Prediction of unconfined compressive and Brazilian tensile strength of fiber reinforced cement stabilized fly ash mixes using multiple linear regression and artificial neural network

Chore, H.S.,Magar, R.B. Techno-Press 2017 Advances in computational design Vol.2 No.3

This paper presents the application of multiple linear regression (MLR) and artificial neural network (ANN) techniques for developing the models to predict the unconfined compressive strength (UCS) and Brazilian tensile strength (BTS) of the fiber reinforced cement stabilized fly ash mixes. UCS and BTS is a highly nonlinear function of its constituents, thereby, making its modeling and prediction a difficult task. To establish relationship between the independent and dependent variables, a computational technique like ANN is employed which provides an efficient and easy approach to model the complex and nonlinear relationship. The data generated in the laboratory through systematic experimental programme for evaluating UCS and BTS of fiber reinforced cement fly ash mixes with respect to 7, 14 and 28 days' curing is used for development of the MLR and ANN model. The data used in the models is arranged in the format of four input parameters that cover the contents of cement and fibers along with maximum dry density (MDD) and optimum moisture contents (OMC), respectively and one dependent variable as unconfined compressive as well as Brazilian tensile strength. ANN models are trained and tested for various combinations of input and output data sets. Performance of networks is checked with the statistical error criteria of correlation coefficient (R), mean square error (MSE) and mean absolute error (MAE). It is observed that the ANN model predicts both, the unconfined compressive and Brazilian tensile, strength quite well in the form of R, RMSE and MAE. This study shows that as an alternative to classical modeling techniques, ANN approach can be used accurately for predicting the unconfined compressive strength and Brazilian tensile strength of fiber reinforced cement stabilized fly ash mixes.

PVA섬유를 혼합한 미생물 고결토의 공학적 특성

박성식,최선규 한국지반공학회 2016 한국지반공학회논문집 Vol.32 No.8

In this study, Polyvinyl alcohol (PVA) fiber was used to increase strength (unconfined compressive strength and tensilestrength) of bio-cemented sand using microorganism. Ottawa sand was mixed with PVA fibers having three fiber contents(0, 0.4, and 0.8%). The fiber mixed sand was treated 14 times by using Microbially Induced Calcite Precipitation (MICP)which included culture (2 times per day) during 7 days to improve its engineering properties. The Bacillus Sporosarcinapasteurrii (Bacillus sp.) was used for urease activity. The specimen was prepared as a cylindrical specimen of 5 cmin diameter and 10 cm in height. Unconfined compressive strength and tensile strength were measured after cementation. Moreover, calcium carbonate content and SEM analyses were performed with a piece of sample. An average value ofunconfined compressive strength increased and then slightly decreased but an average value of tensile strength ratioincreased with increasing carbonate content the in same condition. Unconfined compressive strength and tensile strengthincreased about 30% and 160%, respectively. A strength ratio of unconfined compressive strength to tensile strengthrepresenting the brittleness decreased from 8 to 4 when fiber content increased from 0.0 to 0.8%. Such bio-cementedsand can be applied into slope area to prevent its shear failure or increase its tensile strength.

인공신경망을 활용한 석탄회 CLSM의 일축압축강도 및 Flow 예측

임소영,천병식 한양대학교 우리춤연구소 2013 우리춤과 과학기술 Vol.9 No.3

최근 환경에 대한 인식이 높아지는 가운데 정부는 2008년 주요 정책으로 저탄소 녹색성장을 제시하였고, 에너 지, 환경관련 기술과 산업 등에서 미래 유망품목과 신기술을 개발하기 위해 총력을 기울이고 있다. 그러나 에 너지 관련 부문에서는 현 전력시스템을 획기적으로 대체하여 본격적으로 상용화되기까지 많은 시간이 필요하 기 때문에 당분간 국내 전력의 대부분은 화력발전과 원자력발전에 의존해야 하는 실정이다. 특히 국내 전력의 65%정도를 차지하고 있는 화력발전의 경우 발전소에서 부산되고 있는 석탄회는 약 600만톤이며, 2010년 석탄 회 발생량은 약 736만톤으로 추후 석탄회 매립량은 증가될 것으로 전망된다. 그러나 우리나라 화력발전소 주 변에는 이미 막대한 양의 석탄회가 폐기 매립되어 있고 일부 화력발전소에서는 석탄회 매립장 용량이 한계에 부딪혀 최악의 상황에 처해있다. 따라서 화력발전소에서 발생되는 석탄회를 효율적으로 재활용하여 처리할 수 있는 기술 개발이 필요하다. 이에 본 연구에서는 석탄회의 재할용 방안의 하나로서 화력발전소 석탄회 매 립장에 매립되어 있는 석탄회를 이용하여 저강도 고유동화재(CLSM, Controlled Low Strength Material)의 재 료를 개발하기 위해 인공신경망 학습을 통해 flow 및 일축압축강도를 실험을 통하지 않고도 CLSM의 Flow 및 일축압축강도를 예측하고자 한다. 본 연구에서는 은닉층은 2, 3개, 모멘텀상수는 0.8, 0.9 목표시스템 오차값 0.01, 0.001 은닉층의 노드 수는 4, 6, 8와 학습율은 0.2, 0.3으로 변화시키면서 학습 횟수는 최대 100,000번을 학습하여 각각의 변화에 따른 인공 신경망 모델의 학습효율 및 예측능력을 평가하고 이를 기준으로 CLSM의 Flow 및 압축강도 산정에 적합한 최 적인공신경망 모델을 결정하였다. 저강도 고유동화재에 대한 Flow 및 압축강도 시험결과를 바탕으로 인공신경망을 이용한 CLSM의 Flow 및 압 축강도의 학습결과 결정계수(R2)값이 R2=0.89∼0.92, R2=0.93∼0.96 으로 높은 상관관계를 보였다. 또 한 인공 신경망의 학습과정에서 전혀 접하지 않은 검증용 자료를 통한 CLSM의 Flow 및 압축강도의 예측결과 결정계 수(R2)값이 각각 0.70, 0.76으로 Model 1의 구조가 가장 적합한 모델로 판단된다. Presently, the use recycling the Fly ash is limited to the cement raw material, ready-mixed concrete blending material, filling, cutting and etc. The fly ash is refined and recycled over 90% among the coal ash with many researches, however the bottom ash is unable to be mostly recycled and is reclaimed in the ash pond. In this research, a property of flow and the unconfined compressive strength for developing the material of the Controlled Low-Strength Material by using the coal ash reclaimed in ash pond of the thermoelectric power plant. A characteristic of flow and strength of CLSM depend on the combination ratio including the fly ash, bottom ash, cement, water quantity and etc. however, actually they are very difficult to draw the mechanism about the mixing ratio of each components and flow and strength. Therefore, the method of calculation drawing the flow about the component ratio of CLSM and compression strength value is needed for the valid practical use of CLSM. Thus, in this research, a flow and the unconfined compressive strength of CLSM will predict using the artificial neural network learning without an experiment. The unconfined compressive strength and flow were used age of 28days 45 among 60 obtained from the indoor test for the learning and others were used to verify for the constructed artificial neural network. In this research, node number of hidden layer 4, 6, 8, learning rate into 0.2, 0.3, the study frequency studied a maximum 100,000, momentum 0.8, 0.9 target system error 0.01, 0.001 and hidden layer 2, 3 evaluated the learning efficiency of the artificial neural network model according to each change and prediction ability. constant determined the optimum artificial neural network model which is suitable for a flow and compressive strength estimate of CLSM, based on this. And the study result about six models in which the study result is excellent was used for the analysis. In the analyzed result learning, the coefficient of determination value(R2) of a flow and the compressive strength showed the correlation which is high in R2=0.89~0.92 and R2=0.93~0.96. And the coefficient of determination value(R2) of the flow of the foreseen outcome CLSM through verification data and the compressive strength of the structure of a model 1 is determined as 0.70, 0.76 as the most suitable model.

Unconfined Compressive Strength of Clayey Soils Stabilized with Waterborne Polymer

Seyed Abolhassan Naeini,Bahman Naderinia,Ehsan Izadi 대한토목학회 2012 KSCE Journal of Civil Engineering Vol.16 No.6

Improvement and stabilization of soils are widely used as an alternative to substitute the lacking of suitable material on site. Soils may be stabilized to increase strength and durability or to prevent erosion and dust generation. The use of nontraditional chemical stabilizers in soil improvement is growing daily. A new stabilizing agent was developed to improve the mechanical performance and applicability of clayey soils. In this study a laboratory experiment is conducted to evaluate the effects of plasticity index and waterborne polymer on the Unconfined Compression Strength (UCS) of clayey soils. The laboratory tests include sieve analysis,hydrometer, Atterberg limits, modified compaction and unconfined compression tests. Three clayey soils with different plasticity indexes were mixed with various amounts of polymer (2, 3, 4 and 5%) and compacted at the optimum water content and maximum dry density. The unstabilized and stabilized samples were subjected to unconfined compression tests to determine their strength at different curing times. The results of the tests indicated that the waterborne polymer significantly improved the strength behavior of unsaturated clayey soils. Also, an increase in plasticity index causes a reduction in unconfined compression strength.

일축압축강도에 의한 선행압밀응력 예측 및 분석

송창섭,김명환,Song, Chang Seob,Kim, Myeong Hwan 한국농공학회 2016 한국농공학회논문집 Vol.58 No.6

This study was to evaluate the feasibility of pre-consolidation pressure distribution characteristic of western and southern coastal region, using correlation of unconfined compressive strength and preceding research equation. Pre-consolidation of western and southern region showed similar trends undrained shear strength and pre-consolidation pressure in proportion to unconfined compressive strength. Predicted results of U.S. NAVY. (1982) equation revealed a small error western 9.7 % and southern 0.4 %. Prediction correlation results of pre-consolidation using unconfined compressive strength revealed an error western 16.8 % and southern 0.7 %. It was reported that less than 20 percent of pre-consolidation pressure prediction result of Casagrande forecasting error. Estimates of pre-consolidation pressure are possible, before the standard consolidation test, because it was reported that less than 20 % of the forecasting errors of Casagrande.

인공신경망을 이용한 퇴적암의 압축강도 예측

이상호,김동락,서인식,Lee, Sang-Ho,Kim, Dong-Rak,Seo, In-Shik 한국농공학회 2012 한국농공학회논문집 Vol.54 No.5

A evaluation for the strength of rock includes a lot of uncertainty due to existence of discontinuity surface and weakness plain in the rock mass, so essential test results and other data for the resonable strength analysis are absolutely insufficient. Therefore, a analytical technique to reduce such uncertainty can be required. A probabilistic analysis technique has mainly to make up for the uncertainty to investigate the strength of rock mass. Recently, a artificial neural networks, as a more newly analysis method to solve several problems in the existing analysis methodology, trends to apply to study on the rock strength. In this study the unconfined compressive strength from basic physical property values of sedimentary rock, black shale and red shale, distributed in Daegu metropolitan area is estimated, using the artificial neural networks. And the applicability of the analysis method is investigated. From the results, it is confirmed that the unconfined compressive strength of the sedimentary rock can be easily and efficiently predicted by the analysis technique with the artificial neural networks.

바톰애시를 이용한 환경친화적 뒤채움재

이관호(Lee, Kwan-Ho),김성겸(Kim, Seong-Kyum) 한국산학기술학회 2012 한국산학기술학회논문지 Vol.13 No.3

바톰애시와 현장발생토사를 혼합한 유동성뒤채움재에 실험적 연구를 수행하였다. 유동성과 일축압축강도를 이용하여 4가지 다른 배합조건에 대한 각각의 최적배합비를 결정하였다. 현장발생토 25-45%, 바톰애시 30%, 플라이 애쉬 10-20%, 고무분말 0-3%, 시멘트 3% 및 물 22%의 범위에서 최적배합비가 결정되었다. 각각의 혼합물은 20cm 이상의 유동성, 3일 양생시 127 kPa 및 28일 양생시 206-980 kPa 일축압축강도 조건을 만족하였다. 시험재료는 상온 양생 및 습윤양생 2가지 조건을 이용하였다. 전체 혼합물에 대한 변형계수(E50)는 0.07-0.08 * qu 로 나타났다. 또한, 습윤양생 시편의 일축압축강도가 상온양생 시편에 비해 약 10% 정도 큰 값을 나타나내었다. 전체혼합물의 내부마찰 각은 36.5-46.6도, 점착력은 49.1-180 kPa 범위로 측정되었다. 고무분말이 추가된 case 4번의 경우 다른 case에 비해 점착력은 크게, 내부마찰각은 작은 값을 나타내었다. 유동성채움재의 공용 성능을 위해 실시한 pH실험 결과 배합초기 12이상 강알칼리성으로 평가되었다. Couple of laboratory for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out. The optimum mix ratios for 4 cases with flowability and unconfined compressive strength were determined. The optimim mixing ratios were 25 to 45% of insitu soil, 30% of bottom ash, 10 to 20% of fly ash, 0 to 3% of crumb rubber, 3% of cement and 22% of water. Each mixture was satisfied the standard specification, minimum 20cm of flowability and 127 kPa of unconfined compressive strength. Two different curling methods, at room temperature and wet condition, were adopted. The average secant modulus(E50) was 0.07 to 0.08 * qu. The compressive strength at wet condition showed 10% larger than at room temperature. The range of internal friction angle and cohesion for mixtures were 36.5o to 46.6o and 49.1 to 180 kPa, respectively. The mixture with crumb rubber(case 4) showed higher choesion and lower internal friction angle than the others. The pH of all the mixtures was over 12 which is strong alkine.

유기산 재료를 이용한 사질토의 안정화 메커니즘에 관한 연구

기정서(Jungsu Ki),Eric Yee,이종휘(Jonghwi Lee),천병식(Byungsik Chun) 한국지반환경공학회 2013 한국지반환경공학회논문집 Vol.14 No.6

지반개량분야에서는 수많은 공법들이 지금까지 발전을 거듭하여 개발되어왔다. 그러나 대부분의 공법들은 지반의 강도 증진에만 중점을 두었으며 환경문제 발생에 대한 구체적인 해결방안을 제시하지 못하고 있다. 이에 최근에 들어 친환경적으로 지반의 강도를 증대시키는 방법으로 유기산 재료를 이용한 지반개량이 개발되어왔으나 아직 근본적인 안정화 메커니즘에 대해서는 잘 알려지지 않았다. 따라서 본 연구에서는 친환경 개량재인 유기산 재료를 활용한 일축압축강도시험 및 pH시험을 통해 안정화 메커니즘에 대해 규명하였다. 그 결과, 유기산 처리가 된 샘플이 유기산 처리가 되지 않은 샘플보다 시간에 따른 더 큰 일축압축강도를 보였다. 또한, 유기산 재료에 의해 미생물들의 증식이 촉진되며, 토양의 공극 감소를 통해 토양이 개량된다는 것을 규명할 수 있었다. 향후 유기산 재료를 활용한 지반개량 공법의 지속적인 연구가 필요하다고 사료된다. The field of ground amelioration, many construction methods have been developed more prosperously up to now, but even now, the majority focuses on the improvement of ground strength. And they could not suggest concrete solutions to the occurrence of environmental issues. To address this problem, soil improvement methods employing organic acid materials have recently been developed as eco-friendly technologies for increasing the soil strength, but details regarding the basic stabilization mechanism are not known yet. Against this background, this research was conducted to examine the soil stabilization mechanism; for this purpose, unconfined compressive strength and pH tests were conducted by using an improved eco-friendly organic acid material. The test results revealed that the samples processed with the organic acid showed a considerable increase in the unconfined compressive strength over time as compared to the strength of the samples that were processed without the organic acid. It was also confirmed that the organic acid material promoted microbial breeding and improved the soil structure by reducing the volume of the voids in the soil. Therefore, the sustainable development of this method needs to be analysed more in the future.

터널천단변위와 암석 또는 암반의 일축압축강도를 이용한 시공 중인 터널의 예비 안정성 평가

박영화,문홍득,하만복 한국도로학회 2015 한국도로학회논문집 Vol.17 No.6

PURPOSES: It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS: Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS: In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.

터널천단변위와 암석 또는 암반의 일축압축강도를 이용한 시공 중인터널의 예비 안정성 평가

박영화,문홍득,하만복 한국도로학회 2015 한국도로학회논문집 Vol.17 No.6

PURPOSES: It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS: Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS: In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.