• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.99-111
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• 1999

The frictional capacity of auger-cast piles is often very small because of the disturbance of the soil surrounding the pile during the excavation process. Usage of expansive agents and a pressurized injection technique for auger-cast piles should improve the frictional resistance between pile and soil. This paper presents the test results of auger-cast model piles installed with expansive mortar in laboratory compacted weathered soil. The model piles were installed in a calibration chamber with a variation in the amount of expansive agent, the injection process and the chamber pressure. It was observed that the pile shaft resistance increases with the increased amount of expansive agent, and also increases when mortar is pressure injected. The shaft resistance increased up to 24% for the pile installed only with expansive mortar and increased up to 56% for the pile installed with the pressurized injection of expansive mortar, compared with that of piles with plain mortar.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.195-215
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• 2017

This paper proposes gob-side entry retaining by roof break and filling in thick-layer soft rock conditions based on the thick-layer soft rock roof strata migration law and the demand for non-pillar gob-side entry retaining projects. The functional expressions of main roof subsidence are derived for three break roof direction conditions: lateral deflection toward the roadway, lateral deflection toward the gob and vertically to the roof. These are derived according to the load-bearing boundary conditions of the main roadway roof stratum. It is concluded that the break roof angle is an important factor influencing the stability of gob-side entry retaining surrounding rock. This paper studies the stress distribution characteristics and plastic damage scope of gob-side entry retaining integrated coal seams, as well as the roof strata migration law and the supporting stability of caving structure filled on the break roof layer at the break roof angles of $-5^{\circ}$, $0^{\circ}$, $5^{\circ}$, $10^{\circ}$ and $15^{\circ}$ are studied. The simulation results of numerical analysis indicate that, the stress concentration and plastic damage scope to the sides of gob-side entry retaining integrated coal at the break roof angle of $5^{\circ}$ are reduced and shearing stress concentration of the caving filling body has been eliminated. The disturbance of coal mining to the roadway roof and loss of carrying capacity are mitigated. Field tests have been carried out on air-return roadway 5203 with the break roof angle of $5^{\circ}$. The monitoring indicates that the break roof filling section and compaction section are located at 0-45 m and 45-75 m behind the working face, respectively. The section from 75-100 m tends to be stable.

• Korean Journal of Plant Resources
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• v.36 no.1
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• pp.62-90
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• 2023

This study was conducted to study the vascular plants of Balbaeksan, located on the border between Gyeongsan-si and Cheongdo-gun, Gyeongsangbuk-do. It was performed 13 times from September 2020 to November 2021, and the investigated vascular plants were identified as a total of 93 families, 302 genera, 485 species, 10 subspecies, 40 varieties, 13 varieties, and 545 taxa. Endemic plants were investigated in 18 taxa, 9 taxa of rare plants; Vulnerable (VU) 5 taxa, Least concerned (LC) 3 taxa, Data Deficient (DD) 1 taxa, Red List plants 5 taxa; 3 taxa of least concerned (LC), 2 taxa of Not Evaluated (NE), 183 taxa of biological resources subject to export approval, 78 taxa of specific taxonomy; There were 9 taxa of grade IV, 20 taxa of grade III, 20 taxa of grade II, and 28 taxa of grade I. 4 taxa of plants subject to climate change adaptation; 2 taxa of endemic plants, 1 taxa of southern plants, 1 taxa of northern plants, 4 taxa of climate change biomarker species, 2 taxa of candidate species of climate change biomarker, 65 taxa of exotic plants, and 3 taxa of ecosystem disturbance species. Plants 235 taxa (43.1%), medicinal plants 257 taxa (47.2%), ornamental plants 148 taxa (27.2%), woody plants 54 taxa (9.9%), herbaceous plants 37 taxa (6.8%), industrial plants 15 Taxa (2.8%), 11 taxa (2.0%) of fiber-bearing plants, and plants of unknown use were identified as 73 taxa (13.4%). The flora of Mt. Balbaek was investigated for the first time, and plants to be preserved in order to secure useful plant resources and biological sovereignty were identified. So continuous monitoring is necessary to prevent the introduction of foreign plants that may be caused by the recent increase in the number of people coming and going.