• Title/Summary/Keyword: stress dip

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Experimental research on the evolution characteristics of displacement and stress in the formation of reverse faults

  • Chen, Shao J.;Xia, Zhi G.;Yin, Da W.;Du, Zhao W.
    • Geomechanics and Engineering
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    • v.23 no.2
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    • pp.127-137
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    • 2020
  • To study the reverse fault formation process and the stress evolution feature, a simulation test system of reverse fault formation is developed based on the analysis of reverse fault formation mechanism. The system mainly consists of simulation laboratory module, operation console and horizontal loading control system, and data monitoring system. It can represent the fault formation process, induce fault crack initiation and simulate faults of different throws. Simulation tests on reverse fault formation process are conducted by using the simulation test system: horizontal loading is added to one side of the model. the bottom rock layer cracks under the effect of the induction device. The crack dip angle is about 29°. A reverse fault is formed with the expansion of the crack dip angle towards the upper right along the fracture surface and the slippage of the hanging wall over the foot wall. Its formation process unfolds five stages: compressive deformation of rock, local crack initiation, reverse fault penetration, slippage of the hanging wall over the foot wall and compaction of fault plane. There is residual structural stress inside rock after fault formation. The study methods and results have guiding and referential significance for further study on reverse fault formation mechanism and rock stress evolution.

A numerical analysis study on the effects of rock mass anisotropy on tunnel excavation (암반의 이방성이 터널 굴착에 미치는 영향에 대한 수치해석적 연구)

  • Ji-Seok Yun;Sang-Hyeok Shin;Han-Eol Kim;Han-Kyu Yoo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.26 no.4
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    • pp.327-344
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    • 2024
  • In general tunnel design and analysis, rock masses are often assumed to be isotropic. Under isotropic conditions, material properties are uniform in all directions, leading to a higher evaluation of tunnel stability. However, actual rock masses exhibit anisotropic characteristics due to discontinuities such as joints, bedding planes, and faults, which cause material properties to vary with direction. This anisotropy significantly affects the stress distribution during tunnel excavation, leading to non-uniform deformation and increased risk of damage. Therefore, thorough pre-analysis is essential. This study analyzes the displacement and stress changes occurring during tunnel excavation based on rock anisotropy. A three-dimensional numerical analysis was performed, selecting anisotropy index and dip angles as variables. The results showed that as the anisotropy index increased, the displacement in the tunnel increased, and stress concentration became more pronounced. The maximum displacement and shear stress were observed where the dip planes met the tunnel.

A Study on the Characteristics of Stress Transfer around Cavern due to Cavern size and Rock Joint Orientation by Laboratory Model Test (모형실험을 통한 공동규모와 절리 방향성에 따른 공동배면의 응력전이 특성에 대한 연구)

  • Kim, Sang-Hwan;Shin, Beom-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.03a
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    • pp.595-606
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    • 2009
  • This paper presents the characteristics of stress transfer around carven due to cavern size and rock joint properties by laboratory model test. In order to perform this study, eight different scaled model tests were carried out according to excavation stage. The limited numerical analysis were also performed to verify the model test results. The amount of stress transfer around the cavern is increased and then decreased by longitudinal arching effect according to tunnel excavation. It is founded that the stress developed around the cavern during excavation is increased when the cavern size and joint orientation are increased. It is also investigated that shear behaviour (such as stress, deformation) developed around cavern is considerably depended on the characteristic of fill material, dip and direction of joints. It is suggested that the behaviour will be verified throughout the 3D numerical prediction.

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A Composite Fault-plane Solution of Microearthquakes in the Yangsan Fault Area during 1996 (1996년 양산단층 일대의 미소지진을 이용한 복합단층면해)

  • Lee, Gi Hwa;Jeong, Tae Ung
    • Journal of the Korean Geophysical Society
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    • v.2 no.4
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    • pp.235-240
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    • 1999
  • From the seismic network data of the Korea Institute of Geology, Mining & Materials during 1995-1996, we derived a composite fault-plane solution of the microearthquakes occurred in the Yangsan fault area. The composite fault-plane solution of nine events shows the orientation of fault 15 ± 3°in strike, 60 ± 8°in dip and 140°in rake or 128 ± 3°in strike, 56 ± 8°in dip and 37°in rake. The compressional axis of the stress field trends ENE to WSW, and this field suggests strike-slip motion with thrust component. The result is consistent with the 1996 Yeong-weol event and the stress field in and around the Korean Peninsula, previously reported.

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Fault Plane Solutions for the June 26, 1997 Kyong-ju Earthquake (1997년 6월 26일 경주지진의 단층면해 비교해석)

  • Chung, Tae-Woong;Kim, Woo-Han
    • Journal of the Korean Geophysical Society
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    • v.3 no.4
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    • pp.245-250
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    • 2000
  • By using amplitude ratios (SV/P, SH/P, SV/SH) and P and S wave polarities, we obtained fault plane solutions of the June 26, 1997 Kyong-ju earthquake. The solutions show $150{\pm}4^{\circ}$ in strike, $63{\pm}6^{\circ}$ in dip and $65{\pm}7^{\circ}$ in rake, or $18{\pm}12^{\circ}$ in strike, $26{\pm}3^{\circ}$ in dip and $120{\pm}5^{\circ}$ in rake. This result implies the stress field trending ENE-WSW, which is remarkably consistent with the previous results obtained from the moment tensor inversion, and from the composite fault plane solution for the events occurred around the Yangsan fault area.

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Impact of rock microstructures on failure processes - Numerical study based on DIP technique

  • Yu, Qinglei;Zhu, Wancheng;Tang, Chun'an;Yang, Tianhong
    • Geomechanics and Engineering
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    • v.7 no.4
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    • pp.375-401
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    • 2014
  • It is generally accepted that material heterogeneity has a great influence on the deformation, strength, damage and failure modes of rock. This paper presents numerical simulation on rock failure process based on the characterization of rock heterogeneity by using a digital image processing (DIP) technique. The actual heterogeneity of rock at mesoscopic scale (characterized as minerals) is retrieved by using a vectorization transformation method based on the digital image of rock surface, and it is imported into a well-established numerical code Rock Failure Process Analysis (RFPA), in order to examine the effect of rock heterogeneity on the rock failure process. In this regard, the numerical model of rock could be built based on the actual characterization of the heterogeneity of rock at the meso-scale. Then, the images of granite are taken as an example to illustrate the implementation of DIP technique in simulating the rock failure process. Three numerical examples are presented to demonstrate the impact of actual rock heterogeneity due to spatial distribution of constituent mineral grains (e.g., feldspar, quartz and mica) on the macro-scale mechanical response, and the associated rock failure mechanism at the meso-scale level is clarified. The numerical results indicate that the shape and distribution of constituent mineral grains have a pronounced impact on stress distribution and concentration, which may further control the failure process of granite. The proposed method provides an efficient tool for studying the mechanical behaviors of heterogeneous rock and rock-like materials whose failure processes are strongly influenced by material heterogeneity.

The effect of radial cracks on tunnel stability

  • Zhou, Lei;Zhu, Zheming;Liu, Bang;Fan, Yong
    • Geomechanics and Engineering
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    • v.15 no.2
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    • pp.721-728
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    • 2018
  • The surrounding rock mass contains cracks and joints which are distributed randomly around tunnels, and in the process of tunnel blasting excavation, radial cracks could also be induced in the surrounding rock mass. In order to clearly understand the impact of radial cracks on tunnel stability, tunnel model tests and finite element numerical analysis were implemented in this paper. Two kinds of materials: cement mortar and sandstone, were used to make tunnel models, which were loaded vertically and confined horizontally. The tunnel failure pattern was simulated by using RFPA2D code, and the Tresca stresses and the stress intensity factors were calculated by using ABAQUS code, which were applied to the analysis of tunnel model test results. The numerical results generally agree with the model test results, and the mode II stress intensity factors calculated by ABAQUS code can well explain the model test results. It can be seen that for tunnels with a radial crack emanating from three points on tunnel edge, i.e., the middle point between tunnel spandrel and its top with a dip angle $45^{\circ}$, the tunnel foot with a dip angle $127^{\circ}$, and the tunnel spandrel with $135^{\circ}$ with tunnel wall, the tunnel model strength is about a half of the regular tunnel model strength, and the corresponding tunnel stability decreases largely.

Fault plane solutions of the December 13, 1996 Yeongweol earthquake (1996년 12월 13일 영월지진의 진원단층면 방향)

  • Park, Chang Eop;Sin, Jin Su;Ji, Heon Cheol;Gang, Ik Beom;Ryu, Yong Gyu
    • Journal of the Korean Geophysical Society
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    • v.1 no.1
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    • pp.23-30
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    • 1998
  • Fault-plane solutions of the December 13, 1996 Yeongweol earthquake with magnitude 4.5 is obtained using the grid test technique. Thirty polarities of P waves recorded at KMA, KIGAM, KSRS and JAPAN stations are used for the event. The obtained fault plane solution shows strike-slip motion with significant amount of thrust component. The orientation of the fault is 180±20° in strike, 50±5° in dip and 150±5° in rake, or 292±3° in strike, 65±5° in dip and 30±10° in rake. These solutions are similar to those of earthquakes occurred at Sagju (Jan. 7, 1980), Pohang (Apr. 15, 1981) and offshore Gunsan (Oct. 6, 1976). The compressional axis of the stress field is trending from ENE to WSW, which is consistent with the previously defined typical regional tectonic stress orientation in and around Korean Peninsula.

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Mechanical properties of tailings with dipping interlayers under high confining pressure

  • Qinglin, Chen;Zugui, Li;Zeyu, Dai;Xiaojun, Wang;Chao, Zhang
    • Geomechanics and Engineering
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    • v.31 no.6
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    • pp.557-571
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    • 2022
  • Landslides are often triggered by weak interlayers initiated in tailings dam foundations, and hazards gradually occur. This is serious for landslides in high tailings dams due to their high potential energy. Tailing samples with a fine-grained interlayer at a set dip angle were prepared. Consolidated undrained (CU) triaxial shear tests were carried out by using a high-pressure triaxial apparatus. The results were compared with the results under a low confining pressure. Four reasons were summarized for high tailings dams more prone to instability than low dams. The shear strength of the samples with dipping interlayers decreases with increasing dip angle. An obvious straight drop in the stress path after the peak occurs in samples with dipping interlayers at an angle of 60°. The effect of the interlayer on the mechanical behaviour of tailings is very sensitive, especially for the sample with a dipping interlayer at an angle of 60°. Shear slipping along the interlayer should be given more attention in tailings dams. Compared with the results under low confining pressure, the stress decreases continuously for the samples with dipping interlayers at large angles under high confining pressure. The positive pore pressure, which reduces the effective stress, occurred in tailings samples under high confining pressure. The residual strength of tailings under high confining pressure is smaller than that under low confining pressure. These factors increase the dam break risk and the disaster impact for high tailings dams.

A Numerical Analysis on the Coating Thickness in Continuous Hot-Dip Galvanizing (연속 아연 도금 코-팅 두께에 관한 수치 해석적 연구)

  • Lee, Dong-Won;Shin, Seung-Young;Kim, Byung-Ji;Kwon, Young-Doo;Kwon, Soon-Bum
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2955-2960
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    • 2007
  • To control the coating thickness of zinc in the process of continuous hot-dip galvanizing, it is known from early day that the gas wiping through an air knife system is the most effective because of the obtainable of uniformity of coating thickness, possibility of thin coating, working ability in high speed and simplicity of control. But, the gas wiping using in the galvanizing process brings about a problem of splashing from the strip edge for a certain high speed of coating. And, it is known that the problem of splashing is caused mainly by the existence of separation bubble at the neighbor of the strip surface. In theses connections, in the present study, we proposed two kinds of air knife systems having the same expansion rate of nozzle, and the jet structures and coating thicknesses from a conventional and new proposed nozzles are compared. In numerical analysis, the governing equations consisted of two-dimensional time dependent Navier-Stokes equations, standard ${\kappa}-{\varepsilon}$ turbulence model to solve turbulence stress and so on are employed. As a result, it is found that it had better to use the constant rate nozzle from the point view of the energy saving to obtain the same coating thickness. Also, to reduce the size of separation bubble and to enhance the cutting ability at the strip, it is recommendable to use an air knife having the constant expansion rate nozzle.

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