• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.23-30
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• 2011

In this study, Terzaghi's formula was modified to solve problems considering the dilatancy effect of the soil for estimating the earth pressure acting on tunnel. It is performed for the comparison with Terzaghi's formula and modified Terzaghi's formula, tunnel model test result of Kobe University Rock Mechanics Laboratory. From comparison results of the earth pressure acting on tunnel, the earth pressure calculated by the Terzaghi's formula was estimated largest value. The earth pressure measured through the tunnel model test was least value. The difference between the earth pressure derived from Terzaghi's original formula and that derived from the modified formula was caused by the dilation effect, which was caused by the soil volume change. The difference between the earth pressure derived from the modified formula and the earth pressure measured through the tunnel model test, earth pressure results from the energy making failure surface. The results of FEM analysis were almost consistent with the results of mathematical analysis.

• Geotechnical Engineering
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• v.13 no.3
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• pp.101-122
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• 1997

A spiting reinforcement system is composed of a series of radially installed reinforcing spites along the perimeter of the tunnel opening ahead of excavation. The reinforcing spill network is extended into the in-situ soil mass both radially and longitudinally The sailing reinforcement system has been successfully used for the construction of underground openings to reinforce weak rock formations on several occasions. The application of this spiting reinforcement system is currently extended to soft ground tunneling in limited occasions because of lack of reliable analysis and design methods. A method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground is presented. The shape of the potential failure wedge for the case of smile-reinforced shallow tunnel is assumed on the basis of the results of three dimensional finite element analyses. A criterion to differentiate the spill-reinforced shallow tunnel from the smile-reinforced deep tunnel is also formulated, where the tunnel depth, soil type, geometry of the tunnel and reinforcing spites, together with soil arching effects, are considered. To examine the suitability of the proposed method of threedimensional stability analysis in practice, overall stability of the spill-reinforced shallow tunnel at facing is evaluated, and the predicted safety factors are compared with results from twotimensional analyses. Using the proposed method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground, a parametric study is also made to investigate the effects of various design parameters such as tunnel depth, smile length and wadial spill spacing. With slight modifications the analytical method of threeiimensional stability analysis proposed may also be extended for the analysis and design of steel pipe reinforced multi -step grouting technique frequently used as a supplementary reinforcing method in soft ground tunnel construction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.155-164
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• 2016

The changes in earth pressure and ground settlement due to the underground excavation nearby the existing retaining wall according to the separation distance between underground excavation and retaining wall, were studied experimentally. A soil tank having 160 cm in length and 120 cm in height, was manufactured to simulate the underground excavation like tunnel by using 5 separated bottom walls. The variation of earth pressure was measured according to the excavation stages by using 10 separated right walls simulating the retaining wall. The results showed that the earth pressure was changed by the lowering of first bottom wall(B1), however the earth pressure was not changed significantly by the lowering of third bottom wall(B3) since B3 had sufficient separation distance from retaining wall. Lowering of first bottom wall(B1) induced the decrease of earth pressure in lower part of retaining wall, on the contrary, lowering of first bottom wall(B1) induced the increase of earth pressure in middle part of retaining wall proving the arching effect.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.171-182
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• 2007

For minimizing the effect on the focus of civil traffic and environment conditions related to the excavation at the traffic jamming points, an underground station tunnel was planned with 35.5 m in length and bigger area than $200\;m^2$ in sedimentary rock mass. It faced the case that the overburden was just under 13 m. Not based on a pattern design but on the case histories of similar projects and arching effect, the design of large section tunnel under shallow overburden was investigated on three design subjects which are shape effect on the section area, application method of support pressure, and supporting and tunnel safety. According to the mechanical effect from section shape, a basic design and a preliminary design was obtained, and then supporting method of large section was planned by the supporting of NATM and a pipe roof method for subsidence prevention and mechanical stability. From the comparative study between both designs, it was found that the basic design was suitable and acceptable for the steel alignment of tunnel lining, safety and the design parameter restricted by the limit considered as partition of the excavation facilities. Through the analysis result of preliminary design showing the mechanical stability without stress concentration in tunnel arch level, it also was induced that shape effect of the large section area and yielding load obtained from deformation zone in the surrounding rock mass of tunnel have to be considered as major topics for the further development of design technique on the large section tunnel.