• 한국산학기술학회논문지
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• 제12권1호
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• pp.500-506
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• 2011

본 연구에서는 일반적으로 연약지반 개량 공사에 사용하는 심층혼합처리 공법을 도심지 공사에서 지반개량 공법으로 적용하는 방안을 평가하였다. 심층혼합처리 공법을 협소한 도심지 현장에서도 시공이 가능하도록 소형화시킨 시공 장비를 사용하여 서울 시내 재개발 현장에서 기초 지반개량 목적으로 적용하고 개량한 지반의 강도 특성, 지반교반 시 발생한 진동, 시공위치와 인접한 석축구조물에 발생한 변위를 측정하였다. 강도 시험 및 현장계측 결과 심층혼합처리 공법은 원지반의 강도를 효과적으로 개량시켰으며 시공 시 발생시킨 진동과 인접 구조물에 발생한 변위가 미소하여 도심지 공사에서 요구하는 기준을 만족시키는 것으로 판단되었다. 따라서 심층혼합처리 공법은 소음 및 진동 문제가 중요한 고려사항인 도심지 공사에서 기초공법으로 유용하게 적용할 수 있을 것으로 판단된다.

• Geomechanics and Engineering
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• 제21권4호
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• pp.357-369
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• 2020

Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 2차
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• pp.61-67
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• 2010

Thick soft clay deposits which are generally located at the west and south coast of the Korean peninsula have complicated characteristics according to their orientation and formation history. Thus, several geotechnical problems could possibly occur when those soft clay deposits are used as foundations for marine structures. Deep cement mixing (DCM) method is one of the most widely used soft soil improvement method for various marine structures, nowadays. DCM method injects binders such as cement into the soft ground directly and mixes with the in-situ soil to improve the strength and other geotechnical properties sufficiently. However, the natural impacts induced by dynamic motions such as ocean waves, wind, typhoon, and tusnami give significant influences on the stability of marine structures and their underlaying foundations. Thus, the dynamic properties become important design criteria to insure the seismic stability of marine structures. In this study, the dynamic behavior of cemented Busan clay is evaluated. Laboratory unconfined compression test and resonant column test are performed on natural in-situ soil and cement mixed specimens to confirm the strength and strain-dependent dynamic behavior variation induced by cement mixing treatment. Results show that the unconfined compressive strength and shear modulus increase with curing time and cement content increment. Finally, the optimized cement mixing ratio for sufficient dynamic stability is obtained through this study. The results of this study are expected to be widely used to improve the reliability of seismic design for marine structures.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1294-1300
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• 2009

Recently, excavations in highly congest urban area have been increased. For the excavations conducted in extremely narrow spaces, we have been developing a novel soil reinforcement system of temporary retaining walls by using deep cement mixing method. The developing method installs largerdiameter ($\Phi$=300~500mm) and shorter reinforcement blocks than previous reinforcement system for mobilizing friction with soils, therefore it has advantages of not only shortening the length of reinforcement system but also reducing the amount of reinforcement. In this study, we performed a numerical analysis of the new reinforcement system by using a commercial finite element program, and evaluated the behavior of the reinforced retaining wall system under various conditions of the length, the diameter, the spacing, and the angle of the reinforcement system.

• 한국지반신소재학회논문집
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• 제15권2호
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• pp.1-12
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• 2016

본 연구에서는 기존의 심층혼합처리공법용 안정재의 문제점을 해결하기 위해 탈황분진을 이용하여 개발한 친환경 지반안정재(CMD-SOIL)의 적용성을 평가하기 위해 실내배합시험 및 현장시험시공을 실시하였다. 실내배합시험 결과 함수비, 투입비 및 W/B 변화에 따른 CMD-SOIL의 일축압축강도가 기존의 고로슬래그 시멘트와 비교하여 최대 1.136배 큰 것으로 나타났고, 패각이 함유된 흙 재료에서는 최대 1.222배, 부상토가 혼합된 시료에서는 최대 1.363배 큰 것으로 나타났다. 또한 현장시험시공 결과, 실내배합강도와 현장강도의 비(${\lambda}$)가 0.77로 나타나 기존의 연구결과(${\lambda}=2/3$)와 유사한 경향을 보이고 있어 기존의 안정재와 비교하여 동등 이상의 성능을 발휘할 수 있을 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.323-330
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• 1999

Daylight collapse have been occurred by about 5.0m deep at ground surface and collapse of the crown head part of the tunnel have connected to the ground surface during first step of shotcrete work after blasting of upper half section of the tunnel driving at two-way double track tunnel face section on highway construction. This study is for a successful illustration case for the earth improvement method through applying such strengthening methods as cement milk grouting, S.G.R grouting,, steel pipe reinforced multi-step grouting etc. for the purpose of earth strengthening of loosened earth block occurred by tunnel collapse.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 3차
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• pp.96-103
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• 2010

The GK immersed tunnel as a part of the Busan-Geoje Fixed Link Project, introduced the immersed tunnel method into Korea for the first time. This challeging project to be completed in 2010 will open a new era to link oceans of the world with optimized design and safety for future use. The immersed tunnel method would possibly suitable for use in construction of a sub sea tunnel from Korea to Japan and from Korea to China that could potentially be built in the distant future. We hope the techniques learned from the Busan-Geoje Fixed Link Project can be applied to further projects in the near future.

• Computers and Concrete
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• 제32권3호
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• pp.327-337
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• 2023

Concrete is the most widely used building material, with various types including high- and ultra-high-strength, reinforced, normal, and lightweight concretes. However, accurately predicting concrete properties is challenging due to the geotechnical design code's requirement for specific characteristics. To overcome this issue, researchers have turned to new technologies like machine learning to develop proper methodologies for concrete specification. In this study, we propose a highly accurate deep learning-based predictive model to investigate the compressive strength (UCS) of lightweight concrete with natural aggregates (pumice). Our model was implemented on a database containing 249 experimental records and revealed that water, cement, water-cement ratio, fine-coarse aggregate, aggregate substitution rate, fine aggregate replacement, and superplasticizer are the most influential covariates on UCS. To validate our model, we trained and tested it on random subsets of the database, and its performance was evaluated using a confusion matrix and receiver operating characteristic (ROC) overall accuracy. The proposed model was compared with widely known machine learning methods such as MLP, SVM, and DT classifiers to assess its capability. In addition, the model was tested on 25 laboratory UCS tests to evaluate its predictability. Our findings showed that the proposed model achieved the highest accuracy (accuracy=0.97, precision=0.97) and the lowest error rate with a high learning rate (R2=0.914), as confirmed by ROC (AUC=0.971), which is higher than other classifiers. Therefore, the proposed method demonstrates a high level of performance and capability for UCS predictions.

• 한국지반공학회논문집
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• 제28권6호
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• pp.71-79
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• 2012

해안지역의 연약지반을 개량하기 위한 지반개량공법으로 가장 많이 사용되었던 모래다짐말뚝공법이나 사석치환공법은 최근 거의 사용되지 않으며, 대신 시멘트로 연약점토를 강제 교반시켜 고형화시키는 DCM(Deep Cement Mixing)공법이 많이 사용되고 있다. DCM공법이 주로 적용되는 해안지역에는 점토 이외에 모래와 같은 사질토도 존재하므로 본 연구에서는 해수에 포함된 염분과 양생방법이 시멘트로 고결된 모래의 일축압축강도에 어떤 영향을 미치는 지 연구하였다. 다섯 종류의 시멘트비를 사용하여 다짐방법으로 공시체를 제작한 다음 3일 동안 양생시켜 일축압축시험을 실시하였다. 혼합수로 해수 또는 증류수를 사용한 다음 해상에서 이루어지는 DCM공법을 고려하여 공시체를 해수에 수침시켜 양생하였다. 또한 육상조건과 비교하기 위하여 증류수로 수중양생하거나 대기중 양생도 실시하였다. 혼합수로 해수를 사용한 다음 구속압이 없는 상태로 해수에서 수중양생할 경우 공시체에 여러 균열이 발생하여 고결력이 발현되지 않았다. 시멘트비와 양생방법이 동일한 경우, 혼합수와 양생수로 해수를 사용한 공시체의 일축압축강도는 해수를 사용하지 않은 공시체보다 최대 3.5배 정도 낮게 나타났다. 또한 공시체의 수중양생 시 사용한 양생수보다는 공시체 제작 시 사용한 혼합수에 염분이 포함될 경우 강도 저하에 더 큰 영향을 미쳤다. 시멘트비가 동일한 경우, 사용한 물에 관계없이 대기중 양생한 공시체의 강도가 수중양생한 공시체보다 평균 2배 정도 높게 나타났다.

• 한국지반공학회논문집
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• 제23권7호
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• pp.99-104
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• 2007

심층혼합처리공법은 항만기초, 토류벽구조, 차수벽 및 가시설, 그리고 거축기초와 교량기초 등에서 다양하게 사용되어오고 있다. 이 공법은 지반개량을 통한 침하방지와 안정성확보를 위한 지반강도를 확보하기 위해 시멘트와 혼화제를 현장토와 혼합하는데 있어서 가장 효율적이고 경제적이어야 한다. 본 연구에서는 교반날개의 각도, 교반속도 등에서 다양한 교반조건을 적용하여 실내실험을 수행하였다. 실내실험은 현장 타설장비를 1:8 비율로 축소하여 제작하였다. 최적의 교반조건을 도출하기 위하여 다양한 교반조건에 따른 심층혼합처리 개량체의 강도를 분석하였다. 연구결과, 심층혼합처리공법의 교반조건은 개량체의 강도와 형상에 아주 큰 영향을 미치고 있음을 확인하였다.