• Title/Summary/Keyword: 발파지수

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Fast Delineation of the Depth to Bedrock using the GRM during the Seismic Refaction Survey in Cheongju Granite Area (굴절법 탄성파탐사 현장에서 GRM을 이용한 청주화강암지역 기반암 깊이의 신속한 추정)

  • Lee, Sun-Joong;Kim, Ji-Soo;Lee, Cheol-Hee;Moon, Yoon-Sup
    • Economic and Environmental Geology
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    • v.43 no.6
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    • pp.615-623
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    • 2010
  • Seismic refraction survey is a geophysical method that delineates subsurface velocity structure using direct wave and critically refracted wave. The generalized reciprocal method(GRM) is an inversion technique which uses travel-time data from several forward and reverse shots and which can provide the geometry of irregular inclined refractors and structures underlain by hidden layer such as low velocity zone and thin layer. In this study, a simple Excel-GRM routine was tested for fast mapping of the interface between weathering layer and bedrock during the survey, with employing a pair of forward and reverse shots. This routine was proved to control the maximum dip of approximately $30^{\circ}C$ and maximum velocity contrast of 0.6, based on the panel tests in terms of dipping angle and velocity contrast for the two-layer inclined models. In contrast with conventional operation of five to seven shots with sufficient offset distance and indoor data analysis thereafter, this routine was performed in the field shortly after data acquisition. Depth to the bedrock provided by Excel-GRM, during the field survey for Cheongju granite area, correlates well with the elevation of the surface of soft rock from the drill core and SPS logging data. This cost-effective routine developed for quickly delineating the bedrock surface in the field survey will be readily applicable to mapping of weathering zone in narrow zone with small variation of elevation of bedrock.

A Study on the Geotechnical Characteristics of Tunnel Collapse (국내외 터널 붕락의 지반공학적 특징에 관한 연구)

  • Seo, Kyoungwon;Kim, Woongku;Baek, Kihyun
    • Journal of Korean Society of societal Security
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    • v.2 no.4
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    • pp.75-81
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    • 2009
  • This paper presents the geotechnical characteristics of tunnel co \l apse based on the case studies. For domestic cases, most collapses are likely to happen along the weakest zone of shear strength due to the change of stresses induced by excavation specially when soft or weathered rock exist in front of a tunnel. In other words, the collapse of a tunnel occurs along the highly weathered fractured zone due to blasting and excavation. In Europe, collapses have been occurred by one joint group even though the ground is relatively fresh and for the rocks of which RQD is over 50%. In addition, the amount of ground water flow does not seem to be seriously affected by the RQD range.

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An Evaluation of the Impact of Ammonium Nitrate Explosion Occurred in Beirut Port (베이루트항에서 발생한 질산암모늄 폭발에 의한 영향 평가)

  • Yong-Kyun Yoon
    • Explosives and Blasting
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    • v.41 no.4
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    • pp.1-8
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    • 2023
  • On August 4, 2020, 2750 tons of ammonium nitrate stored in a storage warehouse at the Port of Beirut exploded. This explosion is said to be the largest ammonium nitrate explosion ever. By applying the TNT equivalency method, TNT equivalent amount corresponding to the explosion energy of 2750 tons of ammonium nitrate was calculated, and it is found to be 856 tons. Overpressure and impulse were calculated in a range up to 3600 m from the blast using the Kingery-Bulmash explosion parameter calculator tool. As the distance from the explosion center increases, the overpressure and impulse decrease exponentially, but the overpressure decreases more significantly, showing that overpressure is more affected by distance than the impact. As a result of applying the damage criteria to evaluate the effects of overpressure and impulse on the structure, the critical distances at which partial collapse, major damage, and minor damage to the structure occur are found to be approximately 500, 800, and 2200 m from the center of the explosion, respectively. The probit function was applied to evaluate the probability of damage to structures and human body. The points where the probability of collapse, major damage, minor damage, and breakage of window-panes to structures are greater than 50% are found to be approximately 500, 810, 2200, and 3200 m, respectively. For people within 200 m from the center of the explosion, the probability of death due to lung damage is more than 99%, and the 50% probability of eardrum rupture is approximately 300 m. The points with a 100% probability of death due to skull rupture and whole body impact due to whole body displacement are evaluated to be 300 and 100 m, respectively.

A Model Study of Processing Methods of Seismic Refraction Data for Mapping Geological Discontinuities - GRM, GLI, Tomography (지질불연속면에 대한 탄성파 굴절법탐사 자료처리 고찰 - GRM, GLI, Tomography)

  • Kim, Ji-Soo;Kim, Su-Hyun;Lee, Jun-Ho;Kim, Won-Ki;Lee, Yong-Jae
    • The Journal of Engineering Geology
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    • v.16 no.4 s.50
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    • pp.327-335
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    • 2006
  • Three processing strategies of seismic refraction data are tested in terms of velocity and depth profiles or structures for mapping of geological discontinuities: GRM(generalized reciprocal method), GLI(generalized linear inversion), Tomography. The test data used in this study are the shot gathers reconstructed by numerical modeling for the structures of 3 planar layers(horizontal, inclined), the buried vertical fracture zones, and vertical fault zones. Tomography is shown to be very efficient for mapping of more complicated tone such as vertical fault and buried fracture zones, whereas GRM and GLI can be useful for horizontal and/or inclined layers, probably on their bases of analysis of first arrivals in travel time curves.

Ground-Roll Suppression of the Land Seismic Data using the Singular Value Decomposition (SVD) (특이값 분해를 이용한 육상 탄성파자료의 그라운드롤 제거)

  • Sa, Jin-Hyeon;Kim, Sung-Soo;Kim, Ji-Soo
    • The Journal of Engineering Geology
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    • v.28 no.3
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    • pp.465-473
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    • 2018
  • The application of singular value decomposition (SVD) filtering is examined for attenuation of the ground-roll in land seismic data. Prior to the SVD computation to seek singular values containing the highly correlatable reflection energy, processing steps such as automatic gain control, elevation and refraction statics, NMO correction, and residual statics are performed to enhance the horizontal correlationships and continuities of reflections. Optimal parameters of SVD filtering are effectively chosen with diagnostic display of inverse NMO (INMO) corrected CSP (common shot point) gather. On the field data with dispersion of ground-roll overwhelmed, continuities of reflection events are much improved by SVD filtering than f-k filtering by eliminating the ground-roll with preserving the low-frequency reflections. This is well explained in the average amplitude spectra of the f-k and SVD filtered data. The reflectors including horizontal layer of the reservoir are much clearer on the stack section, with laminated events by SVD filtering and subsequent processing steps of spiking deconvolution and time-variant spectral whitening.

Removal of Seabed Multiples in Seismic Reflection Data using Machine Learning (머신러닝을 이용한 탄성파 반사법 자료의 해저면 겹반사 제거)

  • Nam, Ho-Soo;Lim, Bo-Sung;Kweon, Il-Ryong;Kim, Ji-Soo
    • Geophysics and Geophysical Exploration
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    • v.23 no.3
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    • pp.168-177
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    • 2020
  • Seabed multiple reflections (seabed multiples) are the main cause of misinterpretations of primary reflections in both shot gathers and stack sections. Accordingly, seabed multiples need to be suppressed throughout data processing. Conventional model-driven methods, such as prediction-error deconvolution, Radon filtering, and data-driven methods, such as the surface-related multiple elimination technique, have been used to attenuate multiple reflections. However, the vast majority of processing workflows require time-consuming steps when testing and selecting the processing parameters in addition to computational power and skilled data-processing techniques. To attenuate seabed multiples in seismic reflection data, input gathers with seabed multiples and label gathers without seabed multiples were generated via numerical modeling using the Marmousi2 velocity structure. The training data consisted of normal-moveout-corrected common midpoint gathers fed into a U-Net neural network. The well-trained model was found to effectively attenuate the seabed multiples according to the image similarity between the prediction result and the target data, and demonstrated good applicability to field data.

Image Enhancement of the Weathered Zone and Bedrock Surface with a Radial Transform in Engineering Seismic Data (엔지니어링 탄성파자료에서 방사변환을 통한 풍화대 및 기반암 표면의 영상강화)

  • Kim, Ji-Soo;Jeon, Su-In;Lee, Sun-Joong
    • The Journal of Engineering Geology
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    • v.22 no.4
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    • pp.459-466
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    • 2012
  • A difficulty encountered in engineering seismic mapping is that reflection events from shallow discontinuities are commonly overlapped with coherent noise such as air wave, direct waves, head waves, and high-amplitude surface waves. Here, the radial trace transform, a simple geometric re-mapping of a trace gather (x-t domain) to another trace gather (v-t domain), is applied to investigate the rejection effect of coherent linear noises. Two different types of data sets were selected as a representative database: good-quality data for intermediate sounding (hundreds of meters) in a sedimentary basin and very noisy data for shallow (${\leq}50m$) mapping of the weathered zone and bedrock surface. Results obtained with cascaded application of the radial transform and low-cut filtering proved to be as good as, or better than, those produced using f-k filtering, and were especially effective for air wave and direct wave. This simple transform enables better understanding of the characteristics of various types of noise in the RT domain, and can be generally applied to overcoming diffractions and back-scatterings caused by joints, fractures, and faults commonly that are encountered in geotechnical problems.

Electrical resistivity and seismic reflection mapping for the southeastern part of the Yongdong basin (Cretaceous), Korea (영동분지(백악기) 남동부의 전기비저항 및 탄성파탐사자료 해석)

  • Kim, Ji-Su;Han, Su-Hyeong;Lee, Cheol-U;Kim, Bok-Cheol;Yang, U-Heon;Son, Ho-Ung;Son, Yeong-Gwan
    • Journal of the Korean Geophysical Society
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    • v.3 no.2
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    • pp.77-90
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    • 2000
  • Five electrical resistivity dipole-dipole and two seismic reflection surveys were performed in the southeastern margin of the Yongdong basin to delineate the shallow basin architecture. To investigate the intra-basin structure, twenty four resistivity sounding points and three dipole-dipole lines were selected especially in the vicinity of volcanic masses. The basin-fault boundaries are identified in electrical dipole-dipole resistivity section as high resistivity-contrast of approximately $1,500\;{\Omega}{\cdot}m$, characterized as a band of high standard-deviation. They are also effectively clarified in the seismic reflection data: amplitude and continuity contrasts in the common shot gather, first-arrival profiles, complex attribute plots. The intra-basin resistivity structures are constructed by interpolating vertical electrical sounding data and dipole-dipole profiles. The high-resistivity anomalies most likely originate from the northsouth-trending and northeast-dipping volcanic masses, which are to be further quantitatively investigated with geomagnetic and magnetotelluric surveys.

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Resolution of Shallow Marine Subsuface Structure Image Associated with Acquisition Parameters of High-resolution Multi-channel Seismic Data (고해상 다중채널 탄성파탐사 자료취득변수에 따른 천부 해저지층영상의 해상도)

  • Lee Ho-Young;Koo Nam-Hyung;Park Keun-Pil;Yoo Dong-Geun;Kang Dong-Hyo;Kim Young-Gun;Seo Gab-Seok;Hwang Kyu-Duk;Kim Jong-Chon;Kim Ji-Soo
    • Geophysics and Geophysical Exploration
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    • v.6 no.3
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    • pp.126-133
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    • 2003
  • High-resolution shallow marine seismic surveys have been carried out for the resources exploration, engineering applications and Quaternary mapping. To improve the resolution of subsurface structure image, multichannel digital technique has been applied. The quality of the image depends on the vertical and horizontal resolution and signal to noise (S/N) ratio which are associated with the data acquisition parameters such as sample interval, common midpoint (CMP) interval and CMP fold. To understand the effect of the acquisition parameters, a test survey was carried out off Yeosu and the acquired data were analyzed. A 30 $in^3$ small air gun was used as a seismic source and 8 channel streamer cable with a 5 m group interval was used as a receiver. The data were digitally recorded with a shot interval of 2 s and sample interval of 0.1 ms. The acquired data were resampled with various sample intervals, CMP intervals and CMP folds. The resampled data were processed, plotted as seismic sections and compared each other. The analysis results show that thin bed structure with ${\~}1m$ thickness and ${\~}6^{\circ}$ slope can be imaged with good resolution and continuity and low noise using the acquisition parameters with a sample interval shorter than 0.2 ms, CMP interval shorter than 2.5 m and CMP fold more than 4. Because seismic resolution is associated with the acquisition parameters, the quality of the subsurface structure can be imaged successfully using suitable and optimum acquisition parameters.