The Usage of Copper Slag as The Construction Materials

국내의 동제련 과정에서 부산물로 발생되는 동제련 슬래그는 연간 70여만톤 정도이며, 주로 시멘트의 원료, 선박의 녹을 제거하는 샌드블라스팅용 등으로 사용되고 있다. 본 논문에서는 동제련 슬래그를 천연골재 대체용 재료로 이용되는 것 외의 다른 건설재료로써의 그 가능성을 밝히고자 하였으며, 광물원석에서 구리를 제련하는 동제련 과정 중 부산물로 발생되는 동제련 슬래그의 지반공학적인 활용 방안에 ?淪臼? 검토하였다. 동제련 슬래그에 대한 기본적인 물성 시험 및 화학적 분석을 실시하고, 대상토인 해성점토 및 육성점토에 혼합하여 다양한 지반공학적인 시험을 실시하였다. 다짐특성 시험결과, 동제련 슬래그가 첨가될수록 다짐특성이 개선되므로 도로공사시 노견토로의 활용이 가능할 것으로 사료되며, 동제련 슬래그는 샌드 드레인 재료로 사용되는 모래의 입도기준에 모두 만족하는 것으로 나타났다. 샌드 매트용 JIS 및 한국도로공사의 시방기준을 만족하며, 장기 시공시, 동제련 슬래그는 철강 슬래그에 비하여 수경성이 적으므로 연직 배수재나 필터재, 샌드 매트용 재료로써 적합한 것으로 사료된다. 본 논문에서의 연구결과에서 동제련 슬래그는 건설재료로써 지반공학적 특성이 우수하며, 환경보전 및 자원절약, 그리고 사회 경제적 측면에서의 이점으로 인해서 향후 건설부분에서 기존의 재료를 대체할 수 있는 건설용 재료로 예상된다.Copper slag is produced about 700,000 tons annually though copper refining process in Korea. In the paper, a laboratory investigation was carried out to estimate the geotechnical properties of copper slag and examine the feasibility of using the copper slag as a substitute for conventional construction materials and the improvement of the soft clay deposit. The specific gravity of copper slag is 3.45, and pH is 7.83. And the size distribution of the copper slag is well graded, so usage of copper slag will be extended in Geotechnical engineering fields. Copper slag has the permeability of 3.502× 10 exp (-2) ㎝/sec, which is satisfied with the criterion of sand drainage materials.. At the same time, it is thought to be suitable material for sand mat since it meets JIS and Korea Highway Corporation of grain size distribution. The content of CaO from steel slag is about 40 percent while that of CaO from copper slag is about 5 percent. Based on this fact, copper slag has less hardening property compared to steel slag. Therefore, copper slag can be used as vertical drains, filters, and sand mats for improving the soft deposit.Copper slag is produced about 700,000 tons annually though copper refining process in Korea. In the paper, a laboratory investigation was carried out to estimate the geotechnical properties of copper slag and examine the feasibility of using the copper slag as a substitute for conventional construction materials and the improvement of the soft clay deposit. The specific gravity of copper slag is 3.45, and pH is 7.83. And the size distribution of the copper slag is well graded, so usage of copper slag will be extended in Geotechnical engineering fields. Copper slag has the permeability of 3.502× 10 exp (-2) ㎝/sec, which is satisfied with the criterion of sand drainage materials.. At the same time, it is thought to be suitable material for sand mat since it meets JIS and Korea Highway Corporation of grain size distribution. The content of CaO from steel slag is about 40 percent while that of CaO from copper slag is about 5 percent. Based on this fact, copper slag has less hardening property compared to steel slag. Therefore, copper slag can be used as vertical drains, filters, and sand mats for improving the soft deposit

Structural Formation and Identification of The Clay Microfabric

본 논문에서는 점토의 미소구조를 인공적으로 형성하고 확인하는데 목적이 있다. 기존의논문에서는 각 미소구조를 인공적으로 만들기 위해 한 종류의 화학첨가제를 사용하였지만 본 논문에서는 동일한 대상시료에 대해 구조별로 여러 가지 화학첨가제를 사용하여 어떤 첨가제가 각각의 미소구조를 더 잘 형성시키는지를 SEM과 XRD를 사용하여 비교ㆍ분석하였다. 미소구조를 인공적으로 형성하기 위해 이산구조에는 Calgon과 NaOH를 첨가하였고 면모구조 중 염면모구조를 형성하기 위해서는 NaCl과 CaCl₂를 첨가하였으며 비염면모구조를 위해서는 증류수만을 사용하였다. SEM 분석은 정성적인 분석으로 bulk sample을 수직·수평 방향으로 분석한 결과 시각적으로 각각의 미소구조가 형성된 것을 확인할 수 있었다. 또한 XRD 분석을 실시하여 방향성을 정량적으로 분석한 결과, 면모구조에서는 증류수만 사용하여 형성된 sample이 가장 불규칙한 방향성을 가졌으며 이산구조는 NaOH를 첨가한 경우 점토 입자들이 한 방향으로 집중되어 배열된 결과를 보여주었다.This paper is concerned with artificial formation and identification of a clay microfabric. To prepare each microfabric, dispersion and flocculation, a specified amount of the electrolyte was added to the clay. Many different kinds of chemical additives were used for the each microfabric at this paper. To form the dispersion microfabric of a clay, Calgon and NaOH were added, and NaCl, CaCl₂and distilled water were used for the salt and non-salt flocculation fabric, respectively. The structure of the formed samples was evaluated by the scanning electron microscope(SEM) and the X-ray diffratometer(XRD). As a result of tests, the flocculation fabric formed by distilled water was oriented randomly and the sample fabric formed by NaOH was dispersed in direction.This paper is concerned with artificial formation and identification of a clay microfabric. To prepare each microfabric, dispersion and flocculation, a specified amount of the electrolyte was added to the clay. Many different kinds of chemical additives were used for the each microfabric at this paper. To form the dispersion microfabric of a clay, Calgon and NaOH were added, and NaCl, CaCl₂and distilled water were used for the salt and non-salt flocculation fabric, respectively. The structure of the formed samples was evaluated by the scanning electron microscope(SEM) and the X-ray diffratometer(XRD). As a result of tests, the flocculation fabric formed by distilled water was oriented randomly and the sample fabric formed by NaOH was dispersed in direction

Characteristics of Secondary Compression of a Clay

울산의 '삼산'지역은 유기질을 많이 함유한 점성토가 넓고 두껍게 분포되어 있으며, 이러한 연약지반에 고층 구조물이 축조될 경우, 시간이 경과함에 따라 장기적인 침하가 유발되므로 이차압축을 고려하여야 한다. 본 연구에서는 현장에서 채취한 불교란시료에 대하여 실내 표준압밀시험을 수행하고, 그 결과를 이용하여 포화된 '삼산'지역 연약점토의 이차압축특성을 밝혔다. 분석 결과, 자연함수비와 이차압축의 관계는 Mesri의 선보다 상부에 분포하여 이차압축의 영향이 큰 것으로 나타났으며, 정규압밀점토의 침하거동을 하는 것으로 나타났다. 이차 암축지수, Ca와 일차압축지수, Cc 관계는 Ca=0.049Cc + 0.0017의 선형관계식으로 표현할 수 있으며, Cr/Cc가 0.1-0.2의 범위에 있어 팽창성이 큰 예민점토로 나타났다. 따라서, '삼산'지역 퇴적점토의 침하문제를 취급할 경우 이차압축의 영향을 반드시 고려하여야 할 것으로 판단된다.The organic clay is widely and thickly deposited at 'Samsan', Ulsan. Usually the soft soils are settled continuously due to self-weight during a long period. The long-term settlement depending on the time has to consider teh effect of secondary compression. In this research, the secondary compression characteristics of the soft clay has been analysed from the results of standard consolidation tests with the undisturbed samples. The test results of the 'Samsan' clay has been plotted at the upper part in teh Mesri's chart so the effect of secondary compression could not be ignored. The secondary compression index, Ca has been increased linearly with the compression index, Cc; Ca = 0.049 cc + 0.0017. And the ratio of the swell index and the compression index, Cr/Cc has been ranged from 0.1 to 0.2. Consequently, for prediction of the settlement in 'Samsan', the effect of secondary compression has to be considered.The organic clay is widely and thickly deposited at 'Samsan', Ulsan. Usually the soft soils are settled continuously due to self-weight during a long period. The long-term settlement depending on the time has to consider teh effect of secondary compression. In this research, the secondary compression characteristics of the soft clay has been analysed from the results of standard consolidation tests with the undisturbed samples. The test results of the 'Samsan' clay has been plotted at the upper part in teh Mesri's chart so the effect of secondary compression could not be ignored. The secondary compression index, Ca has been increased linearly with the compression index, Cc; Ca = 0.049 cc + 0.0017. And the ratio of the swell index and the compression index, Cr/Cc has been ranged from 0.1 to 0.2. Consequently, for prediction of the settlement in 'Samsan', the effect of secondary compression has to be considered

Mineralogical Properties of the Sedimental Clay in Ulsan

본 연구에서는 울산광역시 남구 삼산동 일원 2개소에서 채취한 시료에 대하여 토질시험 및 X-선 회절(XRD)분석을 실시하여 점토의 광물학적 특성을 분석하였다. 대표시료의 화학성분 분석을 위해 X-선 형광분석(XRF)을 수행하였으며, 그 입자구조와 화학적 특성을 검토하기 위하여 주사전자현미경(SEM)과 에너지분산분광법(EDX)을 이용하여 비교.검토하였다. X-선 회적분석결과, 삼산지역 점토의 주 구성광물은 석영, 장석, 각섬석, 점토광물 등으로 나타났으며, 점토광물의 함량은 깊이에 따라 증가하였다. 점토광물의 정량분석 결과, 일라이트가 주를 이루고 있었으며, 카올리나이트, 녹니석, 스멕타이트 순으로 나타났다. 화확 성분 분석결과, 그 구성비율은 SiO2, Al203, Fe203의 순으로 나타났으며, 그 외 Na203, K20, MgO, CaO가 미량으로 존재하고 있었다. 울산퇴적 점토의 모양은 판상 및 침상이며, 정육면체의 소금결정과 유공충이 포함되어 있어 유기물 함유량과 밀접한 관계가 있음을 알 수 있었다.The purpose of this study is to examine mienralogical properties of the soft clay that is distributed widely in samsan area, Ulsan. XRD analysis were examined to find the quantities of the clay minerals. And SRF, SEM and EDX analysis were also examined to investigate the chemical compositions and the structures of the clay. The properties of the samples from 2 sites in Samsan area were that the minerals of the clay are illite, kaolinite, chlorite, smectite and etc.. The plenty of illite has 38 to 53% of content in whole study area. And kaolinite has 18 to 30% of content, chlorite has 15 to 25%, and smectite has 4 to 12% of content, respectively. The results of SEM observation showed that appearances of Ulsan clay are sheet, plannar or needle form. Ulsan clay include salt crystal of cubic and foraminifera, which are related with the content of organ.The purpose of this study is to examine mienralogical properties of the soft clay that is distributed widely in samsan area, Ulsan. XRD analysis were examined to find the quantities of the clay minerals. And SRF, SEM and EDX analysis were also examined to investigate the chemical compositions and the structures of the clay. The properties of the samples from 2 sites in Samsan area were that the minerals of the clay are illite, kaolinite, chlorite, smectite and etc.. The plenty of illite has 38 to 53% of content in whole study area. And kaolinite has 18 to 30% of content, chlorite has 15 to 25%, and smectite has 4 to 12% of content, respectively. The results of SEM observation showed that appearances of Ulsan clay are sheet, plannar or needle form. Ulsan clay include salt crystal of cubic and foraminifera, which are related with the content of organ

A Study on Soil Properties by Cone Penetration Test in Ulsan Samsan Area

본 논문에는 피에조콘관입시험을 이용하여 울산 삼산지역 흙의 특성과 거동을 평가하였고, 또한 피에조콘관입시험의 결과들을 불교란 시료를 채취하여 행한 실내 시험결과들과 비교하였다. 울산 삼산지역의 흙은 유기물을 다량 함유하고 있으며 소성이 작은 점토로 나타났다. 과압밀비(O.C.R, overconslidation ration)는 약 1 또는 1 보다 작은 값으로 나타났으며 삼산지역의 흙은 정규압밀토 또는 미압밀토인 것으로 밝혀졌다. 또한 피에조콘관입시험과 표준관입시험 사이의 관계는 Kulhaway & Mayne 이 제안한 경험공식과 도표가 적합한 것으로 나타났다. 간극수압소산시험에 의하여 구해진 수평압밀계수와 Kh/Kv는 각각 1.0 ~ 6.24 ×10-³㎠/sec dhk 1.8 ~ 2.58 이었다.In this paper, the properties of Samsan soil in Ulsan were evaluated by the piezocone test. The results of the piezocone test were compared with the laboratory test results of the undisturbed sample. Samsan soil that contains various kind of organic was found out the low plastic clay. The overconsolitaion ratio (O.C.R) was carried out about 1 or less than 1. Hence it is provided that the soil is the normally consolidated clay or under consolidated clay. In addition, The correlations between the piezocone test and the standard penetration test were conformed to the charts and the empirical formulas by Kulhaway & Mayne. The coefficient of consolidation in horixontal direction and Kh/Kv were estimated at 1.0~6.24 ×10-³㎠/sec and 1.8~2.58 by the pore pressure dissipation test, respectively. Conclusively, it can be evaluated out the properties of Samsan soil by piezocone test and suggested several values of empirical parameters.In this paper, the properties of Samsan soil in Ulsan were evaluated by the piezocone test. The results of the piezocone test were compared with the laboratory test results of the undisturbed sample. Samsan soil that contains various kind of organic was found out the low plastic clay. The overconsolitaion ratio (O.C.R) was carried out about 1 or less than 1. Hence it is provided that the soil is the normally consolidated clay or under consolidated clay. In addition, The correlations between the piezocone test and the standard penetration test were conformed to the charts and the empirical formulas by Kulhaway & Mayne. The coefficient of consolidation in horixontal direction and Kh/Kv were estimated at 1.0~6.24 ×10-³㎠/sec and 1.8~2.58 by the pore pressure dissipation test, respectively. Conclusively, it can be evaluated out the properties of Samsan soil by piezocone test and suggested several values of empirical parameters

A Study on Back Analysis of Measured Displacements of Tunnels

본 논문은 직접법으로 수행한 역해석결과를 제시하였다. 본 연구에서 개발한 역해석 기법은 최적화 기법에 가중치를 적용시켜 구하고자 하는 미지의 물성치를 얻을 수 있었다. 직접법의 장점은 복잡한 수학 방정식이 불필요하여 비선형 문제를 해결할 수 있어 실제현장에 적용가능하다. 그리고 유한차분법을 이용하여 정해석을 실시하였으며, 정해석으로부터 구한 변위를 계측변위로 하여 탄성계수와 초기응력을 대상으로 역해석을 실시한 결과 거의 정확한 값에 수렴하는 것을 확인할 수 있었다. 그리고 현장 계측데이타를 이용하여 역해석을 수행하여 타당한 물성치를 얻어 현장 적용성 검토도 확인하였다.In this paper, the results of back analysis based on the direct method were presented. The presented approach to back analysis with the weighting function was based on an iterative procedure correcting trial value of unknown parameters by minimizing the error function. The advantage of the presented approach was that method might be non-linear back analysis problem without having to rely on a complex mathematical background. By the FDM analysis on the underground structure, the method derived the complete intial state of stress and Young's modulus from the measured displacements. The presented approach was applied to analysis a tunnelling, and the results were satisfactory.In this paper, the results of back analysis based on the direct method were presented. The presented approach to back analysis with the weighting function was based on an iterative procedure correcting trial value of unknown parameters by minimizing the error function. The advantage of the presented approach was that method might be non-linear back analysis problem without having to rely on a complex mathematical background. By the FDM analysis on the underground structure, the method derived the complete intial state of stress and Young's modulus from the measured displacements. The presented approach was applied to analysis a tunnelling, and the results were satisfactory

A Study on Mechanical Properties of Backfill Materials

최근 산업의 발달과 더불어 지하 구조물의 과밀화로 인해 도시 터널의 경우 점점 대심도화되는 경향이 있다. 터널의 시공 중 불가피하게 발생하는 공극 즉 지반과 복공 사이에 존재하게 되는 테일보이드가 지반 변위의 가장 큰 요인으로 작용하게 된다. 그러므로 지반 변위를 최소화하기 위해서는 테일보이드에 대한 뒷채움 효과가 중요하다. 본 논문에서는 다양한 배합비로 구성된 뒷채움 주입재에 대한 각종 실내실험을 통하여 주입재에 대한 물리적, 역학적 특성을 규명하였다. 재료 실험을 통하여 얻은 결과는 다음과 같다. 1. 겔타임은 재료의 교반 정도 등 여러 요소의 영향을 받으나, 물시멘트가 작을수록, 규산비가 작을수록 빨라지는 경향을 보였다. 겔타임은 물시멘트비, 규산비 등에 따라 온도가 20-25℃ 인 경우 15초 -1분30초 정도로 나타났다. 2. 시멘트 함량이 클수록 일축압축강도는 크게 나타났으며, 반면 파괴시의 변형률은 감소하였다. 인장강도는 일축압축강도의 1/15-1/20정도로 나타났다. 3. 삼축압축실험 결과 구속응?쩜? 증가할 수록, 파괴시의 강도, 변형률 모두 증가하였다. 또한 양생기간이 길어질 수록 압축강도는 증가하였으며, 초기 3일간의 양생기간에 현저한 강도 증가를 보였다.In recent years, urban tunnels have more deeply constructed due to congestion of buried structures. In shield tunnelling spaces called tail-void are usually created between the ground and the outer face of the primary lining. In order to reduce the ground deformation, it is important to backfill in tail-void. In this paper, an experimental investigation was undertaken to evaluate the physical and mechanical properties of grouts composed of various mixtures of backfill materials. 1. The gel time depends primarily on the cement content. As the w/c ratio decreases from 5:1 to 2:1, the gel time decreases form about 1 minute 30 seconds to 15 seconds at room temperature. 2. With increases of cement content, the strength of cement - silicate grout increases, but, the strain at failure decreases. Tensile strength obtained from the Brazilian test is about one -fifteenth the unconfined compressive strength. 3. With increases of confined stresses, the strength and strain at failure are all increased. The compressive strength of cement - silicate grout increases with curing time; significant strength increases are obtained in three days.In recent years, urban tunnels have more deeply constructed due to congestion of buried structures. In shield tunnelling spaces called tail-void are usually created between the ground and the outer face of the primary lining. In order to reduce the ground deformation, it is important to backfill in tail-void. In this paper, an experimental investigation was undertaken to evaluate the physical and mechanical properties of grouts composed of various mixtures of backfill materials. 1. The gel time depends primarily on the cement content. As the w/c ratio decreases from 5:1 to 2:1, the gel time decreases form about 1 minute 30 seconds to 15 seconds at room temperature. 2. With increases of cement content, the strength of cement - silicate grout increases, but, the strain at failure decreases. Tensile strength obtained from the Brazilian test is about one -fifteenth the unconfined compressive strength. 3. With increases of confined stresses, the strength and strain at failure are all increased. The compressive strength of cement - silicate grout increases with curing time; significant strength increases are obtained in three days

Swelling Characteristics of Stabilized Soils by Lime with Sulphate and Chemical additives

최근 많이 건설중인 도로에서 연약지반을 노상토로 사용하게 될 경우, 공학적으로 많은 문제점이 발생되기 때문에 생석회, 시멘트 등의 여러 가지 화학첨가제를 첨가하여 지반을 개량하게 된다. 특히 생석회에 의한 토질안정처리공법에서 주된 반응은 생석회와 흙 사이에 장기간에 걸쳐 일어나는 포졸란 반응이며, 산성화된 우수 및 공장의 폐수로 오염된 토양 속의 황산염과 결합하여 토질안정처리의 많은 문제점이 발생되고 있다. 도로의 기층재료로 사용된 생석회 혼합토는 흙 속의 황산염과 반응하여 Ettringite, Thaumasite, Gypsum과 같은 팽창성 반응생성물을 생성하여, 도로의 균열 등 악영향을 미친다. 따라서, 본 연구에서는 생석회와 화학첨가제(CaCl₂, CaSO₄, Fe₂O₃)를 혼합하여 산성화된 우수나 공장지대의 오염된 폐수 속에 포함된 황산염에 대한 영향을 조사하였다. 연구결과, 황산염은 생석회 혼합토의 팽창특성을 변화시키는 것으로 나타났다. 팽창특성은 간극수의 pH가 낮을수록 팽창성이 증가하였으며, CaSO₄를 첨가한 생석회 혼합토의 팽창성이 큰 것으로 나타났다. 팽창성의 증가는 황산염과 반응하여 생성된 침상의 Ettringite의 생성에 기인한 것임을 확인할 수 있었다.Lime has been extensively utilized to stabilize the weak and soft compressible clay deposits. It has been recently reported that the presence of sulphate causes abnormal volume changes in lime-stabilized soils. Volume change in lime-stabilized soils can take place due to ettringite, thaumasite, and gypsum, which are complex calcium-silicate-hydroxide-sulphate-carbonate-hydrate minerals. Sulphate compounds cause a variety of serious geotechnical hazards such as swell pressure and damages to light structures and pavements. This paper discusses the influence of sulphate on sulplus soil specimens treated with lime and chemical additives(CaCl₂, CaSO₄, Fe₂O₃). The main objective of this paper is to estimate the physical behavior of lime-treated sulplus soils after curing periods of up to 60 days. The physical and mechanical characteristics were explained by means of a laboratory study. The formation of sulphate compounds due to soil-lime and sulphate reactions were identified by X-Ray Diffraction(XRD) and Scanning Electron Microscope(SEM). The results showed that the sulphate increased swelling properties of soils. Theswelling properties development is probably related to the needle-like crystals which were able to be observed by SEM.Lime has been extensively utilized to stabilize the weak and soft compressible clay deposits. It has been recently reported that the presence of sulphate causes abnormal volume changes in lime-stabilized soils. Volume change in lime-stabilized soils can take place due to ettringite, thaumasite, and gypsum, which are complex calcium-silicate-hydroxide-sulphate-carbonate-hydrate minerals. Sulphate compounds cause a variety of serious geotechnical hazards such as swell pressure and damages to light structures and pavements. This paper discusses the influence of sulphate on sulplus soil specimens treated with lime and chemical additives(CaCl₂, CaSO₄, Fe₂O₃). The main objective of this paper is to estimate the physical behavior of lime-treated sulplus soils after curing periods of up to 60 days. The physical and mechanical characteristics were explained by means of a laboratory study. The formation of sulphate compounds due to soil-lime and sulphate reactions were identified by X-Ray Diffraction(XRD) and Scanning Electron Microscope(SEM). The results showed that the sulphate increased swelling properties of soils. Theswelling properties development is probably related to the needle-like crystals which were able to be observed by SEM

Rapid Inflection Point Method of Consolidation Testing

일반적으로 점성토의 압밀계수는 하중단계마다 일차압밀이 100% 완료되기까지 충분한 재하시간(24h)을 필요로 하는 표준압밀시험을 통해서 구할 수 있다. 하지만, 표준압밀시험으로는 간극수압을 직접 측정하기가 어렵고, 압밀완료시간이 최소한 1주일 이상이 소요된다. 따라서, 신뢰성 있는 값을 확보하면서 신속한 압밀시험 방법의 개발이 요구된다. 본 연구에서는 Inflection Point Method(Francis R. Cour 1971)[2]를 이용하여 신속히 압밀계수를 구하는 Rapid Inflection Point Method에 대한 연구를 수행하였다. 본 연구의 결과로 얻어진 압밀계수는 Taylor방법, Casagrande방법, Rectangular Hyperbolar방법으로 구한 압밀계수와 비교하였고[1], Rapid Rectangular Hyperbolar(A. Sridharan 등, 1999)방법[8]으로 구한 압밀계수와 비교·분석하여 그 적용성을 검토하였다. 또한, 본 연구를 통해서 압밀시간 단축에 관한 타당성을 입증하였다.This study presented the new method for evaluating the coefficient of consolidation by using inflection point method which was based on the fact that time factor, T corresponding to the inflection point of a semilogarithmic plot of a time curve is fixed and equals to T = 0.405 at 70% consolidation. In the proposed method, the next load increment is applied as soon as the necessary time reqaired to identify the inflection point. Thus, the coefficient of consolidation may be easily evaluated. The time required to complete the testing using this rapid consolidation method could be as low as 1∼5 hours compared with 1 or 2 weeks in the case of the conventional consolidation test. Keyword : consolidation, inflection point, rapid consolidation methodThis study presented the new method for evaluating the coefficient of consolidation by using inflection point method which was based on the fact that time factor, T corresponding to the inflection point of a semilogarithmic plot of a time curve is fixed and equals to T = 0.405 at 70% consolidation. In the proposed method, the next load increment is applied as soon as the necessary time reqaired to identify the inflection point. Thus, the coefficient of consolidation may be easily evaluated. The time required to complete the testing using this rapid consolidation method could be as low as 1∼5 hours compared with 1 or 2 weeks in the case of the conventional consolidation test. Keyword : consolidation, inflection point, rapid consolidation metho

Reliability Analysis on Reinforced Walls

일반적으로 옹벽의 설계는 설계자의 주관적 판단에 좌우되므로, 전통적인 설계방법은 설계과정을 수치적으로 일반화하기가 곤란할 뿐만 아니라 최종적인 설계 단면이 가장 적합한 것이라고 확신 할 수 없다. 사용재료의 물성치에 내포되어있는 불확실성을 표현할 수 없음은 물론 불안정상태에서 발휘되고 있는 설계변수의 값이 얼마인가를 명확히 표현할 수 있는 물리적 근거가 모호하다. 특히 보강토 옹벽읙 경우에는 토성치뿐만 아니라 흙/보강재 사이의 불확실성까지 고려되어져야 한다. 본 논문에서는 보강토 옹벽에 적용된 토성치와 흙/보강재 상호매개변수의 불확실성이 안정해석에 얼마나 영향을 미치는지를 확률적인 방법을 이용한 신뢰도 해석을 수행하였다. 신뢰도 해석을 수행한 결과, 흙/보강재 사이의 접속마찰각 δ의 변화가 파괴확률 pf에 가장 큰 영향을 미치는 것으로 나타났다. 보강토체내 뒤채움흙 단위중량 γr 및 보강재 길이 L의 경우 CV값이 20%가 될때 일정 한계치보다 작은 값을 가지면 파괴확률 pf가 급격하게 증가함을 보였으며 배면토제 단위중량 γf은 파괴확률 pf에 큰 영향을 끼치지 못하는 것으로 나타났다.Traditionally, the reliability of retaining walls is achieved through the use of safety factors or margins and adopting conservative assumption in the process of design. However, that is often defined on the basis of subjective judgements. such a traditional design methods are difficult to quantify and lack the logical basis of describing uncertainty. expecially, reingorced walls consider not only soil properties but soil-reinforcement interaction uncertaintees. This paper described how probabilistic description of soil parameters and soil-reinforcement interaction parameters were applied to the stability analysis. The first-order, second moment approach was explored and applied tot he design of reinforced walls. an example illustrated the relative contribution of uncertainties about different parameters to the reliability of the reinforced walls. The results obtained from this study were follows; the reliability of the soil-reinforcement interface friction angle, δwas highly sensitive to the coefficient of variation. However, whenthe backfill soil unit weight, γr and the reinforcement length, L were lower than the limited values, the probabilities of failure were increased. The reliability of the soil unit weight, γf in the unreinforced area was lowly sensitive to the coefficient of variation.Traditionally, the reliability of retaining walls is achieved through the use of safety factors or margins and adopting conservative assumption in the process of design. However, that is often defined on the basis of subjective judgements. such a traditional design methods are difficult to quantify and lack the logical basis of describing uncertainty. expecially, reingorced walls consider not only soil properties but soil-reinforcement interaction uncertaintees. This paper described how probabilistic description of soil parameters and soil-reinforcement interaction parameters were applied to the stability analysis. The first-order, second moment approach was explored and applied tot he design of reinforced walls. an example illustrated the relative contribution of uncertainties about different parameters to the reliability of the reinforced walls. The results obtained from this study were follows; the reliability of the soil-reinforcement interface friction angle, δwas highly sensitive to the coefficient of variation. However, whenthe backfill soil unit weight, γr and the reinforcement length, L were lower than the limited values, the probabilities of failure were increased. The reliability of the soil unit weight, γf in the unreinforced area was lowly sensitive to the coefficient of variation