• Tunnel and Underground Space
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• v.29 no.6
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• pp.407-424
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• 2019

To prevent possible accidents by surface subsidence, backfilling operation is known to be one of the most effective methods for ensuring the long-term ground stability because it can eliminate fundamentally the origin of underground mine opening collapse. Also, for effective backfilling of underground mine opening, it is necessary to keep monitoring of backfilled mine opening for analyzing several factors such as filling effect with change of backfill material and characteristics of backfill material. Therefore, in this study, a monitoring system which consists of measuring device and software program has developed to examine the performance of backfilling operation and verify to field applicability to underground mine. Sensors for measuring device have been selected through study of recent research papers and mock-up test has been performed to verify the system compliance. Also, monitoring result of the mock-up test compared to case studies in some countries. From monitoring result fo the mock-up test compared to case studies in some countries, consequently, it was concluded that the developed real-time monitoring system had ensured filed applicability in the underground mine.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.17-33
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• 2011

Recently, the utilization of recycled aggregates for backfilling a power transmission pipeline trench has been considered due to the issues of eco-friendly construction and a lack of natural aggregate resource. It is important to identify the physical and thermal properties of domestic recycled aggregates that can be used as a backfill material. This paper evaluated thermal properties of concrete-based recycled aggregates with various particle size distributions. The thermal properties of the recycled aggregates and river sand provided by local vendors were measured using the transient hot wire method and the transient needle probe method after performing the standard compaction test. The needle probe method considerably overestimated the thermal resistivity of recycled aggregates especially at the dry of optimum water content because of experiencing disturbance while the needle probe is being inserted into the specimen. Similar to silica sand, the thermal resistivity of recycled aggregates decreased when the water content increased at a given dry density. Also, this paper evaluated some of the existing prediction models for the thermal resistivity of recycled aggregates with the experimental data, and developed a new prediction model for recycled aggregates. This study shows that recycled aggregates can be a promising backfill material substituting for natural aggregates when backfilling the power transmission pipeline trench.

• 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 GEO-environmental Society
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• v.11 no.10
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• pp.15-24
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• 2010

In the case of underground power utilities pipe such as circular pipe, the most difficult problem is low compaction efficiency of the bottom of pipe inducing the failure of utilities. To overcome this problem, various studies have been performed and one of these is CLSM(Controlled Low Strength Materials) accelerated flow ability. But underground power utilities pipe backfill materials is also needed to have good thermal property that can dissipate the heat as rapidly as it is generated. So, in this study, we performed thermal resistancy test for various materials such as sand, weathered soil, clay and mixed soil to analyze the thermal characteristics of CLSM(Controlled Low Strength Materials) with accelerated flow ability for various conditions(water content, unit weight, void ratio, curing time) and to evaluate the applicability for backfill material of underground power utilities pipe. The test results of 16 specimens for thermal resistancy test showed good thermal property that maintained below $85^{\circ}C\;cm/W$.

• 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.

• Journal of the Korean Geosynthetics Society
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• v.3 no.1
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• pp.43-52
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• 2004

Laboratory model tests were conducted to assess the behavior characteristics of geogrid reinforced earth walls using fiber-mixed soil backfill with different surcharge loads and reinforcement spacing. The models were built in the box having dimensions, 100cm tall, 140cm long, and 100cm wide. The reinforcements used were geonet(tensile strength, 0.79t/m) and geogrid(tensile strength, 2.26t/m). Decomposed granite soil(ML) with or without polypropylene fiber was used backfill material. Strain gauges and LVDTs were installed on the retaining walls to measure the strain of the reinforcements and the displacements of the wall facings.

• Journal of the Korean GEO-environmental Society
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• v.25 no.10
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• pp.5-10
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• 2024

Flexible pipes have the property of resisting external loads by utilizing the rigidity of the pipe and the surrounding ground, and have recently been in the spotlight because they are lighter in weight and have excellent durability compared to concrete pipes. In this study, the behavior characteristics of buried polyethylene pipe, a representative flexible pipe, were examined. Double-walled and multi-walled polyethylene pipes were used, and the structural behavior of the polyethylene pipe was evaluated based on a 5% deflection of the pipe diameter suggested in the design standards for flexible pipes. For the polyethylene pipe, the material properties of the pipe were identified through a ring stiffness test, and the behavior characteristics in the ground were reviewed through the simulation experiment of the buried polyethylene pipes. In addition, a finite element analysis model was developed based on the results of underground burial simulation experiments, and the behavior characteristics of polyethylene pipes according to backfill conditions were evaluated using the developed finite element analysis model and design equation. As a result of the study, it was confirmed that the capacity of the pipes and the compaction of the backfill are the main factors that determine the structural performance of the buried polyethylene pipe.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4005-4012
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• 2022

As high-level radioactive waste (HLW) generated from nuclear power plants is harmful to the human body, it must be safely disposed of by an engineered barrier system consisting of disposal canisters and buffer and backfill materials. A gap exists between the canister and buffer material in a HLW repository and between the buffer material and natural rock-this gap may reduce the water-blocking ability and heat transfer efficiency of the engineered barrier materials. Herein, the basic characteristics and thermal properties of granular bentonite, a candidate gap-filling material, were investigated, and their effects on the temperature change of the buffer material were analyzed numerically. Heat transfer by air conduction and convection in the gap were considered simultaneously. Moreover, by applying the Korean reference disposal system, changes in the properties of the buffer material were derived, and the basic design of the engineered barrier system was presented according to the gap filling material (GFM). The findings showed that a GFM with high initial thermal conductivity must be filled in the space between the buffer material and rock. Moreover, the target dry density of the buffer material varied according to the initial wet density, specific gravity, and water content values of the GFM.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.369-372
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• 2000

This investigation aims at the optimum mixing of flexible flowable-fill made of Bottom-ash as an industrial waste. Flowable-fill refer to self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. The two primary advantages of flowable fill over traditional methods are its ease of placement and the elimination of settlement. Therefore, in difficult compaction areas or areas where settlement is a concern, flowable fill should be considered. This study compares Bottom-ash with fine aggregate in physical character. The mixing design indicates a various mixing-rate.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.95-98
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• 2003

Waste lime is produced as by-products in chemical industry, Reuse of waste lime mixed with soil for banking and backfill material in civil works was analysed in this study. For this purpose, environmental effect of waste lime admixtures was tested. Thus, this study presents the leaching characterization of waste lime in laboratory batch and column tests. Countermeasure for reduction of environmental effects was suggested from the test results.