• Journal of the Korean GEO-environmental Society
• /
• v.24 no.4
• /
• pp.23-29
• /
• 2023

Ground subsidence shows a mechanism in which the upper ground collapses due to the formation of a cavity due to the movement of soil particles in the ground due to the formation of a waterway because of damage to the water supply/sewer pipes. As a result, cavity is created in the ground and the upper ground is collapsing. Therefore, ground subsidence frequently occurs mainly in downtown areas where a large amount of underground facilities are buried. Accordingly, research to predict the risk of ground subsidence is continuously being conducted. This study tried to present a ground subsidence risk prediction model for two districts of ○○ city. After constructing a data set and performing preprocessing, using the property data of underground facilities in the target area (year of service, pipe diameter), density of underground facilities, and ground subsidence history data. By applying the dataset to the machine learning model, it is evaluated the reliability of the selected model and the importance of the influencing factors used in predicting the ground subsidence risk derived from the model is presented.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.1
• /
• pp.55-61
• /
• 2023

This study aims to develop CLSM fill material for emergency restoration using landfill coal ash. As a result of examining physical properties such as particle size distribution and fines content of landfill coal ash, bottom ash, fly ash, and general soil were mixed, and SP was found to have a density of 2.03 and a residual particle pass rate of 7.8 %. CLSM materials that secure fluidity in unit quantities without using chemical admixtures such as glidants and water reducing agents have a high risk of material separation due to bleeding. As a result of this experiment, it was found that the bleeding ratio did not satisfy the standard in the case of the specimen with a large amount of fly ash and a lot of addition of mixing water. As a result of the compressive strength test, the strength development of 0.5 MPa or more for 4 hours was found to be satisfactory for the specimens using hemihydrate gypsum with a unit binder amount of 200 or more, and the remaining gypsum showed poor strength development. Although it is judged that landfill coal ash can be used as a CLSM material, it is necessary to identify and apply the physical and chemical characteristics of coal ash buried in the ash treatment plant of each power generation company.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.6
• /
• pp.71-85
• /
• 2010

Dynamic analyses of tunnels are widely performed in practice in Korea. Accurate performance of a dynamic analysis is very difficult, requiring appropriate application of lower and lateral boundary conditions, deconvolution, constitutive model, and selection of dynamic soil properties etc. Lack of a systematic guideline on how to perform the dynamic analysis makes it even more difficult to perform an analysis. In addition, dynamic analyses are not needed in most cases and pseudo-static analyses are more than adequate. However, they are performed without a clear understanding on the need for the dynamic analysis and differences between the two methods. In this study, firstly, a guideline for correctly performing a 2D dynamic analysis is developed. Secondly, the differences in the tunnel responses using dynamic and pseudo-static analyses are discussed and compared. The results show that the discrepancies between the dynamic and static analyses are not significant for most cases. It is therefore recommended that the dynamic analyses be performed at tunnel portal, very soft ground, or in cases where spatial variation of the ground motion needs to be considered in the seismic analysis of tunnels in transverse direction.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.10
• /
• pp.87-97
• /
• 2009

The seismic site coefficients are often used with the seismic hazard maps to develop the design response spectrum at the surface. The site coefficients are most commonly developed deterministically, while the seismic hazarde maps are derived probabilistically. There is, hence, an inherent incompatibility between the two approaches. However, they are used together in the seismic design codes without a clear rational basis. To resolve the fundamental imcompatibility between the site coefficients and hazard maps, this study uses a novel probabilistic seismic hazard analysis (PSHA) technique that simulates the results of a standard PSHA at a rock outcrop, but integrates the site response analysis function to capture the site amplification effects within the PSHA platform. Another important advantage of the method is its ability to model the uncertainty, variability, and randomness of the soil properties. The new PSHA was used to develop fully probabilistic site coefficients for site classes of the seismic design code and another sets of site classes proposed in Korea. Comparisons highlight the pronounced discrepancy between the site coefficients of the seismic design code and the proposed coefficients, while another set of site coefficients show differences only at selected site classes.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.11
• /
• pp.47-54
• /
• 2006

Shear wave velocity of uncemented soil can be expressed as the function of effective stresses when capillary phenomena are negligible. However, the terms of effective stresses are divided into the direction of wave propagation and polarization because stress states are generally anisotropy. The shear wave velocities are affected by ${\alpha}$ parameters and ${\beta}$ exponents that are experimentally determined. The ${\beta}$ exponents are controlled by contact effects of particulate materials (sizes, shapes, and structures of particles) and the ${\alpha}$ parameters are changed by contact behaviors among particles, material properties of particles, and type of packing (i.e., void ratio and coordination number). In this study, consolidation tests are performed by using clay, mica and sand specimens. Shear wave velocities are measured during consolidation tests to investigate the stress-induced and inherent anisotropies by using bender elements. Results show the shear wave velocity depends on the stress-induced anisotropy for round particles. Furthermore, the shear wave velocity is dependent on particle alignment under the constant evvective stress. This study suggests that the shear wave velocity and the shear modulus should be carefully estimated and used for the design and construction of geotechnical structures.

• Journal of Korean Society of Forest Science
• /
• v.111 no.1
• /
• pp.50-60
• /
• 2022

In this study, habitat suitability was analyzed for three major honey tree species, namely Kalopanax septemlobus, Tilia amurensis, and Styrax obassis, in the Baekdudaegan Mountains using MaxEnt models. The AUC values indicating the prediction accuracies of the models were 0.747, 0.790, and 0.755 for K. septemlobus, T. amurensis, and S. obassis, respectively. The most important variables for K. septemlobus and T. amurensis were elevation, mean annual temperature, and slope, whereas mean annual temperature, elevation, and mean annual precipitation were the most important predictors for S. obassis. For all three studied species, elevation and mean annual temperature were the most important topographic and climatic factors, respectively, indicating that such variables are crucial for explaining species distribution. Honey tree species are essential resources in forest beekeeping, a high value-added process for improving forest income, and this study identified sites with the potential for management of such species in the Baekdudaegan Mountains, where it may be possible to establish a honey forest. However, the accuracy of the models should be improved through comprehensive analysis with abiotic variables, such as soil properties and aridity, which affect the distribution of honey tree species, as well as biotic variables, such as interspecific competition.

• Journal of Practical Agriculture & Fisheries Research
• /
• v.20 no.2
• /
• pp.31-38
• /
• 2018

This study was conducted to investigate the possibility of biochar as an alternative medium to peatmoss using for Aster spathulifolius. We cultivated A. spathulifolius in four potting media with different mixing rates (v/v) of peatmoss (P) and biochar (B) as follows: B0+P3, B1+P2, B2+P1, and B3+P0 with vermiculite 3 + perlite 3. Also, we analyzed the chemical properties of media and the plant growth characteristics. The results were as follows: In case of media's chemical condition, B0+P3 and B1+P2 treatments showed higher tendency (p < 0.05). Plant height on B0+P3 and B1+P2 treatments was much higher than that on other treatments (p < 0.05). Root length on B1+P2 treatment was higher than on B0+P3 treatment (p < 0.05). B0+P3 and B1+P2 treatments showed higher number of leaves and dry biomass than other treatments. Therefore, our results support that Biochar : Peatmoss : Vermiculite : Perlite (1/3 : 2/3 : 1 : 1, v/v) could be a more economical potting medium for A. spathulifolius than peatmoss : vermiculite : perlite (1 : 1 : 1, v/v).

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.6C
• /
• pp.339-347
• /
• 2008

The penetration of the probe produces the excess pore pressure due to the disturbance. The objective of this study is to evaluate the disturbance zone by using the dissipation of the excess pore water pressure, which was generated due to the penetration of the penetrometer with different size. The CPT, DMT and FVP (Field Velocity Probe) are adopted for in-situ tests. The tests are carried out in the construction site of north container pier of Busan new port, Korea where is accelerating the consolidation settlement using plastic board drains (PBD) and surcharges by crushed gravels. The coefficient of consolidation $(C_h)$ and soil properties are deduced by the laboratory test. The in-site tests are performed after the predrilling the surcharge zone at the point of 90% degree of consolidation. To minimize the penetration effect, the horizontal distance between penetration tests is 3m, the change of the pore pressure is monitored at the fixed depth of 24m. The coefficient of consolidation $(C_h)$ and the $t_{50}s$ are calculated based on the laboratory test and the in-situ data, respectively. The equvalent radi based on the $t_{50}$ shows that the FVP and the DMT produce the smallest and the greatest equivalent radi, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.1C
• /
• pp.65-76
• /
• 2010

Recent earthquake events revealed that severe seismic damages were concentrated mostly at sites composed of soil sediments rather than firm rock. This indicates that the site effects inducing the amplification of earthquake ground motion are associated mainly with the spatial distribution and dynamic properties of the soils overlying bedrock. In this study, an integrated GIS-based information system for geotechnical data was constructed to establish a regional counterplan against ground motions at a representative metropolitan area, Seoul, in Korea. To implement the GIS-based geotechnical information system for the Seoul area, existing geotechnical investigation data were collected in and around the study area and additionally a walkover site survey was carried out to acquire surface geo-knowledge data. For practical application of the geotechnical information system used to estimate the site effects at the area of interest, seismic zoning maps of geotechnical earthquake engineering parameters, such as the depth to bedrock and the site period, were created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation of site classification was also performed to determine the site amplification coefficients for seismic design at any site and administrative sub-unit in the Seoul area. Based on the case study on seismic zonations for Seoul, it was verified that the GIS-based geotechnical information system was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation particularly at the metropolitan area.

• Proceedings of the Plant Resources Society of Korea Conference
• /
• 2020.12a
• /
• pp.70-70
• /
• 2020

참취(Aster scaber)는 국화과에 속하는 여러해살이식물로 취나물로 분류되어 전국에서 재배되고 있으며 최근 성인병 예방 효과와 무공해 건강식품으로 연중 소비가 증대되고 있으며, 주로 시설재배 작형으로 많이 재배하고 있다. 참취 시설재배지는 양분의 과다투입에 의한 염류집적과 잦은 관수로 물리성이 악화 되어 참취의 생육이 저하되어 수량이 감소하여 통상 3년 마다 종묘 갱신이 이루어지고 있다. 본 연구는 토양개량제 처리에 따른 토양 물리화학성과 참취의 생육에 미치는 영향을 검토하여 참취 시설재배 농가에 활용할 수 있는 방안을 개발하고자 시험을 수행하였다. 2018년 4월부터 2020년 11월까지 전라북도 농업기술원 허브산채시험장에서 참취 시설재배를 대상으로 무처리, 볏짚, 왕겨숯, 야자섬유 등을 10a당 1,000kg 처리하여 시기별 토양 이화학성, 생육특성을 조사하였다. 자재 처리 후 토양물리성의 변화는 볏짚 시용에서 가장 낮은 용적밀도 1.35g/cm³와 가장 높은 공극률 49.04%을 보였다. 토양 삼상 중 고상은 왕겨숯에서 52.82%로, 액상은 왕겨숯에서 30.28%로, 기상은 볏짚에서 22.45%로 가장 높았다. 토양 화학적 특성을 조사한 결과 모든 처리구에서 토양유기물 함량은 증가하였고, 유효인산은 함량은 440~487mg/kg로 낮아지는 경향을 보였다. 칼륨은 0.77~0.88cmol_c/kg로 낮아졌고, 칼슘과 11.56~14.09cmol_c/kg, 마그네슘은 2.93~3.22cmol_c/kg로 증가하였다. 생육특성은 볏짚 처리구에서 초장 26.4cm, 엽장 8.7cm, 엽폭 6.7cm, 줄기수 7.2주로 다른 처리구에 비해 좋은 생육이 좋았으며, 수량 또한 볏짚 처리구에서 1,554.3kg/10a로 가장 높았다. 지하부 생육특성은 볏짚 처리구에서 근중 83.7g/주, 근장 28.2cm, 근직경mm로 다른 처리구에 비해 생육이 양호하였다. 참취 다년재배지 정신 전 볏짚을 시용함으로써 토양의 유기물함량 증가와 용적밀도 감소, 공극율 증가 등 토양의 물리화학성을 개선하여 참취 수량성 증대효과가 있는 것으로 판단된다.