• Journal of Soil and Groundwater Environment
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• v.6 no.4
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• pp.61-72
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• 2001

A barrier liner system is placed at the bottom and side slope in landfill to protect a leaking of leachate that the hydraulic conductivity of this system should be less than It 107cm/sec. In this study, the soil-bentonite mixture for the bottom liner system was evaluated in two point of views : changing characteristics of the hydraulic conductivity according to the different mixing ratio of soil-bentonite with the effect of bentonite swelling and the difference method (A & D type) of compaction on the hydraulic conductivity. As the results, maximum dry density (${\gamma}$$_{dmax}$) of SC group mixture was higher than of CL group mixture. However, the result of optimum moisture contents(OMC) of both groups were the contrary. In case of ${\gamma}$$_{dmax}$ by different compaction method, D type was higher than A. But the OMC were the contrary. The difference of ${\gamma}$$_{dmax}$ according to the Compaction energy, “SC” group mixture W3S higher than the “CL” group. In case of OMC of “CL” group was higher than “SC” group. The effecting of swelling was a little bit different on the two factors. According to the result of compaction test, the use of site soil only could not meet the criteria on hydraulic conductivity, but could find a solution for the mixing ratio of bentonite mixture were satisfied to the standard of barriation. The increased in bentonite mixing ratio and degree of swelling, the values of hydraulic conductivity were decreased. Especially the “CL” group with “D” type compaction measured the lowest value with the same conditions. Also, the bentonite mixing ratio has more influenced on the hydraulic conductivity compare with swelling effect. The “SC” group mixture with “A” typo compaction got a big difference from others. The evaluation of economic for the construction cost on the two cases, the lower bentonite mixing ratio of soil-bentonite mixed soil is more economically because of bentonite cost.

• Journal of the Korean GEO-environmental Society
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• v.2 no.2
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• pp.33-39
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• 2001

In order to utilize mass of oyster shells for a partial substitute material for reclamation, the shear characteristics of two-phase mixture soil with oyster shells were investigated with $\overline{CU}$ test. From various experiments, it was found that the increase of mixed ratio of oyster shells causes the shear strength of mixed soil. And this phenomenon not only depends on friction due to confining pressure such as pure clay but also is influenced by shaping skeleton of oyster shells. Also, it was discovered that there were many influences by clay-oyster shell mixture from the study of the secant modulus and dilatancy characteristics of mixed soil. In addition, variation of oyster shell skeleton during shearing stage is examined applying modifying coefficient concept.

• Journal of the Korean GEO-environmental Society
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• v.1 no.1
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• pp.43-50
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• 2000

This paper presents the engineering property of light weight soil made of soil mixed with recycled stylofoam and stabilizer. Recycled stylofoam beads is able to use by lightweight fill materials because it is light, adiabatic, and effective for vibration interception. Especially, recycled stylofoam beads is easy to supply because stylofoam have been recycle item in 1996. In this study, physical and geotechnical properties of the light weight mixed soil(weathered granite soil mixed with Stylofoam Beads) were analyzed by laboratory experiments to examine its suitability for backfill materials. Laboratory tests were performed to evaluated strength, bearing capacity, weight, permeability, microphotograph analysis with variation of mixing ratio. Based on the results, it is concluded that the use of recycled stylofoam beads is acceptable lightweight fill.

• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.159-169
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• 2007

The behavior of fiber-reinforced cemented sands (FRCS) was studied to improve a brittle failure mode observed in cemented sands. Nak-dong River sand was mixed with ordinary Portland cement and a Polyvinyl alcohol (PVA) fiber. A PVA fiber is widely used in concrete and cement reinforcement. It has a good adhesive property to cement and a specific gravity of 1.3. A PVA fiber has a diameter of 0.1 mm that is thicker than general PVA fiber for reinforced cement. Clean Nak-dong River sand, cement and fiber at optimum water content were compacted in 5 layers giving 55 blows per layer. They were cured for 7 days. Cemented sands with a cement/sand ratio of 4% were fiber-reinforced at different locations and tested for unconfined compression tests. The effect of fiber reinforcement form and distribution on strength was investigated. A specimen with evenly distributed fiber showed two times more strength than not-evenly reinforced specimen. The strength of fiber-reinforced cemented sands increases as fiber reinforcement ratio increases. A fully reinforced specimen was 1.5 times stronger than a specimen reinforced at only middle part. FRCS behavior was controlled not only by a dosage of fiber but also by fiber distribution methods or fiber types.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1327-1331
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• 2005

This study was to investigate the reduction of hydration heat by utilizing industrial by-products such as BFS(Blast Furnace Slag). DM(Dredged Mud) was used by parent soil and Ordinary portland cement was used by cementing material. Additive added to reduce the heat of hydration was BFS. From the results of experiment, hydration heat was decreased in accordance with the addition of BFS. The reason was that surface of BFS coated with aluminosulfate. Initial uniaxial strength was low, neither was not long term uniaxial strength. It was concluded that silica rich layer($H_2SiO_4^{4-}$) in solid phase early in the reaction of hydration was difficultly moved in liquid phase due to the increase of ZP(Zeta Potential). However, the ZP in the later hydration was decreased due to the acceleration of mobility of silica rich layer($H_2SiO_4^{4-}$). Therefore, long term physical properties such as uniaxial strength revealed.

• Journal of the Korean GEO-environmental Society
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• v.6 no.2
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• pp.31-38
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• 2005

Flowable fills are self-leveling, liquid-like materials, and self-compacting to 95-100% of the maximum unit weight. Benefits of flowable fills include limited required labor, accelerated construction, ready placement at inaccessible locations, and the ability to be manually re-excavated. Applications for flowable fills include utility trenches, building excavations, underground storage tanks, abandoned sewers and utility lines, and filling underground mine shafts The objective of this study is to estimate engineering property of flowable fills made of soil mixed with recycled stylofoam and stabilizer for using geotechnical field. For this study, the uniaxial compression test, flowable test, and model tests were performed. Based on the results of the tests, the following conclusions are : fills made of soil mixed with recycled stylofoam and stabilizer can be used as flowable fills, minimum stabilizer quantity for using flowable fills ranges from 1.0($kN/m^3$) to 1.2 ($kN/m^3$).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.285-293
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• 2012

The surface tension, which is generated in the unsaturated soils, increases the stiffness of the soils. The objective of this study is to estimate the effect of the surface tension, which varies according to the temperature, on the shear wave velocity. Nine specimens, which have the different degree of saturation (0%, 2.5%, 5%, 10%, 20%, 40%, 60%, 80%, 100%), are prepared by using sand-silt mixtures. Experiments are carried out in a nylon cell designed for the measurement of shear waves. A pair of bender elements, which are used for the generation and detection of shear waves, is installed as a cross-hole type. The shear waves are continuously monitored and measured as the temperature of specimens decreases from $15^{\circ}C$ to $1^{\circ}C$. The results show that shear wave velocities of the fully saturated and fully dried specimens change a little bit as the temperatures of specimens decrease. However, the shear wave velocities of the specimens with the degree of saturations of 2.5%, 5%, 10%, 20%, 40%, 60% and 80% continuously increase as temperature decreases from $15^{\circ}C$ to $1^{\circ}C$. Furthermore, a fully saturated specimen is dried at the temperature of $70^{\circ}C$ in order to observe the shear waves according to degree of saturation. The shear wave velocities measured at the temperature of $70^{\circ}C$ are generally lower than those measured at temperature of $15^{\circ}C$. This study demonstrates that the dependence of shear wave velocities on the temperature according to the degree of saturation should be taken into account in both laboratory and field tests.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.47-56
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• 2014

In winter season, the pore water inside the ground freezes and thaws repetitively due to the cold air temperature. When the freezing-thawing processes are repeated on the ground, the change in soil particle structure occurs and thus the damage of the infrastructure may be following. This study was performed in order to investigate the stiffness change of soils due to the freeze-thaw by using elastic waves. Sand-silt mixtures are prepared with in the silt fraction of 40 %, 60 % and 80 % in weight and in the degree of saturation of 40 %. The specimens are placed into the square freezing-thawing cell by the temping method. For the measurement of the elastic waves, a pair of the bender elements and a pair of piezo disk elements are installed on the cell, and a thermocouple is inserted into soils for the measurement of the temperature. The temperature of the mixtures is decreased from $20^{\circ}C$ to $-10^{\circ}C$ during freezing, is maintained at $-20^{\circ}C$ for 18 hours, is gradually increased up to the room temperature of $20^{\circ}C$ to thaw the specimens. The shear waves, the compressional waves and the temperature are measured during the freeze-thaw process. The experimental result indicates that the shear and the compressional wave velocities after thawing are smaller than those of before freezing. The velocity ratio of after thawing to before freezing of shear wave is smaller than that of the compressional wave. As silt fraction increases from 40 % to 80 %, the shear and compressional wave velocities are gradually increased. This study suggests that the freezing-thawing process in unsaturated soil loosens the soil particle structure, and the shear wave velocity reflects the effect of freezing-thawing more sensitively than the compressional wave velocity.