• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.245-259
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• 2003

This paper deals with an Umbrealla Arch Reinforcement Method (UARM) in tunnelling. It is known that the mechanism of the reinforcement system is too complex to be simulated in existent finite element (FE) frameworks when considering its complex geometry of pipe arrangements and contribution of each component of the reinforcement to reinforcing effect. In this study a 3-D elastoplastic FE procedure is, therefore, proposed by introducing homogenisation technique, which is used to define mathematically elastic as well as elastoplastic characteristics of a reinforced ground material as a composite. A number of practical suggestions are addressed considering staged constructions of tunnels. For illustrative purposes, a series of parametric studies are undertaken and anisotropic characteristics of the reinforced ground as well as effects of the reinforcement on tunnel convergences are investigated. It is found that the reinforced ground material defined in homogenisation framework has its mechanical characteristics reasonably representing inherent geometrical and quantitative characteristics of each of constituents.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.239-250
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• 2004

Numerical analysis were performed to investigate the stability and internal movement of tunnel located beneath the base of abutment of bridge according to the method of supporting tunnel. Two supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method were used in the centrifuge model tests. The slip form of model lining, specially built to simulate the process of tunnel excavating under the condition of accelerated g-level, was used in the centrifuge model tests. Four centrifuge model tests were performed, changing the supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method and the location of model abutment base of bridge. For internal displacement of tunnel, movements of the crown. The left and the right sides of spring line were measured during the proceeds of excavating tunnel in centrifuge model tests. Test results were compared with numerically estimated values of internal displacement of tunnel by using the commercially available FEM software of PENTAGON-3D. It was found that they were in good agreements and the large diameter of pipe supporting method was more stable than the multi-staged grouting method with steel pipes with respect to the internal movement of tunnel.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.199-209
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• 2002

This research is experimental thesis to prepare the structural safety of the upper bridge for support type on tunnel and the effect of settlement. Unit weight test and uni-axial compression test have been performed to simulate the physical property of foundation on the tunnel. Tunnel model of slip form type for centrifuge model has been developed to performed the tunnel excavation while field stress is activated. And the support type of tunnel such as umbrella arch method and large diameter steel pipe reinforce method has been tested for the centrifuge model. After the analysis of experiment, results show that internal displacement of large diameter steel pipe reinforce method is smaller than that of the umbrella arch method.

• Tunnel and Underground Space
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• v.15 no.2 s.55
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• pp.102-110
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• 2005

○ ○ tunnel that is located at Iksan - Jangsu freeway ○ ○, has collapsed during construction at the valley with shallow depth. Although, the site investigations, such as TSP, drilling exploration and so of indicated the presence of discontinuities in this section. The RMR was upgraded and the construction were carried out because that not only actual rock qualities were relatively good during construction but also the tunnel foe was stabilized. However, the tunnel was collapsed at the same time blasting of full face, and surface and underground water was infiltrated due to the settlement of the upper part of the tunnel face. To restore the collapsed section, 3-d tunnel stability analysis was performed and suitable reinforcement methods were chosen. The cavity of the upper tunnel face was stabilized by means of UAM and ALC injection. And the settlement was restored using L.W grouting method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.367-381
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• 2020

This paper presents the seal material mixing ratio of tunnel umbrella arch reinforcement method. Currently, there is no clear standard for the proper gelation time and curing time of the Seal material in Korea, and the quality control is also difficult because it cannot be verified. In response, the ratio of the mixture of the seal material was composed of four types of indoor experiments, and the amount of gelation time and bleed was checked. In addition, a non-cart penetration test confirmed the curing time and compared the ratio of each combination. Further experiments on W/C 120% identified the effect of mixing speed and time on the seal material. A total of three field experiments were conducted based on indoor experiments, and the size and strength of bulb formation were compared by checking the curing time of the specimen and main injection. Comparisons show that the lower W/C, the stronger the strength, the larger the size of the bulb, and the faster the hardening time appears. Based on the results of the gelation time and curing time, it was deemed that the mixing ratio of W/C 120% is most appropriate when applied to the actual site.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.845-862
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• 2009

Recently, Tunnel in soil has been designed frequently because Mountain Tunnel has been increased rapidly due to straight of horizontal curve and residents' complaints, tunnel portal has been planned at closed to surface for minimization of environmental damage. To excavate tunnel in soil, where displacement and crushing occur in tunnel face and crown because of unstable ground condition, appropriate reinforcement method needed. On this paper, through design and construction of the soil tunnel, consider application of reinforcement method, economical efficiency and stability.

• Journal of the Korean Geosynthetics Society
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• v.15 no.2
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• pp.55-64
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• 2016

The construction of the road NATM tunnel, which undergoes the weathered zone of the mountain, was in process with the reinforcement methods such as the rock bolt, shotcrete depositing, and the multi step grout with large diameter steel pipe. The collapse from the ceiling, and on the ground surface area(sink hole), of which were measured to be 25m from the ground surface($V=12m(W){\times}14m(L){\times}5m(H)=840m^3$), as well as excessive displacements in the tunnel, had occurred. In order to execute the necessary reconstruction work, the causes of the surface collapses were inspected through the field investigation, in-situ tests, and numerical analysis. As a result, several proper solutions were suggested for both internal and external reinforcements for the tunnel. As a result of numerical analysis, the collapsed zone of the tunnel was reinforced up to 0.5D~1.0D laterally by the cement grouting on the ground surface, 0.5D longitudinally by the multi step grout with large diameter steel pipe in tunnel. With further reinforcement implemented by rebars in lining, the forward horizontal boring was executed to the rest of the tunnel to evaluate the overall status of the tunnel face. Appropriate reinforcement methods were provided if needed.

• 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.

• Journal of the Korean GEO-environmental Society
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• v.12 no.5
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• pp.59-63
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• 2011

Ground dynamic parameter such as shear elastic modulus and damping ratio is a very important variable in design of ground-structure with repeated load and dynamic load. Shear elastic modulus and damping ratio on small strain below linear limit strain is constant regardless of strain. Shear elastic modulus as the maximum shear elastic modulus and damping ratio as the minimum damping ratio were considered. As a lot of experiment related to the maximum shear elastic modulus, which is in dynamic deformation characteristics, have been conducted, many factors including voiding ratio, over consolidation ratio(OCR), confining pressure, geology time, PI, and the number of load cycle affect to dynamic soil characteristic. However, the research of ground dynamic characteristic improved with grout is absent such as underground continuous wall construction, deep mixing method, umbrella arch method. In order to investigate the dynamic soil characteristics improved with grout, in this study, resonant column tests were performed with changing water content(20%, 25%, 30%) and injection ratio of grout(5%, 10%, 15%), cure time(7th day, 28th day) As a result, shear elastic modulus and damping ratio, which are ground dynamic parameter, are affected by the injection ratio of milk grout, cure time and water content.

• Journal of the Korean Geotechnical Society
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• v.26 no.2
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• pp.15-22
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• 2010

A series of field pull-out tests were carried out to investigate the behaviour of multi-pressurized soil nails. Ten soil nails were constructed in weathered soil and then, subjected to pull-out loads. The test results showed that the ultimate pull-out resistances of soil nails constructed with high pressure were about 42~142% larger than those obtained from conventional soil nails. The deduced interface shear strength at the ground-grout interface was 71 kPa for conventional soil nails, while higher shear strength of 95~166 kPa was obtained for pressurized nails. The diameter of grouted borehole increased by about 12~27% compared to ordinary soil nails under low pressure. Also, the predicted value by the cavity expansion theory is in good agreement with the measured expanded radius of grout under injection pressure by field pull-out tests.