• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.201-214
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• 2013

Lattice girders are widely used as a substitute for H-steel ribs at domestic tunnels. However, lattice girders have a weak point in terms of the support capacity compare to H-steel ribs because of the lower stiffness and the weakness of the welded parts. To improve the weakness of the lattice girder, reformed lattice girders are developed in Korea by adding one more spider and having flat welded surface. Laboratory tests and field measurements were performed for the original and the reformed lattice girders to evaluate the performance of the reformed lattice girders. According to the laboratory compression test, reformed lattice girders have 16% higher load bearing capacity than that of original lattice girders. Reformed lattice girders are more stable than original lattice girders because reformed lattice girders tend to bend less according to the field measurements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.1
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• pp.55-77
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• 2012

A Modern Rock TBM is a tunnel excavation method combining the conventional tunnelling method with the mechanized tunnelling method. It is a hybrid system that excavates a tunnel with TBM and supports the ground by ring beam, wire mesh, rock bolt, shotcrete, i.e., conventional tunnelling method. In the Modern Rock TBM, a ring beam is similar to a steel rib in NATM in the way that uses H-beam. But using a ring beam is more effective than a steel rib because it is installed in a closed-circle. Therefore, improving the performance of the ring beam is a key factor for achieving tunnel stability. In this respect, this study introduces a pressurized ring beam that might be functioning more effectively by confining convergence during tunnel excavation. In order to verify the effect of the pressurized ring beam, a three-dimensional numerical analysis was conducted. The numerical analysis confirms an increase in the minimum principal stress and reduction in the plastic strain that triggers excessive displacement. The analysis result also indicates a decrease in the relative displacement occurring after installing the ring beam, and expansion in spacing between the ring beams.

• Tunnel and Underground Space
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• v.28 no.4
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• pp.325-342
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• 2018

The ${\bigcirc}{\bigcirc}$ mines have been tried in various ways to perform secondary and tertiary mining in fragile rock properties. For such mining, the panels should be maintained while the mining compartments are divided and paneled. In this study, the mining gate between the panels was maintained by a steel beam and the panel life time was probabilistic evaluated. We used Taylor's formula for panel life time and modified the Pert distribution conceptually. The main input data were determined by the Pert distribution, and Monte Carlo simulation was performed to evaluate the panel life time for the probability distribution. As a result, it was analyzed that the panels could be stand-up time from a minimum of 6.5 days to a maximum of 20.6 days when the panel width was 18 to 25 m. At the confidence level of 90%, the panel life time was analyzed as 8.2-15.6 days. The short panel life time is not possible with the panel mining. Therefore, it was planned to construct a steel beam for panel maintenance. As result, it was analyzed that steel beam for panel maintenance with mining plan of less than 3 years according to mine could maintain panel within 90% confidence level.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.19-25
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• 2005

A tunnel that uses the RMR method or the Q-system is called a 'modem tunnel' because the New Austrian Tunneling Method (NATM) is not employed, even though shotcrete and rock bolts are used as support. It is known that the modem tunnel, which is supported by shotcrete, is basically different from the conventional tunnel, which is supported by steel ribs. In order to preserve the load-carrying capacity of the rock mass, loosening and excessive rock deformations must be minimized. Although it is known that this can be achieved by applying shotcrete in the case of the modem tunnel, this has not been clearly demonstrated. In order to inspect the distinctions between the conventional tunnel and the modern tunnel, their support characteristics and the rock loads of the rock mass classifications are compared. Terzaghi's rock load classification was used as the conventional tunnel's representative rock mass classification. The RMR method and the Q-system were adopted as the modem tunnel's representative rock mass classification. The study's results show that the load-carrying capacity of shotcrete, when used as the main support in the modern tunnel, is greater than the load-capacity of the steel ribs used in the conventional tunnel. Because it has been verified that the rock loads of their rock mass classifications are not different, then, according to the rock mass classifications, the load-carrying capacity of the rock mass of the modern tunnel, which uses shotcrete, is not greater than that of the conventional tunnel.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.269-275
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• 2009

The use of lattice girder is increased at the tunnel site in Korea recently for the substitute of H-steel rib. However, field measurements at the lattice girder are rarely performed at the tunnel site and the method of the measurement is not well established. The use of the vibrating wire strain gauges used for the H-steel rib was proven to be not suitable for the strain measurements of the lattice girder according to the previous research. The credibility of the load cell was investigated using laboratory compression tests for load cells, specially manufactured for the lattice girder far this study, installed at the specimen of the lattice girder. The method of the tunnel instrumentation for the lattice girder using the load cell is given from the interpretation of the compression test results.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.93-102
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• 2008

The use of lattice girder is increased at the tunnel site in Korea because of the several advantages over the traditional H-steel rib. The lattice girder supports the ground with shotcretes, forming a combined support system. Therefore, stress measurements at the lattice girder are necessary to calculated the ground loads. However, field measurements at the lattice girder are rarely performed at the tunnel site. The proper way of stress measurements for the lattice girder is not fully established in Korea. The correction of stress measurements at the shotcretes is often disregarded even though the measured stresses include non-stress related strains. Results of the stress measurements obtained from the lattice girder and non-stress shotcretes are used to improve the credibility of the stress measurements at the primary lining.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.279-290
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• 2004

The differential quadrature method (DQM) for a system of coupled differential equations governing the elastic stability of thin-walled curved members is presented, and is applied to computation of the eigenvalues of out-of-plane buckling of curved beams subjected to uniformly distributed radial loads including a warping contribution. Critical loads with warping, which were found to be significant, are calculated for a single-span wide-flange beam with various end conditions, opening angles, and stiffness parameters. The results are compared with the exact methods available. New results are given for the case of both ends clamped and clamped-simply supported ends without comparison since no data are available The differential quadrature method gives good accuracy and stability compared with previous theoretical results.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.17-25
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• 2012

Shotcrete, rockbolt, and steel rib are installed to support ground after tunnel was excavated. These are important supports for NATM applied tunnels. Recently, lattice girder is increasingly used because it is easily installed. In this study, we developed a new lattice girder by increasing contacting area between spider and rod. To verify the effect of the new lattice girder, the 3-point and 4-point flexural strength tests were carried out for LG-$50{\times}20{\times}30$, LG-$70{\times}20{\times}30$, LG-$95{\times}22{\times}32$. As a result, in case of contacting area, strength of new SGS lattice girder is 17.95% higher than that of original lattice girder. In case of weakness point, strength of new SGS lattice girder is 19.37% higher than that of original lattice girder.

• Magazine of korean Tunnelling and Underground Space Association
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• v.25 no.1
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• pp.36-44
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• 2023

• Tunnel and Underground Space
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• v.20 no.3
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• pp.169-182
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• 2010

H-beam and lattice-girder are the two most commonly used steel supports in domestic tunnels. Reinforced Ribs of Shotcrete(R.R.S.), which is frequently used in Scandinavian countries, is yet to be employed in Korea despite its advantages over H-beam or lattice girder in terms of economy and constructional efficiency. In this study, laboratory tests were conducted to determine the most suitable design of R.R.S in domestic tunnels. Various configuration of steel reinforcements including double layer of steel rebars were tested and compared. Reinforcement with H-beam and lattice girder were also analyzed. Results of this study can be of great use in selecting and designing of tunnel supports when the tunnel is excavated by NATM or Norwegian Method of Tunnelling(NMT).