• Tunnel and Underground Space
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• v.18 no.4
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• pp.289-299
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• 2008

Based on the case study on the causes for the failure of cutting slope composed of weathered rock and soil, the factors influencing the design of a cutting slope have been examined, This type of rock and soil is widely distributed on the region whose parent rock is granite. To analyze the stability of the cutting slope, the following series of progress has been conducted: (1) ground characterization by geological survey and ground investigation, (2) the safety factor examination by limit equilibrium analysis and numerical analysis and (3) the comparison and analysis of rainfall and failure history. As a result, the main factors to cause the failure is determined to be the decrease of shear strength in the upper parts whose ground condition is weakened during localized heavy rain. Moreover, the analysis indicates the failure is also closely related to the groundwater inflow path. On the base of this investigation, a reinforcement method is proposed to ensure the stability of the cutting slope.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.167-172
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• 2000

In this study, the behaviors of a cast-in-situ concrete pile embedded in the weathered rock were analysed by a 3D numerical analysis using PENTAGON 3D and the results were compared with those of the field load test. The load-settlement relation and the load transfer relationship were evaluated from the numerical analysis. As a result, the load-settlement relation at the pile top and the axial load distribution with depth were predicted reasonably. And those results were similar with those of the field load test.

• Tunnel and Underground Space
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• v.6 no.3
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• pp.223-233
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• 1996

Geotechnical Information System (GTIS) for efficient management of three dimensional borehole data has been developed. Geotechnical maps in the vicinity of Bulkwangdong, Seoul station, Itaewon, Han river near Yuido, and Jungrangchon were constructed by Kriging method. In Bulkwangdong and Jungrangchon area where boundary between granite and gneiss is present, gneiss has been more weathered than granite, but in Seoul station and Itaewon area where the boundary is also present, granite has been more weathered than gneiss. It has been inferred that when Seoul granite intruded, the strength of gneiss in Bulkwangdong and Jungrangchon area was lowered by the attitude of foliation plane than in Seoul station and Itaewon area, so the gneiss has been easily fractured and weathered in Bulkwangdong and Jungrangchon area. Geotechnical map in the vicinity of Yuido showed that there is an NW-SE trend weakness zone that might be affected by major faults under Han river and it is expected that the fault zone may be present in construction area of Kyoungbu Highspeed Railway that lies below the Han river like the Subway Line No.5.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.337-346
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• 2013

The characteristics of subsidence above a shallow tunnel excavated in weathered rock mass is analyzed. The tunnel is excavated minimum about 11m beneath some buildings and the width of the tunnel is 11m, too. Subsidence pins are installed at 23 locations on surface along the tunnel, 180m long, adjacent to the buildings. Subsidences are measured for about 2 years and they are optimized to analyze three dimensional deformed ground surface, trough width parameter K and sectional volume loss of unit tunnel length Vs of the surface deformation profile.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.5-16
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• 2002

The pullout behavior of large-diameter steel pipe piles(diameter = 2,500mm, length = 38~40m), which were designed as compression piles but used as reaction piles during a static compression load test on a pile(diameter = 1,000m, length = 40m), was investigated. The steel pipe piles were driven by 20m into a marine deposit and weathered soil layer and then socketed by 10m into underlying weathered and soft rock layers. The sockets and pipe were filled with reinforced concrete. The steel pipe and concrete in the steel pipe zone and concrete and rebars in the socketed zone were fully instrumented to measure strains in each zone. The pullout deformations of the reaction pile heads were measured by LVDTs. Over the course of the study, a maximum uplift deformation of 7mm was measured in the heads of reaction piles when loaded to 10MN, and 1mm of residual uplift deflection was measured. In the reaction piles, about 83% and about 12% of the applied pullout loads were transferred in the weathered rock layer and in the soft rock layer, respectively. Also, at an uplift force of 10MN, shear stresses due to the uplift in the weathered rock layer md soft rock layer were developed as much as 125.3kPa and 61.8kPa, respectively. Thus, the weathered rock layer should be utilized as resisting layer in which frictional farce could be mobilized greatly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.197-203
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• 2008

The end bearing behavior of piles socketed in weathered/soft rock is generally dependent upon the rock mass conditions with fractures rather than the strength of intact rock. Therefore, a database which includes 13 load tests performed on cast-in-place concrete piles and soil investigation data at the field test sites was made first, and new empirical relationships between the base reaction modulus of piles in rock and rock mass properties were developed. No correlation was found between the compressive strengths of intact rock and the base reaction modulus of weathered/soft rock. The ground investigation data regarding the rock mass conditions (e.g. Pressuremeter modulus and limit pressure, RMR, RQD) was found to be highly correlated with the base reaction modulus, showing the coefficients of correlation greater than 0.7 in most cases. In addition, the applicability of existing methods for the end bearing capacity of piles in rock was verified by comparison with the field test data.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.431-438
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• 1999

Vertical congressive and horizontal pile load tests were performed to a instrumented large diameter (D : 1,000 mm) drilled shaft. A drilled shaft was penetrated into the weathered soil and weathered rock. PMT was done for evaluation of properties for these strata. It was expected to be difficult to get undisturbed samples of weathered soils and rocks. Thus. PMT was done at the several selected depths. In those strata, to prevent the test bore hole from collapsing, bentonite slurry was used for making the test bore hole. In this study. soil properties was evaluated by means of PMT results and estimating method (direct method, the Memard method) of vertical pile capacity and horizontal pile behaviors were summarized. Also, vertical and horizontal pile capacity were calculated using PMT and pile load test results.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.338-345
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• 2000

In this study, applicability of PMT in domestic area and test procedure were studied. At six test holes of three construction sites in Pusan, PMT using Elastometer-200 type was done. The problems during test were investigated and the test results were analysed. Limit pressure, p$\sub$ι/ could be determined by p- Δv/v method. Using PMT results, marine soil in Pusan could be classified approximately. Net limit pressure value was in the range of 6.4 ∼ 22.5 kg/$\textrm{cm}^2$ in clay, 2.2 ∼ 30.0 kg/$\textrm{cm}^2$ in sand, 13.0 ∼ 58.0 kg/$\textrm{cm}^2$ in weathered soil and 47.0 ∼ 190.0 kg/$\textrm{cm}^2$ in weathered rock. Also, E$\sub$m//p$\sub$ι/ value was in the range of 2.4 ∼ 7.0 in clay, 2.6 ∼ 12.1 in sand, 6.8 ∼ 17.1 in weathered soil and 7.2 ∼ 29.6 in weathered rock.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.424-442
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• 2005

In this paper a design of a large shield Tunnel through weathered soil and weathered rock in 703 section of seoul subway line No.7 extension project is presented. The geological investigation results show that the projecet region consists mostly of weathered soil with some local weathered rock in the tunnel excavation level. A EPB shield TBM is selected as a optimal excavation machine for the large shield Tunnel considering the geological and site conditions. Also, the shield machine head and cutter for the large shield tunnel type are designed considering site geological conditions and average advance rate in similar projects.

• Geomechanics and Engineering
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• v.25 no.2
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• pp.99-109
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• 2021

Tunnel provide faster, safer and convenient way of transportation for different objects. The region where it is construction and surrounding medium has significant influence on the overall stability and performance of tunnel. The present simulation has been carried out in order to understand the behaviour of rock tunnel under static loading condition. The present numerical model has been validated with the laboratory scaled model and field data of underground tunnels. Both lined and unlined tunnels have been considered in this paper. Finite element technique has been considered for the simulation of static loading effect on tunnel through Abaqus/Standard. The Mohr-Coulomb material model has been considered to simulate elastoplastic nonlinear behaviour of different rock types, i.e., Basalt, Granite and Quartzite. The four different stages of rock weathering are classified as fresh, slightly, moderately, and highly weathered in case of each rock type. Moreover, extremely weathered stage has been considered in case of Quartzite rock. It has been concluded that weathering of rock and overburden depth has great influence on the tunnel stability. However, by considering a particular weathering stage of rock for each rock type shows varying patterns of deformations in tunnel.