• Geomechanics and Engineering
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• v.24 no.1
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• pp.81-89
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• 2021

Uniaxial compression tests were conducted on sandstone-CGFB composite samples with different interface angles, and their strength, acoustic emission (AE), and failure characteristics were investigated. Three macro-failure patterns were identified: the splitting failure accompanied by local spalling failure in CGFB (Type-I), the mixed failure with small sliding failure along with the interface and Type-I failure (Type-II), and the sliding failure along with the interface (Type-III). With an increase of interface angle β measured horizontally, the macro-failure pattern changed from Type-I to Type-II, and then to Type-III, and the uniaxial compressive strength and elastic modulus generally decreased. Due to the small sliding failure along with the interface in the composite sample with β of 45°, AE events underwent fluctuations in peak values at the later post-peak failure stage. The composite samples with β of 60° occurred Type-III failure before the completion of initial compaction stage, and the post-peak stress-time curve initially exhibited a slow decrease, followed by a steep linear drop with peaks in AE events.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.113-121
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• 2011

River sand has generally used for the backfill material of underground power cables. The thermal resistivity of it has $150^{\circ}C$-cm/Watt in wet condition and more than double in dry condition. The final goal of this study is to find the backfill material which has a small change in thermal resistivity with various water contents, for example thermal resistivity is $50^{\circ}C$-cm/Watt and $100^{\circ}C$-cm/Watt in wet and dry conditions respectively. In this study it is presented that the comparison of thermal resistivity using stone powder, crush rock, weathered granite soil and Jumunjin sand as well as river sand in the needle method regarding water content, dry unit weight and particle size distribution. As a result, the thermal resistivity of a material is minimized when they have maximum dry unit weight at optimum moisture content and maximum density by appropriately mixing materials for particle size distribution. Therefore thermal resistivity characteristics should be considered two factors: one is the difference between natural dry condition and dry state after optimum moisture content, and the other is the difference between unit weight of raw material and maximum dry density.

• Clean Technology
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• v.24 no.4
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• pp.315-322
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• 2018

Industrial use of waste oyster shells is limited because of requiring excessive energy for converting natural oyster shells in the form of calcium carbonate ($CaCO_3$) into calcium oxide (CaO) for this purpose. This study aimed to develop energy-saving process for producing solidifying agent using waste oyster shells for backfill materials. It was suggested that oyster shells were converted to calcium sulfates which were mixed with sodium hydroxide solution and red clay, forming solid specimen. The optimal concentrations of sulfuric acid for sulfation of oyster shell and sodium hydroxide to generate calcium hydroxide ($Ca(OH)_2$), were determined. Unconfined compressive strength of solid specimen increased with increasing the content of solidifying agent while it increased also with increasing ratio of natural oyster shells to coal ash. The result clearly demonstrates that solidifying agent consisting of sulfuric acid-treated oyster shell, coal ash, and sodium hydroxide solution, can be effectively utilized for preparing backfill materials using natural oyster shell and coal ash. Sulfuric acid-treated oyster shell-based solidifying agent has not been previously developed and will contribute to broaden industrial application of waste oyster shells.

• International Journal of Concrete Structures and Materials
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• v.2 no.1
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• pp.49-55
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• 2008

The disadvantage of PMM's (polymer-modified mortars) that are currently on the market is the utilization of expensive polymer additives and also the cost of the other components. One of the possibilities how to decrease this price is the effective utilization of waste materials which are very inexpensive in spite of their good properties. The combinations of different degree in polymer adhesiveness and waste secondary raw materials - fly ash - are experimentally verified in the paper. The use of fly ash in adhesive materials for ceramic tiles is limited by unsatisfactory initial adhesiveness to sintered ceramic sherd as a result of a running pozzolanic reaction that lowers the efficiency of polymer additives. On the other hand, the use of adhesive and backfill coating materials for gluing ETICS board insulation materials has brought very good results.

• Journal of the Korean Geosynthetics Society
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• v.9 no.4
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• pp.67-73
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• 2010

The most important thing in the design of the reinforced earth retaining wall is to obtain the good backfill materials. However there was a special case using soils mixed with the crushed stone, because the field ran short of good backfill soils. Accordingly in this study various kind of tests were performed according to the mixing content of a crushed stone, which are the gradation curve, the direct shear test and the pullout test. From the test results at first the gradation of soils mixed with crushed stone has been compared with the selecting standard as backfill of reinforced earth wall. And the gradation standard has been satisfied in case of mixing ratio 20% of a crushed stone under 19mm. Also the direct shear test and the pullout test have been performed and at the test results the shear strength parameter and the pullout strength parameter were increased with the increse of the mixing content of a crushed stone. It has been thought that this study will give important data to a designer in designing the reinforced earth wall with soils mixed with crush stones.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1889-1894
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• 2012

A small-scale chamber test laboratory for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out. Laboratory test which was simulated during construction stage was conducted. The vertical deflection of 4.43mm to 6.6mm, and the horizontal deflection of 5.49mm to 15.9 mm were measured during backfilling. In case of loading, the vertical deflection of 2.41mm to 8.69mm, and the horizontal deflection of 1.66mm to 2.53mm were measured. Its residual deflections were 1.40mm to 5.93mm for vertical and 1.66mm to 2.53mm for lateral. The vertical and horizontal deflecto of controlled low strength materials were smaller than that of sand backfill. Also, it was same trend for the measured surface settlement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.121-141
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• 2017

The thermal analysis of an underground power conduit for electrical cables is essential to determine their current capacity with an increasing number of demands for high-voltage underground cables. The temperature rises around a buried cable, caused by excessive heat dissipation, may increase considerably the thermal resistance of the cables, leading to the danger of "thermal runaway" or damaging to insulators. It is a key design factor to develop the mechanism on thermal behavior of backfilling materials for underground power conduits. With a full-scale field test, a numerical model was developed to estimate the temperature change as well as the thermal resistance existing between an underground power conduit and backfill materials. In comparison with the field test, the numerical model for analyzing thermal behavior depending on density, moisture content and soil constituents is verified by the one-year-long field measurement.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.489-496
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• 1999

The objective of this study is to present engineering properties required in use of co-mixtures of fly ash and WFS(Waste Foundry Sand)'s, which are Presently used as fill or (lovable backfill. The fly ash, generated at the Tae-An thermoelectric power plant was used in this research and was classified as Class F. Green Sand, Furane Sand, and Coated Sand, which had been used at a foundry located in Pusan, were used. Laboratory experiments were peformed to obtain the physical properties of the co-mixture of fly ash and WFS. The range of permeability for all the co-mixtures was from 3.0×10/sup -3/㎝/s to 6.0×10/sup -5/㎝/s. The unconfined strength of the 7-day cured specimens composed of Green Sand reached 94% of that of 28-day cured specimens but for the 7-day cured specimens composed of, respectively, Furnace Sand and Coated Sand, only 64% and 66% of the strength of the 28-day cured specimens were reached. Results of the consolidated-untrained triaxial test showed that the specimens composed of Furnace Sand showed a distinct increase of the internal friction angle, while the other specimens showed negligible increase. In the case of 28-day cured specimens, specimens composed of Furnace Sand showed an internal friction angle of 41.8°, while specimens of Green and Coated Sand showed those of 33.5° and 35.0°, respectively. From the shrinkage test, the shrinkage ratios of all specimens did not exceed 0.25%.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.193-203
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• 2004

Arching effects in backfill materials generate a nonlinear active earth pressure distribution on a rigid retaining wall with rough face, and arching effects on the shape of the nonlinear earth pressure distribution depends on the mode of wall movement. Therefore, the practical shape of failure surface and arching effect in the backfill changed with the mode of wall movement must be considered to calculate accurate magnitude and distribution of active earth pressure on the rigid wall. In this study, a new formulation for calculating the active earth pressure on a rough rigid retaining wall rotating about the base is proposed by considering the shape of nonlinear failure surface and arching effects in the backfill. In order to avoid mathematical complexities in the calculation of active earth pressure, the imaginary failure surface composed of four linear surfaces is used instead of the nonlinear failure surface as failure surface of backfills. The comparisons between predictions from the proposed equations and existing model test results show that the proposed equations produce satisfactory predictions.

• Journal of the Korean Geotechnical Society
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• v.30 no.8
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• pp.39-47
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• 2014

Frost heaving and thawing settlement cause unexpected stress around buried pipelines, which results in deformation and permanent demage. A large scale laboratory test has been performed to observe deformation, stress, and temperature of a buried pipe during atmospheric temperature changes. From the experimental results, the stress concentrated around the buried pipe is inevitable and deformation is caused by the frost heaving. Even though backfill materials are sandy soils which are normally assumed to be non frost susceptible, it is revealed that frost demage can happen due to drainage condition, the level of ground water table, and water content.