력에도 영향을 끼칠 것으로 판단된다. 따라서 본 연구에서는 강관말뚝 내·외부 저항 특성에 따른 거동을 수치해석적으로 분석하고자 하며, 지반 침하 발생 전·후의 마찰력 분포, 축력, 침하량을 산정하였다. 해석 결과, 내부 마찰 저항은 외부 마찰 저항보다 적은 영향을 미쳤지만 전체적인 말뚝 거동에 끼치는 영향을 고려하였을 때, 중요한 요소 중 하나이며 설계 시 두 가지 저항요소를 고려할 필요가 있을 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1406-1416
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• 2008

Soil nailing is used as a method of slope stabilization and excavation support. The design method of soil nail are based on experience or assumption of interaction between soil and reinforcement. Most design methods simply considers the tension of reinforcement for analysis of slope stabilization. Soil nails interact with soils under combined loading of shear and tension. Jewell & Pedley(1990) suggested a design equation of shear force with bending stiffness and discussed that the magnitude of the maximum shear force is small in comparison with the maximum axal force. However, they have used a very conservative limiting bearing stress on nails. This paper discusses that the shear strength of soil nails should not be disregarded with proper bearing stresses on nails. The modified FHWA design method was proposed by considering shear forces on nails with bending stiffness.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 가을 학술발표회 논문집
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• pp.79-86
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• 1994

Two case studies on the application of Pile Driving Analyzer (PDA) are introduced. It is shown that the PDA and CAPWAP are effective tools for the construction control of pile foundations with minimum cost and time. The PDA and CAPWAP techniques are able to evaluate the performace of hammer and driving system: to check the stresses in the pile due to driving: to determine the damage of pile: to predict the ultimate bearing capacity of pile: to estimate the important soil paramaters such as the soil resistance, quake, and damping etc.: and to provide the load - displacement curve from the simulated static load test. Theoretical backgrounds of wave mechanics is briefly reviewed and the methodology of construction control using the PDA is also discussed.

• 한국지반공학회논문집
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• 제34권7호
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• pp.51-58
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• 2018

본 연구에서는 하중 조건에 따른 지반-말뚝 상호작용 시스템의 거동 차이를 분석하기 위해 일련의 원심모형 실험을 수행하였다. 정적 하중 조건의 경우, 말뚝 직경의 50% 수준까지 변위제어를 통해 하중을 재하하였으며, 지진 하중 조건의 경우 0.1g~0.4g 수준으로 1Hz 정현파를 가진하였다. 실험 결과로부터 얻은 정적 및 동적 p-y 곡선을 API p-y 곡선과 비교한 결과, API p-y 곡선과 정적 하중조건에서의 실험 p-y 곡선은 최대 지반반력 값이 20% 이내의 오차를 보인 반면, 동적 하중 조건에서의 실험 p-y 곡선과는 최대 지반반력 값이 5배 이상 차이가 발생하였다. 이는 등가정적 해석에서 기존 API p-y 곡선을 적용할 경우 비선형 영역에서 지반 반력을 크게 과소평가하며 보수적 설계를 야기할 수 있음을 의미한다.

• 한국환경복원기술학회지
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• 제5권3호
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• pp.15-22
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• 2002

To analysis of the embanked slope stability using a jointed reinforcement, the internal stability and the external stability have to be satisfied, respectively. But, because the lengths of ready-made steel-grid were limited, the reinforcements must be connecting themselves to the reinforcing. In this study, the mechanical test was carried out to investigate the tensile failure and the pullout failure at the joint parts of them, which was based on the analysis of reinforced slope in field. Through the tensile tests in mid-air for the jointed steel-grid, the deformation behavior was seriously observed as follows : deformation of longitudinal member, plastic deformation of longitudinal member and of crank part. Those effects were due to the confining pressure and overburden pressure of the surrounding ground. The bearing resistance at jointed part of jointed steel-grid was due to the latter only. The maximum tensile forces were higher about 20kN~27kN than ultimate pullout resistance, but, the results of those was almost the same in mid-soil. The failures of steel-grid occurred at welded point both of longitudinal members and transverse members and of jointed parts. The strength of jointed parts itself got pullout force about 20kN, which was about 65% for ultimate pullout force of the longitudinal members N=2. To the stability analysis of reinforced structure including the reinforced slope, the studying of connection effects at jointed part of reinforcement members must be considered. Through the results of them, the stability of reinforced structures should be satisfied.

• 한국지반공학회논문집
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• 제24권8호
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• pp.89-97
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• 2008

본 연구에서는 자켓앵커와 일반앵커에 대한 현장시험을 통해 자켓앵커의 인발력 발휘 메카니즘을 분석하고 자켓앵커의 지층별 단위주면마찰력을 산정하였다. 6개현장에서 실시된 총 12회의 인발적성시험결과 자켓앵커의 극한인발력이 일반앵커의 극한인발력에 비해 약 $15.38{\sim}295.02%$ 정도 큰 것으로 나타났으며, 동일한 하중단계에서 자켓앵커의 소성변위가 일반앵커의 소성변위보다 약 $20.78{\sim}l,496.45%$ 정도 작은 것으로 나타났다. 특히, 자갈층에서는 250% 이상의 극한인발력 증가와 600% 이상의 소성변위 감소가 발생하여 자켓앵커는 그라우트액의 손실이 발생할 수 있는 지반에 적용성이 우수한 것으로 나타났다. 시험에서 산정된 극한인발력을 이용하여 실트 및 점토지반과 모래, 자갈 및 전석층에서의 지반강도별 단위주면마찰력을 제안하였다. 또한 섬유정착보강재 파열압력시험과 최적주입압력 확인시험을 수행하여 적절한 정착지지체를 형성시킬 수 있는 주입압력 추정 도표를 제시하였다.

• Geomechanics and Engineering
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• 제28권3호
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.

• 한국지반공학회논문집
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• 제26권2호
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• pp.15-22
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• 2010

본 연구에서는 현장 인발시험을 통하여 강관다단 가압식 쏘일네일링의 거동특성을 분석하였다. 이를 위하여 총 10공의 쏘일네일을 풍화토에 시공하여 인발시험을 실시하였다. 인발시험 결과에 의하면 쏘일네일의 극한인발력은 가압식 쏘일네일이 중력식 쏘일네일에 비하여 42~142% 증가하는 것으로 나타났다. 네일과 주변지반 경계면에서의 전단강도는 중력식 네일이 71kPa, 가압식 네일이 95~166kPa를 보이는 것으로 확인되었다. 가압식 쏘일네일의 경우 중력식 쏘일네일에 비하여 그라우트의 직경이 약 12~27% 증가하는 것으로 나타났다. 또한, 공팽창이론에 의한 가압 시 지반변위 산정값과 현장 인발시험을 통하여 측정한 값을 비교하였으며, 그 결과는 대체적으로 비슷한 경향을 보였다.