하향력을 받는 말뚝-지반 접촉면의 슬립 효과

정상섬,이철주 한국지반공학회 2003 한국지반공학회논문집 Vol.19 No.3

지반공학분야에서 ISO 규격개발 현황

정상섬,김인균 한국지반공학회 2005 지반 : 한국지반공학회지 Vol.21 No.5

현장시험을 통한 개단말뚝의 폐색효과에 대한 연구

정상섬,고준영 한국지반공학회 2014 한국지반공학회논문집 Vol.30 No.12

This paper presents an experimental study of the plugging effect on the capacity of open-ended piles installed insandy soil. Full-scale tests, including dynamic and static axial-compression load tests, were carried out on threeinstrumented piles with different diameters (508.0, 711.2 and 914.4 mm). To measure the outer and inner shaft resistancesacting on the piles, a double-walled system was utilized with instrumented strain gauges on the outside and inside wallsof the pile. The results of field tests show that the inner shaft resistance was mostly mobilized at the location betweenthe pile tip and 18-34% of the total plug length. It was found that the soil plugging in the lower portion has influenceon the inner shaft resistance. In addition, it can be also demonstrated that the ratio of inner shaft resistance plus annulusload resistance to total resistance decreased with increasing pile diameters. The results of these tests show that therelationship between the degree of plugging and pile diameter is clearly established. Direct observations of the soil plugswere made and used to quantify both the plug length ratio (PLR) and the incremental filling ratio (IFR). Based onthis result, it was found that the N value of the standard penetration test (SPT) is highly correlated with the IFR.

Coupled Effect of Soil Nail/Slope Systems

정상섬,이진형,이선근,Jeong Sang Seom,Lee Jin Hyung,Lee Sun Keun Korean Geotechnical Society 2005 한국지반공학회논문집 Vol.21 No.2

In this paper, a numerical comparison of predictions by limit equilibrium analysis and finite difference analysis is presented for slope/soil-nail system. Special attention is given to the coupled analysis based on the explicit-finite-difference code, FLAC 2D. To this end, an internal routine (FISH) was developed to calculate a factor of safety for a soil nail slope according to shear strength reduction method. The case of coupled analyses was performed for soil nails in slope in which the soil nails 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 method was verified by the comparison with other analysis results. 본 연구에서는 쏘일네일로 보강된 사면을 한계평형 해석법과 2차원 유한차분 해석을 수행하여 그 결과를 비를 분석하였다. 특히, 유한차분법을 이용한 FLAC 2D를 바탕으로 하는 커플링 해석에 주안점을 두었으며, FLAC을 이용하여 전단강도감소기법에 따른 보강사면의 안전율을 계산하기 위해 FLAC의 내장언어인 FISH를 이용하여 작성하였다. 커플링 해석에서 보일네일에 의한 안정화된 사면을 해석하기 위해 쏘일네일 거동과 사면안정을 동시에 고려하였다. 따라서 본 연구에서는 이 두 방법을 적용하여 쏘일네일의 사면내 설치위치, 설치각도, 설치간격 등에 따라 각각의 활동파괴면 및 안전율을 비판분석하였으며 강도정수 감소법을 적용한 해석기법의 적용성과 타당성 분석을 수행하였다.

지반공학분야에서 ISO 규격개발 현황

정상섬,김인균 한국지반공학회 2005 지반 : 한국지반공학회지 Vol.21 No.4

단일 현장타설말뚝의 가상고정점 설계를 보완한 상부기둥-하부말뚝 최적 길이비 분석

정상섬,김재영,Jeong, Sangseom,Kim, Jaeyoung 대한토목학회 2013 대한토목학회논문집 Vol.33 No.5

본 연구에서는 단일 현장타설말뚝의 가상고정점을 고려한 해석과 기둥-말뚝을 3차원 전체 모델링한 해석을 비교 분석하여 가상고정점 해석법의 적정성을 평가하였다. 또한, 말뚝 길이, 기둥 및 말뚝 직경, 철근비, 지반조건 등 주요 영향인자에 따라 단일 현장타설말뚝의 거동 평가를 수행하였으며, 이를 통해 가상고정점 해석을 보완한 최적 기둥-말뚝 길이비를 분석하였다. 본 연구결과, 가상고정점을 고려한 해석은 전체 모델링한 해석과 비교하여 침하량과 수평변위를 작게 예측하였으나, 반대로 축력과 휨모멘트는 가상고정점을 고려한 해석에서 크게 나타났다. 따라서 가상고정점을 통한 해석법은 실제 구조물 거동과 다른 단부조건으로 단일 현장타설말뚝의 정확한 거동을 파악하기엔 무리가 있음을 알 수 있었으며, 이에 단일 현장타설말뚝의 정확한 설계를 위해서는 3차원 전체 모델링한 해석이 필요한 것으로 판단되었다. 또한 본 연구에서는 하부 말뚝 길이와 말뚝의 허용 수평변위 관계를 통해 최적 기둥-말뚝 길이비를 분석하였으며, 이를 통해 가상고정점을 고려한 설계를 다소 보완한 경제적이고 개선된 단일 현장타설말뚝 설계를 수행할 수 있을 것으로 기대되었다. In this study, the virtual fixed point analysis and 3D fully modeling analysis for bent pile structures are conducted by considering various influencing factors and the applicability of the virtual fixed point theory is discussed. Also, the optimized column-pile length ratio is analyzed for supplementing virtual fixed point design and examining a more exact behavior of bent pile structures by taking into account the major influencing parameters such as pile length, column and pile diameter, reinforcement ratio and soil conditions. To obtain the detailed information, the settlement and lateral deflection of the virtual fixed point theory are smaller than those of 3D fully modeling analysis. On the other hand, the virtual fixed point analysis overestimates the axial force and bending moment compared with 3D fully modeling analysis. It is shown that the virtual fixed point analysis cannot adequately predict the real behavior of bent pile structures. Therefore, it is necessary that 3D fully modeling analysis is considered for the exact design of bent pile structures. In this study, the emphasis is on quantifying an improved design method (optimized column-pile length ratio) of bent pile structures developed by considering the relation between the column-pile length ratio and allowable lateral deflection criteria. It can be effectively used to perform a more economical and improved design of bent pile structures.

암반에 설치된 현장타설말뚝의 극한선단지지력에 관한 연구

정상섬,이재환,김도현 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.11

The end bearing capacity of rock-socketed drilled shafts under axial loading is investigated by Hoek-cell tests anda numerical analysis. From the test results, it was found that the ultimate end bearing capacity (qmax) was influencedby pile diameter, rock mass modulus and the spacing of discontinuity. A new ultimate end bearing capacity methodis proposed by taking end bearing capacity influence factors, including rock mass discontinuity, based on field data. Through comparisons with other field data, the proposed qmax method represents a definite improvement in the predictionof ultimate end bearing capacity of rock-socketed drilled shafts.

보강날개로 보강된 수중잠제 지지말뚝의 보강효과 분석

정상섬,홍문현,고준영,Jeong, Sangseom,Hong, Moonhyun,Ko, Jun 대한토목학회 2015 대한토목학회논문집 Vol.35 No.4

본 연구에서는 보강날개로 보강된 수중잠제 지지말뚝의 보강효과를 분석하기 위하여 하중전이거동을 분석하였다. 먼저 3차원 유한요소해석을 통해 말뚝의 변위 및 하중전이곡선(지반반력) 결과로부터 보강효과를 확인하고, 하중전이곡선에서 극한저항력 비율로 보강말뚝의 수평 및 인발하중에 대한 보강계수를 산정함으로써 보강효과를 정량화 하였다. 산정된 보강계수를 쌍곡선 하중전이함수의 극한저항력 $p_u$와 $t_{max}$에 곱해서 보정상수(fitting parameter)로 적용하여 보강효과를 고려한 하중전이함수를 제안하였다. 제안된 하중전이함수가 수치해석 결과를 잘 반영하고 있는지 확인하기 위해 3차원 유한요소해석을 비교하여 보강말뚝의 하중전이거동을 분석하였다. 제안된 하중전이함수를 하중전이법 해석에 적용하여, 실제 수중잠제를 해석한 결과 보강말뚝의 전단력, 휨 모멘트, 변위가 무보강말뚝보다 작게 발생하고, 지반반력은 더 크게 발생하여 비교적 경제적인 설계가 가능할 것으로 판단된다. The use of pile reinforcement is considered as one of the most promising techniques for improving load carrying capacity of piles in offshore area. In this study, to consider the horizontal and uplift bearing capacity of submerged breakwater bearing pile, exclusive analysis on load-transfer behaviour of pile was conducted. First of all, check the reinforcing effect from the three-dimensional finite element method, and estimate load transfer curve (ground reaction force). Based on these results, the reinforcing effect was quantified by estimating the coefficients of horizontal and uplift reinforcement of reinforced piles. Load transfer function with consideration of the reinforcing effect was proposed from estimated coefficients. A comparison of the analysis using the proposed load transfer function with three-dimensional finite element analysis has resulted that the proposed load transfer function is displaying good accuracy of predicting behavior of the load transfer between the pile and soil reinforcement. Interpretation of the submerged structure by applying a load transfer function considering the reinforcing effect, has shown that the reinforced pile's shear, bending moment and displacement are less than that of non-reinforced piles, while the subgrade reaction modulus arises greater. Thus, it is expected to be relatively cost effective in terms of design.

Soil Nail로 보강된 현장타설말뚝의 하중전이 분석

정상섬,함홍규,이대수 한국지반공학회 2004 한국지반공학회논문집 Vol.20 No.1

In this study the load distribution and settlement of soil nailed-drilled shafts subjected to axial loads were evaluated by a load-transfer approach. Special attention was given to the reinforcing effects of soil nails placed from the shafts to surrounding weathered- and soft-rocks based on an analytical study and a numerical analysis. An analytical method that takes into account the number, the positions on the shaft, the grade, and the inclination angle at which the soil nails are placed was developed using a load transfer curve methods. Through the comparative study, it is found that the prediction by present approach simulates well the general trends observed by the in-situ measurements and numerical results SHAFT 4.0. It is also found that the reinforcing effects of soil nails increases in the order of hard-, soft- and weathered-rock since the ultimate shaft resistance far large bored piles in weathered rocks is fully mobilized after small displacements of the shaft, compared to the soft- and hard-rocks and subsequently the side resistance is transferred down to the soil nails.

교각세굴을 고려한 말뚝기초의 해석

정상섬,서정주,원진오 한국지반공학회 2002 한국지반공학회논문집 Vol.18 No.3