• Geomechanics and Engineering
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• v.24 no.1
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• pp.29-42
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• 2021

The utilization of buildings can be improved by extending them vertically. However, the added load of the extension might require building foundations to be underpinned; otherwise, the loads on the foundations might exceed their bearing capacity. In this study, a preloading method was presented aiming at transferring partial loads from existing piles to underpinning piles. A pneumatic-type model preloading device was developed and used to carry out centrifuge experiments to evaluate the load-displacement behavior of piles, the pile-soil interaction during preloading, and the additional loading caused by vertical extension. The results showed that the preloading devices effectively transfer load from existing piles to underpinning piles. In the additional loading test of group piles, the load-sharing ratio of a pile increased with its stiffness. The load-sharing ratio of a preloaded micropile was less than that of a non-preloaded micropile as a result of the reduction in axial stiffness caused by preloading before additional loading. Therefore, a slight reduction of the load-sharing capacity of an underpinning pile should be considered if the preloading method is applied. Further, two full scale preloading devices was developed. The devices preload underpinning piles and thereby produce reaction forces on a reaction frame to jack existing piles upward, thus transferring load from the existing piles to the underpinning piles. Specifically, screw-type and hydraulic-jack type devices were developed for the practical application of foundation underpinning during vertical extension, and their operability and load transfer effect verified via full-scale structural experiments.

• International Journal of Railway
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• v.9 no.1
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• pp.21-26
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• 2016

When excavation under existing structure is planned for a new construction project, the underpinning method is one of the most applicable construction methods. This study introduces a new modified underpinning method which is applied to construct a new subway line in Seoul Metropolitan. The new subway line was designed to pass underneath the existing subway line. Existing subway line carries about 2 million passengers daily, which is 33% of total passengers using subway in Seoul, and is the only circulation line in Seoul. Subway trains are passing 540 times through this section in a day. By applying a new underpinning method, the subway box structure of line is exposed 54m in the air supported by bearing piles. The proposed method was carefully monitored using heavy instrumentation system during construction. This study proposed and verified the application of the modified underpinning method, which can reduce construction period by 1.5 times and the construction cost by 1.2 times comparing with conventional method. The importance of considering construction sequence is investigated and verified by analyzed data non-considering construction sequence. The unexpected heaving which can bring up a dangerous situation for train running stability were measured, so this study shows that the upward movement has to be analyzed in designing process. As the use of underground space increases, the proposed method can be a good example of underground development.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.57-62
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• 1993

Settlements of maximum 23cm have occurred in and Apartment building consturcted on a fill layer with pile foundations. The main reason of the settlements was due to the negative skin friction applied to the pile, and settlement of adjacent ground since most pile tips are acted as a floating foundation founded on the stratum where the SPT N value was mostly less than 30. To underpin this building, the Jumbo Special Pile grouging was adopted, and instrumented data showed little differential settlement after the JSP underpinning.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.11-12
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• 2013

It is required to response to the demand for new space due to high density of population and buildings in urban area. In particular, in case of big cities such as Seoul where the lack of new construction site due to the depletion of available space, existing buildings must be demolished for new construction. Utilization of urban underground space can be an alternative to solve for urban space problems. There are applications of underpinning methods using micropiles for existing buildings. Sometimes, the difficulties come from the compact space available for new foundation underneath the existing ones. In this paper, a novel underpinning method is introduced which can solve the space restriction problems underneath existing columns.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.1
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• pp.131-138
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• 2000

In this study, physical and engineering properties of ordinary portland cement and microcement were investigated to verify reinforcing effect of underpinning of open caisson foundation by using microcement grouting. Laboratory injection tests such as infiltration and injection in case of seepage for the stream bed soil at ${\bigcirc}{\bigcirc}$ Great Bridge in Seoul were carried out. Field injection tests to reinforce open caisson foundation at ${\bigcirc}{\bigcirc}$ Great Bridge were performed and the ability of application by microcement grouting was evaluated. From the test results, physical and engineering properties of microcement are better than those of ordinary portland cement. Also, the ability of infiltration and solidity in case of seepage is better than that of ordinary portland cement. Therefore, it is concluded that microcement is an excellent material to reinforce open caisson foundation of the existing bridge structure under the water and can be used as underpinning material of general foundations.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.247-256
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• 1998

• Magazine of korean Tunnelling and Underground Space Association
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• v.6 no.1
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• pp.48-65
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• 2004

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.2
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• pp.335-344
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• 2019

Micropiles are widely used for foundation underpinning to enhance bearing capacity and reduce settlement of existing foundation. In this study, the main objective is to evaluate underpinning performance of a newly developed micropile called waveform micropile for foundation underpinning during vertical extension. Finite element method (FEM) was used to evaluate the underpinning performance of waveform micropile in terms of load-settlement response of underpinned foundation and load sharing behavior. For comparison, underpinning effects of three conventional micropiles with different lengths were also discussed in this study. Numerical results of load-settlement response for single pile demonstrated that bearing capacity and axial stiffness of waveform micropiles were higher than those of conventional micropiles because of the effect of shear keys of waveform micropiles. When additional loads 20 %, which is according to design loads of the vertical extension, were applied to the underpinned foundation, load sharing capacity of waveform micropile was 40 % higher than conventional micropile at the same size. The waveform micropile also showed better underpinning performance than the conventional micropile of length 1~1.5 times of waveform micropile.

• Human Ecology Research
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• v.61 no.2
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• pp.219-231
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• 2023

This study examined attitudes toward factors underpinning a successful marriage and their associations with marital satisfaction among married men and women in midlife. The sample comprised 201 married men and women aged between 40 and 59 living in Seoul, South Korea, and the data were collected by a self-report survey in 2019. Attitudes toward factors underpinning a successful marriage were measured using 12 items from the European Values Study Master Questionnaire 2008 and marital satisfaction was measured using three items from the Kansas Marital Satisfaction Scale. Exploratory and confirmatory factor analysis were performed in order to identify the factors deemed important for a successful marriage, as well as a t-test to explore gendered domains. Additionally, regression analysis was conducted to examine the association between attitudes toward factors underpinning a successful marriage and marital satisfaction. The results revealed two factors that were deemed important for a successful marriage: 'marital exchange based on conditions' and 'qualitative interaction based on sharing.' Women were more likely to believe that both factors were important for a successful marriage than men. The regression analysis revealed that 'qualitative interaction based on sharing' had a positive association with marital satisfaction, while 'marital exchange based on conditions' had a negative association with marital satisfaction, and also that these associations did not differ by gender. The findings imply that a successful marriage can be achieved when married partners make efforts to maintain their relationships through positive interactions and share intimacy in midlife.

• Korean Architects
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• no.10 s.92
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• pp.45-49
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• 1976