다운홀 탄성파 기법용 전단파 자동 가진원의 개발

방은석,성낙훈,김정호,김동수 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.11

Downhole seismic method is very economic and easy to operate because it uses only one borehole and simple surface source to obtain the shear wave velocity profile of a site. In this study, automatic shear wave source was developed for efficient downhole seismic testing. This source is motor-spring type and easy to control. It can lessen the labor of operator and the working time. Moreover, it can provide better and repetitive signals for data interpretation. By combining developed automatic source with automatic receiver system, PC based data acquisition system, advanced managing program, and semi-automatic downhole performing system were constructed. Through comparison test with manual source, advantages of automatic source were verified. Constructed semi-automatic downhole testing system including automatic shear wave source was applied to the soft soil site. The applicability and reliability were verified and the importance of automating testing system for obtaining reliable result was emphasized.

경주 지역의 지반공학적 지진 민감도 분석

방은석,선창국,김동수,정충기,조성호 한국지반공학회 2001 한국지반공학회논문집 Vol.17 No.1

역사적 지진 발생 기록이 풍부하고 양산 단층 영향권 내에 있어 지진 발생 가능성이 높은 경주 지역을 대상으로 지진민감도 분석을 수행하였다. 지형적 특성을 고려한 지반조사와 현장 및 실내 시험을 통하여 대상 지역 지반의 지층 구성과 각 지층의 동적 특성을 분석 평가하고, 이를 토대로 한 지반 응답 해석을 수행하였다. 9개의 시험공을 시추하여 2개소의 크로스홀 시험과 7개소의 다운홀 시험을 실시하였고, 시추부지 포함 13개소에서 SASW 시험도 수행하였다. X선 회절 및 풍화도 분석과 공진주 시험 등의 실내시험도 병행하였다. 이러한 시험 결과를 바탕으로 El Centro 지진에 의한 지표면 최대 가속도를 등가 선형 부지응답해석을 통해 평가한 결과 붕괴방지 수준에서 0.158g~0.286g, 기능수행 수준에서 0.067g~0.116g의 분포를 보였고 퇴적층에 의하여 형성된 경주 시가지 분지 지형에서 증폭정도가 심하다는 것을 알 수 있었다. 해석 결과로 볼 때, 현행 건교부 기준 설계응답스펙트럼은 경우에 따라 지반 운동을 과소평가하고 지반 고유의 공진 현상을 고려하지 못하였다. 이러한 문제를 해결하기 위하여 개선된 지반 분류방법을 소개하였고 부지고유의 지반응답평가의 중요성에 대해 제시하였다.

연약지반의 복합적 평가를 위한 전기비저항 탄성파 Flat DMT 장비 적용

방은석,김영상,박삼규,김동수 한국지반공학회 2012 한국지반공학회논문집 Vol.28 No.12

Resistivity seismic dilatometer (RSDMT) system is introduced. The resistivity module for obtaining resistivity-depth plot and seismic module for obtaining wave velocity-depth plot are attached to the conventional flat dilatometer testing equipment. To enhance the reliability and repeatability of seismic part in RSDMT, automatic testing system including automatic surface source, PC based data acquisition system and operating program was constructed. To obtain real resistivity value of soil, geometric factor for the array of electrodes in RSDMT was derived empirically. The verification studies for the developed RSDMT system were performed with SPT, CPTu, bender element test and DC resistivity survey. Through one penetration of RSDMT, various soil parameters were obtained and the reliability and repeatability of developed RSDMT system could be checked.

근거리장에서 HWAW 기법의 수치해석적 검증

방은석,박형춘,김동수 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.2

Various field setup and filtering criteria have been suggested to avoid the near field effects in surface wave methods. Unlike other surface wave methods HWAW method uses the near field component positively. It is possible by using maximum energy point based on time-frequency map and inversion method to consider receiver locations from the source point and body wave component. To verify the HWAW method in the near field numerical study was performed and the wave propagation in the stratified soil media was simulated due to a surface point load. All of five representative soil models were used. The experimental dispersion curves, determined by HWAW method at the various receiver distances in the region of near field, all coincided well with the theoretical dispersion curves determined by 3D forward modeling (Kausel’s method). Consequently, it was considered that the HWAW method can provide reliable VS profiles effectively in the near field.

상호검증시험을 통한 효율적인 다운홀 탄성파 기법 수행 시스템의 구성

방은석,김동수,김기석 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.4

Downhole seismic method is very economic and easy of operation because it uses only one borehole and simple surface source to obtain the shear wave velocity (VS) profile of a site. Even though it is widely used by the site investigation companies, universities and institutes, however, the VS profile determined by downhole seismic method has often low reliability due to employment of wrong combinations of field tesing equipment and interpretation method and deficiency of experience. Round robin test was performed and testing equipment and procedure were compared. Adequate downhole seismic testing equipment was constructed based on the comparison and verification study of the round robin test. The data acquisition and software interpretation were also developed for automation and quick test in field. Finally, the effectiveness and applicability were verified through the field test by using the constructed testing system.

다운홀 기법에서 신뢰성 있는 도달시간 정보 산출 방법에 대한 고찰

방은석,이세현,김종태,김동수 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.8

Downhole seismic method is widely used for obtaining shear wave velocity profile of a site because it is simple and economical. Determining accurate travel time of shear wave is very important to obtain reliable result in downhole seismic method. In this paper, comparison study of various travel time determination methods was performed. Numerical study and model chamber test were performed for effective comparison study. Signal traces were acquired by performing downhole test at each numerical simulation and soil box test. Travel time data for each signal traces were determined by using six different methods and VS profiles were evaluated. Comparing travel time data and VS profiles with the reference value, the first arrival picking method proved to be ambiguous and unreliable. Other methods also did not always provide accurate results and the magnitude of error was dependent on the signal to noise ratio. Cross-correlation method proved to be the most adequate method for the field application and it was verified additionally with field data.

지질조사 및 광물자원탐사를 위한 KIGAM 드론 플랫폼 구축

방은석,손정술,강웅,이희욱,김창렬,이창원,김보나,황세호,노상건,손영선,조성준 한국지구물리.물리탐사학회 2020 지구물리와 물리탐사 Vol.23 No.3

A drone platform built by Korea Institute of Geoscience and Mineral Resources (KIGAM) is introduced. The platform consists of various drone systems developed at KIGAM for photogrammetry, remote exploration, physical exploration, field operation methods, a vehicle-based drone control center, as well as a drone data platform for data storage, sharing, analysis, and visualization of the acquired data. The performance of the drone platform is verified using results obtained with the various systems, which are tested individually and in various combined applications. Finally, the possibility of using the KIGAM drone platform for geological surveys and mineral resource exploration is discussed. 한국지질자원연구원에서 구축하고 있는 드론 플랫폼을 소개하였다. 구축중인 플랫폼은 사진측량, 원격탐사, 물리탐사 등을 위한 다양한 드론 시스템과 현장에서 각 시스템을 운용하기 위한 방안과 차량형 드론관제센터, 그리고 취득한자료의 저장, 공유, 분석, 시각화 등을 위한 드론 데이터 플랫폼 등으로 구성된다. 구축한 드론 시스템의 개별적 적용 또는 복합적 적용을 통해 획득한 결과들로부터 그 성능을 검증하였으며 지질조사 및 광물자원탐사를 위한 KIGAM 드론 플랫폼의 활용 가능성에 대해 고찰하였다.

토목건설/노천광산 현장관리를 위한 드론 서비스

방은석,Bang, Eun-Seok 한국지반공학회 2019 지반 : 한국지반공학회지 Vol.35 No.2

HWAW 기법의 비수평 층상구조지반 적용에 대한 고찰

방은석,박헌준,김동수,박형춘 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.4

In HWAW method, experimental dispersion curve is obtained through time-frequency analysis, and inversion procedure is based on the forward modeling which considers full wavefield. Therefore, it enables us to use relatively short testing setup and has advantage for two dimensional subsurface imaging compared with another surface wave methods. Numerical study was performed to verify that the HWAW method can be applied to non-horizontally layerd soil structure. The experimental dispersion curves obtained from HWAW method agreed with the theoretical dispersion curves based on full wavefield. Experimental dispersion curves are mainly more affected by the region between two receivers than by the region from source to the first receiver. Fluctuation phenomena of dispersion curve can be reduced by adequate receiver spacing setup. From numerical study, it was thought that reliable Vs distribution map can be constructed by HWAW method and finally subsurface imaging was tried in the real field.

지표조사를 위한 드론 사진측량/라이다 기술 적용 사례

방은석,이희욱,이창원,김창렬,유영철 대한지질공학회 2022 대한지질공학회 학술발표회논문집 Vol.2022 No.1