• Proceedings of the Korean Geotechical Society Conference
• /
• 2004.03b
• /
• pp.391-398
• /
• 2004

The propagation mechanism of a detonation pressure with fully coupled charge is clarified and the blasting pressure propagated in rock mass is derived from the application of shock wave theory. Probabilistic distribution is obtained by using explosion tests on emulsion and rock property tests on granite in Seoul and then the probabilistic distribution of the blasting pressure is derived from their properties. The probabilistic distributions of explosive properties and rock properties show a normal distribution so that the blasting pressure propagated in rock can be also regarded as a normal distribution. Parametric analysis was performed to pinpoint the most influential parameter that affects the blasting pressure and it was found that the detonation velocity is the most sensitive parameter. Moreover, uncertainty analysis was performed to figure out the effect of each parameter uncertainty on the uncertainty of blasting pressure. Its result showed that uncertainty of natural rock properties constitutes the main portion of blasting pressure uncertainty rather than that of explosive properties.

• Tunnel and Underground Space
• /
• v.3 no.1
• /
• pp.96-107
• /
• 1993

This paper deals with the analysis of rock slope stability using the distinct element method. This method consists in analysis of the interaction of discrete block assemblage delimited by elementary joints, which permits to consider the heterogeneous, anisotropic and discontinuous features of the rock mass. In particular, we were able to show that this method, and especially the BRIG3D software, is an outstanding tool which gives informations of greatest interest in order to analyze the toppling mechanisms. We have confirmed the fundamental role of the rock mass structure with different simulations. In the case of toppling phenomena, the essential parameter is the dip of major discontinuities. It has an influence on the intensity and volume of deformations. The anisotropic and heterogeneous features of the rock mass play also an important role. It is proved by insertion of thick rock bars in the structure or varying rock block sizes in the mass. These models modified considerably the stress distribution and the deformation distribution. Finally, we have analyzed the influence of mechanical parameters such as friction angle and tangential stiffness.

• Journal of the Korean GEO-environmental Society
• /
• v.16 no.2
• /
• pp.33-43
• /
• 2015

This paper investigated the magnitude and distribution of earth pressure on the support system in jointed rock mass by considering different earth pressure coefficients, rock types and joint inclination angles. The study mainly focused on the effect of the earth pressure coefficients on the earth pressure. Based on a physical model test (Son & Park, 2014), extended studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the joints characteristics of rock mass. The results showed that the earth pressure was highly influenced by the earth pressure coefficients as well as the rock type and joint inclination angles. The effects of the earth pressure coefficients increased when the rock suffered more weathering and has no joint slide. The test results were also compared with Peck's earth pressure for soil ground, and clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground. This study indicated the earth pressure coefficients considering the rock types and joint inclination angles are important parameters influencing the magnitude and distribution of earth pressure, which should be considered when designing the support systems in jointed rock mass.

• Tunnel and Underground Space
• /
• v.12 no.1
• /
• pp.19-30
• /
• 2002

Rock joint orientation is one of important geometric attributes that have an influence on the stability of rock structures such as rock slopes and tunnels. Especially, statistical models of the geometric attributes of rock joints can provide a probabilistic approach of rock engineering problems. The result from probabilistic modeling relies on the choice of statistical model. Therefore, it is critical to define a representative statistical model for joint orientation data as well as joint size and intensity and build up a series of modeling procedure including analytical validation. In this paper, we have examined a theoretical methodology for the statistical estimate and hypothesis analysis based upon Fisher distribution and bivariate normal distribution. In addition, we have proposed the algorithms of random number generator which is applied to the simulation of rock joint networks and risk analysis.

• Geomechanics and Engineering
• /
• v.16 no.2
• /
• pp.151-157
• /
• 2018

The constrained conditions of roof and floor for the coal pillar affect the strength of coal pillar very seriously. To analyze the influence of rock mass for the roof and floor on the stability of coal pillar comprehensively, one method based on the mechanical method for the composite rock mass was proposed. In this method, the three rock layers of roof, floor and coal pillar are taken as the bedded composite rock mass. And the influence of rock mass for the roof and floor on the elastic core of coal pillar has been analyzed. This method can obtain not only the derived stress by the cohesive constraining forces for the coal pillar, but also the derived stress for the rock mass of the roof and floor. Moreover, the effect of different mechanical parameters for the roof and floor on the stability of coal pillar have been analyzed systematically. This method can not only analyze the stability of strip coal pillar, but also analyze the stability of other mining pillars whose stress distribution is similar with that of the strip coal pillar.

• Economic and Environmental Geology
• /
• v.32 no.1
• /
• pp.93-100
• /
• 1999

In rock, there are many microsopic structures which influence the mechnical behavior of rock. Many microstructures interact with each other, and furthermore, material constants vary discontinuously within rock, as most rocks are composed of several minerals. Taking into account this feature, it may be possible to contemplate a microstructure of rock as a unit cell by which the rock is constituted periodically. If this idealization is acceptable, the homogenization method can be applied. In this research, various microcracks on rock specimens were observed through a stereoscopic microscope under uniaxial compression. On the other hand, local stress distribution in the periodic-micro structure was calculated by the homogenization method. Then it is shown that there is a possibility to establish a relation between the behavior of microcrack and macroscopic load quantitatively by the linear fracture mechanics.

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 2006.03a
• /
• pp.79-93
• /
• 2006

It is well known that acoustic emission (AE) is indicator of rock fracturing or damage as rock is brought to failure under the uniaxial compressive loads. In this paper, an experimental study on the source location of acoustic emission on the cylindrical specimens of granite under uniaxial compression test was made. The AE source location was made by measuring the six channel AE data. Comparing to this experiment, the numerical method is applied to model the initiation and propagation of fracture by AE using a numerical code, RFPA (Realistic Failure Process Analysis). This code incorporates the mesoscopic heterogeneity in Young's modulus and rock strength characteristic of rock masses. In the numerical models, values of Young's modulus and rock strength are realized according to a Weibull distribution in which the distribution parameters represent the level of heterogeneity of the medium. The results of the simulations show that RFPA can be used not only to produce acoustic emission similar to those measurements in our experiments, but also to predict fracturing patterns under uniaxial loading condition.

• Tunnel and Underground Space
• /
• v.8 no.4
• /
• pp.321-331
• /
• 1998

A reliable analysis of tunnelling is needed to accomplish technically sound design and safe and economical construction. For the reliable analysis, a series of procedures of construction which include excavation and support stages must be considered. In this study, rock-support response behavior is studied and simulated in 2-D and 3-D finite element methods. Through the analysis of rock-support response behavior, the effects of the properties of shotcrete on the load distribution ratio can be quantified. The load distribution ratios for different rock types, different unsupported spans and various lateral earth pressure coefficients can be determined from the results of the 3-D finite element analysis. This load distribution ratios can be applied to a practical tunnel design through understanding of the trend of those various factors affecting the rock-support interaction.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.1
• /
• pp.29-37
• /
• 2016

This study examined the magnitude and distribution of earth pressure on the support system in a jointed rock mass due to the different joint spacing as well as varying the rock type and joint condition (joint shear strength and joint inclination angle). Based on a physical model test and its numerical simulation, a series of numerical parametric analyses were conducted using a discrete element method. The results showed that the magnitude and distribution of earth pressure were strongly affected by the different joint spacing as well as the rock type and joint condition. In addition, the study results were compared with Peck's earth pressure for soil ground, which indicated that the earth pressure in a jointed rock mass could be considerably different from that in soil ground. The study suggests that the joint spacing as well as the rock type and joint condition are important factors affecting the earth pressure in a jointed rock mass and they should be considered when designing a support system in a jointed rock mass.

• Tunnel and Underground Space
• /
• v.19 no.2
• /
• pp.123-131
• /
• 2009

Large scale model tests and numerical analyses were performed in order to investigate the stress distribution on the base of pillar during two-arch tunnel excavation in the regularly jointed rocks. It was observed that the stress was irregularly distributed on pillar and the angle of discontinuities seriously influenced on the stress distribution on the pillar base in the discontinuous rock mass. In the numerical analyses results, It was shown that the stress level of pillar was greatly changed depending on the excavation sequences of two-arch tunnel. It was also observed that stress distributed eccentrically at the pillar as well as at the base of pillar. It is necessary to consider this point for the design of two-arch tunnel.