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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Tunnel and Underground Space
Journal Basic Information
Journal DOI :
Korean Society for Rock Mechanics
Editor in Chief :
Volume & Issues
Volume 6, Issue 4 - Dec 1996
Volume 6, Issue 3 - Sep 1996
Volume 6, Issue 2 - Jun 1996
Volume 6, Issue 1 - Mar 1996
Selecting the target year
A Study on the Automation of Field Instrumentation and the Analysis of MPBX Displacement
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 287~297
Input data play an important role in numerical analyses. However, it is difficult to obtain appropriate data for many reasons. In order to overcome those difficulties, an automatic MPBX(Multi-Position Borehole Extensometer) monitoring system is developed. This system can be applied to the analyses of measured data which include evaluation of the stabiliyt, efficiency of construction and the validity of numerical analyses. At first, the MPBX among field measurement tools is considered in this study. Also, 3-dimension finite element analyses are carried out to verify the influence of geological conditions and excavation sequence on the MPBX displacement. The effect of geological conditons on the displacement can be estimated qualitatively qualitavely from the measured data by plotting displacement vs. depth.
A Study on the Tunnel Stability using Grouting Technique
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 298~305
Grouting technique is frequently used where a tunnel structure is passing through the shallow overburden area or where the thickness of hard rock above the tunnel is rather thin. However, engineering background on design process of the grout reinforcement does not seem to be fully understood until now. Mechanics of composite material is, therefore, introduced in this study to investigate the orthotropic material properties of the composites containing soil(or rock) and grouting material. These orthotropic material properties can be used to represent the reinfocement effects quantitatively. The model developed in this study is next applied to a typical tunnel structure and the grouting effect is analyzed numerically. The idea used in this study can be expanded to a situation where a pipe roofing or a forepoling technique is adopted and a simplified design procedure, similar to the model model introduced in this study, can be developed.
Application of Time Domain Reflectometry to the Monitoring or Rock Mass Deformation with Coaxial Cable
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 306~315
This paper presents an application of the TDR(Time Domain Reflectometry) to the monitoring of the deformation of rock mass with grouted coaxial cables through laboratory tests. The grouted cable can easily deform together with the rock mass movements, and the deformed cable loses its original capacitance and the reflected waveform produced along the deformed cable consequently represents a change of voltage pulse. Therefore, it is possible to monitor the deformation of rock mass by measuring the changes in these reflection signatures. Shear test of the cemented mortar containing a specimen of coaxial cable showed that the shear deformation correlated linearly with the reflection coefficient, so the TDR was effective to monitor the displacement of the rock mass. Bending test were carried out in order to determine the influence of the crooked cables on the monitoring of rock mass movements. Controlled cirmping and shearing test upon a cable of 50 m long, 12.7 mm diameter showed not only the fact that the reflection amplitudes decreased as the cable length increased but also the proper crimping depth, width and interval between two adjacent crimps. Two coaxial cables-one 100 m long and other 175m long-were installed and grouted into the separate boreholes drilled in a sedimentary formation. The behavior of the cable was monitored with metallic TDR cable tester to measure rock mass deformation based on the interpretative techniques developed through laboratory tests.
Estimation of Engineering Properties of Rock by Accelerated Neural Network
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 316~325
A new accelerated neural network adopting modified sigmoid function was developed and applied to estimate engineering properties of rock from insufficient geological data. Developed network was tested on the well-known XOR and character recognition problems to verify the validity of the algorithms. Both learning speed and recognition rate were improved. Test learn on the Lee and Sterling's problems showed that learning time was reduced from tens of hours to a few minutes, while the output pattern was almost the same as other studies. Application to the various case studies showed exact coincidence with original data or measured results.
Development of finite element analysis model for multi-step excavation problem
Lee, Youn-Kyou ;
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 326~334
In underground construction the multi-step excavation sequence is commonly adopted for the convenience of the underground work. A numerical simulation method which is capable of analyzing the effects of excavation sequence on the stability of the opening is greatly needed. In this study a two dimensional finite element code was developed based on the effective numerical algorithm for the multistep excavation. The practical applicability of the model was verified for the simplified excavation sequences.
A study on the relationship between the thermal properties of rock and the enviroment in underground spaces
Lee, Chang-Woo ;
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 335~341
This fundamental study analyzes the relationship between rock thermal properties and psychrometric properties in underground space and has a ultimate goal to develope technologies for predicting major environmental variables. The study is divided into 2 subjects (1) developement of a basic model for predicting temperature and humidity, (2) analysis of the validity of the model through application to a local underground storage space for military supplies. The basic model is built for the network of tunnel-shaped underground spaces. The model takes into account rock thermal properties and changes in moisture content in the air due to condensation/evaporation on the rock surface. Using lumped-parameter analytical method, heat flux from or to the surrounding rock is calculated and then the psychrometric properties(air quantity, pressure, temperature, humidity) are estimated through network simulation. The model can be utilized regardless of the tunnel type. The study site is a local storage space built in rock, mainly granite gneiss and quartz-porphyry. It is a U-shaped tunnel, 593.5m long and 6x6.5m wide. Relative humidity inside has to be strictly controlled under 55% to avoid erosion of a certain types of supplies stored in 6 chambers with the capacity of 300~1.000 ton. The thermal conductivity varies between 2.734 and 2.779W/m
and the thermal diffusivity is in the range of 1.119 and
the specific heat between 910 and
. Relative errors of the predicted values of dry/wet temperature and relative humidity are 0.8~3.0%, 0~7.5% and 0~7.0%, respectively. Apparent errors associated with the rock surface temperature seems to be partly due to the intrinsic limitations in the infrared thermometer used in this study.
Monitoring Rock Physical Property Changes due to Excavations Using Horizontal Crosshole Georadar Tomography
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 342~347
The changes of electromagnetic wave velocity in rock were monitored to investigate rock behaviors due to the drill & blasting excavations through georadar tomography during the construction of the underground rock laboratory (5 m wide, 6 m high, and 140 m long) at Mabuk-Ri, Goosung-Myun, Yongin-Si, Kyunggi-Do. Two horizontal boreholes spaced 1.4 m apart were drilled parallel to the test tunnel before excavating it, high-resolution crosshole georadar tomography with about 500 MHz electromagnetic waves was performed at pre-excavation phase (May, 1996) and post-excavation phase (August, 1996). The data were acquired with the combination of 34 sources and 44 receivers with space of 0.3 m. Only 11 continuous receivers were selectively utilized with one fixed source. Sampling interval was 0.4 ns and each trace has 512 samples. The first arrival of each trace was picked manually with a picking software. The total number of rays used in inversion amounted to 34x11 and the size of pixel was determined to be 0.3 m. As an inversion technique, SIRT(Simultaneous Iterative Reconstruction Technique) was applied in this study. The velocity of electromagnetic waves at post-excavation phase decreased as large as 15% in comparison with that at pre-excavation phase, which may be attributed to the creation of micro-cracks in rock due to excavations and saturation with groundwater. Small amount of borehole deviation made a critical effect in radar tomography. Totally different tomograms were created after borehole deviation corrections.
암반 불연속면의 정량적 기재에 관한 고찰
Tunnel and Underground Space, volume 6, issue 4, 1996, Pages 348~364