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조철현,정현기,조광호,Jo, Churl-Hyun,Chung, Hyun-Key,Cho, Kwang-Ho 한국구조물진단유지관리공학회 1999 한국구조물진단유지관리공학회 논문집 Vol.3 No.2
There is an increasing need for the estimation of foundation piles whose depths are unknown. Especially in repair and reinforcement works or in safety inspection and assessment to the big structures whose foundations are piles, the accurate information about the depth of foundation piles is one of the most important factors. A borehole magnetic tool has been developed and tested to meet this object. The fundamental base is that there usually exist many re-bars inside the foundation structure such as piles, and these re-bars are ferromagnetic materials which cause strong induced magnetic field comparable to the earth magnetic field. It utilizes flux-gate type magnetometer which measures 3-components of the magnetic field. Taking vertical derivatives of vertical component of the measured magnetic field, we can expect the error limit of estimating the depth of the pile end less than 20 cm in favorable condition. The maximum measurable distance is about 3 m to the pile from the borehole. The field data show that borehole magnetics is one of the most accurate, fast, and reliable methods for this object so far, as long as there is no magnetic materials such as deep located steel pipe or power cables close to the foundation piles.
조철현(Jo Churl Hyun),차영호(Cha Young Ho),양종화(Yang Jong Hwa),방기문(Bang Ki Moon) 한국철도학회 2005 한국철도학회 학술발표대회논문집 Vol.- No.-
To ensure the safety of the tunnelling without the loss of economy, the tunnel seismic profiling(TSP) method for the prediction ahead of tunnel face, begins to be used routinely in these days. TSP method does not interfere the tunnelling works while the horizontal drilling does, and its prediction length is longer than that of the drilling. Yet the most frequently adopted technique of TSP in Korea is the multi-shot and 2 receiver array using in-hole receivers, even though this array requires as many as 26 drill-holes for receiver installation and ballasting, which results in 3~6 hours of suspension in excavation work. In this paper, multi-receiver and lesser shot array using side-wall attached 3 component geophones is to be described to prove the efficiency in terms of the survey time as well as the reliability of the method by comparison of the predicted weak points and the face mapping results. The predictions mostly agreed with the real fractures or joint developed zones which have been confirmed during the excavation. It also has been found that TSP method can be effectively applied to perform draining ground water ahead of tunnel face by imaging the geologic discontinuities.
경기도 화성 고정리 공룡알 화석지 공룡생태박물관 부지선정을 위한 지구물리 및 지질조사
김한준 ( Han Joon Kim ),정갑식 ( Gap Sik Jeong ),이보연 ( Bo Yeon Yi ),조철현 ( Churl Hyun Jo ),이광배 ( Kwang Bae Lee ),이준호 ( Jun Ho Lee ),주형태 ( Hyeong Tae Jou ),이광훈 ( Gwang Hoon Lee ) 한국지구물리·물리탐사학회 2010 지구물리와 물리탐사 Vol.13 No.4
In this study, we investigated the geologic structure of the basement and overlying sediments of the construction site of the dinosaur egg fossil museum in Hwasung, Gyeonggi Province through refraction seismology, drilling, and downward seismic velocity measurements in the drill holes. The construction site (350 x 750 m2) is located in the reclaimed area south of Sihwa Lake, Gojeong-ri. About 6,950 m of seismic refraction data consisting of 11 lines were acquired using a sledge hammer source. Drilling to the basement was performed at five sites. Sediment samples from drilling were analysed for grain-size distribution and age dating. At two drill holes, seismic velocity was measured with depth using a hammer as a seismic source. The geological structure of the study area consists of, from top to bottom, a tidal flat layer (5 - 12 m thick), a weathered soil layer (2 - 8 m thick), and the basement. The basement is interpreted as Cretaceous sedimentary rocks that tend to be shallow eastward. The volume of the tidal flat sediments and wcathcred soil in the study area is estimated as 1.4 x 106 m3, weighing 3.5 x 106 tons. The rate of sea level rise since 8,000 yrs BP is estimated to be 0.1 -0.15 cm/yr.