• Tunnel and Underground Space
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• v.23 no.2
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• pp.110-119
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• 2013

It is generalized to measure the arch settlement and convergence during tunnel construction for monitoring its mechanical stability. The initial convergence rate a day is defined from the first convergence measurement and the final convergence defined as the convergence measured lastly. The initial and the final tunnel arch settlement are defined like the preceding convergence. In the study, the relations between the initial and final displacements of a shallow tunnel are analyzed. The measurements were performed in the tunnel of subway 906 construction site in Seoul. The overburden is 10-20 m and the tunnel goes through weathered soil/rock. The width and height of the tunnel are about 11.5 m, 10m, respectively. So this is a shallow tunnel in weak rock. The length of tunnel is about 1,820 m and the tunnel was constructed in 2 stages, dividing upper and lower half. The numbers of measurement locations of arch settlement and convergence are 184 and 258, respectively. As a result, the initial displacement rate and the final displacement are comparatively larger in the section of weathered soil.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.545-553
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• 2008

Face mapping and displacement monitoring during tunnel construction are the most influential information for the stability assessment of ground and around structures. Especially, the result of face mapping and displacement analysis is essential to the excavation and support design in NATM which is based on the drilling and blasting. However, there have not been so many studies to put those useful information into practice for decision-making process during construction. The study reviewed the tunnel behaviour based on the RMR rating and displacement monitoring when the geological condition of rock mass varies inevitably. The study analysed the crown settlement using convergence equation in order to compensate the disparity induced by the location and time of measurement and found a distinct relation between the geological condition and the line of influence. As a result of analysing the various parameters related to the tunnel convergence according to the geological condition, the study suggested the basic knowledge about the relation between face mapping and displacement behaviour of tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.233-243
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• 2008

A tunnel behavior predicted in the investigation and design stage is often different from its actual behavior due to mainly the complexity of ground conditions. In a tunnel construction, therefore, it is necessary to ensure the stability of the tunnel by predicting the behaviors of the ground and the supports through observations and measurements, and modifying immediately excavation and reinforcing methods when necessary. To do so, it is important to be able to predict the final tunnel behavior based on the initial tunnel behavior as early as possible. In this study, the correlations were obtained between the initial and the final convergence by analyzing statistically the convergence measurement data, collected from two domestic road tunnels under construction using NATM. In order to estimate the unknown displacements, occurred during the period between the excavation and the first measurement, two methods were used - one is the method by means of regression analysis using a modified exponential function and the other the method by a simple linear regression analysis using the data measured within the distance from tunnel face equal to the tunnel diameter (D). Finally, the relationships were obtained between the initial and final convergence, including the non-measured displacements estimated from the two different methods, by performing linear regression analyses. The regression analysis results showed that there are clear linear relationships between the initial and final convegence and the difference between the two linear regression equations was not that large for when using the exponential function and the simple linear function to estimate the non-measured displacements.

• Tunnel and Underground Space
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• v.11 no.2
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• pp.146-155
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• 2001

An inverse calculation method to obtain sectional forces, axial force and flexural moment of a tunnel concrete lining was developed by utilizing convergence measurements acquired at the maintenance stage. To monitor the behavior of the lining, DOCS system was applied to a subway tunnel section. The method was proved to be effective, yielding the same results as measured forces of buried instruments. Many effects such as vibration of sensors, vibration due to test train operation, the variation of temperature and high voltage were checked and a new management scheme for tunnel maintenance was proposed.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.515-526
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• 2015

Predicting and measuring tunnel convergence is very crucial for estimating tunnel stability and economical construction of NATM tunnels. The method to estimate the tunnel convergence that occurs before and after construction is proposed based on literature reviews. The total displacement occurring related to tunnel construction is determined to be about 2.5 times that of measured displacements. The results of displacement measurements at two tunnels constructed with similar rock types are examined for the investigation of factors affecting the tunnel convergence. The average convergence of Gyungju A Tunnel is about 6.7 times bigger than that of Daejeon B Tunnel. The possible causes of the large convergence in Gyungju A Tunnel are suggested. In order to predict the convergence of tunnels, careful investigation of the geological structures in the ground surface and the influence of external conditions as well as careful face mapping of the tunnel face should be conducted.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.3
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• pp.209-215
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• 2004

Together with the requirements of tunnels, its construction methods and technologies have been pretty much developed, but frequent accidents happened under the constructions are just one of important problems which should be improved. To detect the potential hazardous factors in or ahead of time, speedy and accurate observation are absolutely required, but currently surveying method using tapes, level and total station, has been generally taken in measuring of tunnel convergence and crown. The purpose of this study is, as using of industrial photogrammetry system which is supplying more accuracy and speedy in the measure of tunnel convergence and crown. From the result of this study, we have got up to 1/20,000 accuracy and totally 6 minutes, from picturing 5 sections by one person to data edition, has been taken except setting targets.

• Tunnel and Underground Space
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• v.13 no.6
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• pp.476-485
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• 2003

The purpose of this study is to present an analysis method for the prediction of the change of ground conditions. To this end, three-dimensional convergence displacements is analyzed in several ways to estimate the trend of displacement change. Three-dimensional arching effect is occurred around the unsupported excavation surface including tunnel face when a tunnel is excavated in a stable rock mass. If the ground condition ahead of tunnel face changes or a weak fracture zone exists a specific trend of displacement change is known to be occurred from the results of the existing researches. The existence of a discontinuity, whose change in front of the tunnel face, can be predicted from the ratio of L/C (longitudinal displacement at crown divided by settlement at crown) etc. Therefore, the change of ground condition and the existence of a fracture zone ahead of tunnel face can be predicted by monitoring three-dimensional absolute displacements during excavation, and applying the methodology presented in this study.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.567-576
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• 2007

In order to assess the on-site applicability of 3D absolute displacement monitoring of tunnel using digital photogrammetry, the displacement of the optical target placed at the measurement section was investigated, as planned in the OO tunnel construction site. The targets on 3 measurement lines only were considered for each point of measurement for the reconstruction of 3D cubic model for the digital vision monitoring. For each 3D model, 3 or more images have to be obtained at each point. On the last 2 measurement lines, 6 targets (crown, left and right walls) were continuously overlapped to construct 3D models so that 6 or more apices can be shared by 2 3D models. In order to compare the measurement methods of 3D absolute displacements in tunnel excavation, i. e, total station and digital image measurement, both the digital image measurement and optical measurement were conducted for 10 times in the same work section. The time and measurement results of both methods were compared.

• Tunnel and Underground Space
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• v.15 no.1 s.54
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• pp.1-8
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• 2005

Measurement of convergence was/is carried out manually throughout the world for tunnels under construction. However, manual method has certain limitations in terms of applicability for the tunnels in operation. This paper describes state of the art of convergence monitoring systems which are available for measuring displacement of existing tunnels. These technologies are analyzed as follows: 1 The Sofo system using the fiber optic sensors has been applied to the stress measurement of the tunnel lining. It has not yet been used for the monitoring of tunnel convergence because of its cost and reliability 2. A TPMS(Tunnel Profile Monitoring System) using tilt sensors and displacement sensors is used for the convergence monitoring of highway tunnels, subway tunnels and underground ducts. 3. A BCS(Bassett Convergence System) using a pair of tilt sensors can be used for the convergence monitoring of tunnels, however the accuracy of the measurement has to be improved because it uses AC input voltage during data acquisition. The system has to be validated before it can be applied to the tunnels in operation. Convergence monitoring systems using TPMS and/or BCS are recommended to be evaluated and improved by a series or tests in tunnels under construction in order to be applied to the main measuring section and the tunnels in operation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.20-26
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• 2001

In this paper, we design tunnel inner section displacement measurement system which is composed of potentiometer-type displacement sensors, microcontroller-based intelligent sensing head and host computer for the management system and acquisition data. Multiple node communication bus connects the intelligent sensing heads with the host computer. For safe and re1iab1e network operation we use daisy-chain configuration, termination resistor, fail-safe biasing circuit. For tole enhancement of system utilization, we use modbus protocol. The acquisition data are transmitted to host computer and managed by database. Several data request conditions and sorting conditions are provided by management software. The utilization of designed system is confirmed by experiment.