• Proceedings of the Korean Geotechical Society Conference
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• 1993.03a
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• pp.21-26
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• 1993

Using the well-known FLAC program an analylical parametric study was made to investigate the horizontal and vartical solution zone applied to the mountain water tunnel analysis. In the analyses two different heights(30m, 130m) of overburden soils measured from the center of a tunnel and three different coafflclants of lateral earth pressures(0.25, 0.75, 0.5) were adopted. Also the effected of plliar width between twin tunnels, having two different heighte of overburdon soils as well as different soil conditions, were analyzed.

• Journal of the Speleological Society of Korea
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• no.78
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• pp.33-41
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• 2007

Alpine caves, subterranean passages, are extensively controlled by folds and faults. Caves of the regions demonstrate a significant dip of the passages due to the structural deformations. There are many vertical voids and shaft. Speleo-scapes in the internal caves are various. Calcite formations show the water table alternations which indicate the uplifting and erosional base level droppings during at least the Quaternary. Around cave entrenches there are remnants of the Fluvial terraces on the middle of the hills. These relationship between cave locations and terraces will generate a key to the Plestocene history of the south Korean peninsula. Hence, the Korean karst is turned as "the overburden alpine karst".

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.57-66
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• 2013

In this study, pullout tests were carried out to evaluate pullout characteristics of waste fishing net (WFN), which added into bottom ash for recycling both bottom ash and WFN. Three different mesh size of WFN (WFN20:$20mm{\times}20mm$, WFN30:$30mm{\times}30mm$, WFN40:$40mm{\times}40mm$) and geogrid were added as a reinforcement. Pullout characteristics of waste fishing net were compared with those of the geogrid. Pullout test results showed that pullout strength and stiffness of WFN20 are a little less than those of geogrid. However, the pullout friction angle of WFN20 is similar to that of geogrid due to bearing resistance induced from transverse rib because thickness of WFN20 is greater than geogrid. Pullout test results also indicated that distribution of residual strain along reinforcement after test depends on overburden stress. Residual strain at the tip of reinforcement increased with an increase in overburden stress due to concentration of pullout force on the tip of reinforcement.

• Explosives and Blasting
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• v.23 no.2
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• pp.57-66
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• 2005

A major concern with blasting at surface mines is generation of ground vibration, air blast, flyrock, dust & fume and their impact on nearby structures and environment. A study was conducted at a coal mine in India which produces 10 million tonne of coal and 27 million cubic meter of overburden per annum. Draglines and shovels with dumpers carry out the removal of overburden. Detonation of 100 tonnes of explosives in a blasting round is a common practice of the mine. These large sized blasts often led to complaints from the nearby inhabitants regarding ground vibrations and their affects on their houses. Eighteen dragline blasts were conducted and their impacts on nearby structures were investigated. Extended seismic arrays were used to identify the vibration characteristics within a few tens meters of the blasts and also as modified by the media at distances over 5 km. 10 to 12 seismographs were deployed in an array to gather the time histories of vibrations. A signature blast was conducted to know the fundamental frequency of the particular transmitting media between the blast face and the structures. The faster decay of high frequency components was observed. It was also observed that at distances of 5km, the persistence of vibrations in the structures was substantially increased by more 10 seconds. The proximity of the frequency of the ground vibration to the structure's fundamental frequencies produced the resonance in the structures. On the basis of the fundamental frequency of the structures, the delay interval was optimized, which resulted into lower amplitude and reduced persistence of vibration in the structures.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.259-267
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• 2002

Recently, Umbrella Arch Method(UAM) is commonly used in order to enhance the stability of tunnel itself and stabilize the adjacent surface structure. But quantitative estimation of reinforcement effect is needed because UAM is designed and constructed only on the basis of empirical experience. By using 3-dimensional finite element method, parametric study is performed for elastic modulus of ground and overburden, and reinforcement effect is analyzed quantitatively. From the results, surface settlement decreases about 9%∼27% in soil tunnel, about 4%∼24% in weathered rock tunnel and 4%∼17% in soft rock tunnel when applied with UAM. The prediction equation for final surface settlement is suggested through regression analysis and the equation is expressed as exponential function which has variable Smax, unknown coefficient i and k.

• Advances in Computational Design
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• v.5 no.4
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• pp.417-443
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• 2020

Tunnels have been an integral part of human civilization. Due to complexity in its design and structure, the stability of underground structures under extreme loading conditions has utmost importance. Increased terrorism and geo-political conflicts have forced the engineers and researchers to study the response of underground structures, especially tunnels under blast loading. The present study has been carried out to seek the response of tunnel structures under blast load using the finite element technique. The tunnel has been considered in quartzite rock of northern India. The Mohr-Coulomb constitutive model has been adopted for the elastoplastic behaviour of rock. The rock model surrounding the tunnel has dimensions of 30 m x 30 m x 35 m. Both unlined and lined (concrete) tunnel has been studied. Concrete Damage Plasticity model has been considered for the concrete lining. Four different parameters (i.e., tunnel diameter, liners thickness, overburden depth and mass of explosive) have been varied to observe the behaviour under different condition. To carry out blast analysis, Coupled-Eulerian-Lagrangian (CEL) modelling has been adopted for modelling of TNT (Trinitrotoluene) and enclosed air. JWL (Jones-Wilkins-Lee) model has been considered for TNT explosive modelling. The paper concludes that deformations in lined tunnels follow a logarithmic pattern while in unlined tunnels an exponential pattern has been observed. The stability of the tunnel has increased with an increase in overburden depth in both lined and unlined tunnels. Furthermore, the tunnel lining thickness also has a significant effect on the stability of the tunnel, but in smaller diameter tunnel, the increase in tunnel lining thickness has not much significance. The deformations in the rock tunnel have been decreased with an increase in the diameter of the tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.217-226
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• 2003

This study is focused on the finding out load transfer mechanism in the ground near the tunnel during tunnel excavation in the jointed sandy ground. Laboratory model tests were performed on various cases of the overburden heights above tunnel crown, location, and degree of discontinuity planes. For model tests, a movable plate was installed in the midst of the bottom of sandy ground. This plate, moving downwards, was intended to model the stress relaxation during tunnel excavation. The load transfer was measured at the fixed separated bottom plates adjacent to the movable plate. As the result, the loosening zone and the load-transfer form around the tunnelling site were affected by the overburden height and the characteristics of discontinuous planes. And large loosening zone was developed along the discontinuous planes which were close to the tunnel.

• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.66-74
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• 2007

The analysis of ground subsidence stability was conducted for the residential area located on the limestone corrosion zone. For the investigation of the cavity distribution in limestone region, various geophysical investigations such as electroresistivity tomography, electromagnetic prospecting are carried out. Geotechnical field tests with drilling are also carried out for the evaluation of the ground characteristics. Based upon their results, numerical modeling is performed for the simulation and prediction of the ground subsidence with the conditions of cavity geometry and groundwater level. The main factor to cause the ground subsidence is estimated as the draw down of the groundwater level below soil overburden, which disturbs the mechanical equilibrium of ground and drives washing away the overburden soil through the cavity and solace subsidence. It seemed that it is essential to maintain the groundwater level continuously above the shallow cavity for the prevention of the ground subsidence on the limestone corrosion zone.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.289-296
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• 2014

A simple analytical approach for stability assessment of underground storage caverns against ground uplift of overburden rock above the rock caverns for high pressurized fluid such as compressed air energy storage (CAES) and compressed natural gas (CNG) was developed. In the developed approach, we assumed that failure plane of the overburden is straight upward to ground surface, and factor of safety can be calculated from a limit equilibrium analysis in terms of this cylindrical shape failure model. The frictional resisting force on the failure plane was estimated by Hoek-Brown strength criterion which replaces with Mohr-Coulomb criterion such that both intact rock strength and rock mass conditions can be considered in the current approach. We carried out a parametric sensitivity analysis of strength parameters under various rock mass conditions and demonstrated that the factor of safety againt ground uplift was more sensitive to Mohr-Coulomb strength criterion rather than Hoek-Brown criterion.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1136-1143
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• 2008

The Vertical Drains(Sand Drains, Pack Drain, PBD) is used for Vertical Drains Method in domestic. Each of the drains is selected after it consider a field condition and efficiency of drain. A discharge capacity is very important factor, which to estimate a efficiency. And the smear Zone where disturbance area of in-suit by installation of Vertical Drains is important factor to select a drains. In this study, the complex discharge capacity test was operated for discharge capacity comparison of the Wing Drain and PBD. And a model test was operated to apprehend smear zone of the Wing Drain and PBD. From these tests, it was apprehended an engineering characteristic of vertical drain. The results of the complex discharge capacity test, a discharge capacity fell below $20cm^3/sec$ to $1cm^3/sec$ in more than overburden load $2.5kg/cm^2$. The Wing Drain maintained a over $40cm^3/sec$ in more than overburden load $2.5kg/cm^2$ and minimum discharge capacity $8cm^3/sec$. The results of the smear zone test, a influence bounds of smear zone was more larger in case of the Wing Drain(rectangle) than the PBD. But when a discharge capacity of Wing Drain is considered, it was concluded which smear zone bounds difference was effected in comparison with PBD. I think that it minimized a mandrel section to minimize a smear zone effect range