Hyung-Sik Yang

An Assessment of Rock Pillar Behavior in Very Near Parallel Tunnel

Focusing on the load tunnel, this study assessed the behavior of rock pillars with less than 0.5D of the minimized distance between the two horizontal tunnels by using a three dimensional numerical analysis. Based on a parameter affecting the behavior of rock pillars, this study evaluated different safety factors according to pillar width, depth and rock conditions. It turned out that as the pillar width increases, the current curve of safety factors in accordance with depth and rock conditions shows more of the nonlinear behavior. Judging from the minimum safety factor, the study suggested a design chart, working on the minimized distance between the two horizontal tunnels.

Groundwater flow characterization in the vicinity of the underground caverns in fractured rock masses by numerical modeling

Groundwater inflow into the caverns constructed in fractured bedrock was simulated by numerical modeling: NAP-SAC (DFN, discrete fracture network model) and NAMMU (CPM, continuous porous media model), which is a finite-element software package for groundwater flow in 3D fractured media developed by AEA Technology, UK. The input parameters for modeling are based on surface fracture survey, core logging and single hole hydraulic test data. In order to predict the groundwater inflow as accurately as possible, the anisotropic hydraulic conductivity was considered. The anisotropic hydraulic conductivities were calculated from the fracture network properties and the in-situ fracture data. With a minor adjustment during model calibration, the numerical modeling is able to reasonably reproduce groundwater inflows into the cavern as well as the travel lengths and the surface arrival times through the flow paths.

Utilization of Cement Kiln Dust in Industry Cement Bricks

ABSTRACT Solid waste management is one of the major environmental concerns around the world. Cement kiln dust (CKD), also known as by-pass dust, is a by-product of cement manufacturing. The environmental concerns related to Portland cement production, specifically emissions to the atmosphere and the disposals of CKD are becoming progressively significant. CKD is fine-grained, particulate material chiefly composed of oxidized, anhydrous, micron-sized particles collected from electrostatic precipitators during the high temperature production of clinker. Some of the cement kiln dust that is generated is reused in the cement plant and some is landfilled. Recently, there have been trends of utilizing it for soil stabilization and treatment of sewage. The beneficial uses of CKD include serving as filler material in highway construction and maintenance and as a component of cement mortar/concrete. Also, attempts have been made to use it to make cement bricks for use in industrial construction, and this paper provides a review of the results and issues associated with this use. The paper reports the results of tests conducted by the authors to investigate the properties of cement-CKD combinations and the extent to which such combination are used to manufacture cement bricks. All of the properties of the bricks that were tested found to be satisfactory according to the Egyptian Code, e.g., compressive strength was satisfactory in the range of 59.9 to 213.3 kg/cm2, water absorption was directly increased from 3.8 to 5.9% and the density ranged between 2.1 and 2.2 gm/cm3 with different percentage of cement kiln dust from 0 to 40%. In comparing the different types of bricks and their costs, this study found that cement bricks that include CKD as a component had acceptable properties and cost far less than other types of bricks. In addition, the use of CKD in the bricks precludes the need to dispose large quantities of this material in landfill.

Performance of pillar design in underground stone mines that include discontinuities

This paper describes a pillar design methodology that was developed from a study of pillar performance in operating stone mines. A number of methodologies have been developed to calculate full-scale mine pillar strengths based on laboratory scale strength obtained from specimens. Data were collected on rock mass quality, pillar conditions, mining dimensions and intact rock strength. Results showed that current mining practices have resulted in generally stable pillar layouts, without recent cases of extensive pillar collapses; however, failure of the pillars was found to be related to spalling of hard brittle rock, shearing along pre-existing angular discontinuities or progressive extrusion of soft infill material on bedding planes. A numerical model (FLAC3D) for the entire rock mass has been developed in order to analyze the stability of the entire underground opening. A preliminary monitoring phase has been realized, aimed at controlling abandoned rock structure movement at the most significant discontinuities. Some measurements of the vertical stress in the pillars and in the walls have also been performed and were used for model calibration. Once the model has been calibrated, analysis of the actual stress and deformation conditions can then be evaluated, the stability condition of the entire structure can be computed and a forecast analysis of what intervention could be realized to guarantee underground public access can be performed. The developed strength equation can be used to design stable pillar layouts, keeping in mind that the safety factor is greater than 1.5 and the width:height ratio of the pillars is between 0.6 and 0.8. It is concluded that, by applying the developed equation and selecting appropriate input parameters, it should then be possible to calculate the factor of safety.

Stability Analysis of Rock Pillar in the Diverging Area of Road Tunnel

Abstract In this study, the behavior of rock pillar in the diverging area of road tunnel was assessed by using a three dimensional numerical analysis. Based on parameters affecting the behavior of rock pillar, different safety factors according to pillar width, depth and rock conditions were evaluated. It turned out that as the pillar width increases, the change curve of safety factors in accordance with depth and rock conditions shows more of the nonlinear behavior. By the assessment of the minimum safety factor, a safety factor chart on the behavior of rock pillar in the diverging area of road tunnel was suggested. Key words Tunnel diverging area, Rock pillar, Safety factor chart초 록 본 연구에서는 도로터널 분기부 암반 필라의 거동을 3차원 수치해석 방법으로 검토하였다 . 암반 필라의 거동에 영향을 미치는 매개변수로 암반 필라의 이격거리 , 토피고, 암반등급 변화에 따른 안전율을 평가하였다 . 필라의 이격거리가 증가할수록 토피고와 암반등급에 따른 안전율 변화 곡선은 비선형 거동을 보였으며 , 도로터널 분기부에서 암반 필라의 거동 특성을 최소 안전율을 기준으로 안전율 도표로서 제안하였다 .핵심어 터널 분기부, 암반 필라, 안전율 도표 1. 서 론 최근 국토교통부에서 검토하고 있는 대심도 지하도로망 구축사업인 서울시의 U-Smartway 사업이 발표되면서, 도심지의 대심도 지하공간을 활용한 대규모 터널 건설에 대한 관심이 증대되고 있다. 포화상태에 다다르고 있는 대도시의 천층 및 중층 지하공간 이외에 대심도의 지하공간을 활용함으로써 사업비의 상당 부분을 차지하는 용지보상비를 최소화하겠다는 개념이다 .도심지 상습 지․정체 해소를 위한 지하도로 노선 계획 시 교통량 분산을 위하여 유출 (분류, diverging) 및 유입(합류, merging)부를 터널 내에 설치하여 인터체인지(IC) 역할을 담당하게 하고 있다. 해외에서는 선진국을 중심으로 대도시의 교통체증을 해소함과 동시에 지상 녹지공간을 확보하기 위해 다양한 도심지 지하도로의 건설을 활발히 진행하고 있다 . 대표적인 사례로 미국 보스턴의 Big Dig 프로젝트, 프랑스 파리의 A86, 스페인 마드리드의 M30 등을 들 수 있다(장수호 등, 2009).터널 내 분기부의 지반 및 터널 상호간의 거동은 단선터널과는 상이하며, 병설터널의 안정성과 직접적인 관련이 있는 터널 중심간격 (C.T.C)이 무엇보다 중요한 검토요건인 만큼 필라(pillar)의 안정성 검토에 대한 연구의 필요성이 대두되고 있다 . 터널 내 분기부의 설계 시 필라의 폭은 분류 및 합류되는 각도와 상관성을 가지며, 이에 따라 도로의 선형 , 공사비, 주행성, 시공성 등에 커다란 영향을 미치고 있다 .본 연구에서는 도로터널 분기부를 대상으로 암반 필라의 거동에 대한 연구를 수행하였다 .

An Analysis of Stability on Rock Slope by Changing Water Level

A quarry with 105 m height large cut slope was analyzed. Beside RMR and SMR methods, FLAC2D were adopted to analyze slope stability. As a result, slope of andesite had a possibility of failure. Wet slope showed low safety factor. Soil nailing was recommended to solve it. Since safety factor of slope largely depend on underground level, investigation for it seemed necessary.

Characterization of Complete Radial Displacement of Tunnel Using a Horizontal Inclinometer

ABSTRACT Measuring the displacement of a tunnel is prerequisite in evaluating the stability, which also makes it possible to understand the geological condition ahead of the tunnel face. In fact, the displacement of a tunnel occurs before, during and after the excavation. Generally, the measurement is undertaken only behind the face, which allows a certain amount of displacement, the so-called ‘pre-measurement-displacement’. The measured displacement is only a part of the total radial displacement. Therefore, the pre-measurement-displacement should be determined in order to characterize the complete radial displacement of the tunnel. A horizontal inclinometer was used to measure the degree of settlement ahead of the tunnel face at the study site, which was relatively easy to install from the other portal of the tunnel. The results from the measurement of the settlement ahead of the face enabled a complete radial displacement curve to be constructed using a nonlinear regression analysis. It was found that the crown displacement of the tunnel at the study site started to occur at a distance equivalent to three times of the tunnel diameter ahead of the tunnel face. Taking into consideration the complete displacement characteristics, the possible settlement could be about 40% of the total displacement of the tunnel. Based on the complete radial displacement, it was possible to determine the appropriate support characteristics and the time of installation.

Robust Design of Pillar Arrangement for Safe Room-and-Pillar Mining Method

The arrangement of pillars is a key design parameter in the execution of the room-and-pillar mining method. The objective of this study is to provide safe, reliable and a robust design for pillar arrangements for economic and efficient mineral recovery. Four design parameters have been considered in this study, including the degree of pillar superposition, pillar stiffness, and the pillar width; and the distance between crown pillars. The numerical analysis shows that the stability of mines is significantly affected by the discordance of the pillar arrangement between adjacent levels along with four design factors (e.g. pillar stiffness, overlap ratio, and width and thickness of the crown pillar). The pillar stiffness had the highest average affecting ratio (e.g. 71.8%), while the average affecting ratios of the pillar width, thickness of the crown pillar, and pillar overlap ratio were 18.9%, 5.77%, and 3.6%, respectively. The stiffness had the greatest influence on the safety factor when the strength/stress ratio was used to calculate the safety factor.

Assessment for the sympathetic detonation characteristics of underwater shaped charge

Abstract Understanding the sympathetic detonation of explosives is important from the standpoint of storage requirements and handling. Water has higher density than air, and hence, a shockwave propagates faster through water than through air. The main objective of this study is to measure the critical distance for the assessment of shock sensitivity of a shaped underwater charge. Explosive gap tests were performed to analyze the underwater sympathetic detonation of a shaped charge and the AUTODYN code was utilized to validate the shock sensitivity results for RDX explosives. To simulate sympathetic detonation, the Lee–Tarver reaction rate model of RDX was adopted, which was implemented in the AUTODYN material library. The shaped charge water gap model was simulated by the AUTODYN Euler mesh. The critical gap distance of the underwater shaped charge was quantitatively investigated.

Experiment and Evaluation of Mist Diffusion from Water Tube for Blasting Dust Control in accordance with the Explosives Position

A water tube with detonating cord was devised to control the blast dust. Water diffusion experiments with different detonating cord positions were conducted during the series of experiments to optimize the design parameters of the tube. Images from high speed camera were analyzed to evaluate the results. AUTODYN program was adopted to simulate the diffusion process of water and compared with the images. Diffusion of water shows cross flow in case of external charge while the internal case shows radial flow. A bubble ring was formed during the numerical analysis of internal charge case as occurred in underwater blast. An additional bubble ring was formed by the reflection pressure from the ground. And the Weber number was determined as sufficient for spray atomization performance of the water tube.