• Tunnel and Underground Space
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• v.17 no.5
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• pp.350-359
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• 2007

Most large cut slopes of open pit mines, roadways, and railways are steeply inclined and composed with rocks that do not contain soils. However, these rock slopes suffer both weathering and fragmentation. In the case of steep slopes, falling rock and collapse of a slope may often occur due to surface erosion. Cast-in place concrete and rubble work are the most widely used earth structure-based pressure supports that act as restraints against the collapse of the rock slope. In order to overcome the shortcomings of conventional retaining walls, a segmental grid retaining wall is being used with connects precasted segments to construct the wall. In this study, laboratory model test was conducted to estimate deformation behavior of segmental grid retaining wall with configuration of rear strecher, height and inclination of the wall. In order to examine the behavior characteristics of a segmental grid retaining wall, this research analyzes the aspects of spacial displacement through relative displacement according to change in the inclination of the wall. Also, the walls behavior according to the formation and status of the rear stretcher which serves the role of transferring the load from the header and the stretcher which make up the wall, the displacement of backfill materials in the wall, and the location of the maximum load were surveyed and the characteristics of displacement in the segmental grid retaining wall were observed. The test results of the segmental grid retaining wall showed that there was a sudden increase in failure load according to the decrease in the wall's height and the size of the in was greatly decreased. Furthermore, it revealed that with identical inclination and height, the structure of the rear stitcher did not greatly affect the starting point or size of maximum horizontal displacement, but rather had a stronger effect on the inclination of the wall.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.33-39
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• 2012

With the increase of steel production research interest on the recycling of slag as a by-product also increases steadily. Currently in Korea a lot of researches on blast-furnace slag have been made. However, the researches on the steel slag have been rarely made. Also, a research of steel slag, especially the use of oxidation furnace slag as aggregates for concrete progress, is performing actively, but the research results on the furnace slag are almost nothing. Recently, the research about the furnace slag as backfill material and embankment material confirmed the possibility of the clay soil amendment. Therefore, the object of this study is to review the possibility as civil engineering materials for soil improvement and to find the optimum mixture ratio of furnace slag. This research analyzed the ingredient component of the reduced slag by SEM, XRF, XRD tests and examined the strength increase using unconfined compression tests when the clay and reduced slag are mixed each other. Through this test, the definite strength increase is confirmed according to the mixture of the reduced slag and the possibility of soil improvement is also confirmed based on this result. The object of the study is both utilizing the by-product for civil engineering purpose and effective recycling by the application of the furnace slag for soil improvement.

• Journal of the Korean GEO-environmental Society
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• v.11 no.5
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• pp.25-34
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• 2010

In this study characteristics for reclaimed ash was studied to enlarge the usage of reclaimed ash which is reaching to 72 million ton producted from whole thermal power plants in South Korea. Fly ash and bottom ash are reclaimed separately at some of thermal power plants. However, typically bottom ash and fly ash are mixed when they are buried at most of the thermal power plant, as a result the engineering characteristics of ponded ash are not investigated properly. In order to investigate the engineering characteristics of the ponded ash, laboratory tests were performed with ponded ash and fly ash from youngheung and samcheonpo thermal power plants. Specific gravity, unit weight, and grain size analysis test were fulfilled to evaluate the physical characteristics and triaxial permeability test, direct shear test, unconfined compressive strength test, compaction test were performed to evaluate the mechanical characteristics. And also engineering characteristics of coal ash from anthracite and Bituminous thermal power plants were compared and studied respectively. As a result of the study, it was confirmed that using coal ash from Bituminous thermal power plants can be effective in the place where lightweight materials are required and using coal ash from anthracite thermal power plants can be effective as backfill material which require higher permeability. Finally, it was confirmed that fly ash from youngheung thermal power plants which has the lowest permeability among the tested material is suitable for a field requiring impermeable material.

• Journal of the Korean Geotechnical Society
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• v.29 no.7
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• pp.37-46
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• 2013

Various sizes of gravels are included in the most field soils that are utilized for civil constructions. Especially, the small amounts of gravel are often included in selected soils for backfill materials, earth dams, and subbase ground. In such cases, the small amounts of mixed gravel and its shape may influence the determination of dry density of soils, which results in an inaccurate degree of compaction for soils in the field. In this study, a dry density of sand with various gravel contents (0, 10, 17, 23, 29 and 33%) and three different sizes (2.0-2.36, 3.35-4.75, 5.6-10.0 mm) was experimentally investigated for compacted or loosely packed conditions. The loosely packed sand with gravels was simulated by pouring sand into compaction mould and its density was determined. When a 33% of gravel content was mixed with sand, its dry density increased up to 15-20% for compacted specimen and 20-23% for loosely packed specimen. When a gravel content and size were the same, a dry density of compacted specimen was $0.1-0.16g/cm^3$ higher than that of loosely packed specimen. Even though the same gravel content was used, a dry density of sand with big gravels was $0.04-0.08g/cm^3$ higher than that of sand with small gravels for compacted specimen and $0.03-0.05g/cm^3$ for loosely packed specimen.

• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.19-26
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• 2021

The high-level radioactive waste (HLW) produced from nuclear power plants is disposed in a rock-mass at a depth of hundreds meters below the ground level. Since HLW is very dangerous to human being, it must be disposed of safely by the engineered barrier system (EBS). The EBS consists of a disposal canister, backfill material, buffer material, and so on. When the components of EBS are installed, gaps inevitably exist not only between the rock-mass and buffer material but also between the canister and buffer material. The gap can reduce water-retarding capacity and heat release efficiency of the buffer material, so it is necessary to investigate properties of gap-filling materials and to analyze gap spacing effect. Furthermore, there has been few researches considering domestic disposal system compared to overseas researches. In this reason, this research derived the peak temperature of the bentonite buffer material considering domestic disposal system based on the numerical analysis. The gap between the canister and buffer material had a minor effect on the peak temperature of the bentonite buffer material, but there was 40% difference of the peak temperature of the bentonite buffer material because of the gap existence between the buffer material and rock mass.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.25-32
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• 2007

Because of the increasing use of clayey soil as the backfill in reinfurced soil structures and embankments, nonwoven geotextiles of drain capability have been receiving much attention. However, there are few studies on the deformation behavior analysis of nonwoven geotextiles in reinforced soil structures in the site because nonwoven geotextiles which have low tensile stiffness and higher deformability than geogrids and woven geotextiles, are difficult to measure their deformation by using strain gauges. In this study, it was suggested that a new and more convenient method could measure the deformation behaviour of nonwoven geotextile using a strain gauge and examine the availability of the method by conducting laboratory tests and applying to two geosynthetics reinforced soil (GRS) walls in the site. The result of wide-width tensile test conducted under confining pressure of 70 kPa shows that the local deformation of nonwoven geotextile to be measured with strain gauges has a similar pattern to the total deformation measured with LVDT. In the GRS walls, nonwoven geotextile shows a larger deformation range than the woven geotextile and geogrid. However, the deformation patterns of these three reinforcement materials are similar. The function of strain gauges attached to nonwoven geotextile in the walls works normally for 16 months. Therefore, the method proposed in this study for measuring nonwoven geotextile deformation using a strain gauge has proved useful.

• Journal of the Korean Geotechnical Society
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• v.40 no.1
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• pp.29-37
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• 2024

In this study, recycled concrete aggregates (RCA) were treated in a 5-kg-scale prototype reactor with carbon dioxide (CO₂) to enhance their material quality and geotechnical performance. The aggregate crushing value (ACV) and California bearing ratio (CBR) were measured on untreated RCAs and CO₂-treated RCAs. After CO₂ treatment, the ACV decreased from 35.6% to 33.2%, and the CBR increased from 97.5% to 102.4%. The CO₂ treatment caused a reduction of fine particle generation and an increase in bearing capacity through carbonation. When CO₂ treatment was performed with mechanical agitation, which provided additional enhancement in mechanical quality, the ACV was reduced further to 30.3%, and the CBR increased to 137.7%. If upscaled effectively, the proposed CO₂ treatment technique would be an effective method to reduce carbon emissions in construction industries.

• Journal of Navigation and Port Research
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• v.26 no.3
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• pp.323-328
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• 2002

Soil-steel structures have been used for the underpass, or drainage systems in the road embankment. This type of structures sustain external load using the correlations with the steel wall and engineered backfill materials. Buried flexible conduits made of corrugated steel plates for the coastal road was tested under vehicle loading to investigate the effects of live load. Testing conduits was a circular structure with a diameter of 6.25m. Live-load tests were conducted on two sections, one of which an attempt was made to reinforce the soil cover with the two layers of geo-gird. Hoop fiber strains of corrugated plate, normal earth pressures exerted outside the structure, and deformations of structure were instrumented during the tests. This paper describes the measured static and dynamic load responses of structure. Wall thrust by vehicle loads increased mainly at the crown and shoulder part of the conduit. However additional bending moment by vehicle loads was neglectable. The effectiveness of geogrid-reinforced soil cover on reducing hoop thrust is also discussed based on the measurements in two sections of the structure. The maximum thrusts at the section with geogrid-reinforced soil cover was 85-92% of those with un-reinforced soil cover in the static load tests of the circular structure; this confirms the beneficial effect of soil cover reinforcement on reducing the hoop thrust. However, it was revealed that the two layers of geogrid had no effect on reducing the overburden pressure at the crown level of structure. The obtained values of DLA decrease approximately in proportion to the increase in soil cover from 0.9m to 1.5m. These values are about 1.2-1.4 times higher than those specified in CHBDC.

• Korean Journal of Heritage: History & Science
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• v.57 no.3
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• pp.6-22
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• 2024

This paper examines the characteristics of wooden wells from the Three Kingdoms period that were discovered in the Yeongsan River basin, in addition to their functions based on the distribution of the remains and excavated artifacts found near the wells. A total of 11 wooden wells have been found at six archeological sites along the middle and upper reaches of the Yeongsan River basin. These wooden wells were built in a wider variety of forms than wells made of other materials due to the ease of processing resulting from the physical properties of wood. However, due to the limited geological conditions in which these wells can be installed and their rapid decay, the discovery of such wells is rare. They tend to be located in the clay and mud layers of old river channels or near river channels where it was relatively easy to obtain water from the riverbed. The wooden wells are mostly square or rectangular in shape and were assembled transversely, and some include support beams in their construction. The backfill was reinforced with either stone, a mixture of stone and clay, or a mixture of clay and pottery shards. The material mainly used was pine wood boards, with wood from chestnut trees being used as a sub-material. Various artifacts, such as pottery and wooden containers, animal bones, and seeds, have been excavated in small quantities. The excavated pottery items consist mostly of flat cups with a cover, mounted cups, pottery stands, wide-mouthed jars with a hole, and round pottery. Based on the environment and remains of the sites, the wells are thought to have been used for domestic and production purposes. The assumed primary function was to obtain domestic water, as most of the wells were located within residential spaces where the area's inhabitants lived. The wells were also used to obtain water for agricultural purposes, as well as for productive purposes such as for operating kilns and smelters. Lastly, the wooden wells were also found to be strongly associated with rites, as evidenced by the artifacts found inside them.