• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.87-97
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• 2008

Behaviors of cemented engineered soils, composed of rigid sand particle and soft rubber particle, are investigated under $K_o$ condition. The uncemented and cemented specimens are prepared with various sand volume fractions to estimate the effect of the cementation in mixtures. The vertical deformation and elastic wave velocities with vertical stress are measured. The bender elements and PZT sensors are used to measure elastic wave velocities. After cementation, the slope of vertical strain shows bilinear and is similar to that of uncemented specimen after decementation. Normalized vertical strains can be divided into capillary force, cementation, and decementation region. The first deflection of the shear wave in near field matches the first arrival of the primary wave. The elastic wave velocities dramatically increase due to cementation hardening under the fixed vertical stress, and are almost identical with additional stress. After decementation, the elastic wave velocities increase with increase in the vertical stress. The effect of cementation hinders the typical rubber-like, sand-like, and transition behaviors observed in uncemented specimens. Different mechanism can be expected in decementation of the rigid-soft particle mixtures due to the sand fraction. a shape change of individual particles in low sand fraction specimens; a fabric change between particles in high sand fraction specimens. This study suggests that behaviors of cemented engineered soils, composed of rigid-soft particles, are distinguished due to the cementation and decementation from those of uncemented specimens.

• Journal of the Korean Geotechnical Society
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• v.26 no.4
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• pp.37-45
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• 2010

Salt cementation, a typical naturally-cemented phenomenon, may occur due to water evaporation under the change of climate. Capillary force may influence the distribution of cement in granular soils. This study addresses the effect of capillary force on salt cementation using five different techniques: cone penetration test, electrical conductivity measurement, photographic imaging technique, nondestructive imaging technique, and process monitoring by elastic wave. Glass beads modeling a particulate media was mixed with salt water and then dried in an oven to create the cementation condition. Experimental results show that salt cementation highly concentrates at the top of the small particle size specimens and at the middle or the bottom of the large particle specimens. The predicted capillary heights are similar to the locations of high salt concentration in the cemented specimens. Five suggested methods show that the behavior of salt-cemented granular media heavily depends on the capillary force.

• Journal of the Korean Geotechnical Society
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• v.28 no.6
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• pp.53-61
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• 2012

The purpose of this study is to understand the mechanism of cementation of soil induced by bacteria. In order to understand the mechanism of cementation of soft soils treated with bacteria, six types of specimens(Not treated, Normal concentration bacteria treatment, High concentration bacteria treatment, Supernatant high concentration bacteria treatment, Double high concentration bacteria treatment, and 25% Specimen high concentration bacteria treatment) were made. Scanning Electron Microscope (SEM), EDX and X-ray diffraction (XRD) analyses were performed on the soft silt and loose sand specimens. Compared with the normal bacteria concentration treated specimen, a clearer cementation between particles was observed in the 25% specimen high bacteria concentration treated specimen. On the basis of the preliminary results, it appears that microbial cementation can occur in the soft soil.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.89-98
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• 2006

In this study, the iron and aluminium electrode was put in marine clay which was taken from south coast in Korea to increase the undrained shear strength by inducing the densification and cementation between clay particles and precipitation which was developed by electrode decomposition. For raising the cementation rate and reducing treatment time, high electric current( 2.5A) was applied in each electrode at semi-pilot scale soil box with marine clay. After the tests, the undrained shear strength was measured at designated points using cone penetration test device and sampling was conducted simultaneously in order to measure water content, pH and electric conductivity which would be the key for configuring the cementation effects indirectly. The iron electrode decomposition test results show that the water content adjacent to anode section decreased in 35% and increased in 13% at cathode section. The measured shear strength however, was increased considerably comparing to initial shear strength because of cementation effect between iron ions and soil particles. In case of aluminium electrode decomposition test, the distribution of measured shear strength and degree of improvement were more homogeneous than iron electrode decomposition test.

• Journal of the Korean Geotechnical Society
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• v.35 no.1
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• pp.31-42
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• 2019

About 3% of Casein is included in milk and it accounts for 80% of milk's protein. It has an adhesive property when mixed with calcium hydroxide and sodium hydroxide solutions. It has been usually used to bond woods under dry condition but becomes weak when exposed to moisture. Such weakness is very critical when casein is applied for soil cementation under groundwater condition. Therefore, this study was aimed to protect such weakness by changing or adding certain ingredients of casein adhesive. Two types of cemented specimens were prepared with Nakdong river sand and tested for unconfined compressive strength and durability. Each specimen was mixed with casein or cement. Ingredients of casein binder suggested by the University of Wisconsin, which is called a standard casein recipe, was also prepared. This study tried 6 different types of casein binder recipe. Among them, one with 30% hydroxide calcium increase and 50% hydroxide sodium decrease compared with the standard casein was most effective. Based on the most effective casein recipe, cemented sand with 1-4% of casein ratio was prepared and tested. The unconfined compressive strength and durability index were 6,253kPa and 92% for the specimen with 4% of casein ratio and 1,500kPa and 62% for the one with 8% of cement ratio. Therefore, casein cemented sand showed better performance. In addition, over 3% of casein cemented sand had over 80% durability index.

• Journal of the Korean Geotechnical Society
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• v.25 no.5
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• pp.75-86
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• 2009

Salt, one of the most common soluble materials in engineering soil, may have an effect on mechanical behaviors of soils under its cementation process. In order to investigate this natural phenomenon, non-soluble material by using glass beads is mixed with salt electrolyte and cemented by using oven to evaporate water. Three different sizes of glass bead particles, 0.26, 0.5, and 1.29 mm, with different salt concentration, 0, 0.1, 0.2, 0.5, 1.0, and 2.0M, are explored by using P- and S-waves, excited by bender elements and piezo disk elemets, respectively. The velocities of the P-wave and S-wave of the particulate medium cemented by salt show three stages with the degree of saturation: 1) S-wave velocities increase while P-wave velocities reduce with degree of saturation changing from 100% to 90%; 2) Both velocities are stable with degree of saturation varying from 90% to 10%; 3) The velocities change enormously when the specimens are nearly dry with degree of saturation from 10% to 0%. Besides, the resonance frequencies of S-wave show similar stages to the S-wave velocities. This study demonstrates meaningful trends of elastic wave characteristics of geo-materials according to the cementation of dissolved salt.

• Journal of the Korean Geotechnical Society
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• v.28 no.3
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• pp.67-75
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• 2012

This paper presents an environment-friendly sand cementation method by precipitating calcium carbonate using plant extracts. The plant extracts contain urease like $Sporosarcina$ $pasteurii$, which can decompose urea into carbonate ion and ammonium ion. It can cause cementation within sand particles where carbonate ions decomposed from urea combine with calcium ions dissolved from calcium chloride or calcium hydroxide to form calcium carbonate. Plant extracts, urea and calcium chloride or calcium hydroxide were blended and then mixed with Nakdong River sand. The mixed sand was compacted into a cylindrical specimen and cured for 3 days at room temperature ($18^{\circ}C$). Unconfined compression test, SEM and XRD analyses were carried out to evaluate three levels of urea concentration and two different calcium sources. As urea concentration increased, the unconfined compressive strength increased up to 10 times those without plant extracts because calcium carbonate precipitated more, regardless of calcium source. It was also found that the strength of specimen using calcium chloride was higher than that of specimen using calcium hydroxide.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.471-484
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• 2019

Liquefaction occurs by a temporal loss of sediment strength as a consequence of increased pore water pressure during the re-arrangement of unconsolidated, granular sediments. Liquefaction is dependent on the physical properties of the sediments and cause surface cracks, landslide, and the formation of soft-sediment deformation structures(SSDS). SSDS is formed by the combined action of the driving force and deformation mechanism(liquefaction, thixotropy, and fluidization) that is triggered by endogenic or exogenic triggers. So research on the SSDS can unravel syndepositional geological events. If detailed sedimentologic analysis together with surrounding geological context suggest SSDS formed by earthquakes, the SSDS provide a clue to unravel syndepositional tectonic activities and detailed paleoseismological information(> Mw 5) including earthquakes that leave no surface expression.

• Journal of the Korean GEO-environmental Society
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• v.18 no.10
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• pp.15-22
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• 2017

The soil improvement method so far has been developed with an emphasis on enhancing the strength of the ground. A soil improvement method using a excellent cementitious stabilizer in economical efficiency and handling property is mainly used. The soil improvement method using cementitious stabilizer is effective but environmental and human harmful substances are detected and environmental problems such as carbon dioxide emission and groundwater pollution are pointed out. Therefore, as part of an alternative method capable of solving such problems, researches on the soil improvement method incorporating biological technology are being actively carried out. This study was conducted to investigate the characteristics of strength change when mixed with environmentally friendly soil binder and microorganism in clay, and it was analyzed by uniaxial compression test, direct shear test, SEM, XRD. As a results of the test, we confirmed the cementation caused by microbially induced calcite precipitation and the strength increase enhancement by it.

• Journal of the Korean Geotechnical Society
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• v.30 no.1
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• pp.93-101
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• 2014

In this study, a blast furnace slag having latent hydraulic property with an alkaline activator for resource recycling was used to solidify sand without using cement. Existing chemical alkaline activators such as $Ca(OH)_2$ and NaOH were used for cementing soils. An alkaliphilic microorganism, which is active at higher than pH 10, is tested for a new alkaline activator. The alkaliphilic microorganism was added into sand with a blast furnace slag and a chemical alkaline activator. This is called the microorganism alkaline activator. Four different ratios of blast furnace slag (4, 8, 12, 16%) and two different chemical alkaline activators ($Ca(OH)_2$ and NaOH) were used for preparing cemented specimens with or without the alkaliphilic microorganism. The specimens were air-cured for 7 days and then tested for the experiment of unconfined compressive strength (UCS). Experimental results showed that as a blast furnace slag increased, the water content and dry density increased. The UCS of a specimen increased from 178 kPa to 2,435 kPa. The UCS of a specimen mixed with $Ca(OH)_2$ was 5-54% greater than that with NaOH. When the microorganism was added into the specimen, the UCS of a specimen with $Ca(OH)_2$ decreased by 11-60% but one with NaOH increased by 19-121%. The C-S-H hydrates were found in the cemented specimens, and their amounts increased as the amount of blast furnace slag increased through SEM analysis.