• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.3
• /
• pp.463-473
• /
• 2017

Bentonite swells when it comes into contact with water and makes it a viscous fluid. Thus it is widely used in civil engineering works for waterproofing. Utilizing the properties of bentonite, the slurry shield TBM supports excavated face with pressurized slurry as well as transporting excavated muck. When bentonite is in contact with seawater, due to the change of double layer thickness, its expandability and viscosity are lowered. This may cause problems for excavation stability and muck discharge due to the increase of sea water inflow when Slurry TBM is used under sea water conditions. In this study, the change of slurry condition caused by the inflow of sea water during tunnel excavation with Slurry TBM was investigated and a slurry management guideline was proposed. For this purpose, a laboratory test was carried out based on the slurry management criterions applied in the field, and a method applicable to the field where sea water is affected has been proposed.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.10 no.3
• /
• pp.257-267
• /
• 2008

Tunnels acting as drains involve groundwater-related problems such as deterioration of drainage systems or leakage through the linings. Generally initial and minor leakage problems can not be recognized by naked eyes. When the leakage over the linings is noticed, damages to structures and facilities have already occurred and could be considerable. Therefore it is vital to recognize initial leakage as early as possible and provide appropriate measures. Detection of leakage under operation requires installing piezometer. However, that may cause destruction of water proofing sheet which is generally not allowed. In this study electric resistivity method, one of the geophysical surveys, was adopted to detect possible leakage through tunnel linings. Physical lining models were made in the laboratory. The electric response was monitored for varying hydraulic conditions. It is shown that the method is very useful to detect initial leakage and monitor the malfunction of drainage system. Furthermore the method can also be used to check the quality of any repairing works of linings.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.22 no.6
• /
• pp.611-622
• /
• 2020

Recently, tunneling projects using shield TBM are increasing in Korea, but the information of client for machine design and manufacturing considering the characteristics of the tunneling phase is not formal, and it is difficult to optimized machine for suitable tunneling works. This paper suggest as for reference the required terms that can be used in Korea on the design items and detailed requirements for ordering of EPB shield TBM based on overseas case study. It would be hope that the TBM user can request the overall tunneling plan and required machine specification when ordering TBM, and the TBM supplier can design and manufacturing that is clear condition and suitable machine for the successful project, so that there are no residential civil complaints and for safe tunneling as well, shield TBM tunneling method will be activated.

• Journal of Korea Multimedia Society
• /
• v.14 no.8
• /
• pp.1041-1049
• /
• 2011

According to the development of society and infrastructure, effective underground facility management is growing more important them ever. In the process various monitoring systems are studied and developed for water works pipe-network. Especially, RTD-1000 system with the based on Pc. Reflector-monitoring device is constructed and steered by several local governments. But, this system have to be improved result from based on PC system structure at the point of resource management, heat, power consumption and size. In this paper, RTD-2000 is proposed are a substitution of improved RTD-1000 with many respect and portable one. This system is designed and implemented with ARM-9 development kit based on WinCE and LCD eliminate TDR(Time Domain Reflector-Meter). Various surveillance programs based on windows are mounted on RTD-1000 are replaced with dedicated embedded application softwares. Simulation and evaluation for performance comparison are performed for the prove of effectiveness of RTD-2000.

• Korean Journal of Construction Engineering and Management
• /
• v.6 no.1 s.23
• /
• pp.125-132
• /
• 2005

Domestic construction firms make every effort to save cost and, contrarily, enhance quality for competitive advantage in the market. Structural work of building construction takes chaise of the total cost and schedule, thus elaborate planning and management of the work help to lead the project into a successful way. Therefore, the idea to save time and cost and enhance constructability securing quality and safety of the work should be developed after analyzing the designed documents and site conditions comprehensively in the initial construction planning phase. Value Engineering (VE) technique is introduced in the substructural work in this paper to save cost creatively and systematically in the design and construction phase. A practical VE model that is applied to the underground building work systematically is proposed to save cost and it applies to the actual project to confirm the effectiveness of the model.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.15 no.2
• /
• pp.81-95
• /
• 2013

When collapse occurs due to explosion near a tunnel, fragmentation zone should be comprehended quickly to recover the function of the tunnel itself. In this study, a method to interpret explosion behavior and predict the fragmentation zone fast. For this purpose, the various 3D-meshes were generated using SolidWorks and explosion analyses were carried out using AUTODYN. The influence of explosion variables such as source location on fragmentation volume were examined by performing sensitivity analyses. Also, a training database for an artificial neural network analysis had been established and the optimal training model was selected, and the predicted results for fragmentation volume and radius were verified. The suggested method had demonstrated that it could be effective for the fast prediction of fragmentation zone.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.4
• /
• pp.561-571
• /
• 2019

Drilling and charging of the blast holes during NATM tunneling works take more than 30% of construction time among the whole tunneling work process. Prediction of ground condition ahead of tunnel face has been studied by several researchers by correlating percussion pressure and drilling speed during tunneling work with the ground condition and/or RMR values. However, most of the previous researches were conducted in the granite rock condition which is the most representative igneous rock in the Korean peninsula. In this study, drilling speeds in igneous rocks were analyzed and compared with those in sedimentary rocks (most dominantly composed of conglomerates, sandstones, and shales) under the similar RMR ranges; it was identified that the drilling speed is pretty much affected by rock types even in a similar RMR range. Under the similar RMR values, the drilling speed was faster in sedimentary rocks compared with that in igneous rock. Moreover, while the drilling speed was not much affected by change of the RMR values in igneous rocks, it became faster in sedimentary rocks as the RMR values got lower.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.6
• /
• pp.423-438
• /
• 2021

The blade of motor grader is used for scattering and leveling the aggregates on the foundation of road construction site. The paper performed a design improvement research of the blade part to enhance the working efficiency of motor graders. The scattering works of aggregates by blade driving were simulated by DEM (discrete element method) of a dynamic code. The four design parameters were selected and a specific leveling scenario for the simulation was determined. The nine blade models were numerically experimented, and the sensitivity of each factors was analyzed. Next, the design factors that influence a blade performance have been selected by ANOVA, and these key design factors were applied to the progressive quadratic response surface method (PQRSM). The optimum set of design factors of the blade was finally proposed.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.12 no.4
• /
• pp.285-294
• /
• 2010

As there are increasing number of tunneling works these days, shotcrete is used as primary supports in order to secure the stability of tunnels. The quality of shotcrete has a direct influence on tunnels, because it is a primary support which secures the stability of completed tunnels as well as the stability of tunnels under excavation. Especially in case that ordinary shotcrete is used under weak rock conditions or at water gushing sections, more shotcrete is needed and rebound ratio increases. As a result, it is hard to keep economic feasibility. In addition to it, in subway construction, there are cases of separated excavation and it may have a bad influence on construction period or quality. Therefore, in this study, we are going to evaluate the early strength of powder type accelerator.

• Tunnel and Underground Space
• /
• v.17 no.3 s.68
• /
• pp.175-185
• /
• 2007

When filling material such as clay is included along the discontinuity, it may cause instability on a slope even if the direction of discontinuity works in a positive way. In the study area, slope sliding occurred at the boundary between a clay filling material and weathered soil because the physical properties differ across the boundary; and this is very similar to the situation where foliation in a rock works as a weak zone during a structural behavior, causing an inter-layer slip. In most analysis, if there exists a clay filling material, a single discontinuity is assumed to perform analysis. In those cases, the discontinuity is modeled as a slip surface within clay. Therefore, the characteristics of the boundary are not considered in the analysis, so that ultimately the physical property of clay usually prevails. The result of evaluating the slope stability affected by clay filling material shows the significant difference in the safety level due to the strength parameter depending on the failure type of the discontinuity by a filling material.