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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korean Tunnelling and Underground Space Association
Journal Basic Information
Journal DOI :
Korean Tunnelling and Underground Space Association (KTA)
Editor in Chief :
Volume & Issues
Volume 12, Issue 6 - Nov 2010
Volume 12, Issue 5 - Sep 2010
Volume 12, Issue 4 - Jul 2010
Volume 12, Issue 3 - May 2010
Volume 12, Issue 2 - Mar 2010
Volume 12, Issue 1 - Jan 2010
Selecting the target year
Quantitative assessment of spalling depth and width using statistical inference theory in underground openings
Bang, Joon-Ho ; Lee, In-Mo ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 1~14
Until now, the evaluation method of spalling depth using Martin et al. (1999)'s linear regression relations has long been known applicable. However, it is not likely that the proposed equation is applicable to the openings other than circular type and mostly overpredict the spalling depth in comparison with actual spalling cases. Moreover, the evaluation method to estimate the spalling width has not been presented yet; it is essential to evaluate the spalling width in addition to the spalling depth, because the shape of the spalled region influences the choice of suitable rock reinforcement. In this study, linear regression equations, in which normalized spalling depth (
) and normalized spalling width (
) are functions of three spalling evaluation indices,
, are established based on in-situ spalling observations and CWFS simulation results. Confidence intervals of 95% using the statistical inference theory are used in verifying the reliability of linear regression equations. Spalling depth (
) and spalling width (
) predicted from the proposed linear regression relations, which take three spalling evaluation indices into account, showed reasonable match with in-situ observations by adopting weighting factors considering the degree of variance of linear regression relations.
Assessment of spalling occurrence using fuzzy probability theory and damage index in underground openings
Bang, Joon-Ho ; Lee, Kang-Hyun ; Lee, In-Mo ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 15~29
Spalling is a kind of instability phenomenon of surrounding rock around underground openings subjected to high in-situ stress according to the development of extension fractures. Three kinds of spalling criteria have been presented so far; however, all spalling criteria have the range of values so that the fuzziness and vagueness of spalling criterion cannot be avoided. In this study, a new fuzzy probability model is proposed to predict the probability of spalling in a systematic way by using fuzzy probability theory. Many of the underground opening projects worldwide are evaluated with the proposed method. Prediction results expressed as the spalling probability agree well with the in-situ observations. In particular, a new fuzzy probability model considering all three evaluation indices of spalling by adopting weighting factors based on relative reliability among three evaluation indices is able to resolve erroneous prediction of spalling by choosing only one prediction method. Moreover, the more reasonable value of spalling probability could have been obtained by adopting the modified damage index to the newly proposed fuzzy probability model.
Modeling of rock dilation and spalling in an underground opening at depth
Cho, Nam-Kak ; Lee, Yong-Joo ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 31~41
This paper presents both numerical and physical modeling approaches for the dilation and spalling of rock recognized as typical process of rock around an underground opening at depth. For physical approach, laboratory testing of rectangular beams using a synthetic rock was used to investigate the onset of dilation and spalling. The beams are axially compressed and subjected to 4-point bending to provide non-uniform compressive stresses which are similar to the maximum tangential stress distribution around circular openings. Discrete element numerical analyses using commercial code
(Particle Flow Code) were performed to evaluate the stress path at various locations in the beams. The findings from these approaches suggest that the onset of dilation in laboratory tests appears to be a good indicator for assessing the stress magnitudes required to initiate spalling.
A study on an interval of tunnel cross passage considering inclination and internal airflow
Rie, Dong-Ho ; Kim, Ha-Young ; Yoo, Ji-Oh ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 43~49
The escape connecting gallery in a tunnel on a road is one of emergency equipment to ensure safety for passer in the tunnel against the tunnel fire. Government stipulate over 500m tunnel has the cross passage at intervals of less then 250 m. However, this lump estimated interval is generated the concerns of exaggeration and under construction because peculiarity of the tunnel ex. The velocity of the tunnel airflow, an incline, degree of a fire, and innering area are not considered. The study indicate the way to estimate of the cross passage considered an incline and the velocity of the tunnel airflow for efficient application of cross passage on the tunnel design. As a result, in 0.0 m/s and 1.0 m/s of the velocity of the tunnel airflow case, the movement of smoke is influenced by the incline however, in 20 m/s case, it isn't influenced by incline much. According to the velocity of tunnel airflow and the incline, optimum interval of cross passage is not corresponded. Therefore established lump estimate that has 250 m intervals would be changed to estimate of optimum interval of cross passage that considered about the properties of tunnel, the velocity of the tunnel airflow, incline, degree of a fire and innering area of the tunnel.
Study on flexural toughness and flexural tensile strength of fiber reinforced concrete by mixture ratio of different fibers
Park, Hong-Yong ; Ryu, Jong-Hyun ; Jo, Yong-Bum ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 51~60
Recently, a new type of polyolefin fiber having a good mechanical properties is being developed, and it is necessary to examine a possibility for the new fiber together to be used as a reinforcing fiber with other types of fiber or by itself. The objective of this study is to find flexural toughness and tensile strength of concrete reinforced with steel and polyolefin fibers. Four point beam tests were performed with 324 specimens following two standard tests methods: KS F 2566 and ASTM C 1399-02. From the test results, the effects of volume fraction of fibers, and aspect ratio of steel fiber on the toughness and tensile strength were investigated, and the optimal ratio of steel fiber to polyolefin fiber was suggested.
Study on evaluation of bond strength of cone-shaped button cablebolt
Choi, Jung-In ; Kim, Won-Keun ; Lee, Dong-Seok ; Lee, Seok-Won ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 61~73
The cablebolt which secures a workability and stability has been used in foreign countries as one of supporting materials with rebar rockbolt especially in construction of large underground structures. However, only the rebar rockbolt has been applied up to now to all the constructions of underground structures in Korea due to an absence of recognition of cablebolt and large underground structure projects. Consequently, the research for a performance evaluation and verification of cablebolt is very limited and only the proto-type field tests have been conducted. In this study, the cone-shaped button cablebolt is developed by modifying an existing button cablebolt. To evaluate a performance and applicability of cone-shaped button cablebolt, the laboratory pull tests are conducted and bond capacity is analyzed under a various conditions. The rebar rockbolt, plane cablebolt, and bulb cablebolt which has a similar mechanical behavior with cone-shaped button cablebolt, are also tested and their bond capacities are evaluated and compared with cone-shaped button cablebolt under the same condition. The results show that the bond capacity is in the order of (cone-shaped button cablebolt
bulb cablebolt) > rockbolt > plane cablebolt. It is found that the bond capacity of cone-shaped button cablebolt developed in this study is at least equivalent with an existing high performance cablebolt developed in foreign countries, therefore the cone-shaped button cablebolt could be used as one of supporting materials for underground structures in construction field.
Evaluation of engineering characteristics and field applicability of inorganic thixotropic-grout for backfilling of shield TBM tail voids
Kim, Dae-Hyeon ; Jung, Du-Hwoe ; Jeong, Gyeong-Hwan ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 75~85
The focus of this study is to evaluate the field applicability of the newly developed inorganic thixotropic-grout in various ways. In order to do this, the volume stability and the permeability of the inorganic thixotropic-grout have been measured and compared to the existing silica type grouts. In addition, the filling capability of the grout into the tail void has been evaluated through both an experiment with a miniature tail-void filling equipment and a test filling at the shield TBM construction site. The volume loss of the inorganic thixotropic-grout after a 14 day-curing under the atmosphere condition was appeared to be minimal. The excellent waterproofing ability of the inorganic thixotropic-grout was confirmed through a permeability test. The toxicity of the inorganic thixotropic-grout has been evaluated through a toxicity test of aquatic fishes (KS M 0111) and the pH value of the liquid eluviated from inorganic thixotropic-grout was measured as an average of 8.0 and a fatality rate of goldfish after 96 hours was 10% or so. The existence of harmful heavy metals in the liquid eluviated from the inorganic thixotropic-grout has been also examined through an atomic absorption spectroscopy (AAS) test. Any of harmful heavy metals were not detected and the detected level of
and Cd was far below the standard. Based on both an experiment with a miniature tail-void filling equipment and a test filling at the shield TBM construction site, the filling ability of inorganic thixotropic-grout into the tail void was proved to be excellent.
Determination of K values from tunnel model tests in sandy ground
Lee, Yong-Joo ; Ryu, Chang-Youl ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 87~94
This study mainly focused on the subsurface settlement due to shallow and deep tunneling in sandy ground. In order to figure out theoretical deformation patterns in association with the ground loss during the progress of tunneling, laboratory model tests using aluminum rods and finite element analyses using the CRISP program were carried out. As a result of comparison between the model test and the finite element analysis, the similar deformation patterns were found. In addition, it was identified that the most K values obtained from both the FEA and the model tests were distributed between Dyer et al. (1996) and Moh et al. (1996) of the field observation data. Based on the model test data, the linear equation of K for the sandy soil could be obtained.
A study of mechanism and numerical analysis of PNT method
Chae, Sung-Eun ; Seo, Dong-Hyun ; Im, Gi-Woon ; Chun, Sung-Yul ; Kim, Sang-Hwan ;
Journal of Korean Tunnelling and Underground Space Association, volume 12, issue 1, 2010, Pages 95~103
In this paper, a new soft ground tunneling technique termed the PNT method(Pre-Nailed Tunneling Method) is studied. Mechanism of the method is investigated in terms of theoretical and numerical approaches. The pre-nailing effects are validated by performing two dimensional numerical analyses. It is identified that the method is successful in soft grounds, and greatly efficient in reducing the ground deformation by nailing the ground. To develop the design guidelines of the method, numerical parametric analyses on the installation range and angle were also carried out.