• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1050-1056
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• 2008

Many cut slopes are situated on national highways. In this study, we chose rock slopes of moderated weathering grade to analyze general strength parameters of cut slopes. We analyzed the strength parameters of selected rock slopes by the experience method. Also, we arranged the strength parameters by area and rock types.

• Computers and Concrete
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• v.24 no.3
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• pp.249-258
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• 2019

In order to investigate the strength recovery of fire-damaged concrete after post-fire curing, concrete specimens were heating at $2^{\circ}C/min$ or $5^{\circ}C/min$ to 400, 600 and $800^{\circ}C$, and these exposed specimens were soaked in the water for 24 hours and following by 29-day post-fire curing. The compressive strength and split tensile strength of the high-temperature-exposed specimens before and after post-fire curing were tested. The proportion of split aggregate in the split surfaces was analyzed to evaluate the mortar-aggregate interfacial strength. After the post-fire curing process, the split tensile strength of specimens exposed to all temperatures was recovered significantly, while the recovery of compressive strength was only obvious within the specimens exposed to $600^{\circ}C$. The tensile strength is more sensitive to the mortar-aggregate interfacial cracks, which caused that the split tensile strength decreased more after high-temperature exposure and recovery more after post-fire curing than the compressive strength. The mortar-aggregate interfacial strength also showed remarkable recovery after post-fire curing, and it contributed to the recovery of split tensile strength.

• Journal of the Society of Disaster Information
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• v.13 no.1
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• pp.35-42
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• 2017

In this study, to quantitatively evaluate the strength characteristics of the inflatable liquid used for the recovery of soft ground or partial settlement, the inflatable liquids were prepared by dividing the inflatable capacity and the strength characteristics were analyzed according to the conditions. The experimental group was divided into two groups: relatively high expansion group and low expansion group. The specimens were prepared by controlling the volume of 10 ~ 30% of the maximum expansion volume, and the strength of the specimens were evaluated. The compressive strength of the high expansion group and low expansion group was about 2.1 times.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.97-104
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• 2008

The objective of this study was to investigate the strength characteristics of frozen clay. Compressive strength tests were performed on frozen clay with different water contents at various temperatures. The dry density of specimens and strain rate was kept constant. Test results showed that compressive strength increased with increasing water content and decreasing temperature. The increase in peak strength became more significant the lower the temperature for a given water content. The failure mode changed from brittle to ductile deformation with increasing water content and decreasing temperature. Tests also showed an increase in deformation modulus with increasing peak strength, increasing water content and decreasing temperature.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1555-1558
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• 2008

In this paper, result of whole test, When the Transfer Distance is increasing, Strength of Backfilling Material of NATM Composite lining Tunnel due to increasing Gravity was increased, but that is higher the Air Flotation than increasing Strength. So, That was predicted a drop of Permeability. And Performing the placing Lightweight Foamed Mortar, we think that it's performance in drain material was lost. Therefore We conclude that Proper Transfer Distance that taking Permeability through minimizing of Air Flotation Loss and getting the Need Strength is 50m.

• Journal of the Society of Disaster Information
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• v.2 no.1
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• pp.129-137
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• 2006

The present work is attempt to evaluate the temperature dependence of blast furnace slag concrete(BFSC) based on the concrete strength cured with different curing temperatures and ages. A equivalent substitution index(ESI) was induced to explain temperature dependence of concrete quantitatively as well as concrete strength. The results from compressive strength showed substantial crossover effect. which is the phenomenon that the compressive strength cured at low temperature becomes stronger than the one cured at high temperature. The crossover effect found more definitely on BFSC than plain concrete.. The ESI became 1.1 and 1.0 for the BFSC cured at $20^{\circ}C$ and $30^{\circ}C$ after age of 56 days, respectively. Which means that the contribution to strength development of blast furnace slag per unit mass is stronger than that of the Portland cement. It was considered therefore that the optimum curing temperature for BFSC is $20^{\circ}C$.

• Structural Engineering and Mechanics
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• v.52 no.5
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• pp.889-901
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• 2014

Very long life fatigue tests were carried out on 16Mn steel base metal and its welded joint by using the ultrasonic fatigue testing technique. Specimen shapes (round and plate) were considered for both the base metal and welded joint. The results show that the specimens present different S-N curve characteristics in the region of $10^5-10^9$ cycles. The round specimens showed continuously decreasing tendency while plate specimens showed a steep decreasing step and an asymptotic horizontal one. The fatigue strength of round specimen was found higher than plate specimen. The fatigue strength of as-welded joint was 45.0% of the base material for butt joint and 40% for cruciform as-welded joint. It was found that fracture can still occur in butt joint beyond $5{\times}10^6$ cycles. The cruciform joint has a fatigue limit in the very long life fatigue regime ($10^7-10^9$ cycles). Fatigue strength of butt as-welded joint was much higher as compared to cruciform as-welded joint. Improvement in fatigue strength of welded joint was found due to UPT. The observation of fracture surface showed crack mainly initiated from welded toe at fusion areas or geometric discontinuity sites at the surface in butt joint and from welded toe in cruciform joint.

• Geomechanics and Engineering
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• v.30 no.3
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• pp.281-291
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• 2022

Complex rock masses include various joint planes, bedding planes and other weak structural planes. The existence of these structural planes affects the mechanical properties, deformation rules and failure modes of jointed rock masses. To study the influence of the parameters of a nonpersistent joint network on the mechanical properties and failure modes of jointed rock masses, synthetic rock mass (SRM) technology based on discrete elements is introduced. The results show that as the size of the joints in the rock mass increases, the compressive strength and the discreteness of the rock mass first increase and then decrease. Among them, the joints that are characterized by "small but many" joints and "large and clustered" joints have the most significant impact on the strength of the rock mass. With the increase in joint density in the rock mass, the compressive strength of rock mass decreases monotonically, but the rate of decrease gradually decreases. With the increase in the joint dip angle in rock mass, the strength of the rock mass first decreases and then increases, forming a U-shaped change rule. In the analysis of the failure mode and deformation of a jointed rock mass, the type of plastic zone formed after rock mass failure is closely related to the macroscopic displacement deformation of the rock mass and the parameters of the joints, which generally shows that the location and density of the joints greatly affect the failure mode and displacement degree of the jointed rock mass. The instability mechanism of jointed surrounding rock is revealed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.105-111
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• 2023

In this study, the mechanical properties of high-strength concrete according to the substitution rate of NSH(Non-sintered Hwangto) as an alternative material for cement were measured and evaluated. Through UPV(Ultrasonic pulse velocity) analysis, the compressive strength prediction equation was proposed, and the substitution rate of NSH was set at 15 % and 30 %. The evaluation items were compressive strength and UPV, and the curing period was set to 24 hours. In compressive strength and UPV, as the NSH substitution rate increased, lower strength and lower UPV were shown. In addition, the correlation number(R² ) between compressive strength and UPV was 0.99 for NC(Normal Concrete), 0.97 for NSHC(Non-sintered Hwangto Concrete)33-15, and 0.94 for NSHC33-30.

• Journal of the Society of Disaster Information
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• v.8 no.4
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• pp.336-346
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• 2012

In recent years, the number of unforeseen weather hazards increased significantly, and subsequent financial loss in public and private sector has increased as well. Research has been increasingly focused on the actual damage assessment in the event of a disaster through effective and comprehensive disaster countermeasures to deal with and improve a better anti-disaster strategy. Through investigation of existing domestic and foreign property loss related to current damage analysis, the comparison and analysis in terms of current estimated methodology of the full extent of the damage results is proposed. In this study, a more efficient damage index and natural disaster damage assessment is suggested and more specifically, the basic standards of declared disaster areas and the strength of private property damage index will be also be discussed.