• Geomechanics and Engineering
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• v.38 no.3
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• pp.249-260
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• 2024

In order to study the mechanical propertied and change rules of undrained shear behavior of saline soil under the freeze-thaw cycles, an improved constitutive model reflecting the effects of freeze-thaw cycles was proposed based on the traditional Duncan-Chang model. The saline soil in Qian'an County, western Jilin Province, was selected as the experimental object. Then, a set of freeze-thaw cycles (0, 1, 10, 30, 60, 90, 120) tests were conducted on the saline soil specimens, and conventional consolidated undrained triaxial shear tests were conducted on the saline soil specimens that underwent freeze-thaw cycles. The stress-strain relationship was obtained by the triaxial shear test. The model parameters have a corresponding regression relationship with the number of freeze-thaw cycles. Finally, based on the function expression of the model parameters, the modified Duncan-Chang model with the number of freeze-thaw cycles as the influence factor was established, whilst the calculation program of the modified model is compiled. Based on the test results, the stress-strain relationship of the saline soil specimen shows strain hardening. The shear strength gradually decreases with the increase of freeze-thaw cycle. The 10 freeze-thaw cycles are the turning point in the trend of changes of the mechanical properties of saline soils. The calculated and experimental stress-strain relationship are compared, and the comparison between the calculated value of the model and the experimental value showed that the two had a good consistency, which verified the validity of the modified Duncan-Chang model in reflecting the effects of the freeze-thaw cycle.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.663-671
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• 2023

Freeze-thaw cycles induce strength loss at the frozen soil-concrete interface and deterioration of bonding, which causes construction engineering problems. To clarify the deterioration characteristics of the interface under the freeze-thaw cycle, a frozen soil-concrete sample was used as the research object, an interface scanning electron microscope test under the freeze-thaw cycle was carried out to identify the micro index information, and an interface shear test was carried out to explore the loss law of interface shear strength under the freeze-thaw cycle. The results showed that the integrity of the interface was destroyed, and the pore number and pore size of the interface increased significantly with the number of freeze-thaw cycles. The connection form gradually deteriorates from surface-to-surface contact to point-to-surface contact and point-to-point contact, and the interfacial shear strength decreases the most at 0-3 freeze-thaw cycles, with small decreases from to 3-8 cycles. After 12 freeze-thaw cycles, the interfacial shear strength tends to be stable, and shear the failure occurs internally in the soil.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.3
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• pp.60-74
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• 1980

Soil-cement mixtures involve problems in it's durability in grain size distribution and mineral composition of the used soils as well as in cement content, compaction energy, molding water content, and curing. As an attempt to solve the problems associated with durability of weathered granite soil with cement treated was investigated by conducting tests such as unconfined compression test, it's moisture, immers, wet-dry and freeze-thaw curing, mesurement of loss of weight with wet-dry and freeze-thaw by KS F criteria and CBR test with moisture curing on the five soil samples different in weathering and mineral composition. The experimental results are summarized as follows; The unconfined compressive strength was higher in moisture curing rather than in the immers and wet-dry, while it was lowest in freeze-thaw. Decreasing ratio of unconfined compressive strength in soil-cement mixtures were lowest in optimum moisture content or in the dry side rather than optimum moisture content with freeze-thaw. The highly significant ceofficient was obtained between the cement content and loss of weight with freeze-thaw and wet-dry. It was possible to obtain the durability of soil-cement mixtures, as the materials of base for roads, containing above 4 % of cement content, above 3Okg/cm$_2$ of unconfined compressive trength with seven days moisture curing or 12 cycle of freeze-thaw after it, above 100% of relative unconfined compressive strength, 80% of index of resistance, below 14% of loss of weight with 12 cycle of wet-dry and above 1. 80g/cm$_2$ of dry density.

• Geomechanics and Engineering
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• v.8 no.3
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• pp.361-375
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• 2015

Constructions over soft and loose soils are one of the most frequent problems in many parts of the world. Cement and cement-lime mixture have been widely used for decades to improve the strength of these soils with the deep soil mixing method. In this study, to investigate the freeze-thaw effect of sand improved by polymers (i.e., styrene-acrylic-copolymer-SACP, polyvinyl acetate-PVAc and xanthan gum) and fly ash, unconfined compression tests were performed on specimens which were exposed to freeze-thaw cycles and on specimens which were not exposed to freeze-thaw cycles. The laboratory test results concluded that the unconfined compressive strength increased with the increase of polymer ratio and curing time, whereas, the changes on unconfined compressive strength with increase of freeze-thaw cycles were insignificant. The overall evaluation of results has revealed that polymers containing fly ash is a good promise and potential as a candidate for deep soil mixing application.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.4
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• pp.40-55
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• 2023

Arbor Day is a day that encourages people to plant trees and symbolizes the timing of planting. Arbor Day has been honored on April 5th in Korea, but it often does not agree to actual planting time due to global warming. This study confirmed the discrepancy between Arbor Day and regional soil-thawing times and reviewed alternative dates for tree planting using satellite-based soil-thaw data (FT-ESDR) from 1991 to 2020. Study results showed that the start time of planting on the Korean Peninsula, which was indicated by soil-thaw dates, was March 24 during 1991-2000, and it progressively changed to March 17 during 2011-2020. Should Arbor Day be changed based on soil-thaw periods, mid-March would be the most comprehensive, suitable alternative period considering the number of governmental administration units (cities and counties) and the land area of soil-thaw. Tree-Planting Day (March 14) and International Day of Forests (March 21) were found suitable for alternative dates to Arbor Day because they were close to the average soil-thaw time of Korean Peninsula (March 19) and land area whose soil-thaw time was within 10 days from those two dates ranged from 52.5% to 58.8% centered geographically on the mid-section of the peninsula. Since the periods of soil-thaw will continue to change due to climate change, it is necessary to reflect the trend of advancing planting periods in the future if Arbor Day is changed to an earlier date.

• Geomechanics and Engineering
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• v.14 no.3
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• pp.301-306
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• 2018

Stabilization of clayey soil has been studied from past to present by mixing different additives to the soil to increase its strength and durability. In recent years, there has been an increasing interest in stabilization of soils with natural pozzolans. Despite this, very few studies have investigated the impact of pozzolanic additives under freeze-thaw cycling. This paper presents the results of an experimental research study on the durability behavior of clayey soils treated with lime and perlite. For this purpose, soil was stabilized with 6% lime content by weight of dry soil (optimum lime ratio of the the soil), perlite was mixed with it in 0%, 5%, 10%, 20%, 25% and 30% proportions. Test specimens were compacted in the laboratory and cured for 7, 28 and 84 days, after which they were tested for unconfined compression tests. In addition to this, they were subjected to 12 closed system freeze-thaw cycles after curing for 28 days. The results show that the addition of perlite as a pozzolanic additive to lime stabilized soil improves the strength and durability. Unconfined compressive strength increases with increased perlite content. The findings indicate that using natural pozzolan which is cheaper than lime, has positive effect in strength and durability of soils and can result cost reduction of stabilization.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.2
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• pp.43-53
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• 1989

In this research programs, a series test was conducted to show the effects of freeze/thaw process on the various soil properties. The tests were carried out taken from the west sea shore of Korean peninsular and the west sea shore of Scotland, and their results are as follows; 1. There was a positive total heave in a freezing run, although water may he expelled for the sample initially. The water flow must he reverse' from expulsion to intake. 2. The confining pressure had an overriding influence on the heave and frost penetration, a sudden change of the axial strain at failure with strain rate was observed occuring at a strain rate between 10-5 and 10-6, and the initial friction angle of frozen clay was appeared zero. 3. There was shown a significant decrease in liquid limit of soil which was subjected to freeze/thaw process for the initial value of about 20% because of soil particles aggregation. 4. The cyclic freeze/thaw caused a sinificant reduction in shear strength and its thixotropic regain. The frozen/thawed soil exibited negative strength regain, particularly at high freeze/thaw cycles. 5. The freezing temperature greatly influenced on the failure strength of soils and this. Trend was more pronounced the lower the freezing temperature and shown the ductile failure with indistinct peaks.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.3
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• pp.70-80
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• 1989

In this research program special triaxial compression tests and dehydration-swelling tests under the condition of freeze-thaw process were conducted to show the effects of freezethaw process on the physical properties of weathered granite soil, and their results as follows; 1.Consolidation settlement of weathered granite soil mass was increased due to freeze-thaw process, and the initial tangent coefficient of dense state was higher than that of loose state. 2.Compression behaviour of soil was increased according to the decrease of freezing temperature, and when the freezing temperature was reached under - 10$^{\circ}$C, the compression rate was not influenced by change of freezing temperature. 3.The experiments showed that the void ratio and permeability of soil were converged into their values of shrinkage limit, and the permeability was higher due to the freeze-thaw process and as the lower the freezing temperature. 4.The decrease of liquid limit was indicated as the lower the freezing temperature, and as more the freeze4haw cycles, the moisture content was shown the lower side. 5.It was shown that the shrinkage was decreased by freeze-thaw process and not influenced by way of freezing temperature, but dehydration rate was higher.

• Geomechanics and Engineering
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• v.25 no.1
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• pp.41-48
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• 2021

In cold regions, the integrity of the infrastructures built on weak soils can be extensively damaged by weathering actions due to the cyclic freezing and thawing. This damage can be mitigated by exploiting soil stabilization techniques. Generally, ordinary Portland cement (OPC) is the most commonly used binding material for investigating the chemo-hydromechanical behavior. However, due to the environmental issue of OPC producing a significant amount of carbon dioxide emission, calcium sulfoaluminate (CSA) cement can be used as one of the eco-sustainable alternatives. Although recently several studies have examined the strength development of CSA treated sand, no research has been concerned about CSA cement-stabilized sand affected by cyclic freeze and thaw. This study aims to conduct a comprehensive laboratory work to assess the effect of the cyclic freeze-thaw action on strength and durability of CSA cement-treated sand. For this purpose, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were performed on the stabilized soil specimens cured for 7 and 14 days which are subjected to 0, 1, 3, 5, and 7 freeze-thaw cycles. The test results show that the strength and durability index of the samples decrease with the increase of the freeze-thaw cycles. The loss of the strength and durability considerably decreases for all soil samples subjected to the freeze-thaw cycles. Overall, the use of CSA as a stabilizer for sandy soils would be an eco-friendly option to achieve sufficient strength and durability against the freeze-thaw action in cold regions.

• Magazine of the Korean Society of Agricultural Engineers
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• v.20 no.1
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• pp.4599-4613
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• 1978

This study was intended to investigate the effects of bituminous material content of soil-cement mixtures on their durability. For the purpose, unconfined compressive strength test, Freeze-thaw test, and wet-dry test were performed with three types of soil. Each type of soil was mixed with three levels of cement content and each soil-cement mixture was mixed with four levels of bituminous material content. For the unconfined compressive strength test, Freeze-thaw test and wet-dry test, 324, 108, and 108-specimens were prepared respectively. Unconfined compressive strength was measured at age of 7-days, 14-days and 28-days using 108-specimens in each age. The soil-cement loss rate due to freeze-thaw and wet-dry were calculated after 12 cycles of test using 108-specimens in each test. The results are summarized as follows : 1. Optimum moisture content was increased with increase of cement content, but maximum dry density was changed irregulary with increase of the cement content. 2. The unconfined compressive strength was increased with increase of cement content, bituminous material content and curing age. Cement is more effective factor than bituminous material on unconfined compressive strength of soil-cement Mixture. 3. It is estimated as the most economical cement content that the recommended cement content of A.S.T.M. because increasing rate of unconfined compressive strength at age of 28-days was low when cement content is above the recommanded cement content of A.S.T.M. among all types of soil. 4. Although a portion of cement content is substituted for bituminous material, the necessary unconfined compressive strength can be obtained. 5. The soil-cement loss was more influenced by wet-dry than Freeze-thaw 6. The bituminous material is more effective on the decrease of soil-cement loss than increase of unconfined compressive strength 7. The void ratio of soil-cement mixture was changet irregularly with increase of cement content, but that was decreased in proportion to the increase of bituminous material content. 8. The regression equation between the unconfined compressive strength and soil-cement loss rate were obtained as table 7.