• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.21-32
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• 2006

Factors affecting the electrical properties of bentonite slurry were identified and electric conduction mechanism in slurry was examined. Electrical conductivity of bentonite and soil-bentonite slurry linearly increases with the bentonite content. Test result indicated that the change In electrical conductivity of slurry was mainly caused by dissolved cations from bentonite particles. The relationship between electrical conductivity and bentonite content was affected by the initial electrical conductivity of slurry solution and fine content in soil-bentonite mixture. Such influences were evaluated and the calibrated relationships were suggested. Based on the suggested relationship between electrical conductivity and bentonite content, bentonite content in various bentonite and soil-bentonite slurry can be quantitatively evaluated by using electrical conductivity measurement method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.85-90
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• 2002

This study aims to propose a fundamental report for pozzolan reaction of discarded Bentonite by heat-treatment as concrete mineral admixture. As discarded bentonite is clay mineral to contain a great quantity a lot of $SiO_2$ and $Al_{2}O_{3}$, it is anticipated to reveal pozzolan reaction ability by heat-treatment. To find out pozzolan reaction ability of discarded Bentonite slurry by heat-treatment, the experiment is excuted Phenolphtalein test, setting test, pH test and the analysis by X-ray diffractor. As a result of this study, discarded Bentonite slurry can be utilized as concrete mineral admixture by heat-treatment and especially, pozzolan reaction ability of discarded Bentonite slurry is superior to the situation of 50$0^{\circ}C$~$700^{\circ}C$, 60min.

• Geotechnical Engineering
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• v.13 no.2
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• pp.9-16
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• 1997

Cut-off methods of controlling leachate migration from waste landfills and contaminated sites are studied. Permeability and chemical compatibility tests are prrforlned on slurry wall materials including soil-bentonite, cement-bentonite, cement / fly ash-bentonite, plastic concrete. Hydraulic conductivity of soil-bentonite mixture is the lowest of these four bacuill materials. The leachate from municipal solid waste has little influence on the permeability of the backfill materials. The bentonite slurry becomes flocculated and aggregated when exposed to the leachate. The results of the permeability test showed that the hydraulic conductivities of the backfill materials are in the order soil-beiltonite, Plastic concrete, cement-bentonite. And the result c: the compatibility test showed increase in permeability due to the effects of leachate. Thus, in designing the slurry wall it is essential to check the behaviour of the bentonite slurry and backfill materials on the compatibility with the contaminants.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.237-247
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• 2022

To investigate the curing temperature effect on the engineering properties of ground granulated blast furnace slag-cement bentonite (GGBS-CB) slurry for cutoff walls, the laboratory experiments including the setting time, unconfined compressive strength, and permeability tests were carried out. The mixing procedure for GGBS-CB slurry was as follows: (1) montmorillonite-based bentonite slurry was first fabricated and hydrated for four hours, and (2) cement or GGBS with cement was added to the bentonite slurry. The dosage range of GGBS was from 0 to 90 % of cement by mass fraction. The GGBS-CB slurry specimens were cured and stored in environmental chamber at temperature of 14±1, 21±1, 28±1℃ and humidity of 95±2% until target days. The highest average temperature of three seasons in South Korea was selected and used for the tests. The experimental results indicated that in early age (less than 28 days) of curing the engineering properties of GGBS-CB slurry were primarily affected by the curing temperature, whereas the replacement ratio of GGBS became a main factor to determine the properties of the slurry as the curing time increased.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.97-104
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• 1998

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.407-426
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• 2008

The bentonite slurry has been used as the stabilize suspension for wet process bored pile construction in Thailand. The bentonite suspension has benefit on filtration in the sand layer, but it creates thick cake film along pile shaft and loose sedimentation at pile toe. The base grouting technique was widely used to rectify the soft base or loose sedimentation problem of bored pile. The base grouting technique was not increased only end bearing capacity, but was also more increase in skin friction capacity of the bored piles. The comprehensive researches on base grouting was carried out by installing PVC casing inside the shaft to allow the drilling through the pile base in order to collect the soil sample below the pile tip. The polymer based slurry recently was used to replace the bentonite slurry to overcome the thick cake film along pile shaft as well as loose sedimentation at pile toe. The extent research on polymer slurry by physical model was performed to verify the real behavior of polymer. The appropriate mixing ratio of polymer was proposed. The design skin friction coefficient, $\beta$ and end bearing coefficient, Nq, for sand layer base on fully instrumented tested pile were proposed. The application on remedial of the lose capacity bored pile with large displacement in Bangladesh was proposed and discussed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.463-473
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• 2017

Bentonite swells when it comes into contact with water and makes it a viscous fluid. Thus it is widely used in civil engineering works for waterproofing. Utilizing the properties of bentonite, the slurry shield TBM supports excavated face with pressurized slurry as well as transporting excavated muck. When bentonite is in contact with seawater, due to the change of double layer thickness, its expandability and viscosity are lowered. This may cause problems for excavation stability and muck discharge due to the increase of sea water inflow when Slurry TBM is used under sea water conditions. In this study, the change of slurry condition caused by the inflow of sea water during tunnel excavation with Slurry TBM was investigated and a slurry management guideline was proposed. For this purpose, a laboratory test was carried out based on the slurry management criterions applied in the field, and a method applicable to the field where sea water is affected has been proposed.

• KCI Concrete Journal
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• v.14 no.4
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• pp.151-159
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• 2002

This study investigates experimentally the optimum mix proportion and design factors of the stabilizing liquid used for excavation of the massive and deep slurry wall in LNG in-ground tank before pouring concrete. Considering those site conditions, the stabilizing liquid used for excavation of slurry wall has to be satisfied with some requirements including specific gravity, fluid loss, cake thickness, funnel viscosity and sand content in order to construct the safe and qualified slurry wall. For this purpose, we select materials including bentonite, polymer and dispersion agent. After performing many tests for materials and mix design process, we propose the optimum mix proportion that the upper limit ratio of bentonite is $2.0\%$, polymer is $0.1\%$ considering the funnel viscosity and dispersion agent is $0.05\%$considering the fluid loss of the stabilizing liquid. Also, we select all materials which are consisted of GTC4 as bentonite, KSTP as polymer and Bentocryl 86 as dispersion agent. Based on the results of this study, the optimum mix proportion of the stabilizing liquid is applicable to excavate the deep and massive slurry wall in LNG in-ground tank successfully.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.5-17
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• 2013

Slug tests can be adopted to estimate hydraulic conductivity of the slurry trench wall backfill for its abilities to reflect the in-situ performance of the construction. A comprehensive three-dimensional numerical model is developed to simulate the slug test in a slurry trench wall considering the presence of bentonite cake on the interface boundaries between the wall and the surrounding soil formation. Influential factors such as wall width (i.e., proximity of wall boundary), well deviation, vertical position of well intake section, compressibility of wall backfill, etc. are taken into account in the model. A series of simulation results are examined to evaluate the bentonite cake effect in analyzing practical slug test results in the slurry trench wall. The results show that the modified line-fitting method can be used without any correction factor for the slug test in the slurry trench wall with the presence of bentonite cake. A case study is reanalyzed with the assumption of existing bentonite cake. The results are compared with the previously reported results by the approaches assuming no bentonite cake (constant-head boundary) or upper-bound solution (no-flux boundary). The case study demonstrates the bentonite cake effect and the validity of the modified line-fitting method in the estimation of the hydraulic conductivity of the slurry wall backfill.

• Geomechanics and Engineering
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• v.38 no.6
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• pp.603-609
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• 2024

In downtown subway project most of excavated soil is discarded externally, whereas in road construction excavated soil is used as filling material and management of surplus soil becomes important factor for success of the project. Excavated materials from slurry shield TBM are discharged through discharge pipe to slurry treatment plant and excavated soil mixed with bentonite are separated in separation plant by grain size. Fine material has been discarded together in filter cake without recycling. Its volume can vary according to geologic condition but statistically fine material as filter cake is about 5%~30% out of overall excavated volume. However, filter cake is non-toxic and can be recycled when mixed in the appropriate proportions with coarse aggregate. Therefore, in this study, utilization of excavated soil from a slurry shield TBM were examined and lab tests were conducted to find the proper way for mixing filter cake and aggregate to be recycled as fill material for road construction.