• 한국터널지하공간학회 논문집
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• 제19권5호
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• pp.799-812
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• 2017

쉴드 TBM 터널에 대한 2차원 수치해석 시 기존 연구에서는 뒤채움재 및 실제적인 내공변위 분포를 적절히 고려하지 않았다. 따라서 본 연구에서는 이를 보완하고자 gap parameter 적용 시 굴착면에서 발생하는 실제적인 내공변위분포를 고려하고, 적정한 뒤채움재 물성치를 적용한 모델링 방법을 제시하였다. 이를 위해 단일층 풍화토 지반을 대상으로 gap parameter와 토피고가 굴착면의 지반손실량과 지표손실량으로 구성되는 체적손실량에 미치는 영향을 분석하였다. 그 결과 대부분의 지표침하가 굴착 직후에 발생하였으며, 토피고 및 gap parameter가 증가할수록 수치해석을 통해 얻은 지표침하곡선의 영향범위가 제안된 이론식보다 넓게 나타났다. 따라서 2차원 수치해석 시 쉴드 TBM 터널의 거동을 정확히 평가하기 위해서는 하중분담률을 이용하여 gap parameter를 적용하고, 뒤채움재의 물성치도 적절히 고려해야 한다고 판단된다.

• 한국터널지하공간학회 논문집
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• 제26권4호
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• pp.303-314
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• 2024

쉴드 TBM (tunnel boring machine) 시공은 일반적으로 세그먼트 설치를 위해 규칙적으로 굴진을 멈추는 것이 요구되어, TBM 굴착과 세그먼트 설치를 병행하는 연속굴착형 쉴드 TBM의 개발에 대한 연구가 국내외에 추진되고 있다. 하지만, 연속굴착형 쉴드 TBM은 기존 쉴드 TBM과 다른 굴착 공정과 이에 따른 특별한 장비 및 유압 시스템이 요구된다. 또한, 연속굴착형 쉴드 TBM 설계 및 시공 사례가 적으므로 연속굴착형 쉴드 TBM 시공을 위한 사전 리스크 평가가 반드시 수행되어야 한다. 본 논문에서는 연속굴착형 쉴드 TBM에 특화된 4가지 사건과 8가지 요인 간의 인과관계를 규명하였다. 이를 기반으로 전문가 설문조사와 리스크 매트릭스를 이용하여 최종적으로 리스크 등급을 도출하였다. 리스크 평가 결과, 붕괴/지표침하의 영향도와 TBM 선형이탈 관련 인과조합의 발생확률이 높게 평가되었다. 또한, 연속적으로 수행되어야 하는 테일보이드(tail void) 뒷채움 미흡과 추진 잭 손상으로 인한 붕괴/지표침하를 방지하기 위한 리스크 저감조치가 사전에 적용해야 함을 알 수 있었다. 이에 따라, 리스크 저감 조치로서 나선형 세그먼트를 따라 배면 전 범위 탐지가 가능한 비파괴탐사 기술 개발과 순차적 추진 잭 가력 방식 고안 및 최적 페데스탈 각도 선정을 제안하였다.

• 한국도로학회논문집
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• 제11권2호
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• pp.239-247
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• 2009

매설관은 기존 포장의 제거와 굴착후 다짐 및 재포장에 의해 시공되며 주변지반의 침하와 균열, 재포장부의 침하발생과 평탄성 저하를 초래한다. 본 연구에서는 매설관의 설치와 뒷채움재의 다짐 및 재포장 등 일련의 시공과정에서 간과되고 있는 포장하부구조의 물성치 획득방법으로서 공내재하시험 및 동평판재하시험을 채택하였다. 공내재하시험 비교 결과, 관매설 및 새로운 뒷채움재의 다짐으로 인해 충분한 하부지반 강성이 굴착전에 비하여 획득되지 못함을 확인하였다. 재포장층의 두께는 기존층에 비하여 더 두껍게 설계되어야 함을 의미한다. 동평판시험은 공내재하시험에 비하여 층표면 강성을 파악하기에는 효과적이지만 매설관의 하부구성층 또는 뒷채움재 등의 전체 강성 또는 다짐도를 정확히 파악할 수 없음을 확인하였다.

• Structural Engineering and Mechanics
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• 제61권2호
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• pp.245-253
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• 2017

The increasing lack of good quality soils allowing the development of roadway, motorway, or railway networks, as well as large scale industrial facilities, necessitates the use of reinforcement techniques. Their aim is the improvement of the global performance of compressible soils, both in terms of settlement reduction and increase of the load bearing capacity. Among the various available techniques, the improvement of soils by incorporating vertical stiff piles appears to be a particularly appropriate solution, since it is easy to implement and does not require any substitution of significant soft soil volumes. The technique consists in driving a group of regularly spaced piles through a soft soil layer down to an underlying competent substratum. The surface load being thus transferred to this substratum by means of those reinforcing piles, which illustrates the case of a piled embankment. The differential settlements at the base of the embankment between the soft soil and the stiff piles lead to an "arching effect" in the embankment due to shearing mechanisms. This effect, which can be accentuated by the use of large pile caps, allows partial load transfer onto the pile, as well as surface settlement reduction, thus ensuring that the surface structure works properly. A technique for producing rigid piles has been developed to achieve in a single operation a rigid circular pile associated with a cone shaped head reversed on the place of a rigid circular pile. This technique has been used with success in a pile-supported road near Bourgoin-Jallieu (France). In this article, a numerical study based on this real case is proposed to highlight the functioning mode of this new technique in the case of industrial slabs.

• 한국지반환경공학회 논문집
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• 제1권1호
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• pp.57-63
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• 2000

준설토의 체적변화는 여수토를 통해 물과 함께 빠져나간 토립자의 유실량과 침강되어 새로이 형성된 지반 표면에서의 건조수축과 지반 내에서의 자중압밀에 의한 침하량의 합으로 생각할 수 있다. 그러나 현재까지 체적변화요인과 관련하여 자중압밀과 건조수축에 관한 연구에 비해 토립자의 유실과 관련된 연구는 미미한 실정이다. 따라서, 본 연구에서는 준설토의 체적변화요인 중 여수토를 통해 외부로 유실되는 토량을 보다 명확히 규명하기 위해 준설작업을 실시하기 전의 원지반과 준설토를 투기하여 조성된 매립 지역에서, 각각 채취한 시료에 대한 비중계 분석결과에 Marsal의 수정파쇄율을 적용하여 평균잔류율곡선에 의한 유실률 평가방법을 제안하였고, 이를 검증하기 위하여 기존의 방법을 이용하여 평가한 유실률과 비교 검토해 보았다.

• Geomechanics and Engineering
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• 제19권5호
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• pp.407-420
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• 2019

This paper illustrates the results of a series of seismic geotechnical centrifuge experiments to explore dynamic structure-soil-structure interaction (SSSI) of two structures (named S1 and S2) installed on ground surface. A dense homogeneous ground is prepared in an equivalent shear beam (ESB) container. Two structural models are designed to elicit soil-foundation-structure interaction (SFSI) with different masses, heights, and dynamic characteristics. Five experimental tests are carried out for: (1) two reference responses of the two structures and (2) the response of two structures closely located at three ranges of distance. It is found that differential settlements of both structures increase and the smaller structure (S2) inversely rotates out of the other (S1) when they interact with each other. S2 structure experiences less settlement and uplift when at a close distance to the S1 structure. Furthermore, the S1 structure, which is larger one, shows a larger rocking and a smaller sliding response due to the SSSI effects, while S2 structure tends to slide more than that in the reference test, which is illustrated by an increase in sliding response and rocking stiffness as well as a decrease in moment-to-shear ratio (M/H·L) of the S2 structure.

• 한국환경복원기술학회지
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• 제9권5호
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• pp.10-21
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• 2006

For analyze of the bearing capacity, skin friction and settlements of pile on axial compressive loading, both Load transfer tests of pile and pile loading test in field have application to commonly before pile installing. A bearing capacity of pile was affected by the characteristics of surrounding ground of pile. Especially, that is very different because of evaluation of settlement due to each soil conditions of ground depths. The ground characteristics using evaluation of bearing capacity of pile through load transfer analysis depends on N values of SPT, and then a bearing capacity of pile installed soft ground and refilled area may be difficult to rational evaluation. An evaluation of bearing capacity on pile applied axial compressive loading was effected by strength of ground installed pile, unconfined compressive strength at pile tip, pile diameter, rough of excavated surface, confining pressure and deformation modules of rock etc and these are commonly including the unreliability due to slime occurred excavation works. Load transfer characteristics considered ground conditions take charge of load transfer of large diameter pile was investigated through case study applied load transfer tests. To these, matrix analytical technique of load transfer using finite differential equation developed and compared with the results of pile load test.

• 대한원격탐사학회지
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• 제31권4호
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• pp.303-319
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• 2015

The objectives of this paper are to measure surface imperviousness using three different classification methods: per-pixel, sub-pixel, and object-oriented classification. They are tested on high-spatial resolution QuickBird data at 2.4 meters (four spectral bands and three principal component bands) as well as a medium-spatial resolution Landsat TM image at 30 meters. To measure impervious surfaces, we selected 30 sample sites with different land uses and residential densities across image representing the city of Phoenix, Arizona, USA. For per-pixel an unsupervised classification is first conducted to provide prior knowledge on the possible candidate spectral classes, and then a supervised classification is performed using the maximum-likelihood rule. For sub-pixel classification, a Linear Spectral Mixture Analysis (LSMA) is used to disentangle land cover information from mixed pixels. For object-oriented classification several different sets of scale parameters and expert decision rules are implemented, including a nearest neighbor classifier. The results from these three methods show that the object-oriented approach (accuracy of 91%) provides more accurate results than those achieved by per-pixel algorithm (accuracy of 67% and 83% using Landsat TM and QuickBird, respectively). It is also clear that sub-pixel algorithm gives more accurate results (accuracy of 87%) in case of intensive and dense urban areas using medium-resolution imagery.

• 한국농공학회논문집
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• 제64권3호
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• pp.75-83
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• 2022

Recent settlements and sinkhole openings in urban areas have caused social problems such as damage to roads and structures, fear of the public, and loss of property. Several studies have demonstrated that surface subsidence and sinkhole opening are greatly affected by rainfall and rainfall intensity in urban areas. In this paper, we analyzed the relationship with the characteristics of recorded rainfall data using the ground subsidence database reported in major cities. The correlations were found using sedimentation and precipitation data from 2010 to 2014. The duration and intensity of a given precipitation have evolved to obtain an effect on ground sedimentation rate (SR). The results show that the relationship between SR and precipitation is asymptotic and can be modeled by a hyperbolic equation. Through this study, it is possible to predict the occurrence of ground subsidence due to precipitation in advance.

• Geomechanics and Engineering
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• 제30권5호
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• pp.461-469
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• 2022

One of the most important factors that should be considered for using any ground improvement technique is the stability of stabilized soil and the durability of the provided solution for getting the required engineering properties. Generally, most of the earth structures that are constructed on clayey soils are exposing movements due to the long periods of drying or wetting cycles. Over time, environmental changes may result in swells or settlements for these structures. In order to mitigate this problem, this research has been performed on mixtures of high plasticity clay with traditional additives such as lime, cement and non-traditional additives such as polypropylene fiber. The purpose of the research is to assess the most appropriate ground improvement technique by using commercially available additives for resisting the developed desiccation cracks during the drying process and resisting the volume changes that may result during wet/dry cycles as an attempt to simulate the changes of environmental conditions. The results show that the fiber-reinforced samples have the lowest volumetric deformation in comparision with cement and lime stabilized samples, and the optimum fiber content is identified as 0.38%. In addition, the desiccation cracks were not visible on the samples' surface for both unreinforced and chemically stabilized samples. Regarding cracks resistance resulting from the desiccation process, it is observed, that the resistance is connected with the fiber content and increases with the increase of the fiber inclusion, and the optimum content is between 1% and 1.5%.