• Tunnel and Underground Space
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• v.13 no.2
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• pp.77-86
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• 2003

The finite element method and statistics of the convergence measurement are useful method of the stability analysis of the tunnel adjacent to the pier. It is the purpose of the this case study to certificate of validity of the application of those methods. The safety of the pilot tunnel method and LW pre-grouting has been evaluated from the FEM analysis. The three-dimensional finite element method is carried out for the decision of the level of stress redistribution at the two-dimensional numerical analysis. An analysis of the convergence is carried out by the estimation of preceding convergence at tunnel excavation. F-examination is applied for this estimation. As results of that analysis, The F-value is from 10.81 to 158.74 and the coefficient of determination is from 0.82 to 0.99. An analysis of convergence is carried out by using regression analysis. Consequently, it is shown that the convergence can be modeled as following function C(t)=a[1-exp(-bt)].

• Tunnel and Underground Space
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• v.18 no.5
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• pp.366-374
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• 2008

Tunnelling under water table induces many geotechnical problems because of groundwater. In subsea tunneling, reduction of face stability can induce flooding in the vicinity of a fracture zone characterized by high permeability and high water pressure. In this study, the effects of high water pressure on the stability of a tunnel face in a limited zone with high permeability(hazardous zone) are analyzed. On the basis of the 'advance core' concept, the seepage force acting on a hypothetical cylinder ahead of a tunnel face is modeled. This study focuses on the hydraulic behavior of the ground ahead of the tunnel face by three-dimensional steady-state seepage analyses. The impact of the hazardous zone on the seepage force and stability of the tunnel face are simulated and analyzed. In light of the analysis results, it is estimated that the distance from the tunnel face to the exterior boundary limit, which the seepage force significantly affects the stability of the tunnel face, of a hypothetical cylinder is approximately 5 times the tunnel radii. Despite the restrictive assumptions of this study, the results are highly indicative regarding the risks of hazardous zones.

• Proceedings of the KSEE Conference
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• 2006.10a
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• pp.119-140
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• 2006

The rock excavation work by doing blasting breaks the rock by using a shock pressure and gas pressure produced when explosive explodes and the shock wave by shock pressure propagated three-dimensionally from the exploding center is on the decrease notably to the distance, however, $0.5{\sim}20%$ of energy produced by blasting propagates into the ground outside a crack zone by the shape of an elastic wave, on the ground it appears as a ground vibration with a seismic amplitude and a seismic cycle, it is called a blasting vibration. on the other side, what propagated in the air is called a blasting sound. The blasting sound of both means the things which the shock sound within the range the audible frequency($20{\sim}20000Hz$) of the elastic wave in the air influences the response system of a human body, it doesn't harm physically to any structures but influences unreasonably a work accomplishment, such as a work discontinuance due to the outbreak of a public complaint by a mental pain, reduction of a blasting scale, etc.. So, this study is examined at about 20 sites on the installation time and method of soundproofing facilities for reduction of the sound accompanied with a tunnel blasting work.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.4 s.56
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• pp.107-115
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• 2009

The number of railway tunnel design is increasing recently compare to a great number of highway tunnel design which had increased with a lot of highway construction in the 70's and 80's. Therefore, there is more or less difference of time between highway tunnel and railway tunnel. In this paper, numerical analysis on two kinds of tunnels, such as two-forked road highway ventilation tunnel and double track railway tunnel with 4.3m of center line, in cases of with support materials condition and without support materials condition were conducted. Finally, stability of two kinds of tunnels were compared and analyzed through comparing of principal stresses and deviator stresses in the near base rock of tunnels using results of numerical analysis.

• Korean Journal of Construction Engineering and Management
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• v.9 no.5
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• pp.186-193
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• 2008

The SPS, Strut as a Permanent System, method is widely adopted for the main structural member in addition to temporary strut function for the shuttering of excavation work. Although the SPS method has contributed to cost saving, time reduction, enhancement of structural stability, improvement of construction environment and so on at the building construction site, it caused the problems of increase of basement height and additional work for fire protection of steel structure. The increase of basement height caused the increase of shuttering depth and excavation, and the fire protection caused the additional cost as well as the deterioration of construction environment. In order to improve the problems, this paper is to propose a modularized hybrid structural system(HSD). The detail of the system is introduced and the structural performance and constructibility are proved through the experiment and site application.

• Journal of the Korean GEO-environmental Society
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• v.14 no.7
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• pp.5-12
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• 2013

The safety and structural integrity of buried pipes are usually at risk from constructing loading and compaction of backfill materials. The backfill material should be strong enough to help resistance and redistribute loads so that the buried pipe remains unaffected. Due to the many problems associated with buried pipes, there have been multiple studies on the development of a sustainable backfill material. In this study, a Controlled Low Strength Material made of coal ash was considered as a buried pipe backfill material. To determine the feasibility and performance of this backfill material, a numerical simulation was conducted with the results confirmed by a field test. Results showed maximum settlement to be 2 mm with the elastic strain of the buried pipe to be about 0.006.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.61-71
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• 2005

Cemented Sand and Gravel (CSG) is a material made by simple mixing of rock-based raw materials such as excavated soil and riverbed gravel together with cement and water. The use of CSG material for cofferdam and large dam is gradually increasing in Japan because a quarry and aggregate plants can be diminished. Also, the CSG method can reduce dam construction cost, construction duration and destruction of environment. In this paper, the basic strength characteristics of CSG, such as compressive strength, modulus of elasticity and stress-strain curve were investigated by unconfined compression test and large triaxial compression test. From the results of the experimental study, the correlation equations between elastic modulus and unit cement, age are proposed.

• Geotechnical Engineering
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• v.13 no.4
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• pp.163-176
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• 1997

It has long been recognized that the H-beam steel rib has many shortcomings when used as a steel support in tunneling. One of the major shortcomings is the shotcrete shadow created behind H-beam flange which eventually reduces the load bearing capacity of shotcrete shell. In many European countries, plate girder as the H-beam steel rib has been replaced by lattice girder which has many advantages over the H-beam steel rib. Successful application of the lattice girder as a steel support requires a thorough investigation on the load bearing capacity of the lattice girder. Therefore, laboratory bending and compression tests were conducted on lattice girders with the aim of investigating the load bearing capacity of the lattice girders. The results of tests show that the load bearing capacity of laIn twice girders is higher than that of H-beams, which indicates that the lattice girder can be effectively used as a support in tunneling.

• Geotechnical Engineering
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• v.10 no.3
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• pp.79-96
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• 1994

A tunnel design expert system entitled NESTED is developed using the artificial neural network. The expert system includes three neural network computer models designed for the stability assessment of underground openings and the estimation of correlation between the RMR and Q systems. The expert system consists of the three models and the computerized rock mass classification programs that could be driven under the same user interface. As the structure of the neural network, a multi -layer neural network which adopts an or ror back-propagation learning algorithm is used. To set up its knowledge base from the prior case histories, an engineering database which can control the incomplete and erroneous information by learning process is developed. A series of experiments comparing the results of the neural network with the actual field observations have demonstrated the inferring capabilities of the neural network to identify the possible failure modes and the support timing. The neural network expert system thus complements the incomplete geological data and provides suitable support recommendations for preliminary design of tunnels in rock masses.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.115-131
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• 2011

Recently, considering the aspects of disaster prevention and environmental damage, the construction of a twin tunnel is increasing. When constructing a twin tunnel, the stresses are concentrated at the pillar so that stability of the tunnel is decreased. Since the previous studies on the behavior of a twin tunnel pillar are mainly restricted to the estimation of the tunnel behavior and the analysis of surface settlement, there is a limit to a quantitative stability estimation of the pillar. Therefore, it was quantitatively investigated how the pillar width of a twin tunnel affects its stability. To ensure this end, global tunnel safety factors obtained numerically using shear strength reduction technique, local safety factors of a pillar using the equation that Matsuda et al. suggested, and strength/stress ratios of the pillar were estimated and their results were analyzed for two sections with different rock covers. For a reasonable design of a twin tunnel pillar, it was turned out that strength/stress ratio, the local pillar safety factor, and global tunnel safety factor should be used interrelatedly rather than independently.