Earticle

Of the 17,106 domestic reservoirs(as of December 2020), 14,611 are older than 50 years, and these old reservoirs will gradually increase over time. The injection grouting method is most applied to the reinforcement method of the aging reservoir. However, the injection grouting method is not accurate in uniformity and reinforced area. An laboratory model test was conducted to evaluate the applicability of the deep mixing method, which compensated for these shortcomings, as a reservoir reinforcement method. As a result of calculating the hydraulic conductiveity for each method through the model test results, the injection grouting method was calculated as a hydraulic conductiveity value that was about 7.5 times larger than that of the deep mixing method. As a result of measuring the water level change in the laboratory model test, it was found that the water level change decreased in the injection method and deep mixing method compared to the non-reinforcement method. In addition, deep mixing method showed a water level change of about 15% based on 40 hours compared to the injection method, indicating that the water-reducing effect was superior to that of the injection method.

The purpose of this paper is to develop the new deep mixing method installed automatic control equipments for the better construction in deep mixing and grouting. Civil, geotechnical, electronic, and communication experts have worked together for a long time for the development of automatic measuring devices using wire and wireless transmitting-receiving set. A series of laboratory and field experiments were carried out to check the reliability and field applicability of this system. New total automatic control system including automatic devices for checking angle, depth and quantity of injected grout was invented from the result of this research.

본 연구에서는 2차원 및 3차원 유한요소 해석을 이용하여 심층혼합처리 공법에 의한 연약지반 개량시 개량 심도를 결정 하였고, 그 결과는 다음과 같았다. 1. 2차원 해석 결과는 3차원 해석 결과 보다 약 10% 정도 크게 해석되었다. 2. 연약지반의 치환율이 5%이하 일 때 침하량은 급격히 증가하였다. 3. 심층혼합공법으로 연약지반 개량시 횡방향 간격 3m, 종방향 간격 6m, 그리고 8m의 심도로 개량하는것이 가장 경제적인 것으로 나타났다. 4. 심층혼합공법으로 연약지반 개량시 2차원 유한요소 해석보다 3차원 유한요소 해석으로 결정되어야 한다.

The study decided the improvement depth of soft ground of deep mixing method through 2 and 3 dimension finite element method and following results were acquired. 1. 2 dimension analysis shows settlement 10% more estimated than 3 dimension analysis. 2. When the rate of replacement is under 5%, the settlement sharply increased. 3. The most economical design for the levee was decided 3.0m for width direction, 6.0m for length direction and 8.0m for improvement depth. 4. When the soft ground is developed through deep mixing method, the decision of improvement should be decided through 3 dimension analysis than 2 dimension analysis.

Deep mixing method has been used for ground improvement and foundation system for embankment, port and harbor foundations, retaining wall, and liquefaction mitigations. It has attractive benefits because it is not only improved strength of soft ground but superior for prevention of settlement. However, the quality controls of improved mass affect to the efficiency of the deep mixing method is not properly established. These effects vary depending upon the construction environments and conditions of agitation in consideration of an agitator. The strength and shape of the improved column are not unique and these are affected by mechanical properties of agitators. In this study, in order to investigate the efficiency of deep mixing method for ground improvement on a soft clay ground, experimental studies are performed considering mechanical properties of agitator; the location of exit-hole of admixtures, an angle of mixing wing and a speed of revolution. The experiments are conducted with the simulated apparatus for deep mixing plant that reduced the scale in 1:8 of the real plant. According to the results, the diameter and shape of improved column mass vary depending on the mechanical properties and operating conditions of agitator. Its quality is better when the exit-hole of admixtures is located in the mixing wing, when an angle of mixing wing is large, and when the speed of revolution is rapid.

The purpose of this paper is to present and discuss some of harbor foundation constructed on seashore soft ground by Deep Wing Mixing in deep mixing method. A series of laboratory and field experiments including unconfined compressive strength, permeability, geo-physical survey, sea water concentration, lateral and settlement measurement, field core sample were carried out to check physical, mechanical and environmental characteristics of solidified foundation soil treated by HWS solidifying agent. The results from this research showed that Deep Wing Mixing method could be efficiently applied in the construction site of seashore structure foundation.

연약지반 개량을 위한 심층혼합처리공법에 활용하기 위하여 순환자원 활용 무기결합재를 개발하고, 현장 적용성을 평가하였다. 개발 무기결합재는 고로슬래그 미분말과 탈황부산물 및 순환유동층 보일러의 고칼슘 플라이애시를 활용하여 시멘트를 90 % 대체하였다. 개발 무기결합재의 기초 성능 평가를 위해 화학성분과 페이스트 강도특성을 평가하여 슬래그시멘트와 비교 분석하였다. 또한 현장에서 채취한 원지반 토사와 혼합하여 실내 배합시험을 실시하고, 이를 심층혼합처리 현장에 적용하여 개발 무기 결합재의 현장 적용성을 평가하였다. 실내시험 및 현장적용 결과, 순환자원을 재활용한 개발 무기결합재는 심층혼합처리공법에 유용하게 활용될 수 있음을 확인하였다. 그러나 실제 현장은 혼합처리 및 양생 조건 등이 실내보다 열약함으로, 사전에 대상 현장의 토질조건을 반영한 실내 배합시험을 반드시 실시해야 하며, 적절한 현장 품질관리를 위해서는 실내 배합시험 결과를 보수적으로 평가할 필요가 있다.

This study was the application of an inorganic binder made from recycled resources in the Deep Mixing Method(DMM) for improving soft ground beneath road embankments. The chemical composition and paste strength characteristics of the recycled resource-based inorganic binder were compared and analyzed against those of blast furnace slag cement. Additionally, laboratory mixing tests were conducted using soil samples from the original ground, the recycled resource-based inorganic binder, and blast furnace slag cement to compare their compressive strengths. The field applicability of the recycled resource-based inorganic binder in the Deep Mixing Method was evaluated at the same site. Based on a comprehensive review of laboratory test results and field application outcomes, it is concluded that the recycled resource-based inorganic binder can potentially replace blast furnace slag cement in the Deep Mixing Method for ground improvement.

세계 무역 및 항만 산업 환경이 변화함에 따라 선박의 대형화 및 고속화에 대한 대응 필요성이 높아지고 있다. 이에 따라 부산, 울산 등 광역도시를 중심으로 신항만의 건설이 이루어지고 있다. 일반적으로 신항만 건설은 모래 또는 자갈을 사용한 다짐공법이 적용되고 있다. 하지만 모래 또는 자갈이 부족하고, 단가상승으로 인해 경제성 확보가 어려워 최근에는 단시간에 요구되는 압축강도를 확보할 수 있는 심층혼합공법이 사용되고 있다. 따라서 본 연구에서는 순환자원을 이용한 CMD-SOIL을 울산지역에 적용하고, 실내 배합시험 및 현장 확인 보링 결과를 분석하여 적용성을 판단하고자 하였다. 시험결과, CMD-SOIL은 설계 배합강도 이상을 나타내었고, 고로슬래그 시멘트와 유사한 성능을 확보할 수 있는 것으로 분석되었다. 또한 현장에서의 확인 보링 결과, 설계 기준강도 이상을 충분히 확보할 수 있어 울산지역에서의 현장 적용성을 고려할 때 CMD-SOIL의 활용이 가능할 것으로 판단된다.

As global trade and maritime port environments change, the need to respond to larger and faster ships is increasing. Accordingly, new ports are being built around metropolitan cities such as Busan and Ulsan. In general, a compaction method using sand or gravel is applied to the construction of a new port. However, due to the lack of sand or gravel and the difficulty in securing economic feasibility due to the increase in unit price, the deep mixing method has recently been used. Therefore, in this study, CMD-SOIL using circulating resources was applied to the Ulsan area, and the applicability was determined by analyzing the laboratory mixing test and boring results at in-situ. As a result of the test, it was analyzed that it showed more than the design mixing strength, and it was possible to secure the similar performance as blast furnace slag cement. In addition, it was analyzed that the design standard strength can be sufficiently secured as a result of in-situ boring. Therefore, considering the field applicability in the Ulsan, it is judged that the use of CMD-SOIL is possible.

연약지반 개량 공법 중 심층혼합공법에 대한 설계 기법으로는 복합지반으로 해석하는 방법과 말뚝지반으로 해석하는 방법이 있다. 그러나 이러한 해석에 대한 비교 연구는 부족한 실정으로 설계 시 해석 기준을 명확하게 정의 내리는 것에 어려움이 있다. 본 연구에서는 2차원 및 3차원 해석을 통해 성토 높이와 연약지반의 심도, 보강구간의 치환율을 변화시키며 각 조건별로 복합지반과 말뚝지반을 가정하여 해석하였다. 그 결과 최저 개량 심도는 3차원 해석에 비해 2차원 해석 결과가 6.85~9.08% 더 깊은 결과를 도출하였다. 또한 말뚝지반 해석의 경우 복합지반 해석에 비해 개량 심도는 12.22~14.45% 더 깊은 것을 확인하였다. 이 결과를 통하여 보다 정확한 설계를 위해서는 2차원 해석보다는 3차원 해석을 실시해야 하고, 경제적인 설계를 위해서는 복합지반으로 해석해야 하며, 안정적인 설계를 위해서는 말뚝지반 해석을 실시해야 된다고 판단된다.

Design techniques for the deep mixing method, one of the soft ground improvement methods, include two ways to interpret the ground as composite ground and pile ground. However, since comparative studies on these two approaches are insufficient, it is difficult to clearly define the analysis criteria in the design. In this study, two-dimensional and three-dimensional analyses have been performed with different conditions. The three conditions, the embankment height, depth of soft ground, and replacement ratio of reinforcement zones were varied and the analysis was performed on the basis of the assumption of composite ground and pile ground for each condition. As a result, the minimum depth of improvement in the two-dimensional analysis was deeper by 6.85~9.08% than in the three-dimensional analysis. The pile ground analysis showed that the depth of improvement was deeper by 12.22~14.45% than the composite ground analysis. Based on these results, it is concluded that for more accurate design, three-dimensional analysis should be performed rather than two-dimensional analysis. also, it is judged that necessary to analyze the ground as composite ground for economical design, and as the pile ground analysis for stable design.

국제 물류수송을 위해 연약지반에서의 항만개발이 활발하게 추진됨에 따라 항만구조물의 안정성 확보를 위해 시멘트를 원지반 흙과 혼합하여 연약지반에 직접 개량체를 형성하는 심층혼합공법의 적용도 지속적으로 이루어지고 있다. 그러나 시멘트의 경우 제품의 생산과정에서 많은 온실가스를 배출하는 문제가 있어 탄소중립이라는 국가적 목표 달성을 위해 새로운 대체재료의 개발 및 사용이 사회적으로 요구되고 있다. 이에 따라 본 연구에서는 순환자원을 재활용하여 시멘트와 유사한 경화반응을 유도할 수 있도록 개발된 CMD-SOIL을 심층혼합공법용 지반개량재로 사용하여 현장에 적용하고, 적용성을 평가함으로써 시멘트의 대체 가능성을 판단하고자 하였다. 연구결과, 설계기준강도 대비 CMD-SOIL의 압축강도는 현장 배합시험에서 1.46 ~ 2.64배, 확인보링에서 대비 1.2 ~ 5.03배 높은 수준을 나타내어 항만구조물의 안정성 확보에 요구되는 충분한 압축강도의 발현이 이루어지는 것으로 분석되었다. 또한 설계기준강도에 대한 현장에서의 압축강도의 비(λ)도 0.63 ~ 1.14로 기존의 연구결과와 유사한 결과를 나타내어 포틀랜드 시멘트, 고로슬래그 시멘트 등의 기존의 재료와 비교할 때 적용성의 차이는 없어 시멘트를 대체하여 심층혼합공법용 지반개량재로서의 사용이 가능할 것으로 분석되었다.

As port development in soft ground is actively promoted for international logistics and transportation, the Deep Mixing Method (DMM) is continuously applied to form an improved column body directly in the ground by mixing cement with soil to secure the stability of the structure. However, in the case of cement, there is a problem of emitting a lot of greenhouse gases during the production process, so the development and use of new alternative materials are socially required to achieve the national goal of carbon neutrality. Accordingly, in this study, CMD-SOIL, developed to induce a hardening reaction similar to cement by recycling recycled resources, was used as a ground improvement material for the DMM. In addition, it was attempted to determine the possibility of replacing cement by conducting on-site test construction and evaluating applicability. As a result of the study, the compressive strength of CMD-SOIL compared to the design reference strength was 1.46 to 2.64 times higher in the field mixing test and 1.2 to 5.03 times higher than in the confirmed boring. In addition, the ratio (λ) of the compressive strength in the field to the design reference strength was 0.63 to 1.14, which was similar to the previous research results. Therefore, in the case of CMD-SOIL, it is possible to express the compressive strength necessary to secure stability, and there is no difference in applicability compared to existing materials such as ordinary portland cement and blast furnace slag cement, so it was analyzed that it could be used as a ground improvement material for the DMM.

Demands for the automatic measurement on angle and depth of equipment were arisen for the better construction in deep mixing method and grouting method. Civil, geotechnical, electronic, and communication experts worked together for the development of automatic measuring devices using wire and wireless transmitting-receiving set. The results on the development of automatic devices in an industrial installation will be presented.

국가관리 간척지내 원예단지 조성에 필요한 기반기술 중에 하나인, 온실기초 연구가 부족한 실정이며 고사양의 PHC파일을 대체하기 위한 대안을 검토하고자 하였다. 지반개량공법 중 심층혼합처리공법(DCM) 적용시 허용지지력과 침하량 산정을 통하여 온실기초 공법으로써의 적용가능성을 검토하였다. 새만금간척지 농생명용지 1공구 지반조사를 통해 지반 특성을 파악하고, Terzaghi, Meyerhof, Hansen, Schmertmann 이론식을 적용하여 허용지지력과 침하량을 산정하였다. 직경 800mm를 기준으로, 독립 기초 폭과 길이가 3-6m이고, 기초 심도 3-7m 조건에서 허용지지력과 침하량을 검토하였다. 온실기초 심도가 얕고 콘크리트 매트 간격이 넓을수록 시공비가 절감되는 측면을 고려하여 독립 기초 폭과 길이가 4m, 기초 심도가 3m인 경우가 가장 적합한 것으로 판단되었다. 독립 기초 폭과 길이가 4m이고, 기초 심도가 3m인 조건에 대한 해석 결과로 허용지지력은 169kN/m², 침하량은 2.73mm로 지지력은 이론식 대비 5.6%의 오차를, 침하량은 62.3%의 오차범위를 나타냈다. 향후, 위 검증된 설계 값을 기준으로 구조 시험과 침하모니터링을 통해 신뢰성을 검증하고자 한다. 그 외 나무말뚝, 헬리컬기초 등 유리온실, 내재해형온실에 적용 가능한 기초 공법과의 비교 검증을 통해 각각의 장, 단점을 파악하고 PHC 파일의 대체 가능 유무를 검토할 예정이다. 이는 온실 유형별 시공 공법을 선정하는데 필요한 기초 데이터로 제시될 수 있을 것으로 기대된다.

In order to expand facility agriculture and reduce greenhouse construction costs in reclaimed land, a greenhouse foundation method that satisfies economic feasibility and structural safety at the same time is required. As an alternative, the allowable bearing capacity and settlement were reviewed when the DCM(Deep cement mixing) method was applied among the soft ground reinforcement methods. To examine the applicability of the greenhouse foundation, the allowable bearing capacity and settlement were calculated by applying the theory of Terzaghi, Meyerhof, Hansen, and Schmertmann. In case of the diameter of 800mm and the width and length of the foundation of 4m, the allowable bearing capacity was 179kN/m² and the settlement was 7.25mm, which satisfies the required bearing capacity and settlement standards. The calculation results were verified through FEM(Finite element method) analysis using the Mohr-Coulomb material model. The allowable bearing capacity was 169kN/m² and the settlement was 2.52mm. The bearing capacity showed an error of 5.6% compared to calculated value, and the settlement showed and error of 65.4%. Through theoretical calculations and FEM analysis, it was confirmed that the allowable bearing capacity and settlement satisfies the design criteria as a greenhouse foundation when the width and length of the foundation were 4m. Based on the verified design values, it is expected to be able to present the foundation design criteria for greenhouses through empirical tests such as bearing capacity tests and long-term settlement monitoring.

As the Deep Cement Mixing Method is composed of drilled natural soft soil structure and injected cement slurry to be mix together in it, the nature of excavated ground is influenced directly to the application of constructability. Also the nature of in situ soil is the main material, the mix design and construction work plan should be established before the investigation of soil which is performed through the whole site confirm the soil parameter before construction. The nature of investigated soil and water level as should be performed accurately.

심층혼합처리공법에서 원지반과 개량재에 의해 형성되는 혼합처리토에 산업폐기물중 하나인 폐타이어와 기존 토목공사에서 섬유보강재로 사용되고 있는 강섬유를 혼합하여 보강재 및 개량재의 혼합비에 따른 개량체의 압축강도 특성을 파악하기위해 실내실험을 실시하였다. 개량재(시멘트, 시멘트계 고화재)의 경우는 건토중량에 대한 혼합비를 5%, 10%, 15%로 하였으며, 보강재(폐타이어, 강섬유)의 경우는 건토중량에 대한 혼합비를 0.5%, 1%, 2%로 하였다. 그 결과 개량재의 혼합비가 증가함에 따라 일축압축강도는 증가하였으며, 보강재를 첨가한 경우에는 폐타이어분말의 입자크기와 강섬유의 형상비가 작을수록 강도가 크게 나타났으며, 첨가량이 많아질수록 강도가 저하되는 경향이 나타났다.

Lab-scale deep soil mixing experiments were carried out to investigate the effect of reinforcements on solidified marine soft soils. In the experiments, normal portland cement and HWS(a kind of the cement-type solidifying agent) were used as the solidifying in the mixing rates of 5%, 10%, 15% on the weight base of dried soil and waste tire powder, steel fiber were added to the treated soil as the reinforcement in the mixing rates 0.5%, 1%, 2%. At the result of, unconfined compressive strength increases as agent mixing rates increases, particle size of waste tire powder and aspect ratio of steel fiber decreases, and reinforcement mixing rates decreases.

본 연구에서는 심층혼합처리공법에 관하여 저자들에 의해 수행된 국내/외 설계, 시공 및 품질관리에 대한 평가와 고찰을 수행하였고, 추후 DCM 공법의 발전을 위한 개선 사항들을 제시하였다. 본 연구 결과, 실내배합실험 시 강도에 대한 단면적 보정이 필요하고, 외삽법 적용 시 실제와 다른 결과가 도출될 수 있으므로 주의가 요구됨을 알 수 있었다. 설계 시 개량율과 개량형식 등을 모두 고려하여 적용 가능한 설계법을 선정해야 하며, 안전율이 적용된 허용압축강도는 안정성 검토를 위한 기준치를 의미하는 것이지 설계 지반정수가 아님을 확인하였다. 응력분담비의 경우 관행적인 값을 적용하기 보다는 설계 조건을 반영한 실험 및 이론적 응력분담비를 산정해야 경제적인 설계를 수행할 수 있었다. 시공 시 선천공이 예상되는 경우 증가된 함수비가 원지반 대비 크지 않은 경우 함수비 증가를 고려하지 못한 결과를 사용하여도 큰 문제가 발생하지 않는 경우도 있었다. 또한, 개량길이 대비 선단처리 길이의 비율이 높은 경우 시공 시 단위길이당 설계 시멘트량이 적게 주입될 수 있음을 확인하였다. 품질관리 시 개량체 코어링은 1축 개량체는 D/4~2D/4, 다축 개량체는 D/4 지점이 최적인 것으로 평가되었다. 품질관리를 위한 항목으로 개량체의 일축압축강도와 더불어 TCR을 고려하는 기준이 국내 실정에 더 적합할 것으로 판단된다.

In this study, evaluation and consideration of domestic/overseas design, construction, and quality control performed by the authors on the deep cement mixing method were performed, and improvements for the development of the DCM method were suggested in the future. As a result of this study, it was found that the cross-sectional area correction for strength is required during the laboratory test of mix proportion, and caution is required because the extrapolation method may lead to different results from the actual one. Applicable design methods should be selected in consideration of both the improvement ratio and the type of improvement during design, and it was confirmed that the allowable compressive strength to which the safety factor was applied refers to the standard value for stability review and not the design parameters. In the case of the stress concentration ratio, rather than applying a conventional value, it was possible to perform economical design by calculating the experimental and theoretical stress concentration ratio reflecting the design conditions. In the case where pre-boring is expected during construction, if the increased water content is not large compared to the original, there were cases where a major problem did not occur even if the result that did not consider the increase in water content was used. In addition, it was confirmed that when the ratio of the top treatment length to the improved length is high, a small amount of design cement contents per unit length can be injected during construction. In the case of quality control, it was evaluated that D/4~2D/4 for single-axis and D/4 point for multi-axis were optimal for coring of grouting mixtures. As an item for quality control, it is judged that the standard that considers the TCR along with the unconfined compressive strength of grouting mixtures is more suitable for the domestic situation.

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.

In this study, laboratory mixture design test and field test were performed to evaluate applicability of eco-friendly binder material (CMD-SOIL) using desulfurized dust in deep cement mixing method (DCM). As a result of laboratory mixture design test, the uniaxial compressive strength of CMD-SOIL was up to 1.136 times bigger than slag cement by changing the water content, mixing rate, and W/B. Also, it had shown the strength up to 1.222 times bigger in shell content and up to 1.363 times in mixing of floating soil. As a result of field test, field strength/laboratory design criterion strength ratio (${\lambda}$) is shown 0.77. And this result was similar to earlier studies. From this result, CMD-SOIL can show the same efficiency compared with existing binder.

To establish the design criteria for construction of the rubble mound on improved ground, two kinds of analyses for the soil deformation behavior and the slope stability were performed on various cases for rubble mounds, soft grounds and back fills with application of the finite element method and the Bishop simplified method. The horizontal displacements and settlements at the crest of rubble mounds were analyzed as a function of the safety factor of embankments. The analyzed result shows that the soil movement increases considerably when the safety factor of rubble mounds is lower than 1.3.

본 연구에서는 오거비트에 대한 향후 연구개발 방향을 설정하기 위하여 전체 심층혼합처리공법에 대한 한국, 미국, 일본 및 유럽에서의 출원 공개/등록된 특허를 중심으로 특허 동향을 분석하였다. 심층혼합처리공법을 대상으로 기술 범위에 따라 1차적으로 날개 형태와 로드의 개수로 분류하고, 2차적으로 스크류 타입과 회전축의 타입에 따라 8가지로 분류하였다. 특허 검색 결과 총 2,815개가 검색되었으며 중복제거 및 필터링을 통하여 448건의 유효 분석대상 특허를 선별하였다. 특허건수와 성장단계를 통한 포트폴리오 분석 결과 성장가능성이 높다고 판단되는 오거를 핵심기술로 선정하였으며, 이에 대한 특허장벽 분석을 통하여 핵심기술과 유사성이 높은 특허가 있을 경우 회피설계 및 타기술과 차별화된 기술 개발을 할 수 있는 기초자료를 제시하였다.

To set up the future research and development direction for Auger bit, this study analyzed publicized patent trends of Deep Cement Mixing method (DCM) in Korea, USA, Japan, and Europe. DCM method was firstly classified into wing shapes and the number of rods according to the technical scope, and secondly, classified into 8 types according to type of screw and rotation axial. A total of 2,815 patents were searched and 448 validated patents were selected through de-duplication and filtering. As a result of the analysis of the portfolio through the number of patents and growth stages, it was selected as the core technology that auger is deemed to have high growth potential and if there is a patent similar to core technology through a patent barrier analysis, the basic data is suggested to develop the design around and differentiated technologies.