• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.241-244
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• 2007

Cement-grouts are injected into limestone cavities beneath the road in the project area, in order to improve strength and reduce permeability; the extent to which grout has penetrated in cavities need to be monitored in order to determined effectiveness of cement-grout. Geophysical approaches, offer great potential for monitoring the grout injection process in a fast and cost-effective way as well as showing whether the grout has successfully achieved the target. This paper presents the ability of surface electrical resistivity to investigate the verification of the grout placement. In order to image the cement-grout, time-lapse surface electrical resistivity surveys were conducted to compare electrical resistivity images before and after injection. Cement-grout was imaged as anomalies exhibiting low resistivity than the surrounding rocks. In accordance with field monitoring, laboratory study was also designed to monitor the resistivity changes of cement-grout specimens with time-lapse. Time-lapse laboratory measurements indicated that electrical methods are good tool to identify the grouted zone. Pre-and post grouting electrical images showed significant changes in subsurface resistivity at grouted zone. The study showed that electrical resistivity imaging technology can be a useful tool for detecting and evaluating changes in subsurface resistivity due to the injection of the grout.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.109-112
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• 2006

기존 상용 전기탐사장비의 한계는 간척지 갯벌 등 해성퇴적층 하부지반조사 적용이 매우 힘들거나, 불가능한 것으로 인지되어 왔다. 최근 전 세계적으로 해저면 또는 연안지역환경 전기탐사 필요성이 대두됨에 따라 자체개발 발전기 전원 5 Ampere 대전류 송신 전기탐사 현장적용이 광양만에서 확인된다. 항만관련 기반시설 연안투자는 지속 확대될 것으로 기존 탐사방법 지반조사에서 탈피하여 항만 교량, 해저터널, 해저 가스 층 등의 효과적 적용 가능성이 기대된다. 한편 조석변화를 고려한 대전류 전기 비저항탐사를 수위별로 시간대 측정하여 연약구역 효과를 비교 시도하였다. 대전류 송신은 탐사전선저항 길이를 고려한 덜 무거운 케이블 선택 설계가 현장야업 시 중요하다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 특별 심포지엄 논문집
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• pp.31-42
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• 2007

Dc resistivity monitoring has been increasingly used in order to understand the changes of subsurface conditions in terms of conductivity. The commonly adopted interpretation approach which separately inverts time-lapse data may generate inversion artifacts due to measurement error. Eventually the contaminated error amplifies the artifacts when reconstructing the difference images to quantitatively estimate the change of ground condition. In order to alleviate the problems, we defined the subsurface structure as four dimensional (4-D) space-time model and developed 4-D inversion algorithm which can calculate the reasonable subsurface structure continuously changing in time even when the material properties change during data measurements. In this paper, we discussed two case histories of resistivity monitoring to study the ground condition change when the properties of the subsurface material were artificially altered by injecting conductive materials into the ground: (1) dye tracer experiment to study the applicability of electrical resistivity tomography to monitoring of water movement in soil profile and (2) the evaluation of cement grouting performed to reinforce the ground. Through these two case histories, we demonstrated that the 4-D resistivity imaging technique is very powerful to precisely delineate the change of ground condition. Particularly owing to the 4-D inversion algorithm, we were able to reconstruct the history of the change of subsurface material property.