• Geomechanics and Engineering
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• v.23 no.2
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• pp.179-187
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• 2020

Freezing-thawing cycles have significant effect on soils engineering behavior in frozen areas. This effect is more considerable in fine-graded than coarse-grained soils. The objective of this study is improving soil durability and strength in continues freezing-thawing cycles. For getting this purpose mixture of Polyvinyl Acetate (PVAc) and Ethylene Glycol Monobutyl Ether (EGBE) has been added to fine-grained soil and final prepared samples were tested at different freezing-thawing cycles. PVAc was mixed with 1%, 2% and 3% of soil weight. Half of PVAc weight was used as weight of EGBE. Freezing-Thawing cycles were exposed to samples and they were tested at different cycles. Results showed that adding mixture of PVAc+EGBE improved strength and durability of samples up to 10 freezing-thawing cycles. Unconfined compress strength tests were applied to samples and stress and strain of samples were tested on failure time. Behavior of samples was different at different percentages of mixture. Results showed that increasing amount of PVAc from 1% to 2% had more considerable effect on final stress than 2% to 3%. Using higher percentages of PVAc + EGBE mixture leaded to that samples carried more strain before collapsing. Another result gained from tests was that, freezing-thawing effect was more considerable after fourth cycles. It means differences between first and fourth cycles were more considerable than differences between fourth and tenth.

• Geomechanics and Engineering
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• v.22 no.3
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• pp.227-236
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• 2020

Expansive soils are renowned for their swelling-shrinkage property and these volumetric changes resultantly cause huge damage to civil infrastructures. Likewise, subgrades consisting of expansive soils instigate serviceability failures in pavements across various regions of Pakistan and worldwide. This study presents the use of polypropylene fibers to improve the engineering properties of a local swelling soil. The moisture-density relationship, unconfined compressive strength (UCS) and elastic modulus (E₅₀), California bearing ratio (CBR) and one-dimensional consolidation behavior of the soil treated with 0, 0.2, 0.4, 0.6 and 0.8% fibers have been investigated in this study. It is found that the maximum dry density of reinforced soil slightly decreased by 2.8% due to replacement of heavier soil particles by light-weight fibers and the optimum moisture content remained almost unaffected due to non-absorbent nature of the fibers. A significant improvement has been observed in UCS (an increase of 279%), E₅₀ (an increase of 113.6%) and CBR value (an increase of 94.4% under unsoaked and an increase of 55.6% under soaked conditions) of the soil reinforced with 0.4% fibers, thereby providing a better quality subgrade for the construction of pavements on such soils. Free swell and swell pressure of the soil also significantly reduced (94.4% and 87.9%, respectively) with the addition of 0.8% fibers and eventually converting the medium swelling soil to a low swelling class. Similarly, the compression and rebound indices also reduced by 69.9% and 88%, respectively with fiber inclusion of 0.8%. From the experimental evaluations, it emerges that polypropylene fiber has great potential as a low cost and sustainable stabilizing material for widespread swelling soils.

• Geomechanics and Engineering
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• v.13 no.1
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• pp.25-41
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• 2017

In recent years, the amount of sludge ash (SA) has considerably increased due to rapid urbanization and population growth. In addition, its storage in landfills induces environmental pollution and health problems. Therefore, its disposal in an environmentally friendly way has become more important. The main goal of this study is to investigate the reusability of sludge ash as an additive with polypropylene fiber (PF) to stabilize marginal sand based on the compressive strength performances from UCS tests. For this purpose, a series of UCS tests was conducted. Throughout the experimental study, the used inclusion rates were 10, 15, 20 and 30% for sludge ash and 0, 0.5 and 1% for polypropylene fiber by total dry weight of the sand+sludge ash mixture and the prepared samples were cured for 7 and 14 days prior to the testing. Freezing and thawing resistance of the mixture including 10% sludge ash and 0, 0.5 and 1% polypropylene fiber was also examined. On the basis of UCS testing results, it is said that sludge ash inclusion remarkably enhances UCS performance of sand. Moreover, the addition of polypropylene fiber to the admixtures including sand and sludge ash significantly improves their stress-strain characteristics and post-peak strength loss as well as UCS. As a result of this paper, it is suggested that sludge ash be successfully reused with polypropylene fiber for stabilizing sand in soil stabilization applications. It is also believed that the findings of this study will contribute to some environmental concerns such as the disposal problem of sludge ash, recycling, sustainability, environmental pollution, etc. as well as the cost of an engineering project.

• Journal of the Korean Geotechnical Society
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• v.31 no.7
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• pp.41-52
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• 2015

Volcanic rocks in Jeju Island have vesicular structure caused by various environmental factors, and indicate the differences in geological and mechanical characteristics from region to region. In addition, the bedrock of Jeju Island shows stratified structure, that is, soft layers composed of pyroclastic rocks or cavities are irregularly developed between the basalt layers by several times of volcanic activity. In this study, various physical tests and unconfined compressive strength test were conducted for intact rocks sampled in northwestern onshore and offshore of Jeju Island. The results obtained in the tests were compared with the physical and mechanical characteristics of intact rocks sampled in southeastern offshore of Jeju Island. As a results, it was confirmed that the physical and mechanical characteristics of basalts sampled in northwestern Jeju Island were similar to those of basalts sampled in southeastern offshore of Jeju Island. In addition, it was possible to estimate approximate design parameters from the correlation of mechanical properties with physical properties of basalts in Jeju Island.

• The Journal of Engineering Geology
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• v.13 no.2
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• pp.227-238
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• 2003

Understanding of a creep behavior in rocks under a constant load, due to visco-elastic properties of rock, is an essential element to predict a long term ground deformation. In order to clarify the creep characteristics of the mudstone in Duho formation at Pohang basin, deposited during Tertiary, a series of laboratory tests including physical properties, unconfined compressive strength and uniaxial creep tests, was performed. The mudstone showed a higher creep potential due to 26% of clay minerals such as illite and chlorite. The unconfined compressive strength of the rock was $462{\;}kg/\textrm{cm}^2$ in average, and four creep tests were performed under constant stress of 40 to 70 % of the strength. The creep constants in the empirical and theoretical equations were deduced from the time-strain curves obtained from the tests. Among the several equations, the empirical equation proposed by Griggs and theoretical equation of Burger’s model are appreciated as the best one to express the creep behavior of the mudstone. Instantaneous elastic strain was linearly increased with stress level but strain velocity during the first creep is decreased with a similar pattern by time lapse regardless the stress level.

• Journal of the Korean GEO-environmental Society
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• v.1 no.1
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• pp.19-26
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• 2000

This study is and experimental study to investigate the possibility of the utilization of paper ash as the cover and liner materials in the waste disposal landfill and other construction materials. A series of tests were performed to evaluate basic properties, compaction, compressive strength, consolidation, permeability, and CBR of paper ash. The sample used in these tests was obtained from four paper mills which are located in near Ch$\hat{o}$ngju. Bentonite and lime were used as addictives to improve permeability properties of paper ash. It was found that the maximum dry unit weight increases with the increase of the bentonite and lime contents. The results of unconfined compression tests show that paper ash meets the criteria of the unconfined compression strength. It is recognized that the permeability coefficient decreases as increasing bentonite content and the percentage of bentonite needed to make the permeability coefficient below $1{\times}10^{-7}cm/sec$ was 30%.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.25-34
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• 2003

This paper is focused on an experimental study in order to investigate the utilization of sewage sludge ash as the cover and liner materials for the waste disposal landfill or as construction materials. A series of tests were performed to evaluate the basic properties, compaction, compressive strength, consolidation, permeability, and CBR of sewage ash. Specially, clay bricks were made as increasing replacement ratio of sewage ash (such as 5, 10, 15, 20, 25, 30%). And tests were fulfilled for its quality. Bentonite and lime were used as the additives to improve permeability properties of sewage sludge ash. As a result of tests, it was shown that the permeability coefficient decreases as increasing bentonite content and the percentage of bentonite was roughly needed 20% to keep the permeability coefficient below $1{\times}10^{-7}cm/sec$. The results of unconfined compression tests show that sewage ash meets the criteria of the unconfined compression strength for cover material. It was shown that the compressive strength decreases as increasing the replacement ratio of sewage sludge ash and the maximum replacement ratio of sewage sludge ash to satisfy the quality standards of the third degree bricks was about 15%.

• Journal of the Korean GEO-environmental Society
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• v.7 no.4
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• pp.43-52
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• 2006

There were huge damages of human beings and their properties in many areas of the basin of the Nak-Dong river by the unusual weather and the localized downpour recently. In this research against disasters, we want to know strength of the cemented sand that is mixed with cement and poor-graded sand, to estimate CSG(Cemented Sand and Gravel) method used coffer dam in Japan, which is the materials of riverbed in the basin of the Nak-Dong river for levee's construction. For that, we want to provide the fundamental data which need in the examination of adaptation of levee's material, design and analysis by investigating compressive strength by curing period and cement content, elastic modulus and stress by transformation from compaction test, CBR test, unconfined compression test and triaxial compression test as changing cement content from 2% to 8% at two sites in the basin of the Nak-Dong river.

• Journal of the Korean GEO-environmental Society
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• v.11 no.4
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• pp.5-12
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• 2010

Soil mixture using bentonite as a cutoff material is used a lot for various structures such as landfills, banks and dams as cutoff materials. But seepage water is expected to seep since shear failure of filter layer occurs due to external load, embankment load when constructed. Generally, only coefficient of permeability of Soil Mixture is considered irrespective of the changes of intensity on amount of additives. This research is to study on how the changes of amount of bentonite affects permeability and strength of soil mixture. So successive experiments for measuring permeability and strength were conducted as the amount of bentonite changes from 0 to 4%, mixing with the bed material and then making specimens. Around construction site of B dam. As a result, 2.085E-07 cm/sec was shown when the amount of Soil Mixture was 4%. It is proved that unconfined compressive strength and tensile strength increase as the amount of bentonite increases, but saturation shear strength of bentonite soil mixture from the CD experiment is hardly influenced by the amount of bentonite.

• Journal of the Korean GEO-environmental Society
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• v.11 no.4
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• pp.33-42
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• 2010

The lightweight foamed concrete is used to reduce the weight of the backfill material. When it is applied, the volume is often contracted due to segregation, necessitating re-injection. In this study, it was manufactured a new lightweight foamed concrete by adding plasticizer and tested the engineering properties of the material. The tests included unconfined compressive strength test, unit weight test, flow test, pH test, and permeability test. The plasticizer is shown to have an important influence on the flow. It was shown that 2~2.4% of plasticizer was adequate. The new material was shown to have positive influence on the flow and reduction of weight when applied to the backfill of the structures.