• Journal of Energy Engineering
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• v.28 no.1
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• pp.10-16
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• 2019

The purposes of this study is to secure subsidence stability and economical efficiency of lightweight foamed concrete. The composition of lightweight foamed concrete was designed for OPC by substituting with constant contents of calcium sulfaluminate and fly ash. It is found that the flow of lightweight foamed concrete decreased with early ettringite formation by CSA. The initial strength increased with the decrease of drying time of lightweight foamed concrete when CSA was substitution to 10%. The settlement deep of foamed concrete improved the settlement stability by replacing CSA, which prevented shortening of the coagulation time and bubble puffing.

• Tunnel and Underground Space
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• v.27 no.6
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• pp.377-386
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• 2017

This study was carried out to predict the future technology on the prevention and reclamation of mining induced subsidences in Korea. We summarized the technical improvement of ground surveys and investigation, ground stability assessment, ground reinforcement, ground monitoring system and so on. It is essential to improve the technology that we try to collect and review all the data that is implemented on the site of mined area in Korea and collaborate all the members of public and private business sectors. We, also, try to expand our business area to related industry such as tunnelling, civil infrastructure, underground environmental assessment etc, and continue to develop oversea's market.

• Tunnel and Underground Space
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• v.25 no.4
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• pp.332-340
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• 2015

Ground subsidence occurring in mine area can cause an enormous damage of loss of lives and properties, and a systematic survey should be conducted a series of field investigation and ground stability analysis in subsidence area. This study describes the results from field investigation and ground stability analysis in a limestone mine located in Cheongwon-gun, Chungcheongbuk-do, Korea. Rock mechanical measurements and electrical resistivity surveys are applied to obtain the characteristics of in-situ rock masses and the distribution patterns of subsurface weak zone, and their results are extrapolated in numerical analysis. From the field investigation and stability analysis, it is concluded that the subsidence occurrence in this limestone mine is caused mainly by subsurface limestone cavities.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.493-507
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• 2016

Scaled model tests were performed to investigate the stability of a foundation located above limestone cavities. Cavity shape was assumed to be an ellipse having 1/3 for the ratio of minor to major axis lengths. 12 different test models which have various depths, locations, inclinations, sizes and numbers of cavity were experimented and they were classified into 5 different groups. Crack initiation pressure, maximum pressure, deformation behaviors, failure modes and subsidence profiles of test models were obtained, and then the influences of those parameters on the foundation stability were investigated. No cavity model showed a general shear failure, whereas the models including various cavities showed the complicated three different failure modes which were only punching failure, both punching and shear failures, and double shear failure. The stability of foundation was found to be decreased as the cavity was located at shallower depth, the size and number of cavity were increased. Differential settlements appeared when the cavity was located under the biased part of foundation. Furthermore, subsidence profiles were found to depend on the distribution of underground cavities.

• The Journal of Engineering Geology
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• v.34 no.2
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• pp.249-262
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• 2024

Retaining walls are widely used in the construction of underground structures. This study reviews the stability of the high-strength joint buried pile method at a site in Korea. [Consider giving details of the location.] The method is assessed by considering the amount of ground settlement, as calculated by finite element analysis and measured at the site. Comparison of the measured and numerical results confirmed the method's stability and field applicability. Settlement of 13.42~13.65 mm was calculated for seven cross-sections [The Abstract should be comprehensible without reference to the main text. The labels A-A' to G-G' should not be introduced here without explanation.] using numerical analysis, and the measured settlement reached a maximum of 2.00 mm. The observed differences and variations [Please state what differed/varied.] did not exceed the design expectations in any section. Instruments installed at the back of the excavation area were used to assess the conditions. An underground gradient meter recorded a cumulative horizontal displacement of between -0.40 and 0.60 mm, and an underground water meter recorded slight displacements of between -0.21 and 0.28 m compared with the initial measurements. A surface settlement meter observed very little movement, with a maximum of -2.00 mm compared with the initial measurement, thereby confirming the establishment of a stable state within the management criteria.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.484-492
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• 2016

This study is the numerical analysis for the ground stability assessment in ${\bigcirc}{\bigcirc}$mine. The subsidence factors applied to the numerical analysis were as follows. First, the deterioration of the rock mass properties by excavation of the disturbed zone. Second, using the average lateral pressure coefficient of Korea. Third, a study of the mine history. Fourth, the excavating collapsed rock mass in numerical analysis based on the assumption that the rock mass around the goaf was collapsed due to the mining. The developed methods were applied to the cross section (5+10) of the actual subsidence in ${\bigcirc}{\bigcirc}$mine. The feasibility of the numerical analysis methods was confirmed by providing the same results as those of the actual subsidence. Next, the developed methods were applied to the cross section (3+10) that had a high probability of subsidence and the ground stability was evaluated. The analysis results show that the vertical displacement for the 5+10 cross section occurs at a maximum of 46 mm, whereas the analysis results show that the vertical displacement for the 3+10 cross section occurs at a maximum of 7 mm. Hence, it is concluded that the probability for subsidence is low.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.1-10
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• 2013

Recently, the closed landfills are usually converted into parks or playground by the check the stability of landfill because they settle unevenly making them unsuitable for structures. When the closed landfill reuse, environmental and structural stability is important. To increase the bearing capacity and reduce the probable settlement of a foundation on waste disposal ground, a layer of geosynthetics(Geocell) is placed on the waste disposal ground. In this paper, the analysis of long-term settlement parameter correlation was performed, also the evaluation of bearing capacity reinforcement effect was conducted by field test. The settlement measured in the field, and input the same ground index when an integer to identify each model were compared by calculating the settlement. In addition, by adjusting the parameters of each model to identify the most similar to the value of field measurement parameters were calculated. Based on the analysis results, when the using the Park's model C(intermediate) = 0.0678, the expected settlement is similar to the field measurement results. Also, the bearing capacity of geocell reinforced ground is 1.193~1.554 times higher than that of unreinforced ground.

• Journal of the Korean Geotechnical Society
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• v.32 no.3
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• pp.5-13
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• 2016

Stability analysis was conducted to analyze the application of pile-supported embankment to concrete slab track on the soft ground in Korea. Pile efficiency and tension of geosynthetics in accordance with the hight of embankment and the depth of soft soil were carried out by theoretical and numerical methods. Theoretical method predicted more conservatively than the numerical method for all the cases presented herein. The settlement stability is satisfied to allowable criteria of high speed railway in Korea. The pile-supported embankment has great potential for application to soft ground condition.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.131-138
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• 2012

This paper aims to present accurately analytical modeling method for underpinning using uncertainty reduction, obtained from comparison between numerical analysis and Site measuring data during construction and service stages. Combination of various conditions should be considered for using numerical analysis to predict the behavior of the structure accurately, even though complexly considered the conditions, real construction should be secured the stability by applying the actual instrument measurement data because predicted results are including the considerable uncertainty. In order to secure the stability during construction, the real time instrument measurements together with numerical analysis results performed before construction state are complementary used actively. From the results of this study, the significant settlements are occurred not only in underpass structure of adjacent excavation area but also in the permanent steel pipe structures were analyzed. From the site measurement results of underpass settlement, the settlements are occurred in every stages of excavation, furthermore observed tendency is asymmetrical excavation patterns are settled more than symmetrical excavation patterns. The essential consideration points for numerical analysis are construction sequence, the direction of the existing facilities, the methods of elements modeling, the applied factors for nature of material and different results would be occurred depending upon inputting the above factors.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.511-524
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• 2015

Groundwater causing subsidence in limestone mines is uncommon, and thus relatively poorly investigated. This case study investigated the cause and possibility of future subsidence through an evaluation of ground stability at the Samsung limestone mine, Chungcheongbuk-do. The ground near the mine area was evaluated as unstable due to rainfall permeation, and subsidence in the unmined area resulted from groundwater level drawdown. Future subsidence might occur through the diffusion of subsidence resulting from the small thickness of the mined rock roof, fracture rock joints, and poor ground conditions around the mine. In addition, the risk of additional subsidence by limestone sinkage in corrosion cavities, groundwater level drawdown due to artificial pumping, and rainfall permeation in the limestone zone necessitates reinforcements and other preventative measures.