• Journal of the Korean GEO-environmental Society
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• v.13 no.5
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• pp.51-57
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• 2012

The purpose of study is to understand the possibility of biogrout of soil induced by bacteria. Microbial Calcium Carbonate Precipitation(MCP) has been analysed using the microorganism Bacillus Pasteurii. In order to understand the biogrout of soft ground treated with microbial calcium carbonate precipitation, four types of specimens(sterilization soil, non-sterilization soil, reaction solution and microorganism solution with pre-treatment mix and reaction solution and microorganism solution with post-treatment mix) were made. Scanning Electron Microscope(SEM), EDX and X-ray diffraction(XRD) analyses were performed on the soft ground specimens. On the basis of the preliminary results, it appears that microbial treatment methods using calcium carbonate precipitation may be possible to improve property of biogrout.

• Journal of the Korean Geotechnical Society
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• v.28 no.6
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• pp.53-61
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• 2012

The purpose of this study is to understand the mechanism of cementation of soil induced by bacteria. In order to understand the mechanism of cementation of soft soils treated with bacteria, six types of specimens(Not treated, Normal concentration bacteria treatment, High concentration bacteria treatment, Supernatant high concentration bacteria treatment, Double high concentration bacteria treatment, and 25% Specimen high concentration bacteria treatment) were made. Scanning Electron Microscope (SEM), EDX and X-ray diffraction (XRD) analyses were performed on the soft silt and loose sand specimens. Compared with the normal bacteria concentration treated specimen, a clearer cementation between particles was observed in the 25% specimen high bacteria concentration treated specimen. On the basis of the preliminary results, it appears that microbial cementation can occur in the soft soil.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.95-100
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• 2008

In the design of ground improvement using band-shaped prefabricated vertical drains (PVD), it is required to determine a reasonable equivalent circle of PVDs. In this paper, a series of numerical analyses on soft clay ground improved by PVD were carried out in order to investigate the resonable equivalent circle of PVD considering consolidation behavior of improved soft clay ground by PVD. The applicability of numerical analyses, in which an elasto-viscoplastic three-dimensional consolidation finite element method was applied, could be confirmed comparing with consolidation behavior simulated at the laboratory. And, through the results of the numerical analyses, consolidation behaviors of soft clay ground with elapsed time were elucidated, together with the equivalent circle of PVD considering consolidation behaviors.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.284-287
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• 2011

본 연구에서는 합리적인 잔교용 설계기준을 마련하기 위한 기초적인 연구로써 지반조건을 고려한 잔교의 거동특성을 분석하고자 하였다. 본 연구에서 고려한 잔교는 구조적인 합리성과 시공성(조립시공)이 우수한 조립식 잔교를 대상으로 하였다.(강효기 외, 2010) 서해안의 연약지반을 고려하기 위해 지반스프링을 이용한 해석모델을 개발하고, 다양한 해석조건에 대한 해석을 수행하여 그 특성을 파악하고자 하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5C
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• pp.155-162
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• 2011

Settlement prediction based on field monitored data, which is used to control subsequent surcharges, is very important in construction management for soft ground improvement with the preloading method. Observational settlement prediction methods, which are suggested for an instantaneous loading, have been widely used in fields. However, they have difficulties in the settlement prediction with subsequent surcharge change. In this paper, a simple method to predict the settlement with subsequent surcharge change is suggested. The suggested method adopts assumptions to simplify the complex field condition and utilizes observational methods. The suggested method is applied to a large consolidation test result, FDM analysis results, and field monitored settlement data to confirm its practicability. From the applications, the suggested method produces reasonable prediction results with various subsequent surcharge changes.

• Journal of the Korean GEO-environmental Society
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• v.21 no.11
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• pp.11-20
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• 2020

For water barrier and reinforcing grout in soft ground, the verification of durability was conducted over the initial and long-term ages under various curing conditions. The grout was made of water glass system, fast-hardening mineral (FHM) system, and acrylic polymer system. There were three types of curing conditions that were tab water curing, artificial seawater curing, and atmospheric curing. And the various tests were performed for each sample by age, uniaxial compressive strength, length change, and weight change. As artificial seawater, MgCl₂ and MgSO₄ aqueous solutions were prepared and used, respectively. As the test results, the fast-hardening mineral system and acrylic polymer system were cured stably without significant change in durability in tap water and artificial sea water, whereas water glass system showed a very rapid drop in durability under artificial sea water conditions compared to tap water. In atmospheric curing conditions, durability is lowered compared to water curing in all cases, and in particular, the weight loss in the FHM system and water glass system is about 62% and 60%, respectively, resulting in a significant decrease in durability.

• Computational Structural Engineering
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• v.10 no.4
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• pp.4-11
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• 1997

본 기사에서는 호안의 안벽 및 방파제의 조성에 있어 기존 공법에 비해 경제성, 공사기간 및 시공장비 측면에서 유리하며, 특히 대수심 조건에 적합한 강판셀 공법에 대하여 소개하였다. 강판셀공법은 거치식과 근입식 공법으로 분류할 수 있으며 전자는 지반이 양호한 곳에, 후자는 지반이 비교적 연약한 부지에 적합하다. 본 기사에서는 강판셀공법의 설계절차와 실제 시공사례에 대해 소개하였다.

• Journal of the Korea Construction Safety Engineering Association
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• s.45
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• pp.60-70
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• 2008

Mechanized tunnelling by TBMs has been extensively adopted for last two decades. Nevertheless, only few case histories have been reported. Unlike NATM tunnels, the case histories of the weak zone have been seldom reported for the mechanized tunnelling, even in the other countries. In this study, a collapse of TBM tunnel occurred in the severely altered weak rock zones between volcaniclastic rocks and granitic rocks was briefly described. A systematic geotechnical investigation, which was performed to examine the cause of the collapse, was carried out at the site and then characteristics of the rocks in the zones were evaluated. Moreover, This study propose a guide line of estimateing the possibility of collapse in TBM tunnels through comparing experimental results with surveying results of general rocks.

• Journal of the Korean GEO-environmental Society
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• v.15 no.3
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• pp.5-13
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• 2014

This paper presents the results of a numerical investigation on applicability of Light-weighted Foam Soils (LWFS) consisted of dredged soils for soft ground improvement. The engineering properties of LWFS were comprehensively investigated based on the previous experimental tests. And three dimensional numerical models which reflect soft ground conditions were adopted to evaluate the applicability of LWFS compared to SCP and DCM. A number of cases were analyzed using a stress-pore pressure coupled model. The results indicated that LWFS method enables to reduce more settlement, lateral flow and heaving than SCP method and enable to reduce more residual settlement than DCM method. Also it was revealed that such effect depends on the properties of LWFS such as unit weight, unconfined compressive strength, deformation modulus and Poisson's ratio.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.2
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• pp.107-118
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• 2021

Due to the acceleration of road construction, the number and extension of tunnels are increasing every year. A lot of research has been done on the collapse of tunnels, but research on the invert heaving is insufficient. Therefore, in this study, a sensitivity analysis was performed using a geotechnical general-purpose program to analyze the effect of the invert curvature of a tunnel excavated on the soft ground. As a result, it was quantitatively confirmed that the stability of a tunnel was increased as the curvature of the tunnel invert was increased so that the safety factor was calculated to be large regardless of the ground conditions and the thickness of the support. In addition, it was confirmed that the stability of the tunnel was increased by reducing the convergence of the tunnel and the maximum bending stress supported by shotcrete. Therefore, when a tunnel is excavated on soft ground, it is believed that applying a curvature to the invert will increase the stability of the tunnel.