• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.225-235
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• 2013

Cutter forces acting on a disc cutter in TBM are the key parameters for TBM design and its performance prediction. This study aimed to experimentally evaluate cutter forces with different ring shapes in a hard rock. The stiffness of a cutter ring was indirectly estimated from a series of full-scale linear cutting tests. From the experiments, it was verified that the rolling stress acting on a V-shape disc cutter was much higher than on a CCS disc cutter even though the penetration depth by a V-shape disc cutter could be increased in the same cutting condition. Finally, it is suggested that a prediction model considering the shape parameters of a disc cutter should be used for its better prediction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.351-359
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• 2007

Multi-axial compression tests have been frequently conducted to evaluate the in situ properties of rock masses and the mechanical behaviors of rock strata through the model tests. Without the proper boundary condition for the model tests, the mechanical behavior of rock mass would deviate, as can be expected, from the in situ conditions. The boundary condition will affect the internal stress distribution of the specimens and cause some distortion on the measurement. In this study, a design process regarding the steel brush, which has been employed for multi-axial compression test to reduce the frictional restraint along the specimen/loading platen interface, is introduced. The individual brushes are regarded as a simple column and beam to calculate the cross-sectional size and length of the brushes in consideration of the buckling capacity and the allowable deflection.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.5
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• pp.497-506
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• 2014

In this study, analysis results described in the companion paper was used to determine shapes of room-and-pillar underground structure. To select optimized shapes, structural stability, space applicability and vehicle applicability were considered. In the structural stability step, ratio between strength and stress of the pillar and the critical strain at the roof span were adopted. The space applicability was used to retain the sufficient space of underground structure as its purpose is for human activity. The vehicle applicability was used to consider a radius for rotation of construction equipments in the room-and-pillar underground structure. From the given procedure in this study, proper shapes of rock pillar and room can be selected to design supports at the pillar and roof.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.5
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• pp.471-485
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• 2014

The monitoring method of geotechnical structures using acoustic emission(AE) and microseismicity(MS) is to detect the microscopic deformation and fracture behavior in the inner structures by measuring induced acoustics and vibrations. It can identify a pre-indication of failure by taking advantage of the characteristics that the amount and occurrence rates of AE and MS increase rapidly prior to large scale destruction of the target structures. The monitoring system consisting of high-quality sensors, high-speed data acquisition device and the operation program is required for the practical application of this method. Recently, the AE and MS monitoring systems have been localized. In particular, the developed operation software which can analyze and interpret the measured signals was demonstrated through a number of applications to domestic fields. This report introduces the configuration and features of developed monitoring system, then the challenges and future direction of AE monitoring in geotechnical structures are discussed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.377-387
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• 2016

In recent, in case that the underpass is constructed by trenchless method, its stability increases by reinforcing steel pipe with re-bar and mortar after propulsion into the ground to form pipe-roof. Therefore, it can be predicted that the integrated pipe-roof decreases the stress acting on the underpass by sharing load. In this study, to analyze the effect of integrated pipe-roof and behavior of stress around underpass, experimental tests for the rectangular and arch cross section of the underpass are performed using soil chamber. As a result, stress and strain acting on the underpass decrease due to sharing load by integrated pipe-roof. This phenomenon is more pronounced by increasing the stiffness of pipe-roof. Furthermore it can be expected that cross-section of underpass can be economically designed.

• Tunnel and Underground Space
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• v.25 no.2
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• pp.144-154
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• 2015

Mechanical energy is accumulated in the object when stress is exerted on rock specimens, and the failure is occurred when the stress is larger than critical stress. The accumulated energy is emitted as various forms including physical deformation, light, heat and sound. Uniaxial compression strength test and point load strength test were carried out in low temperature environment, and thermal variation of rock specimens were observed and analyzed quantitatively using thermal infrared camera images. Temperature of failure plane was increased just before the failure because of concentration of stress, and was rapidly increased at the moment of the failure because of the emission of thermal energy. The variations of temperature were larger in diorite and basalt specimens which were strong and fresh than in tuff specimens which were weak and weathered. This study can be applied to prevent disasters in rock slope, tunnel and mine in cold regions and to analyze satellite image for predicting earthquake in cold regions.

• Journal of the Society of Disaster Information
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• v.17 no.1
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• pp.53-59
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• 2021

Purpose & Method: The purpose of this study is the theoretical study on the durability standard of ground structures monitoring sensors. A survey on the durability criteria for construction monitoring sensors of domestic construction companies and the income tax implementation regulations, the standard years of contents such as buildings and the standards of the Public Procurement Service for construction monitoring and construction machinery were analyzed. Result: The durability criterion such as the inclination meter and the strain gauge, which are purchased from the Public Procurement Service prior to installation on the ground structure, is 8 to 10 years. Conclusion: The actual durability analysis by comparing the reliability of various monitoring sensors installed in dams at home and abroad, As a result of comprehensive study on the loss and damage rate of the maintenance monitoring sensor installed in the tunnel, the proper durability period of the built-in type monitoring sensor such as domestic pore pressure meter and earth pressure meter installed in the structure or the ground is 5 to 8 years it seems reasonable.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.2
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• pp.163-174
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• 2009

The large underground structure under earthquake is affected more by soil dynamic characteristic and volume of structure than by structural dynamic characteristic itself. Therefore, it is the purpose of research that the aseismic analysis for caverns including various aseismic analysis factors (rock quality-Q value, soil dynamic characteristic, shape ratio $&$ volume, underground structural dynamic characteristic, and aseismic level) are applied by using the numerical analysis program (SAUS; seismic analysis of underground structures). The result of research is stated that maximum strain, maximum moment, and maximum shear are not sensitive with respect to shape ratio. However those values are sensitive with respect to Q value, volume of underground structure and aseismic level. Based on the results of this research, the assessment for the influence factors of aseismic analysis for large underground structure could be possible.

• Journal of the Korean Geosynthetics Society
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• v.23 no.2
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• pp.19-27
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• 2024

Geotechnical structures such as dams, tunnels, and slopes require regular inspection and monitoring to ensure stability. Domestically, drones and accelerometers have become common tools for inspecting and monitoring various structures. However, drones have difficulty identifying internal changes in structures and the subsurface, and accelerometers generally serve for seismic design or strain measurement purposes. Therefore, this paper proposes to utilize accelerometers to monitor the internal information of the ground on a real-time or periodic basis. The proposed method utilizes a part of the analysis technique from the SASW test to monitor the stability and state changes of geotechnical structures. Cases where SASW was used to evaluate the safety of geotechnical structures, such as slopes, dams, and tunnels, were reviewed to verify the suitability of the technology. To make the proposed method more practical, the study considered using only the first-step analysis to derive the dispersion curve rather than the second-step analysis to determine the shear wave velocity profile, which requires complex analysis. The proposed technique is expected to enable the continuous monitoring and inspection of geotechnical structures by utilizing accelerometers.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.259-276
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• 2006

In rock mass subject to high in-situ stresses, the failure process of rock is dominated by the stress-induced fractures growing parallel to the excavation boundary. When the ratio of in situ stresses compared to rock strength is greater than a certain value, progressive brittle failure which is characterized by popping and spatting of rock debris occurs due to stress concentration. Traditional constitutive model like Mohr-Coulomb usually assume that the normal stress dependent frictional strength component and the cohesion strength component are constant, therefore modelling progressive brittle failure will be very difficult. In this study, a series of numerical analyses were conducted for surrounding rock mass near crude oil storage cavern using CW-FS model which was known to be efficient for modelling brittle failure and the results were compared with those of linear Mohr-Coulomb model. Further analyses were performed by varying plastic shear strain limits on cohesion and internal friction angle to find the proper values which yield the matching result with the observed failure in the oil storage caverns. The obtained results showed that CW-FS model could be a proper method to characterize essential behavior of progressive brittle failure in competent rock mass.