• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.4
• /
• pp.687-699
• /
• 2018

The construction of subsea tunnel differs from that of inland tunnel because of high water pressure due to sea water level and difficulties to reinforce the ground under construction. Therefore, it is very important to prevent trouble in advance when the subsea tunnel is constructed. In this paper, we established lots of databases about characteristics of geological and mechanical parameters on the construction of subsea tunnel using micro slurry TBM which depth is about 60 m. The correlation analysis is conducted to confirm the effect of thrust, torque and RPM among the excavation database on the net penetration rate. Also, An empirical formula is suggested to predict the net penetration rate through the correlation analysis between FPI (Field Penetration Index) and specific energy from the subsea tunnel excavation database.

• Tunnel and Underground Space
• /
• v.31 no.4
• /
• pp.211-220
• /
• 2021

Tunnel collapse often occurs during deep underground tunneling (> 40 m depth) in South Korea. Natural cavities as well as water supply pipes, sewer pipes, electric power cables, artificial cavities created by subway construction are complexly distributed in the artificial ground in the shallow depths of the urban area. For deep tunnel excavation, it is necessary to understand the properties of the ground which is characterized by porous elements and various geological structures, and their influence on the stability of the ground. This study analyzed geological factors for risk assessment in deep excavation in South Korea based on domestic and overseas case study. As a result, a total of 7 categories and 38 factors were derived. Factors with high weights were fault and fault clay, differential stress, rock type, groundwater and mud inrush, uniaxial compressive strength, cross-sectional area of tunnel, overburden thickness, karst and valley terrain, fold, limestone alternation, fluctuation of groundwater table, tunnel depth, dyke, RQD, joint characteristics, anisotropy, rockburst and so forth.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.3
• /
• pp.229-242
• /
• 2009

Numerical analysis has been performed to estimate maximum settlement, maximum horizontal displacement and total settlement volume at the ground surface due to tunnel excavation varying ground condition, tunnel depth and diameter, and construction condition (volume loss at excavation face). The maximum surface settlement from the numerical analysis has been compared with the maximum settlement at tunnel crown considering ground condition, tunnel depth and diameter, and construction condition, and it has been also compared with the maximum horizontal displacement. In addition, the volume loss ($V_L$) at tunnel excavation face has been compared with the total surface settlement volume ($V_s$) with the variation of ground condition, tunnel depth, and tunnel diameter. The results from the numerical analysis have been compared with field measurements to confirm the applicability and validity of the results and by this comparison it is believed that the numerical results in this study can be utilized practically in analyzing the ground movements due to tunnel excavation.

• Geomechanics and Engineering
• /
• v.19 no.4
• /
• pp.315-327
• /
• 2019

Deep excavations for development of subway systems in metropolitan regions surrounded by adjacent buildings is an important geotechnical problem, especialy in Tabriz city, where is mostly composed of young alluvial soils and weak marly layers. This study analyzes the wall displacement and ground surface settlement due to deep excavation in the Tabriz marls using two dimensional finite element method. The excavation of the station L2-S17 was selected as a case study for the modelling. The excavation is supported by the concrete diaphragm wall and one row of steel struts. The analyses investigate the effects of wall stiffness and excavation width on the excavation-induced deformations. The geotechnical parameters were selected based on the results of field and laboratory tests. The results indicate that the wall deflection and ground surface settlement increase with increasing excavation depth and width. The change in maximum wall deflection and ground settlement with considerable increase in wall stiffness is marginal, however the lower wall stiffness produces the larger wall and ground displacements. The maximum wall deflections induced by the excavation with a width of 8.2 m are 102.3, 69.4 and 44.3 mm, respectively for flexible, medium and stiff walls. The ratio of maximum ground settlement to maximum lateral wall deflection approaches to 1 with increasing wall stiffness. It was found that the wall stiffness affects the settlement influence zone. An increase in the wall stiffness results in a decrease in the settlements, an extension in the settlement influence zones and occurrence of the maximum settlements at a larger distance from the wall. The maximum of settlement for the excavation with a width of 14.7 m occurred at 6.1, 9.1 and 24.2 m away from the wall, respectively, for flexible, medium and stiff walls.

• Tunnel and Underground Space
• /
• v.33 no.5
• /
• pp.299-311
• /
• 2023

Continuous excavation technologies are developed to improve the excavation rate of shield TBM. Continuous excavation is a technology that provides thrust to segments, excluding being installed one, to reduce tunneling downtime. This paper investigated the prior technology related to continuous excavation segments. The main technology was classified into helical segment, honeycomb segment, and conventional segment methods. The helical segment method has not been applied in actual construction yet, and the honeycomb segment method has not succeeded in commercialization. The continuous excavation method using conventional segments has been successfully demonstrated. The thrust force and operation method of the thrust jacks for the semi-continuous technology were analyzed. Continuous excavation TBM research is also progressing in Korea, and through the analysis of successful cases, the need to develop independent continuous excavation methods has been identified.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.1455-1460
• /
• 2005

This paper presents the results of an experimental study on the ground deformation by trench excavation for Diaphragm Wall construction. The model tests are performed to investigate the back ground deformation by lowering of slurry level in trench after excavating. Through these, the deformation characteristic of the back ground due to stress release of excavated space was investigated. This study considered relative density of soil mass and the distance between trench and surcharge. An experiment was performed in order to observe the failure pattern of a slurry-supported trench excavated in sandy ground. From model tests, in order to predict reasonably the deformation behavior of the adjacent ground due to the underground excavation, it is significantly recommended that the ground settlement by trench excavation should be considered.

• Geomechanics and Engineering
• /
• v.16 no.6
• /
• pp.635-642
• /
• 2018

Braced excavation systems are commonly required to ensure stability in construction of basements for shopping malls, underground transportation and other habitation facilities. For excavations in deposits of soft clays or residual soils, stiff retaining wall systems such as diaphragm walls are commonly adopted to restrain the ground movements and wall deflections in order to prevent damage to surrounding buildings and utilities. The ground surface settlement behind the excavation is closely associated with the magnitude of basal heave and the wall deflections and is also greatly influenced by the possible groundwater drawdown caused by potential wall leakage, flow from beneath the wall, flow from perched water and along the wall interface or poor panel connections due to the less satisfactory quality. This paper numerically investigates the influences of excavation geometries, the system stiffness, the soil properties and the groundwater drawdown on ground surface settlement and develops a simplified maximum surface settlement Logarithm Regression model for the maximum ground surface settlement estimation. The settlements estimated by this model compare favorably with a number of published and instrumented records.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.03b
• /
• pp.93-100
• /
• 2000

In this study, we used photoelastic coating method which is a kind of model test for examining the stress condition of rock masses around underground structures. Using this method, we could know adaptability and usefulness of photoelastic coating method for various shape of tunnel models. And, in spite of higher cross section efficiency, square shape model showed unstable status because of high stress concentration. So, we cut the slits at the each corner of tunnel, and we could make more stable stress condition by means of moving high stress concentration to rock mass.

• Explosives and Blasting
• /
• v.15 no.2
• /
• pp.53-72
• /
• 1997

It is impossible to precat the behavior of ground soil and structure accurately during underground construction in urban area or excavation in soft ground area because of difference between the assumed design condition and the actual site condition. Therefore, it must be managed by measuring system and correct the difference by real data. Large scale under ground construction in urban area like a seoul subway project has needed for Intelligent Construction technique, a field of the Engineering Contractor. The automated measuring system is developed for the technique. It is described that the procedure and the method of measuring work with application of the automated measuring system.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2010.04a
• /
• pp.307-308
• /
• 2010

The present research carried out displacement measurement and section & capacity measurement of a archcrown of a tunnel by using a laser scanner in underground tunnel excavation work that a bridge construction is being executed.