Due to the constraints in pre site-investigation for tunnel, it is essential to redesign the support structures suitable for rock mass conditions such as rock strength, ground water and discontinuity conditions for safe tunnel construction. For the selection of optimum support, it is very important to carry out the rock mass classification and in-situ measurement in tunnelling. In this paper, in a mountain tunnel designed by NATM in hard rock, the selectable system for optimum support has been studied. The tunnel is situated at Chun-an in Kyungbu highspeed railway line with 2 lanes over a length of 4, 020 m and a diameter of 15 m. The tunnel was constructed by drill & blasting method and long bench cut method, designed five types of standard support patterns according to rock mass conditions. In this tunnel, face mapping based on image processing of tunnel face and rock mass classification by RMR carried out for the quantitative evaluation of the characteristics of rock mass and compared with rock mass classes in design. Also, in-situ measurement of convergence and crown settlement conducted about 30 m interval, assessed the stability of tunnel from the analysis of monitoring data. Through the results of rock mass classification and in-situ measurement in several sections, the design of supports were modified for the safe and economic tunnelling.

Shut-in pressure, reopenting pressure and fracture orientation are very important parameters to be evaluated precisely in in-situ stress measurement by hydraulic fracturing. Graphical methods on pressure-time curves have been conventionally used, even though these are seriously dependent on subjectivity of interpreters. So there have been many demands on new method to objectivity in determining parameters. We have developed integrated hydrofracturing data processing program (HYDFRAC), based on nonlinear regression analysis and can be invoked under the Window graphical user interface. HYDFRAC consiste of three routines, that is shut-in pressure routine, reopening pressure routine, and fracture delineation routine. Each of routines include independent modules according to parameter determination methods. Its application to field tests ensured both objectivity and facility in determining of hydraulic fracturing parameters. Determining shut-in pressures at each pressurization cycles, we adopted the exponential pressure-decay method(EPD method), the bilinear pressure-decay-rate method (PDR method), and the tangent intersection method in order to find the pressurization-cyclic tendency of shut-in pressures. The estimated pressure by PDR method exists in the range of the upper and lower values by EPD method, and lies near to the upper value more than the lower. Being the pressurization cycle increased, the range of upper and lower limits come to be stabilized gradually. By graphical superposition method and bilinear pressure-accumulated volume method, reopening pressures were determined. Vertical and inclined fracture attitudes were determined by applying the directional statistics and sinusoidal curve fitting, respectively. The results of evaluation of hydrofracturing parameters showed that statistical methods could enhance the objectivity better than graphical methods.

Geotechnical Information System (GTIS) for efficient management of three dimensional borehole data has been developed. Geotechnical maps in the vicinity of Bulkwangdong, Seoul station, Itaewon, Han river near Yuido, and Jungrangchon were constructed by Kriging method. In Bulkwangdong and Jungrangchon area where boundary between granite and gneiss is present, gneiss has been more weathered than granite, but in Seoul station and Itaewon area where the boundary is also present, granite has been more weathered than gneiss. It has been inferred that when Seoul granite intruded, the strength of gneiss in Bulkwangdong and Jungrangchon area was lowered by the attitude of foliation plane than in Seoul station and Itaewon area, so the gneiss has been easily fractured and weathered in Bulkwangdong and Jungrangchon area. Geotechnical map in the vicinity of Yuido showed that there is an NW-SE trend weakness zone that might be affected by major faults under Han river and it is expected that the fault zone may be present in construction area of Kyoungbu Highspeed Railway that lies below the Han river like the Subway Line No.5.

Three empirical criteria of rock failure are analyzed in order to understand the meaning of coefficients. Transformation of equations is discussed to apply in the numerical analysis. New failure criterion for intact rocks is proposed in this study, which can be used directly in programming. New equation has the form of parabolic curve($\alpha$=0.5~1.0), and is based on Mohr's shear failure using data from triaxial tests. Its validity will be discussed in the next report.

Cracks have influence on the physical and mechanical and, more importantly, on the engineering properties of the rock. Physical properties including the volumetric deformation coefficient, electrical resistivity, seismic wave velocity, and the mechanical properties such as the elastic constants and strength of rock are affected significantly by the presence of cracks of various sizes. An experimental program was undertaken to investigate the effect of a finite line crack on the diffraction of the plane compressional wave. Horizontal and vertical components of displacement and acceleration curve were obtained using a single-source and multi-receivers system. A theoretical model from numerical analysis implementing the finite element method was compared with the measured data.

In this study, the flow field and the recirculation phenomena are investigated numerically for the model around a tunnel entrance and exit. It turns out that the air entering to the tunnel entrance comes mostly from the upper region of the entrance implying that maintaining the air clear in that region is important for the inside-tunnel ventilation. We also found that the recirculation of the exhaust gas from the exit to the entrance has a maximum effect when the flow velocity at the exit is somewhat lower than that of the entrance.

According to the wide application of diesel equipments in tunneling faces, the air contamination by various toxic gases and carcinogenic diesel particulate matter becomes a serious problem these days. For taking a scientific measures to solve the problem, the way to simulate 3 dimensional flow movement of the working sites is required. In this paper, the newly developed simulation program(3D-FLOW) and the results of a simulation on a model tunneling workings using diesel equipments are introduced. In case of typical model of tunneling face, the gas concentration of human height is about one third of roof concentration and right side half of the tunnel shows better environment than left half. NOx concentration of workings can be estimated about 0.45ppm which is much lower than permissible level(5 ppm).

Safety concern is one of the most important parameters in the design of explosive building demolition. Laboratory experiments were performed to investigate the failure behaviour of concrete columns and the effects of protection materials. Fourteen reinforced columns with two sizes were constructed and the effects of protection materials were tested for two kinds of materials: non woven fabrics and wire net. The results showed that control of gas effects is a key to the control of flying chips. It was recommended to use both wire net and non woven fabrics as primary and secondary protection materials. Such protection method was successfully applied to the explosive demolition of 16 and 17-strory apartment buildings.and the results of a simulation on a model tunneling workings using diesel equipments are introduced. In case of typical model of tunneling face, the gas concentration of human height is about one third of roof concentration and right side half of the tunnel shows better environment than left half. NOx concentration of workings can be estimated about 0.45ppm which is much lower than permissible level(5 ppm).

The types of eletric detonators manufactured in korea include instantaneous, decisecond and millisecond delays but number of delay intervals are only limited from No. 1 to No. 20 respectively. It is not sufficient to control accurately millisecond time with these detonators in large surface blasting. But nonelectric system detonators with an unlimited delay time are recently obtained. In this paper the effect of delay time of nonelectric detonator on the level of vibration in surface blasting was studied. A total of 169 data were recorded in the studied area. Blast point-to-measuring point distances ranged from 25 to 100 meter, where charge weight was 1.26 kg per delay.