• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.1-5
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• 2008

The differential settlement on ordinary concrete buildings and paved roads are often occurred and which caused the failure of structure. The grouting method can be used for correcting the settlement of the structure. However, the grouting method has a disadvantage like that it takes a long time period to get a desired strength, and it is not a continuous in the phase of reinforced effect. In this paper, as an injecting material called GPCON to complement disadvantage, it is estimated about the characteristic that has a high-density expansion. With the changing of ground conditions and amount of injection, the change of physical strength on compression, the stability against chemical material are studied through the filming of SEM. The physical strength with compression is developed to high strength due to mixing with other material. It is not react with most of the material on chemical conditions except the component of alcohol. Through the SEM test. it is confirmed that the strength of material was increased as formation is being densified.

• Journal of the Korean Geosynthetics Society
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• v.17 no.2
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• pp.19-31
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• 2018

Recently the ground subsidence which seriously weakens the safety of cities tends to increase. The purpose of this paper is to develop the materials by using industrial by-products for the application to emergency restoration process in case of ground subsidence. In this paper the laboratory tests including pH test, initial setting test, unconfined compressive strength test, and flow test were performed in order to evaluate the design properties of Controlled Low Strength Material (CLSM). The field test was carried out for evaluating the performance for the early strength of CLSM and the workability for emergency restoration. Test results showed that the strength will be too high to re-excavate the ground when the cement ratio is more than 4%. The optimum mixing ratio appears to be most effective when the mixing ratio of the bottom ash and the gypsum is approximately 50:50 and the cement content is 2%.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.45-53
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• 2015

In general, RC columns are reinforced by spiral or tied steel and a strength of confined concrete is more increased than this of unconfined concrete. And strength and ductility of column are increased by a confinement effect. A confinement effect is affected by concrete strength, spacing, volume and strength of confinement steel. Many researchers suggested various confinement models which reflected these parameters by many experimental results. In this study, a load-strain relationship is evaluated by a confinement model in EC2, and it is compared with Mander model, Saatchioglu-Razvi model and Cusson et al. model. As results, it is appeared that a confinement model in EC2 is able to apply all kinds of concrete strength and a consistency in sectional analysis can be secured using material models in EC2. In parameter studies using material models in EC2, a confinement effect is more affected by a confinement steel than a concrete strength.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.815-826
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• 2009

The paper presents a case study addressing the design and construction aspects for DCM(Deep Cement Mixing) method employed as the foundation of a caisson type breakwater with heavy weight(10,700 ton/EA) and a high design wave height($H_{1/3}$=8.7m). The DCM was designed for the project(Ulsan New Port North Breakwater Phase 1) by optimizing the pattern of DCM columns with a combination of short and long columns (i.e., block type(upper 3m)+wall type(lower)) and considering overlapped section between columns as a critical section against shear force where the coefficient of effective width of treated column($\alpha$) was estimated with caution. It was shown that the value can be 0.9 under the condition with the overlapped width of 30cm. In addition to that, a field trial test was performed after improving conventional DCM equipment (e.g., mixing blades, cement paste supplying pipes, multi auger motor, etc.) to establish a standardized DCM construction cycle (withdrawal rate of mixing blades) which can provide the prescribed strength. The result of the field strength test for cored DCM specimens shows that the averaged strength is larger than the target strength and the distribution of the strength(with a defect rate of 7%) also satisfies with the quality control normal distribution curve which allows defect rate of 15.9%.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.29-40
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• 2023

Xanthan gum and starch compound biopolymer (XS), an environmentally friendly soil-binding material produced from natural resources, has been suggested as a slope protection material to enhance soil strength and erosion resistance. Insufficient wet strength and the consequent durability concerns remain, despite XS biopolymer-soil treatment showing high strength and erosion resistance in the dried state, even with a small dosage of soil mass. These concerns need to be solved to improve the field applicability and post-stability of this treatment. This study explored the utilization of an alkaline-based cation crosslinking method using calcium hydroxide and sodium hydroxide to induce non-thermal gelation, resulting in the enhancement of the wet strength and durability of biopolymer-treated soil. Laboratory experiments were conducted to assess the unconfined compressive strength and cyclic wetting-drying durability performance of the treated soil using a selected recipe based on a preliminary gel formation test. The results demonstrated that the uniformity of the gel structure and gelling time varied depending on the ratio of crosslinkers to biopolymer; consequently, the strength of the soil was affected. Subsequently, site soil treated with the recipe, which showed the best performance in indoor assessment, was implemented on the field slope at the bridge abutment via compaction and pressurized spraying methods to assess feasibility in field implementation. Moreover, the variation in surface soil hardness was monitored periodically for one year. Both slopes implemented by the two construction methods showed sufficient stability against detachment and scouring, with a higher soil hardness index than the natural slope for a year.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.157-166
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• 2008

To investigate the relationship between compressive strength ($q_u$) of Lightweight Air-mixed soil (LAS) and its physical deformation coefficient ($E_{50}$), a series of unconfined compressive tests have been performed on specimens of LAS according to various dredged soil types by percentage of sand, silt and clay. From the results it was found that the cement content ($C_i$) and unit weight (${\gamma}_m$) are most influence factors on strength, and percentage of sand, silt, clay by grain size analysis (KS F2302) have more effect on compressive strength than other physical properties of soil. It was also found that the rate of strength (a) increases with curing time, but it reduces with the increase of percentage of clay ($C_%$).

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.75-83
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• 2004

The Indiana Department of Transportation (INDOT) has permitted the use of Lime Kiln Dust (LKD) as a low-cost construction material in creating a workable platform for soil modification (not for soil stabilization) since the early 1990s on selected projects. However, the enhanced strength of soils with LKD has not been accounted for in the subgrade stability calculations in the design process. This study was initiated to evaluate how the lime kiln dust is a comparable material to hydrated lime. A series of laboratory tests were performed to assess the mechanical benefits of lime kiln dust in combination with various predominant fine grained soils encountered in the State of Indiana, such as A-4, A-6 and A-7-6. In the course of this study, several tests such as the Atterberg limits, standard Proctor, unconfined compression, CBR, volume stability, and resilient modulus were performed. As a result, mixtures of fine grained soils with 5% lime or 5% LKD substantially improve unconfined compressive strength up to 60% - 400%. CBR values for treated soils are in the range of 25 to 70 while those for untreated soils range from 3 to 18. In general, significant increase in resilient moduli of the soils treated with lime and LKD was observed. This indicates that lime kiln dust may be a viable, cost effective alternative to hydrated lime in enhancing the strength of fine grained soils.

• Land and Housing Review
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• v.12 no.3
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• pp.109-119
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• 2021

Global warming caused by greenhouse gas emissions has rapidly increased abnormal climate events and geotechnical engineering hazards in terms of their size and frequency accordingly. Biopolymer-based soil treatment (BPST) in geotechnical engineering has been implemented in recent years as an alternative to reducing carbon footprint. Furthermore, thermo-gelating biopolymers, including agar gum, gellan gum, and xanthan gum, are known to strengthen soils noticeably. However, an explicitly detailed evaluation of the correlation between the factors, that have a significant influence on the strengthening behavior of BPST, has not been explored yet. In this study, machine learning regression analysis was performed using the UCS (unconfined compressive strength) data for BPST tested in the laboratory to evaluate the factors influencing the strengthening behavior of gellan gum-treated soil mixtures. General linear regression, Ridge, and Lasso were used as linear regression methods; the key factors influencing the behavior of BPST were determined by RMSE (root mean squared error) and regression coefficient values. The results of the analysis showed that the concentration of biopolymer and the content of clay have the most significant influence on the strength of BPST.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.31-37
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• 2011

Only a few studies have been conducted using reduced slag as recycled material. The reduced slag in electric furnace is produced as a by-product in making a steel and a few applications of the reduced slag as expensive additives and bonding materials or as the stabilized soils was reported. The purpose of this study is to present the feasibility of the reduced slag as recycled material, especially, in a field of civil engineering. In order to achieve the purpose experiments such as SEM and XRF analysis was conducted for the reduced slag in electric furnace. Based on the results various geotechnical experiments were conducted to know engineering properties of slag-soil mixtures. Weathered soils and clay are mixed with reduced slag for various ratios. As the ratio of reduced slag to weathered soil increases, the maximum dry unit weight of the mixture decreased with increasing optimum moisture content. The results indicates that there is no effect on a reduced slag by compaction efforts. The shear strengths of the weathered soil-slag mixtures are slightly higher or similar to those of weathered soils. The permeability of the weathered soil-slag mixtures is similar to that of silty or sandy soils. Therefore, it is possible to use the mixtures as embankment or backfill materials in the fields. The unconfined strength of the mixtures of reduced slag and clay is higher than that of clay and it tends to increase with the curing time. Therefore it can be used to improve the soft ground.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1C
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• pp.25-31
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• 2006

It is common to use the unconfined compressive strength (UCS) of intact rock to estimate the shaft resistance of rock socketed drilled shaft. Therefore the most design manuals give a guide to use the UCS of rock core to estimate the shaft resistance of rock-socketed drilled shaft. Recently, however the design manuals for highway bridge (KSCE, 2001) and of AASHTO (2000) were revised to use the UCS of rock mass with RQD instead of the UCS of rock core so that the estimated resistance could be representative of field conditions. Questions have been raised in application of the new guide to the domestic main bed rock types. The intrinsic drawbacks in terms of RQD were comprised in the questions, too. As the results, in 2002 the new guide in the design manual for highway bridge (KSCE, 2001) were again revised to use the UCS of rock core to estimate the shaft resistance of rock-socketed drilled shafts. In this paper, various methods which can estimate the UCS of rock mass from intact rock core were reviewed. It seems that among those, the Hoek-Brown method is very reliable and practical for the estimation of the UCS of rock mass from rock cores. As the results, using the Hoek-Brown failure criterion a modified guide for the estimation of the shaft resistance of rock-socketed drilled shafts was suggested in this paper. Through a case study it is shown that the suggested method gives a good agreement with the measured data.