• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1782-1788
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• 2007

This study analyzed ground settlement and ground stress depending on tunnel excavation and the ground reinforcing grouting methods for double line road tunnel through deep weathered zone. Diameter of double line road tunnel was approximately 12m and umbrella arch method and side wall reinforcing grouting were applied. The ring-cut split excavation method and CD-cut excavation method for excavation method were applied. Analysis of failure rate and vertical stress ratio show that the tunnel for which the height of the cover(H) was higher than four times the diameter, it can be considered a deep tunnel. Comparisons of various excavation and ground reinforcement methods were showed that CD-cut method results in lower surface and crown settlement, and lower failure rate than where using Ring-cut split method. In addition the side wall reinforcing grouting resulted in reduction of tunnel displacement and settlement.

• Geomechanics and Engineering
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• v.20 no.4
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• pp.275-285
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• 2020

Excavation usually induces considerable ground settlement in soft ground, which may result in damage of adjacent buildings. Generally, the settlement is predicted through elastic-plastic finite element method and empirical method with defects. In this paper, an analytical solution for predicting ground settlement induced by excavation is developed based on the definition of three basic modes of wall displacement: T mode, R mode and P model. A separation variable method is employed to solve the problem based on elastic theory. The solution is validated by comparing the results from the analytical method with the results from finite element method(FEM) and existing measured data. Good agreement is obtained. The results show that T mode and R mode will result in a downward-sloping ground settlement profile. The P mode will result in a concave-type ground settlement profile.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.3-14
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• 2005

Reliable predictions of the movement of earth retaining structures and the ground adjacent to braced walls in urban excavation are often difficult due to many variable factors. The ground settlement and the damage of adjacent structures in urban excavation has been an important issue. Therefore, the stability of the adjacent structures must be secured with the excavation support and research on the protection of adjacent structure is necessary. This study showed an urban excavation case and introduce observation method for case of damage behavior in urban excavation.

• The Journal of Engineering Geology
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• v.29 no.3
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• pp.289-302
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• 2019

As the occurrence of ground subsidence near the excavation site increases recently, studies are being conducted to predict the possibility of ground subsidence prior to excavation. In this study, the ground subsidence risk rating for pre-excavation (GSRp) developed by the previous study was applied to actual excavation sites to verify its applicability. The final results for the evaluation of the ground subsidence risk level for five excavation sites revealed that GSRp scores were calculated between 40 and 79 points and classified mainly into grades II (Good Ground)~III (Fair Ground). In order to verify the evaluation method, the obtained GSRp grades were compared with the measured horizontal displacements. The horizontal displacements measured in five excavation sites were between 25% and 47% of the allowable displacement, which were well agreed with the low subsidence risk level obtained from GSRp calculation. It is expected that the GSRp method can be used as an evaluation tool for predicting the risk of ground subsidence before excavation if GSRp is verified and supplemented through the additional research for the poor soil with the high risk of ground subsidence.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.118-125
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• 1992

The ground deformation due to the tunnel excavation is dependent on various factors such as ground condition, geometry of the tunnel, excavation method, installation of support members, construction condition of each excavation stage, etc. And the distance from the facing effects significantly the stress conditions of the supported and unsupported ground due to the 3-dimensional structural nature of the excavated tunnel. The concept of ground characteristic line has been applied to properly consider the loading condition given by staged tunnel excavation so that the imaginary supporting pressure is applied against the surface of excavated ground. Discussions on the results of the performed finite element analysis were mainly made with respect to the ground settlement, tunnel displacement, earth pressure, stress mobilized in supporting members.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.10c
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• pp.103-122
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• 2001

For prediction of ground movement per the excavation step, observational results of ground movement during the construction was very different with prediction during the analysis of design. step because of the uncertainty of the numerical analysis modelling, the soil parameter, and the condition of a construction field, etc. however accuratly numerical analysis method was applied. Therefore, the management system through the construction field measurement should be achieved for grasping the situation during the excavation. Until present, the measurement system restricted by ‘Absolute Value Management system’only analyzing the stability of present step was executed. So, it was difficult situation to expect the prediction of ground movement for the next excavation step. In this situation, it was developed that ‘The Management system TOMAS-EXCAV’ consisted of ‘Absolute value management system’ analyzing the stability of present step and ‘Prediction management system’ expecting the ground movement of next excavation step and analyzing the stability of next excavation step by‘Back Analysis’. TOMAS-EXCAV could be applied to all uncertainty of earth retaining structures analysis by connecting ‘Forward analysis program’ and ‘Back analysis program’ and optimizing the main design variables using SQP-MMFD optimization method through measurement results. The application of TOMAS-EXCAV was confirmed that verifed the three earth retaing construction field by back analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.248-259
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• 2010

In the case of relatively good ground and construction condition in the deep excavation for the construction of subway, railway, building etc., flexible earth retaining systems are often used in an economical point of view. It is generally known that the mechanism of behavior in the flexible earth retaining system is relatively more complicated than the rigid earth retaining system. Moreover in the case of long span strut supporting system the analysis of strut axial force change becomes more difficult when the differences of ground condition and excavation work progress on both sides of excavation section are added. When deeper excavation than the specification or installation delay of supporting system is done or change of ground condition is faced due to the construction conditions during construction process, lots of axial force can be induced in some struts and that can threaten the safety of construction. This paper introduces one example of long span deep excavation where struts and rock bolts were used as a supporting system with flexible wall structure. The characteristics of ground deformation and strut axial force change, the measured data obtained during construction process, were analysed, the effects of relatively deeper excavation than the specification on one excavation side and rapid drawdown of ground water level on the other excavation side were deeply investigated from the viewpoint of mutual influences between ground deformations of both excavation sides and strut axial force changes. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Geomechanics and Engineering
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• v.30 no.5
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• pp.423-435
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• 2022

Ground vibration generated repeatedly in blasting tunnel excavation sites is known to be one of the major hazards induced by blasting operations. Various studies have been conducted to minimize these hazards, both theoretical and empirical methods using electronic detonator, the deck charge method, the center-cut method among others Among these various existing methods for controlling the ground vibration, in this study, we investigated the cut method. In particular, we analyzed and compared the V-cut method, which is commonly used in tunnel blasting, to the double-drilled parallel method, which has recently been introduced in tunnel excavation site. To understand the rock fragmentation efficiency as well as the ground vibration controllability of the two methods, we performed in-situ field blasting tests with both cut methods at a tunnel excavation site. Additionally, numerical analysis by FLAC3D has been executed for a better understanding of fracture propagation pattern and ground vibration generation by each cut method. Ground vibration levels, by PPVs measured in field blasting tests and PPVs estimated in numerical simulations, showed a lower value in the double-drilled parallel compared with the V-cut method, although the exact values are quite different in field measurement and numerical estimation.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.77-84
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• 2003

Deep excavations in the urban areas have been frequently going on in large scale. Soil-nailing and Earth-anchor supporting methods are generally used in deep excavation. These construction methods cause ground disturbances during drilling process, and damages of adjacent structures and ground due to the differential settlement throughout construction period, and unexpected behaviors of supporting system according to the characteristics of drilling machine and ground condition. This article introduces two actual examples of adjacent deep excavation for the construction of university buildings in granitic Seoul area. The important results of construction and measurements obtained using Crawler drilling machine for Soil-nailing and Earth-anchor supporting methods are summarized. And some suggestions are given to improve and develop the technique of design and construction in the deep excavation projects having similar ground condition and supporting method.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.43-46
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• 2017

Recently, the development of underground space is being actively carried out in the urban area by saturation, and the excavation works are mainly carried out by various excavation methods by the structures adjacent to the ground and underground excavation. During such excavation work, ground subsidence accidents are occurring due to inattention construction, lack of construction technology, and leakage of ground water. For the prevention of ground subsidence we studied the method of risk influence factors by soil investigation. Analysis of 75 sites soil investigation by U.S.C.S (Unified Soil Classification System), construction method, depth of excavation and we studied the risk influence factors with ground subsidence.